Brazing

From Wikipedia, the free encyclopedia
Jump to: navigation, search
This article is about the metal-joining process. For the cooking technique, see braising.
Brazing practice

Brazing is a metal-joining process whereby(なにによって,そのために,何について,どのようにして,どういう手段で,それによって) a filler metal is heated above melting point and distributed between two or more close-fitting parts by capillary(毛細管,網細血管,毛細(血)管の) action. The filler metal is brought slightly above its melting (liquidus) temperature while protected by a suitable atmosphere, usually a flux(絶え間ない変化,不安定,流れ,流量,溶剤,(理)束,磁束,電束,流動,上げ潮,絶え間のない変化,融剤). It then flows over the base metal (known as wetting) and is then cooled to join the workpieces together.[1] It is similar to soldering(1.(一般的に)結び付けるもの,きずな,2.半田,3.(〜を)半田付けする,(〜を)固く結合する), except the temperatures used to melt the filler metal are higher for brazing.

Fundamentals[edit]

In order to obtain high-quality brazed joints, parts must be closely fitted, and the base metals must be exceptionally(例外的に) clean and free of oxides.(酸化物) In most cases, joint clearances(1.取りかたづけ,掃除,2.手形交換,3.間隔,隙間) of 0.03 to 0.08 mm (0.0012 to 0.0031 in) are recommended for the best capillary(毛細管,網細血管,毛細(血)管の) action and joint strength.[2] However, in some brazing operations it is not uncommon to have joint clearances(1.取りかたづけ,掃除,2.手形交換,3.間隔,隙間) around 0.6 mm (0.024 in). Cleanliness of the brazing surfaces is also important, as any contamination(堕落させるもの,汚すこと,よごれ,汚染,悪影響,汚染物) can cause poor wetting (flow). The two main methods for cleaning parts, prior(前の,先の,より重要な,優先する,小修道院長,大修道院副院長) to brazing, are chemical cleaning and abrasive(すり減らす,研磨剤,研磨の) or mechanical cleaning. In the case of mechanical cleaning, it is important to maintain the proper surface roughness((No gloss)) as wetting on a rough surface occurs much more readily than on a smooth surface of the same geometry.[2]

Another consideration that cannot((No gloss)) be overlooked is the effect of temperature and time on the quality of brazed joints. As the temperature of the braze alloy(合金,合金に用いる安価な金属,まぜ物,品位,純度) is increased, the alloying and wetting action of the filler metal increases as well. In general, the brazing temperature selected must be above the melting point of the filler metal. However, there are several factors that influence the joint designer's temperature selection. The best temperature is usually selected so as to: (1) be the lowest possible braze temperature, (2) minimize(最小限にする,軽視する) any heat effects on the assembly, (3) keep filler metal/base metal interactions to a minimum, and (4) maximize(極大化する,最大にする) the life of any fixtures(固定物,作りつけ備品,開催日,備品) or jigs used.[2] In some cases, a higher temperature may be selected to allow for other factors in the design (e.g. to allow use of a different filler metal, or to control metallurgical effects, or to sufficiently remove surface contamination).(堕落させるもの,汚すこと,よごれ,汚染,悪影響,汚染物) The effect of time on the brazed joint primarily affects the extent to which the aforementioned(前述の) effects are present; however, in general most production processes are selected to minimize(最小限にする,軽視する) brazing time and the associated costs. This is not always the case, however, since in some non-production settings, time and cost are secondary to other joint attributes(1.〜のおかげとする,せいにする,に帰する,の由縁とする,2.属性,特質,特性,属性,依るものとする) (e.g. strength, appearance).

Flux[edit]

In the case of brazing operations not contained within an inert((No gloss)) or reducing atmosphere environment (i.e. a furnace),(厳しい試練,加熱炉,熱しょう室,炉,暖炉,溶鉱炉) flux(絶え間ない変化,不安定,流れ,流量,溶剤,(理)束,磁束,電束,流動,上げ潮,絶え間のない変化,融剤) is required to prevent oxides(酸化物) from forming while the metal is heated. The flux(絶え間ない変化,不安定,流れ,流量,溶剤,(理)束,磁束,電束,流動,上げ潮,絶え間のない変化,融剤) also serves the purpose of cleaning any contamination(堕落させるもの,汚すこと,よごれ,汚染,悪影響,汚染物) left on the brazing surfaces. Flux can be applied in any number of forms including flux(絶え間ない変化,不安定,流れ,流量,溶剤,(理)束,磁束,電束,流動,上げ潮,絶え間のない変化,融剤) paste, liquid, powder or pre-made brazing pastes that combine flux(絶え間ない変化,不安定,流れ,流量,溶剤,(理)束,磁束,電束,流動,上げ潮,絶え間のない変化,融剤) with filler metal powder. Flux can also be applied using brazing rods with a coating of flux,(絶え間ない変化,不安定,流れ,流量,溶剤,(理)束,磁束,電束,流動,上げ潮,絶え間のない変化,融剤) or a flux(絶え間ない変化,不安定,流れ,流量,溶剤,(理)束,磁束,電束,流動,上げ潮,絶え間のない変化,融剤) core. In either case, the flux(絶え間ない変化,不安定,流れ,流量,溶剤,(理)束,磁束,電束,流動,上げ潮,絶え間のない変化,融剤) flows into the joint when applied to the heated joint and is displaced by the molten filler metal entering the joint. Excess flux(絶え間ない変化,不安定,流れ,流量,溶剤,(理)束,磁束,電束,流動,上げ潮,絶え間のない変化,融剤) should be removed when the cycle is completed because flux(絶え間ない変化,不安定,流れ,流量,溶剤,(理)束,磁束,電束,流動,上げ潮,絶え間のない変化,融剤) left in the joint can lead to corrosion,(腐食作用,腐食) impede(妨げる,邪魔する,妨害する) joint inspection,(検査) and prevent further surface finishing operations. Phosphorus-containing brazing alloys(合金,合金に用いる安価な金属,まぜ物,品位,純度) can be self-fluxing when joining copper to copper.[3] Fluxes are generally selected based on their performance on particular base metals. To be effective, the flux(絶え間ない変化,不安定,流れ,流量,溶剤,(理)束,磁束,電束,流動,上げ潮,絶え間のない変化,融剤) must be chemically((No gloss)) compatible(適合する) with both the base metal and the filler metal being used. Self-fluxing phosphorus(【化学】リン,燐(非金属元素)) filler alloys(合金,合金に用いる安価な金属,まぜ物,品位,純度) produce brittle(壊れやすい,堅いがもろい,傷つきやすい,砕けやすい,脆い,薄っぺらな) phosphides if used on iron or nickel.[3] As a general rule, longer brazing cycles should use less active fluxes than short brazing operations.[4]

Filler materials[edit]

A variety of alloys(合金,合金に用いる安価な金属,まぜ物,品位,純度) are used as filler metals for brazing depending on the intended use or application method. In general, braze alloys(合金,合金に用いる安価な金属,まぜ物,品位,純度) are made up of 3 or more metals to form an alloy(合金,合金に用いる安価な金属,まぜ物,品位,純度) with the desired properties. The filler metal for a particular application is chosen based on its ability to: wet the base metals, withstand the service conditions required, and melt at a lower temperature than the base metals or at a very specific temperature.

Braze alloy(合金,合金に用いる安価な金属,まぜ物,品位,純度) is generally available as rod, ribbon, powder, paste, cream, wire and preforms (such as stamped washers).(ワッシャー,洗う人,洗濯女,洗濯機)[5] Depending on the application, the filler material can be pre-placed at the desired location or applied during the heating cycle. For manual brazing, wire and rod forms are generally used as they are the easiest to apply while heating. In the case of furnace(厳しい試練,加熱炉,熱しょう室,炉,暖炉,溶鉱炉) brazing, alloy(合金,合金に用いる安価な金属,まぜ物,品位,純度) is usually placed beforehand since the process is usually highly automated.(自動化する)[5] Some of the more common types of filler metals used are

Atmosphere[edit]

As brazing work requires high temperatures, oxidation(酸化) of the metal surface occurs in an oxygen-containing atmosphere. This may necessitate(必要とする,要請する,必要とさせる,強いて〜させる) the use of an atmospheric(大気の,神秘的な) environment other than air. The commonly used atmospheres are[7][8]

  • Air: Simple and economical. Many materials susceptible to oxidation and buildup of scale. Acid cleaning bath or mechanical cleaning can be used to remove the oxidation after work. Flux tends to be employed to counteract the oxidation, but it may weaken the joint.
  • Combusted fuel gas (low hydrogen, AWS type 1, "exothermic generated atmospheres"): 87% N2, 11–12% CO2, 5-1% CO, 5-1% H2. For silver, copper-phosphorus and copper-zinc filler metals. For brazing copper and brass.
  • Combusted fuel gas (decarburizing, AWS type 2, "endothermic generated atmospheres"): 70–71% N2, 5–6% CO2, 9–10% CO, 14–15% H2. For copper, silver, copper-phosphorus and copper-zinc filler metals. For brazing copper, brass, nickel alloys, Monel, medium carbon steels.
  • Combusted fuel gas (dried, AWS type 3, "endothermic generated atmospheres"): 73–75% N2, 10–11% CO, 15–16% H2. For copper, silver, copper-phosphorus and copper-zinc filler metals. For brazing copper, brass, low-nickel alloys, Monel, medium and high carbon steels.
  • Combusted fuel gas (dried, decarburizing, AWS type 4): 41–45% N2, 17–19% CO, 38–40% H2. For copper, silver, copper-phosphorus and copper-zinc filler metals. For brazing copper, brass, low-nickel alloys, medium and high carbon steels.
  • Ammonia (AWS type 5, also called forming gas): Dissociated ammonia (75% hydrogen, 25% nitrogen) can be used for many types of brazing and annealing. Inexpensive. For copper, silver, nickel, copper-phosphorus and copper-zinc filler metals. For brazing copper, brass, nickel alloys, Monel, medium and high carbon steels and chromium alloys.
  • Nitrogen+hydrogen, cryogenic or purified (AWS type 6A): 70–99% N2, 1–30% H2. For copper, silver, nickel, copper-phosphorus and copper-zinc filler metals.
  • Nitrogen+hydrogen+carbon monoxide, cryogenic or purified (AWS type 6B): 70–99% N2, 2–20% H2, 1–10% CO. For copper, silver, nickel, copper-phosphorus and copper-zinc filler metals. For brazing copper, brass, low-nickel alloys, medium and high carbon steels.
  • Nitrogen, cryogenic or purified (AWS type 6C): Non-oxidizing, economical. At high temperatures can react with some metals, e.g. certain steels, forming nitrides. For copper, silver, nickel, copper-phosphorus and copper-zinc filler metals. For brazing copper, brass, low-nickel alloys, Monel, medium and high carbon steels.
  • Hydrogen (AWS type 7): Strong deoxidizer, highly thermally conductive. Can be used for copper brazing and annealing steel. May cause hydrogen embrittlement to some alloys. For copper, silver, nickel, copper-phosphorus and copper-zinc filler metals. For brazing copper, brass, nickel alloys, Monel, medium and high carbon steels and chromium alloys, cobalt alloys, tungsten alloys, and carbides.
  • Inorganic vapors (various volatile fluorides, AWS type 8): Special purpose. Can be mixed with atmospheres AWS 1–5 to replace flux. Used for silver-brazing of brasses.
  • Noble gas (usually argon, AWS type 9): Non-oxidizing, more expensive than nitrogen. Inert. Parts must be very clean, gas must be pure. For copper, silver, nickel, copper-phosphorus and copper-zinc filler metals. For brazing copper, brass, nickel alloys, Monel, medium and high carbon steels chromium alloys, titanium, zirconium, hafnium.
  • Noble gas+hydrogen (AWS type 9A)
  • Vacuum: Requires evacuating the work chamber. Expensive. Unsuitable (or requires special care) for metals with high vapor pressure, e.g. silver, zinc, phosphorus, cadmium, and manganese. Used for highest-quality joints, for e.g. aerospace applications.

Common techniques[edit]

Brazing and soldering processes classification chart[9]

Torch brazing[edit]

Torch brazing is by far the most common method of mechanized brazing in use. It is best used in small production volumes or in specialized operations, and in some countries, it accounts for a majority of the brazing taking place. There are three main categories of torch brazing in use:[10] manual, machine, and automatic torch brazing.

Manual torch brazing is a procedure where the heat is applied using a gas flame placed on or near the joint being brazed. The torch can either be hand held or held in a fixed position depending on whether the operation is completely manual or has some level of automation.(オートメーション) Manual brazing is most commonly used on small production volumes or in applications where the part size or configuration(構成,配置,配列) makes other brazing methods impossible.[10] The main drawback(戻し税,欠点,障害) is the high labor cost associated with the method as well as the operator skill required to obtain quality brazed joints. The use of flux(絶え間ない変化,不安定,流れ,流量,溶剤,(理)束,磁束,電束,流動,上げ潮,絶え間のない変化,融剤) or self-fluxing material is required to prevent oxidation.(酸化) Torch brazing of copper can be done without the use of flux(絶え間ない変化,不安定,流れ,流量,溶剤,(理)束,磁束,電束,流動,上げ潮,絶え間のない変化,融剤) if it is brazed with a torch using oxygen and hydrogen(水素,元素記号H,h) gas, rather than oxygen and other flammable(可燃性の,可燃性の高い,燃えやすい) gases.

Machine torch brazing is commonly used where a repetitive((けなして)繰り返しの,繰り返しの多い(repetitiousより控えめな語)) braze operation is being carried out. This method is a mix of both automated(自動化する) and manual operations with an operator often placing brazes material, flux(絶え間ない変化,不安定,流れ,流量,溶剤,(理)束,磁束,電束,流動,上げ潮,絶え間のない変化,融剤) and jigging parts while the machine mechanism carries out the actual braze.[10] The advantage of this method is that it reduces the high labor and skill requirement of manual brazing. The use of flux(絶え間ない変化,不安定,流れ,流量,溶剤,(理)束,磁束,電束,流動,上げ潮,絶え間のない変化,融剤) is also required for this method as there is no protective atmosphere, and it is best suited to small to medium production volumes.

Automatic torch brazing is a method that almost eliminates the need for manual labor in the brazing operation, except for loading and unloading((荷を)おろす,から積み荷をおろす,・・から積み荷をおろす,荷降ろしする,積み荷を降ろす) of the machine. The main advantages of this method are: a high production rate, uniform braze quality, and reduced operating cost. The equipment used is essentially the same as that used for Machine torch brazing, with the main difference being that the machinery replaces the operator in the part preparation.[10]

Furnace brazing[edit]

Furnace brazing schematic

Furnace brazing is a semi-automatic process used widely in industrial brazing operations due to its adaptability(順応性) to mass production and use of unskilled labor. There are many advantages of furnace(厳しい試練,加熱炉,熱しょう室,炉,暖炉,溶鉱炉) brazing over other heating methods that make it ideal for mass production. One main advantage is the ease with which it can produce large numbers of small parts that are easily jigged or self-locating.[11] The process also offers the benefits of a controlled heat cycle (allowing use of parts that might distort under localized(一地方に集まる,地方化する) heating) and no need for post braze cleaning. Common atmospheres used include: inert,((No gloss)) reducing or vacuum atmospheres all of which protect the part from oxidation.(酸化) Some other advantages include: low unit cost when used in mass production, close temperature control, and the ability to braze multiple joints at once. Furnaces are typically heated using either electric, gas or oil depending on the type of furnace(厳しい試練,加熱炉,熱しょう室,炉,暖炉,溶鉱炉) and application. However, some of the disadvantages of this method include: high capital equipment cost, more difficult design considerations and high power consumption.[11]

There are four main types of furnaces(厳しい試練,加熱炉,熱しょう室,炉,暖炉,溶鉱炉) used in brazing operations: batch(1.一揃い,一群,(手紙の)一束,(パンなどの)一焼き(分),一回分(のもの),一団,2.【コンピュータ】バッチ(一度に処理するデータの束)) type; continuous; retort(反論する,(鋭く)言い返す) with controlled atmosphere; and vacuum.

Batch type furnaces(厳しい試練,加熱炉,熱しょう室,炉,暖炉,溶鉱炉) have relatively low initial equipment costs and heat each part load separately. It is capable of being turned on and off at will which reduces operating expenses when not in use. These furnaces(厳しい試練,加熱炉,熱しょう室,炉,暖炉,溶鉱炉) are well suited to medium to large volume production and offer a large degree of flexibility in type of parts that can be brazed.[11] Either controlled atmospheres or flux(絶え間ない変化,不安定,流れ,流量,溶剤,(理)束,磁束,電束,流動,上げ潮,絶え間のない変化,融剤) can be used to control oxidation(酸化) and cleanliness(きれい好き,清潔,清潔さ) of parts.

Continuous type furnaces(厳しい試練,加熱炉,熱しょう室,炉,暖炉,溶鉱炉) are best suited to a steady flow of similar-sized parts through the furnace.(厳しい試練,加熱炉,熱しょう室,炉,暖炉,溶鉱炉)[11] These furnaces(厳しい試練,加熱炉,熱しょう室,炉,暖炉,溶鉱炉) are often conveyor((No gloss)) fed, allowing parts to be moved through the hot zone at a controlled speed. It is common to use either controlled atmosphere or pre-applied flux(絶え間ない変化,不安定,流れ,流量,溶剤,(理)束,磁束,電束,流動,上げ潮,絶え間のない変化,融剤) in continuous furnaces.(厳しい試練,加熱炉,熱しょう室,炉,暖炉,溶鉱炉) In particular, these furnaces(厳しい試練,加熱炉,熱しょう室,炉,暖炉,溶鉱炉) offer the benefit of very low manual labor requirements and so are best suited to large scale production operations.

Retort-type furnaces(厳しい試練,加熱炉,熱しょう室,炉,暖炉,溶鉱炉) differ from other batch-type(1.一揃い,一群,(手紙の)一束,(パンなどの)一焼き(分),一回分(のもの),一団,2.【コンピュータ】バッチ(一度に処理するデータの束)) furnaces(厳しい試練,加熱炉,熱しょう室,炉,暖炉,溶鉱炉) in that they make use of a sealed lining called a "retort". The retort(反論する,(鋭く)言い返す) is generally sealed with either a gasket or is welded(溶接する,結合する,溶接される,溶接点,溶接,密着) shut and filled completely with the desired atmosphere and then heated externally by conventional heating elements.[11] Due to the high temperatures involved, the retort(反論する,(鋭く)言い返す) is usually made of heat resistant(抵抗力のある) alloys(合金,合金に用いる安価な金属,まぜ物,品位,純度) that resist oxidation.(酸化) Retort furnaces(厳しい試練,加熱炉,熱しょう室,炉,暖炉,溶鉱炉) are often either used in a batch(1.一揃い,一群,(手紙の)一束,(パンなどの)一焼き(分),一回分(のもの),一団,2.【コンピュータ】バッチ(一度に処理するデータの束)) or semi-continuous versions.

Vacuum furnaces(厳しい試練,加熱炉,熱しょう室,炉,暖炉,溶鉱炉) is a relatively economical method of oxide(酸化物) prevention and is most often used to braze materials with very stable oxides(酸化物) (aluminum, titanium(チタン) and zirconium) that cannot((No gloss)) be brazed in atmosphere furnaces.(厳しい試練,加熱炉,熱しょう室,炉,暖炉,溶鉱炉) Vacuum brazing is also used heavily with refractory(手に負えない) materials and other exotic(1.異国(風)の,外国(産)の,外来の,異国情緒の,風変わりな,魅惑的な,2.外来の物,外人) alloy(合金,合金に用いる安価な金属,まぜ物,品位,純度) combinations unsuited to atmosphere furnaces.(厳しい試練,加熱炉,熱しょう室,炉,暖炉,溶鉱炉) Due to the absence of flux(絶え間ない変化,不安定,流れ,流量,溶剤,(理)束,磁束,電束,流動,上げ潮,絶え間のない変化,融剤) or a reducing atmosphere, the part cleanliness(きれい好き,清潔,清潔さ) is critical when brazing in a vacuum. The three main types of vacuum furnace(厳しい試練,加熱炉,熱しょう室,炉,暖炉,溶鉱炉) are: single-wall hot retort,(反論する,(鋭く)言い返す) double-walled hot retort,(反論する,(鋭く)言い返す) and cold-wall retort.(反論する,(鋭く)言い返す) Typical vacuum levels for brazing range from pressures of 1.3 to 0.13 pascals (10−2 to 10−3 Torr) to 0.00013 Pa (10−6 Torr) or lower.[11] Vacuum furnaces(厳しい試練,加熱炉,熱しょう室,炉,暖炉,溶鉱炉) are most commonly batch-type,(1.一揃い,一群,(手紙の)一束,(パンなどの)一焼き(分),一回分(のもの),一団,2.【コンピュータ】バッチ(一度に処理するデータの束)) and they are suited to medium and high production volumes.

Silver brazing[edit]

Silver brazing, sometimes known as a silver soldering(1.(一般的に)結び付けるもの,きずな,2.半田,3.(〜を)半田付けする,(〜を)固く結合する) or hard soldering(1.(一般的に)結び付けるもの,きずな,2.半田,3.(〜を)半田付けする,(〜を)固く結合する), is brazing using a silver alloy(合金,合金に用いる安価な金属,まぜ物,品位,純度) based filler. These silver alloys(合金,合金に用いる安価な金属,まぜ物,品位,純度) consist of many different percentages of silver and other metals, such as copper, zinc(亜鉛,亜鉛でメッキをする) and cadmium.(カドミウム)

Brazing is widely used in the tool industry to fasten 'hard metal' (carbide, ceramics,(セラミック,製陶の,陶器の) cermet, and similar) tips to tools such as saw blades. "Pretinning" is often done: the braze alloy(合金,合金に用いる安価な金属,まぜ物,品位,純度) is melted onto the hard metal tip, which is placed next to the steel and remelted. Pretinning gets around the problem that hard metals are hard to wet.

Brazed hard metal joints are typically two to seven mils thick. The braze alloy(合金,合金に用いる安価な金属,まぜ物,品位,純度) joins the materials and compensates(補償する,補正する) for the difference in their expansion rates. In addition it provides a cushion between the hard carbide tip and the hard steel which softens impact and prevents tip loss and damage, much as the suspension(負債の返済不納,吊すこと,停止,宙吊り,未決定,停職,懸濁,懸濁液,中止,保留) on a vehicle helps prevent damage to both the tires and the vehicle. Finally the braze alloy(合金,合金に用いる安価な金属,まぜ物,品位,純度) joins the other two materials to create a composite(混成の,合成の) structure, much as layers of wood and glue create plywood.(ベニヤ合板,合板)

The standard for braze joint strength in many industries is a joint that is stronger than either base material, so that when under stress, one or other of the base materials fails before the joint.

One special silver brazing method is called pinbrazing or pin brazing. It has been developed especially for connecting cables to railway track or for cathodic protection installations.((取り付けられた)装置,設備,軍事施設,基地,就任) The method uses a silver- and flux-containing(絶え間ない変化,不安定,流れ,流量,溶剤,(理)束,磁束,電束,流動,上げ潮,絶え間のない変化,融剤) brazing pin which is melted down in the eye of a cable lug.(強く引く) The equipment is normally powered from batteries.

Braze welding[edit]

Braze welding(溶接する,結合する,溶接される,溶接点,溶接,密着) is the use of a bronze or brass filler rod coated with flux(絶え間ない変化,不安定,流れ,流量,溶剤,(理)束,磁束,電束,流動,上げ潮,絶え間のない変化,融剤) to join steel workpieces. The equipment needed for braze welding(溶接する,結合する,溶接される,溶接点,溶接,密着) is basically identical(一致する,同じ,等しい,同一の) to the equipment used in brazing. Since braze welding(溶接する,結合する,溶接される,溶接点,溶接,密着) usually requires more heat than brazing, acetylene((No gloss)) or methylacetylene-propadiene (MAP) gas fuel is commonly used. The name comes from the fact that no capillary(毛細管,網細血管,毛細(血)管の) action is used.

Braze welding(溶接する,結合する,溶接される,溶接点,溶接,密着) has many advantages over fusion(核融合,融解,融合,溶融,合併,連合,統合,総合) welding.(溶接する,結合する,溶接される,溶接点,溶接,密着) It allows the joining of dissimilar(異なる) metals, minimization of heat distortion,(歪み,ゆがめること,歪曲) and can reduce the need for extensive pre-heating. Additionally, since the metals joined are not melted in the process, the components retain their original shape; edges and contours(等高線,輪郭,周,外形,外観,体の線) are not eroded(腐食する,侵食する,腐る) or changed by the formation of a fillet.(首下の丸み,魚をおろす,骨のない切り身にする) Another effect of braze welding(溶接する,結合する,溶接される,溶接点,溶接,密着) is the elimination(削除,除去,予選) of stored-up stresses that are often present in fusion(核融合,融解,融合,溶融,合併,連合,統合,総合) welding.(溶接する,結合する,溶接される,溶接点,溶接,密着) This is extremely important in the repair of large castings.(鋳造,割当,鋳物,投げ込み,投擲,配役,抜け殻) The disadvantages are the loss of strength when subjected to high temperatures and the inability(不可能) to withstand high stresses.

Carbide, cermet and ceramic(セラミック,製陶の,陶器の) tips are plated and then joined to steel to make tipped band saws. The plating acts as a braze alloy.(合金,合金に用いる安価な金属,まぜ物,品位,純度)

Cast iron "welding"[edit]

The "welding" of cast iron is usually a brazing operation, with a filler rod made chiefly of nickel being used although true welding(溶接する,結合する,溶接される,溶接点,溶接,密着) with cast iron rods is also available. Ductile cast iron pipe may be also "cadwelded," a process which connects joints by means of a small copper wire fused(ヒューズ,信管,導火線,にヒューズを付ける,溶かす,溶ける,融合・連合する,ヒューズが飛ぶ,ヒューズを飛ばす) into the iron when previously ground down to the bare metal, parallel to the iron joints being formed as per hub((No gloss)) pipe with neoprene gasket seals. The purpose behind this operation is to use electricity along the copper for keeping underground pipes warm in cold climates.

Vacuum brazing[edit]

Vacuum brazing is a material joining technique that offers significant advantages: extremely clean, superior, flux-free(絶え間ない変化,不安定,流れ,流量,溶剤,(理)束,磁束,電束,流動,上げ潮,絶え間のない変化,融剤) braze joints of high integrity(正直,誠実,完全,完全な状態,正直さ) and strength. The process can be expensive because it must be performed inside a vacuum chamber vessel. Temperature uniformity is maintained on the work piece when heating in a vacuum, greatly reducing residual(残余の,剰余の,残りの) stresses due to slow heating and cooling cycles. This, in turn, can significantly(きわめて,意味深く,意味ありげに) improve the thermal(熱の,温度の,熱による,温泉の,暖かい,上昇温暖気流,熱を持っている) and mechanical properties of the material, thus providing unique heat treatment capabilities. One such capability is heat-treating or age-hardening the workpiece while performing a metal-joining process, all in a single furnace(厳しい試練,加熱炉,熱しょう室,炉,暖炉,溶鉱炉) thermal(熱の,温度の,熱による,温泉の,暖かい,上昇温暖気流,熱を持っている) cycle.

Vacuum brazing is often conducted in a furnace;(厳しい試練,加熱炉,熱しょう室,炉,暖炉,溶鉱炉) this means that several joints can be made at once because the whole workpiece reaches the brazing temperature. The heat is transferred using radiation,(放射線,放射,輻射,放熱,照射,放射能,放射物) as many other methods cannot((No gloss)) be used in a vacuum.

Dip brazing[edit]

Dip brazing is especially suited for brazing aluminum because air is excluded, thus preventing the formation of oxides.(酸化物) The parts to be joined are fixtured and the brazing compound applied to the mating surfaces, typically in slurry((No gloss)) form. Then the assemblies are dipped into a bath of molten salt (typically NaCl, KCl and other compounds) which functions both as heat transfer medium and flux.(絶え間ない変化,不安定,流れ,流量,溶剤,(理)束,磁束,電束,流動,上げ潮,絶え間のない変化,融剤)

Heating methods[edit]

There are many heating methods available to accomplish brazing operations. The most important factor in choosing a heating method is achieving efficient transfer of heat throughout the joint and doing so within the heat capacity of the individual base metals used. The geometry of the braze joint is also a crucial factor to consider, as is the rate and volume of production required. The easiest way to categorize(分類する,類別する) brazing methods is to group them by heating method. Here are some of the most common:[1][12]

  • Torch brazing
  • Furnace brazing
  • Induction brazing
  • Dip brazing
  • Resistance brazing
  • Infrared brazing
  • Blanket brazing
  • Electron beam and laser brazing
  • Braze welding

Advantages and disadvantages[edit]

Brazing has many advantages over other metal-joining techniques, such as welding(溶接する,結合する,溶接される,溶接点,溶接,密着). Since brazing does((No gloss)) not melt the base metal of the joint, it allows much tighter control over tolerances(寛容,寛大,容認,数量過不足容認条件) and produces a clean joint without the need for secondary finishing. Additionally, dissimilar(異なる) metals and non-metals (i.e. metalized ceramics)(セラミック,製陶の,陶器の) can be brazed.[13] In general, brazing also produces less thermal(熱の,温度の,熱による,温泉の,暖かい,上昇温暖気流,熱を持っている) distortion(歪み,ゆがめること,歪曲) than welding(溶接する,結合する,溶接される,溶接点,溶接,密着) due to the uniform heating of a brazed piece. Complex and multi-part((No gloss)) assemblies can be brazed cost-effectively. Welded joints must sometimes be ground flush,(1.紅潮,赤面,赤らみ,輝き,はつらつさ,得意,興奮,意気揚々,(トランプの)フラッシュ,ほとばしり,出水,2.どっと流れる,ほとばしる,接触する,浪費する,3.同一平面上の,平らの,みなぎって / The sound of the toilet flushing in the bathroom distracted and aroused him. -Last Tango in Paris) a costly secondary operation that brazing does((No gloss)) not require because it produces a clean joint. Another advantage is that the brazing can be coated or clad for protective purposes. Finally, brazing is easily adapted to mass production and it is easy to automate(自動化する) because the individual process parameters(パラメーター,変数,媒介変数,母集団特性値,要素,要因,限界) are less sensitive to variation.[14][15]

One of the main disadvantages is: the lack of joint strength as compared to a welded(溶接する,結合する,溶接される,溶接点,溶接,密着) joint due to the softer filler metals used.[1][dubious(あいまいな,半信半疑の,うさんくさい,怪しげな,怪しい,心もとない,疑わしい,曖昧な,はっきりしない,心が決まらない,分からない) ] The strength of the brazed joint is likely to be less than that of the base metal(s) but greater than the filler metal.[citation(引用(quotation, reference)) needed][16] Another disadvantage is that brazed joints can be damaged under high service temperatures.[1] Brazed joints require a high degree of base-metal cleanliness(きれい好き,清潔,清潔さ) when done in an industrial setting. Some brazing applications require the use of adequate(適した,適当な,適切な,十分な◆(類)enough, sufficient) fluxing agents to control cleanliness.(きれい好き,清潔,清潔さ) The joint color is often different from that of the base metal, creating an aesthetic((芸術の)美の,美学の,審美的な,審美眼をもった,趣味のよい,芸術的な,美的な) disadvantage.

Filler metals[edit]

Some brazes come in the form of trifoils, laminated foils(くじく,裏をかく,フルーレ,引き立て役,箔) of a carrier(運搬装置,運び台,電話会社,回線業者,キャリヤ(通信事業者),【電気電子】搬送波,運送業者,保菌者,輸送車両) metal clad with a layer of braze at each side. The center metal is often copper; its role is to act as a carrier(運搬装置,運び台,電話会社,回線業者,キャリヤ(通信事業者),【電気電子】搬送波,運送業者,保菌者,輸送車両) for the alloy,(合金,合金に用いる安価な金属,まぜ物,品位,純度) to absorb mechanical stresses due to e.g. differential(差別的な,差,差異的な) thermal(熱の,温度の,熱による,温泉の,暖かい,上昇温暖気流,熱を持っている) expansion of dissimilar(異なる) materials (e.g. a carbide tip and a steel holder), and to act as a diffusion(普及,拡散,散布,流布) barrier (e.g. to stop diffusion(普及,拡散,散布,流布) of aluminium((No gloss)) from aluminium((No gloss)) bronze to steel when brazing these two).

Braze families[edit]

Brazing alloys(合金,合金に用いる安価な金属,まぜ物,品位,純度) form several distinct groups; the alloys(合金,合金に用いる安価な金属,まぜ物,品位,純度) in the same group have similar properties and uses.[17]

  • Pure metals
Unalloyed. Often noble metals – silver, gold, palladium.
  • Ag-Cu
Good melting properties. Silver enhances flow. Eutectic alloy used for furnace brazing. Copper-rich alloys prone to stress cracking by ammonia.
  • Ag-Zn
Similar to Cu-Zn, used in jewelry due to high silver content to be compliant with hallmarking. Color matches silver. Resistant to ammonia-containing silver-cleaning fluids.
General purpose, used for joining steel and cast iron. Corrosion resistance usually inadequate for copper, silicon bronze, copper-nickel, and stainless steel. Reasonably ductile. High vapor pressure due to volatile zinc, unsuitable for furnace brazing. Copper-rich alloys prone to stress cracking by ammonia.
  • Ag-Cu-Zn
Lower melting point than Ag-Cu for same Ag content. Combines advantages of Ag-Cu and Cu-Zn. At above 40% Zn the ductility and strength drop, so only lower-zinc alloys of this type are used. At above 25% zinc less ductile copper-zinc and silver-zinc phases appear. Copper content above 60% yields reduced strength and liquidus above 900 °C. Silver content above 85% yields reduced strength, high liquidus and high cost. Copper-rich alloys prone to stress cracking by ammonia. Silver-rich brazes (above 67.5% Ag) are hallmarkable and used in jewellery; alloys with lower silver content are used for engineering purposes. Alloys with copper-zinc ratio of about 60:40 contain the same phases as brass and match its color; they are used for joining brass. Small amount of nickel improves strength and corrosion resistance and promotes wetting of carbides. Addition of manganese together with nickel increases fracture toughness. Addition of cadmium yields Ag-Cu-Zn-Cd alloys with improved fluidity and wetting and lower melting point; however cadmium is toxic. Addition of tin can play mostly the same role.
  • Cu-P
Widely used for copper and copper alloys. Does not require flux for copper. Can be also used with silver, tungsten, and molybdenum. Copper-rich alloys prone to stress cracking by ammonia.
  • Ag-Cu-P
Like Cu-P, with improved flow. Better for larger gaps. More ductile, better electrical conductivity. Copper-rich alloys prone to stress cracking by ammonia.
  • Au-Ag
Noble metals. Used in jewelry.
  • Au-Cu
Continuous series of solid solutions. Readily wet many metals, including refractory ones. Narrow melting ranges, good fluidity.[18] Frequently used in jewellery. Alloys with 40–90% of gold harden on cooling but stay ductile. Nickel improves ductility. Silver lowers melting point but worsens corrosion resistance; to maintain corrosion resistance gold has to be kept above 60%. High-temperature strength and corrosion resistance can be improved by further alloying, e.g. with chromium, palladium, manganese and molybdenum. Addition of vanadium allows wetting ceramics. Low vapor pressure.
  • Au-Ni
Continuous series of solid solutions. Wider melting range than Au-Cu alloys but better corrosion resistance and improved wetting. Frequently alloyed with other metals to reduce proportion of gold while maintaining properties. Copper may be added to lower gold proportion, chromium to compensate for loss of corrosion resistance, and boron for improving wetting impaired by the chromium. Generally no more than 35% Ni is used, as higher Ni/Au ratios have too wide melting range. Low vapor pressure.
  • Au-Pd
Improved corrosion resistance over Au-Cu and Au-Ni alloys. Used for joining superalloys and refractory metals for high-temperature applications, e.g. jet engines. Expensive. May be substituted for by cobalt-based brazes. Low vapor pressure.
  • Pd
Good high-temperature performance, high corrosion resistance (less than gold), high strength (more than gold). usually alloyed with nickel, copper, or silver. Forms solid solutions with most metals, does not form brittle intermetallics. Low vapor pressure.
  • Ni
Nickel alloys, even more numerous than silver alloys. High strength. Lower cost than silver alloys. Good high-temperature performance, good corrosion resistance in moderately aggressive environments. Often used for stainless steels and heat-resistant alloys. Embrittled with sulfur and some lower-melting point metals, e.g. zinc. Boron, phosphorus, silicon and carbon lower melting point and rapidly diffuse to base metals; this allows diffusion brazing and allows the joint to be used above the brazing temperature. Borides and phosphides form brittle phases; amorphous preforms can be made by rapid solidification.
  • Co
Cobalt alloys. Good high-temperature corrosion resistance, possible alternative to Au-Pd brazes. Low workability at low temperatures, preforms prepared by rapid solidification.
  • Al-Si
for brazing aluminium.
  • Active alloys
Containing active metals, e.g. titanium or vanadium. Used for brazing non-metallic materials, e.g. graphite or ceramics.

Role of elements[edit]

element role volatility corrosion resistance cost incompatibility description
Silver structural, wetting volatile expensive Enhances capillary flow, improves corrosion resistance of less-noble alloys, worsens corrosion resistance of gold and palladium. Relatively expensive. High vapor pressure, problematic in vacuum brazing. Wets copper. Does not wet nickel and iron. Reduces melting point of many alloys, including gold-copper.
Copper structural ammonia Good mechanical properties. Often used with silver. Dissolves and wets nickel. Somewhat dissolves and wets iron. Copper-rich alloys sensitive to stress cracking in presence of ammonia.
Zinc structural, melting, wetting volatile low cheap Ni Lowers melting point. Often used with copper. Susceptible to corrosion. Improves wetting on ferrous metals and on nickel alloys. Compatible with aluminium. High vapor tension, produces somewhat toxic fumes, requires ventilation; highly volatile above 500 °C. At high temperatures may boil and create voids. Prone to selective leaching in some environments, which may cause joint failure. Traces of bismuth and beryllium together with tin or zinc in aluminium-based braze destabilize oxide film on aluminium, facilitating its wetting. High affinity to oxygen, promotes wetting of copper in air by reduction of the cuprous oxide surface film. Less such benefit in furnace brazing with controlled atmosphere. Embrittles nickel. High levels of zinc may result in a brittle alloy.[19]
Aluminium structural, active Fe Usual base for brazing aluminium and its alloys. Embrittles ferrous alloys.
Gold structural, wetting excellent very expensive Excellent corrosion resistance. Very expensive. Wets most metals.
Palladium structural excellent very expensive Excellent corrosion resistance, though less than gold. Higher mechanical strength than gold. Good high-temperature strength. Very expensive, though less than gold. Makes the joint less prone to fail due to intergranular penetration when brazing alloys of nickel, molybdenum, or tungsten.[20] Increases high-temperature strength of gold-based alloys.[18] Improves high-temperature strength and corrosion resistance of gold-copper alloys. Forms solid solutions with most engineering metals, does not form brittle intermetallics. High oxidation resistance at high temperatures, especially Pd-Ni alloys.
Cadmium structural, wetting, melting volatile toxic Lowers melting point, improves fluidity. Toxic. Produces toxic fumes, requires ventilation. High affinity to oxygen, promotes wetting of copper in air by reduction of the cuprous oxide surface film. Less such benefit in furnace brazing with controlled atmosphere. Allows reducing silver content of Ag-Cu-Zn alloys. Replaced by tin in more modern alloys.
Lead structural, melting Lowers melting point. Toxic. Produces toxic fumes, requires ventilation.
Tin structural, melting, wetting Lowers melting point, improves fluidity. Broadens melting range. Can be used with copper, with which it forms bronze. Improves wetting of many difficult-to-wet metals, e.g. stainless steels and tungsten carbide. Traces of bismuth and beryllium together with tin or zinc in aluminium-based braze destabilize oxide film on aluminium, facilitating its wetting. Low solubility in zinc, which limits its content in zinc-bearing alloys.[19]
Bismuth trace additive Lowers melting point. May disrupt surface oxides. Traces of bismuth and beryllium together with tin or zinc in aluminium-based braze destabilize oxide film on aluminium, facilitating its wetting.[19]
Beryllium trace additive Traces of bismuth and beryllium together with tin or zinc in aluminium-based braze destabilize oxide film on aluminium, facilitating its wetting.[19]
Nickel structural, wetting high Zn, S Strong, corrosion-resistant. Impedes flow of the melt. Addition to gold-copper alloys improves ductility and resistance to creep at high temperatures.[18] Addition to silver allows wetting of silver-tungsten alloys and improves bond strength. Improves wetting of copper-based brazes. Improves ductility of gold-copper brazes. Improves mechanical properties and corrosion resistance of silver-copper-zinc brazes. Nickel content offsets brittleness induced by diffusion of aluminium when brazing aluminium-containing alloys, e.g. aluminium bronzes. In some alloys increases mechanical properties and corrosion resistance, by a combination of solid solution strengthening, grain refinement, and segregation on fillet surface and in grain boundaries, where it forms a corrosion-resistant layer. Extensive intersolubility with iron, chromium, manganese, and others; can severely erode such alloys. Embrittled by zinc, many other low melting point metals, and sulfur.[19]
Chromium structural high Corrosion-resistant. Increases high-temperature corrosion resistance and strength of gold-based alloys. Added to copper and nickel to increase corrosion resistance of them and their alloys.[18] Wets oxides, carbides, and graphite; frequently a major alloy component for high-temperature brazing of such materials. Impairs wetting by gold-nickel alloys, which can be compensated for by addition of boron.[19]
Manganese structural volatile good cheap High vapor pressure, unsuitable for vacuum brazing. In gold-based alloys increases ductility. Increases corrosion resistance of copper and nickel alloys.[18] Improves high-temperature strength and corrosion resistance of gold-copper alloys. Higher manganese content may aggravate tendency to liquation. Manganese in some alloys may tend to cause porosity in fillets. Tends to react with graphite molds and jigs. Oxidizes easily, requires flux. Lowers melting point of high-copper brazes. Improves mechanical properties and corrosion resistance of silver-copper-zinc brazes. Cheap, even less expensive than zinc. Part of the Cu-Zn-Mn system is brittle, some ratios can not be used.[19] In some alloys increases mechanical properties and corrosion resistance, by a combination of solid solution strengthening, grain refinement, and segregation on fillet surface and in grain boundaries, where it forms a corrosion-resistant layer. Facilitates wetting of cast iron due to its ability to dissolve carbon.
Molybdenum structural good Increases high-temperature corrosion and strength of gold-based alloys.[18] Increases ductility of gold-based alloys, promotes their wetting of refractory materials, namely carbides and graphite. When present in alloys being joined, may destabilize the surface oxide layer (by oxidizing and then volatilizing) and facilitate wetting.
Cobalt structural good Good high-temperature properties and corrosion resistance. In nuclear applications can absorb neutrons and build up cobalt-60, a potent gamma radiation emitter.
Magnesium volatile O2 getter volatile Addition to aluminium makes the alloy suitable for vacuum brazing. Volatile, though less than zinc. Vaporization promotes wetting by removing oxides from the surface, vapors act as getter for oxygen in the furnace atmosphere.
Indium melting, wetting expensive Lowers melting point. Improves wetting of ferrous alloys by copper-silver alloys.
Carbon melting Lowers melting point. Can form carbides. Can diffuse to the base metal, resulting in higher remelt temperature, potentially allowing step-brazing with the same alloy. At above 0.1% worsens corrosion resistance of nickel alloys. Trace amounts present in stainless steel may facilitate reduction of surface chromium(III) oxide in vacuum and allow fluxless brazing. Diffusion away from the braze increases its remelt temperature; exploited in diffusion brazing.[19]
Silicon melting, wetting Ni Lowers melting point. Can form silicides. Improves wetting of copper-based brazes. Promotes flow. Causes intergranular embrittlement of nickel alloys. Rapidly diffuses into the base metals. Diffusion away from the braze increases its remelt temperature; exploited in diffusion brazing.
Germanium structural, melting expensive Lowers melting point. Expensive. For special applications. May create brittle phases.
Boron melting, wetting Ni Lowers melting point. Can form hard and brittle borides. Unsuitable for nuclear reactors. Fast diffusion to the base metals. Can diffuse to the base metal, resulting in higher remelt temperature, potentially allowing step-brazing with the same alloy. Can erode some base materials or penetrate between grain boundaries of many heat-resistant structural alloys, degrading their mechanical properties. Has to be avoided in nuclear applications due to its interaction with neutrons. Causes intergranular embrittlement of nickel alloys. Improves wetting of/by some alloys, can be added to Au-Ni-Cr alloy to compensate for wetting loss by chromium addition. In low concentrations improves wetting and lowers melting point of nickel brazes. Rapidly diffuses to base materials, may lower their melting point; especially a concern when brazing thin materials. Diffusion away from the braze increases its remelt temperature; exploited in diffusion brazing.
Mischmetal trace additive in amount of about 0.08%, can be used to substitute boron where boron would have detrimental effects.[19]
Cerium trace additive in trace quantities, improves fluidity of brazes. Particularly useful for alloys of four or more components, where the other additives compromise flow and spreading.
Strontium trace additive in trace quantities, refines the grain structure of aluminium-based alloys.
Phosphorus deoxidizer H2S, SO2, Ni, Fe, Co Lowers melting point. Deoxidizer, decomposes copper oxide; phosphorus-bearing alloys can be used on copper without flux. Does not decompose zinc oxide, so flux is needed for brass. Forms brittle phosphides with some metals, e.g. nickel (Ni3P) and iron, phosphorus alloys unsuitable for brazing alloys bearing iron, nickel or cobalt in amount above 3%. The phosphides segregate at grain boundaries and cause intergranular embrittlement. (Sometimes the brittle joint is actually desired, though. Fragmentation grenades can be brazed with phosphorus bearing alloy to produce joints that shatter easily at detonation.) Avoid in environments with presence of sulfur dioxide (e.g. paper mills) and hydrogen sulfide (e.g. sewers, or close to volcanoes); the phosphorus-rich phase rapidly corrodes in presence of sulfur and the joint fails. Phosphorus can be also present as an impurity introduced from e.g. electroplating baths.[20] In low concentrations improves wetting and lowers melting point of nickel brazes. Diffusion away from the braze increases its remelt temperature; exploited in diffusion brazing.
Lithium deoxidizer Deoxidizer. Eliminates the need for flux with some materials. Lithium oxide formed by reaction with the surface oxides is easily displaced by molten braze alloy.[19]
Titanium structural, active Most commonly used active metal. Few percents added to Ag-Cu alloys facilitate wetting of ceramics, e.g. silicon nitride.[21] Most metals, except few (namely silver, copper and gold), form brittle phases with titanium. When brazing ceramics, like other active metals, titanium reacts with them and forms a complex layer on their surface, which in turn is wettable by the silver-copper braze. Wets oxides, carbides, and graphite; frequently a major alloy component for high-temperature brazing of such materials.[19]
Zirconium structural, active Wets oxides, carbides, and graphite; frequently a major alloy component for high-temperature brazing of such materials.[19]
Hafnium active
Vanadium structural, active Promotes wetting of alumina ceramics by gold-based alloys.[18]
Sulfur impurity Compromises integrity of nickel alloys. Can enter the joints from residues of lubricants, grease or paint. Forms brittle nickel sulfide (Ni3S2) that segregates at grain boundaries and cause intergranular failure.

Some additives(追加の,付加的な,加法的な) and impurities(汚れ,不潔,不純物) act at very low levels. Both positive and negative effects can be observed. Strontium at levels of 0.01% refines grain structure of aluminium.((No gloss)) Beryllium and bismuth(蒼鉛(そうえん),【化】ビスマス(金属元素)) at similar levels help disrupt(分裂させる,中断させる,崩壊させる) the passivation layer of aluminium((No gloss)) oxide(酸化物) and promote wetting. Carbon at 0.1% impairs(害する,損なう,減じる,弱める,悪くする) corrosion(腐食作用,腐食) resistance of nickel alloys.(合金,合金に用いる安価な金属,まぜ物,品位,純度) Aluminium can embrittle mild steel at 0.001%, phosphorus(【化学】リン,燐(非金属元素)) at 0.01%.[19]

In some cases, especially for vacuum brazing, high-purity metals and alloys(合金,合金に用いる安価な金属,まぜ物,品位,純度) are used. 99.99% and 99.999% purity levels are available commercially.((No gloss))

Care has to be taken to not introduce deletrious impurities(汚れ,不潔,不純物) from joint contaminations or by dissolution(分離,分解,溶解,融解) of the base metals during brazing.

Melting behavior[edit]

Alloys with larger span of solidus/liquidus temperatures tend to melt through a "mushy" state, where the alloy(合金,合金に用いる安価な金属,まぜ物,品位,純度) is a mixture of solid and liquid material. Some alloys(合金,合金に用いる安価な金属,まぜ物,品位,純度) show tendency to liquation, separation of the liquid from the solid portion; for these the heating through the melting range has to be sufficiently fast to avoid this effect. Some alloys(合金,合金に用いる安価な金属,まぜ物,品位,純度) show extended plastic range, when only a small portion of the alloy(合金,合金に用いる安価な金属,まぜ物,品位,純度) is liquid and most of the material melts at the upper temperature range; these are suitable for bridging large gaps and for forming fillets.(首下の丸み,魚をおろす,骨のない切り身にする) Highly fluid alloys(合金,合金に用いる安価な金属,まぜ物,品位,純度) are suitable for penetrating deep into narrow gaps and for brazing tight joints with narrow tolerances(寛容,寛大,容認,数量過不足容認条件) but are not suitable for filling(注入) larger gaps. Alloys with wider melting range are less sensitive to non-uniform clearances.(1.取りかたづけ,掃除,2.手形交換,3.間隔,隙間)

When the brazing temperature is suitably high, brazing and heat treatment can be done in a single operation simultaneously.

Eutectic alloys(合金,合金に用いる安価な金属,まぜ物,品位,純度) melt at single temperature, without mushy((かゆのように)柔らかな,弱々しい,涙もろい) region. Eutectic alloys(合金,合金に用いる安価な金属,まぜ物,品位,純度) have superior spreading; non-eutectics in the mushy((かゆのように)柔らかな,弱々しい,涙もろい) region have high viscosity(粘度,粘性) and at the same time attack the base metal, with correspondingly((No gloss)) lower spreading force. Fine grain size gives eutectics both increased strength and increased ductility.(延性,展性,柔軟性,しなやかさ,すなおな性質) Highly accurate melting temperature allows joining process to be performed only slightly above the alloy's(合金,合金に用いる安価な金属,まぜ物,品位,純度) melting point. On solidifying,(凝固させる,凝固する) there is no mushy((かゆのように)柔らかな,弱々しい,涙もろい) state where the alloy(合金,合金に用いる安価な金属,まぜ物,品位,純度) appears solid but is not yet; the chance of disturbing the joint by manipulation(操作,巧みな操作,市場操作,ごまかし,触診) in such state is reduced (assuming the alloy(合金,合金に用いる安価な金属,まぜ物,品位,純度) did not significantly(きわめて,意味深く,意味ありげに) change its properties by dissolving the base metal). Eutectic behavior is especially beneficial for solders(1.(一般的に)結び付けるもの,きずな,2.半田,3.(〜を)半田付けする,(〜を)固く結合する).[19]

Metals with fine grain structure before melting provide superior wetting to metals with large grains. Alloying additives(追加の,付加的な,加法的な) (e.g. strontium to aluminium)((No gloss)) can be added to refine grain structure, and the preforms or foils(くじく,裏をかく,フルーレ,引き立て役,箔) can be prepared by rapid quenching.((No gloss)) Very rapid quenching((No gloss)) may provide amorphous(1.一定の形を持たない,無定形の,明確な形のない,非結晶の,不定形の,まとまりのない,無構造の,形の定まらない,2.アモルファス,非結晶質) metal structure, which possess further advantages.[19]

Interaction with base metals[edit]

Brazing at the Gary Tubular Steel Plant, 1943

For successful wetting, the base metal has to be at least partially soluble(溶解できる,(物質が)溶けやすい,(問題が)解決できる,溶性の) in at least one component of the brazing alloy.(合金,合金に用いる安価な金属,まぜ物,品位,純度) The molten alloy(合金,合金に用いる安価な金属,まぜ物,品位,純度) therefore tends to attack the base metal and dissolve it, slightly changing its composition in the process. The composition change is reflected in the change of the alloy's(合金,合金に用いる安価な金属,まぜ物,品位,純度) melting point and the corresponding change of fluidity.((No gloss)) For example, some alloys(合金,合金に用いる安価な金属,まぜ物,品位,純度) dissolve both silver and copper; dissolved silver lowers their melting point and increases fluidity,((No gloss)) copper has the opposite effect.

The melting point change can be exploited. As the remelt temperature can be increased by enriching the alloy(合金,合金に用いる安価な金属,まぜ物,品位,純度) with dissolved base metal, step brazing using the same braze can be possible.

Alloys that do not significantly(きわめて,意味深く,意味ありげに) attack the base metals are more suitable for brazing thin sections.

Nonhomogenous microstructure of the braze may cause non-uniform melting and localized(一地方に集まる,地方化する) erosions of the base metal.

Wetting of base metals can be improved by adding a suitable metal to the alloy.(合金,合金に用いる安価な金属,まぜ物,品位,純度) Tin facilitates(容易にする,促進する,楽にする) wetting of iron, nickel, and many other alloys.(合金,合金に用いる安価な金属,まぜ物,品位,純度) Copper wets ferrous(鉄の,鉄を含む) metals that silver does((No gloss)) not attack, copper-silver alloys(合金,合金に用いる安価な金属,まぜ物,品位,純度) can therefore braze steels silver alone won't wet. Zinc improves wetting of ferrous(鉄の,鉄を含む) metals, indium as well. Aluminium improves wetting of aluminium((No gloss)) alloys.(合金,合金に用いる安価な金属,まぜ物,品位,純度) For wetting of ceramics,(セラミック,製陶の,陶器の) reactive((刺激に対して)敏感な,反応の早い,反作用的な) metals capable of forming chemical compounds with the ceramic(セラミック,製陶の,陶器の) (e.g. titanium,(チタン) vanadium, zirconium...) can be added to the braze.

Dissolution of base metals can cause detrimental(有害な(injurious, harmful)) changes in the brazing alloy.(合金,合金に用いる安価な金属,まぜ物,品位,純度) For example, aluminium((No gloss)) dissolved from aluminium((No gloss)) bronzes can embrittle the braze; addition of nickel to the braze can offset(1.オフセット,分かれ,相殺するもの,埋め合わせ,2.オフセット印刷,3.分家,分派,4.相殺する) this.

The effect works both ways; there can be detrimental(有害な(injurious, harmful)) interactions between the braze alloy(合金,合金に用いる安価な金属,まぜ物,品位,純度) and the base metal. Presence of phosphorus(【化学】リン,燐(非金属元素)) in the braze alloy(合金,合金に用いる安価な金属,まぜ物,品位,純度) leads to formation of brittle(壊れやすい,堅いがもろい,傷つきやすい,砕けやすい,脆い,薄っぺらな) phosphides of iron and nickel, phosphorus-containing(【化学】リン,燐(非金属元素)) alloys(合金,合金に用いる安価な金属,まぜ物,品位,純度) are therefore unsuitable for brazing nickel and ferrous(鉄の,鉄を含む) alloys.(合金,合金に用いる安価な金属,まぜ物,品位,純度) Boron tends to diffuse(散らす) into the base metals, especially along the grain boundaries, and may form brittle(壊れやすい,堅いがもろい,傷つきやすい,砕けやすい,脆い,薄っぺらな) borides. Carbon can negatively influence some steels.

Care has to be taken to avoid galvanic corrosion(腐食作用,腐食) between the braze and the base metal, and especially between dissimilar(異なる) base metals being brazed together.

Formation of brittle(壊れやすい,堅いがもろい,傷つきやすい,砕けやすい,脆い,薄っぺらな) intermetallic compounds on the alloy(合金,合金に用いる安価な金属,まぜ物,品位,純度) interface(1.接点,仲立ち,liaison,2.中間面,作用を及ぼす領域,境界面,3.人と話す,調和する,interact,communicate) can cause joint failure. This is discussed more in-depth with solders(1.(一般的に)結び付けるもの,きずな,2.半田,3.(〜を)半田付けする,(〜を)固く結合する).

The potentially(潜在的に) detrimental(有害な(injurious, harmful)) phases may be distributed evenly through the volume of the alloy,(合金,合金に用いる安価な金属,まぜ物,品位,純度) or be concentrated on the braze-base interface.(1.接点,仲立ち,liaison,2.中間面,作用を及ぼす領域,境界面,3.人と話す,調和する,interact,communicate) A thick layer of interfacial intermetallics is usually considered detrimental(有害な(injurious, harmful)) due to its commonly low fracture(骨折する,骨折,破砕する,割れ,砕け,破砕(する),破る,砕ける,折る) toughness and other sub-par mechanical properties. In some situations, e.g. die attaching, it however does((No gloss)) not matter much as silicon(シリコン,珪素) chips are not typically subjected to mechanical abuse.[19]

On wetting, brazes may liberate(自由にする,遊離する,作用させる,解放する) elements from the base metal. For example, aluminium-silicon((No gloss)) braze wets silicon(シリコン,珪素) nitride, dissociates(引き離す,分離する,解離する) the surface so it can react with silicon,(シリコン,珪素) and liberates(自由にする,遊離する,作用させる,解放する) nitrogen,(窒素,元素記号N,元素記号n) which may create voids(1.空の,何もない◆(類)empty,空ろな,空虚な,2.〜を放出する,排泄する,放尿する,3.空間,真空) along the joint interface(1.接点,仲立ち,liaison,2.中間面,作用を及ぼす領域,境界面,3.人と話す,調和する,interact,communicate) and lower its strength. Titanium-containing nickel-gold braze wets silicon(シリコン,珪素) nitride and reacts with its surface, forming titanium(チタン) nitride and liberating(自由にする,遊離する,作用させる,解放する) silicon;(シリコン,珪素) silicon(シリコン,珪素) then forms brittle(壊れやすい,堅いがもろい,傷つきやすい,砕けやすい,脆い,薄っぺらな) nickel silicides and eutectic gold-silicon phase; the resulting joint is weak and melts at much lower temperature than may be expected.[19]

Metals may diffuse(散らす) from one base alloy(合金,合金に用いる安価な金属,まぜ物,品位,純度) to the other one, causing embrittlement or corrosion.(腐食作用,腐食) An example is diffusion(普及,拡散,散布,流布) of aluminium((No gloss)) from aluminium((No gloss)) bronze to a ferrous(鉄の,鉄を含む) alloy(合金,合金に用いる安価な金属,まぜ物,品位,純度) when joining these. A diffusion(普及,拡散,散布,流布) barrier, e.g. a copper layer (e.g. in a trimet strip), can be used.

A sacrificial layer of a noble metal can be used on the base metal as an oxygen barrier, preventing formation of oxides(酸化物) and facilitating(容易にする,促進する,楽にする) fluxless brazing. During brazing, the noble metal layer dissolves in the filler metal. Copper or nickel plating of stainless(奇麗な) steels performs the same function.[19]

In brazing copper, a reducing atmosphere (or even a reducing flame) may react with the oxygen residues(残余,残留物,かす,留数,剰余,残基) in the metal, which are present as cuprous oxide(酸化物) inclusions, and cause hydrogen(水素,元素記号H,h) embrittlement. The hydrogen(水素,元素記号H,h) present in the flame or atmosphere at high temperature reacts with the oxide,(酸化物) yielding metallic copper and water vapour, steam. The steam bubbles exert high pressure in the metal structure, leading to cracks and joint porosity. Oxygen-free copper is not sensitive to this effect, however the most readily available grades, e.g. electrolytic copper or high-conductivity copper, are. The embrittled joint may then fail catastrophically without any previous sign of deformation(形をくずすこと) or deterioration.((品質などの)低下,悪化,堕落,退歩,老朽化,下落)[22]

Preform[edit]

A brazing preform is a high quality, precision(精密な,正確,精密,細心,几帳面さ,正確さ) metal stamping used for a variety of joining applications in manufacturing electronic devices and systems. Typical brazing preform uses include attaching electronic circuitry, packaging electronic devices, providing good thermal(熱の,温度の,熱による,温泉の,暖かい,上昇温暖気流,熱を持っている) and electrical conductivity, and providing an interface(1.接点,仲立ち,liaison,2.中間面,作用を及ぼす領域,境界面,3.人と話す,調和する,interact,communicate) for electronic connections. Square, rectangular(長方形の) and disc shaped brazing preforms are commonly used to attach electronic components containing silicon(シリコン,珪素) dies to a substrate(回路基板) such as a printed circuit board.

Rectangular frame shaped preforms are often required for the construction of electronic packages while washer(ワッシャー,洗う人,洗濯女,洗濯機) shaped brazing preforms are typically utilized to attach lead wires and hermetic feed-throughs to electronic circuits and packages. Some preforms are also used in diodes, rectifiers, optoelectronic devices and components packaging.[23]

See also[edit]

References[edit]

  1. ^ a b c d e Groover 2007, pp. 746–748
  2. ^ a b c Scwartz 1987, pp. 20–24
  3. ^ a b Lucas-Milhaupt SIL-FOS 18 Copper/Silver/Phosphorus Alloy
  4. ^ Scwartz 1987, pp. 271–279
  5. ^ a b Scwartz 1987, pp. 131–160
  6. ^ Scwartz 1987, pp. 163–185
  7. ^ The Brazing Guide. GH Induction Atmospheres
  8. ^ Joseph R. Davis, ASM International. Handbook Committee (2001). Copper and copper alloys. ASM International. p. 311. ISBN 0-87170-726-8. 
  9. ^ AWS A3.0:2001, Standard Welding Terms and Definitions Including Terms for Adhesive Bonding, Brazing, Soldering, Thermal Cutting, and Thermal Spraying, American Welding Society (2001), p. 118. ISBN 0-87171-624-0
  10. ^ a b c d Scwartz 1987, pp. 189–198
  11. ^ a b c d e f Scwartz 1987, pp. 199–222
  12. ^ Scwartz 1987, pp. 24–37
  13. ^ "Joining Dissimilar Metals". Deringer-Ney, April 29, 2014
  14. ^ Scwartz 1987, p. 3
  15. ^ Scwartz 1987, pp. 118–119
  16. ^ Alan Belohlav. "Understanding Brazing Fundamentals". American Welding Society. 
  17. ^ "Guidelines for Selecting the Right Brazing Alloy". Silvaloy.com. Retrieved 2010-07-26. 
  18. ^ a b c d e f g Christopher Corti; Richard Holliday (2009). Gold: Science and Applications. CRC Press. pp. 184–. ISBN 978-1-4200-6526-8. 
  19. ^ a b c d e f g h i j k l m n o p q r David M. Jacobson; Giles Humpston (2005). Principles of Brazing. ASM International. pp. 71–. ISBN 978-1-61503-104-7. 
  20. ^ a b Philip Roberts (2003). Industrial Brazing Practice. CRC Press. pp. 272–. ISBN 978-0-203-48857-7. 
  21. ^ "Ceramic Brazing". Azom.com. 2001-11-29. Retrieved 2010-07-26. 
  22. ^ Supplies of Cadmium Bearing Silver Solders Continue (2009-01-20). "Strength of Silver Solder Joints". www.cupalloys.co.uk. Retrieved 2010-07-26. 
  23. ^ Solder Preforms. AMETEK.Inc.

Bibliography[edit]

  • Groover, Mikell P. (2007). Fundamentals Of Modern Manufacturing: Materials Processes, And Systems (2nd ed.). John Wiley & Sons. ISBN 978-81-265-1266-9. 
  • Schwartz, Mel M. (1987). Brazing. ASM International. ISBN 978-0-87170-246-3. 

Further reading[edit]

  • Fletcher, M.J. (1971). Vacuum Brazing. London,: Mills and Boon Limited. ISBN 0-263-51708-X. 
  • P.M. Roberts, "Industrial Brazing Practice", CRC Press, Boca Raton, Florida, 2004.
  • Kent White, "Authentic Aluminum Gas Welding: Plus Brazing & Soldering." Publisher: TM Technologies, 2008.
  • Andrea Cagnetti "Experimental survey on fluid brazing in ancient goldsmith's art" – International Journal of Material Research (2009) DOI 10.3139/146.101783 [1]

External links[edit]