Brazing characteristics of nickel base solder

Nickel base solder has good corrosion resistance and oxidation resistance. It is suitable for brazing alloys (such as stainless steel, heat-resistant steel, etc.) working at high temperature. It is mainly used in furnace brazing, induction brazing and resistance brazing. It mainly uses gas shielded brazing and vacuum brazing. It requires high purity of gas. The high temperature strength and corrosion resistance of the joint are better than other kinds of solder. The melting point of pure nickel is high (1 452 ℃), in order to reduce the melting temperature, the eutectic elements (such as carbon, boron, silicon, phosphorus, etc.) formed with nickel and the elements (such as Ming, manganese, etc.) forming the fusible liquid are often added. These elements have different effects on other properties of nickel based solder, such as wettability, corrosion resistance and heat resistance. Generally speaking, with the increase of chromium and manganese, the high temperature strength increases; boron can also improve the wettability of solder. However, with the increase of boron and carbon, the corrosion resistance of solder to base metal also increases. Nickel base solder contains more silicon, boron, phosphorus and other elements, forming many brittle eutectic, so that the alloy is brittle and can not be processed into various shapes, and can only be supplied in powder form. When used, imported gum or polyvinyl alcohol can be used as binder. It is worth noting that when brazing with nickel based solder, the gap between the welds should be as small as possible, generally no more than 0.10 mm, which requires accurate preparation before welding. Because the gap is too large, brittle casting structure will be formed in the weld, which will greatly reduce the strength and impact toughness of the brazed joint.

Common Nickel Base Solders include:

① 1 nickel base solder (hl701): cr14.0 ~ 18.0%, b3.0 ~ 4.5%, si3.5 ~ 5.5%, Fe ≤ 5%, Ni margin; solid phase line 970 ℃, liquid phase line 1070 ℃.

② No.2 nickel base solder (hl702): cr8.0 ~ 12.0%, b1.8 ~ 2.6%, si2.5 ~ 4.5%, Fe ≤ 4%, Ni margin; solid phase line 970 ℃, liquid phase line 1000 ℃.

③ Bni-3: B2%, si4.5%, fe0.5%, Ni margin; brazing temperature: 1010 ~ 1177 ℃.