Stainless steel can be heated before forging using an electric furnace or a flame furnace. Flame furnaces are often used in production because of their low cost. The furnace gas atmosphere should remain neutral or slightly oxidizing. For austenitic stainless steel, a reducing atmosphere cannot be used to avoid carburization or chromium depletion, which will reduce the resistance to intergranular corrosion; for martensitic stainless steel, 316 stainless steel hexagonal rods cannot use an overly oxidizing atmosphere due to their high carbon content. , to avoid causing serious decarburization.

When heating with a flame furnace, it should also be noted that the gas should be basically free of hydrogen sulfide and other sulfur-containing pollutants. Especially for high-nickel steel, fuel with high sulfur content cannot be used, because sulfur will penetrate into the steel and interact with it. Nickel forms NiS (melting point 797°C) or Ni+Ni3S2 eutectic (melting point 645°C). It is mainly distributed on the grain boundaries, causing the process plasticity of stainless steel to decrease and cracks to form during forging.

Below 700~800℃, the thermal conductivity of stainless steel is smaller than that of ordinary alloy steel. However, the thermal conductivity of stainless steel increases as the temperature increases. The thermal conductivity of 316 stainless steel hexagonal rods tends to be consistent with that of ordinary alloy steel in the range of 700~800°C. Therefore, for blanks with a diameter greater than 100mm, a two-stage heating system should be adopted: in the preheating stage, maintain a furnace temperature of 800~850°C to slow down the heating speed; in the heating and soaking stages, maintain a higher furnace temperature (initial forging) upper temperature limit) so that it can be quickly heated to the starting forging temperature.

For precision forgings with high surface quality requirements, or important forgings with small margins, such as compressor blades, a layer of protective paint (glass lubricant) is often applied to the surface of the blank before heating, and then heated in an ordinary heating furnace. . Glass protective coating can protect metal from oxidation and pollution, and it is also a lubricant during forging processing.

Stainless steel bars often crack during deformation processing, which is difficult to control for a while. Xiao Sun will give you an in-depth explanation today on how to prevent cracking during processing:


The method experience is as follows:


For stainless steel drawn parts with large drawing deformation and difficulty in forming, polyvinyl fluoride films can be used as lubricants in actual production. Polyvinyl fluoride film has excellent tear strength, certain toughness and elongation and is easy to clean. After the dry film is applied, the dry film can deform along with the blank during the drawing process, which can always separate the blank from the mold. In addition, the film itself has a certain porosity and a large number of fiber cracks, so it can also store a certain amount of lubricating oil, so this film Equivalent to a layer of dry film lubricant. This lubrication method can effectively isolate the deformed stainless steel plate from the mold surface, and has good lubrication effect, which is beneficial to improving the service life of the mold and the qualification rate of the product.