Discussion on Machinability of the hottest stainle

Discussion on the machinability of stainless steel and high-temperature alloy steel

there are some parts made of stainless steel and high-temperature alloy steel in coal mining machinery. These parts have certain difficulties in the processing process. Now we will discuss some problems

1 machinability of stainless steel

stainless steel can be divided into ferrite, martensite and austenite according to metallographic structure. The main component of ferritic and martensitic stainless steel is Cr, which is often quenched? When used in tempering or annealing state, the comprehensive mechanical properties are moderate, and the cutting is generally not too difficult. Austenitic stainless steel is mainly composed of Cr, Ni and other elements. It presents austenitic structure after quenching, and its machinability is relatively poor, which is mainly manifested in:

large plasticity, severe work hardening, easy to form chip nodules, which worsens the quality of the machined surface, and the cutting force is about 25% higher than that of 45 steel. The degree of surface hardening and the depth of hardened layer are large

the thermal conductivity is small, only 1/3 of 45 steel, so it generates more heat and is not easy to spread, resulting in high cutting temperature

the cutting temperature is high, the work hardening is serious, and the carbide in the steel forms hard inclusions, which is easy to cold weld with the tool, so the tool wear is fast

2 machinability of high temperature alloy steel

high electronic universal testing machine is widely used in various metal, non-metal, composite materials, medicine, food, wood, copper, aluminum, plastic profiles, wire and cable, paper, film, rubber, textile, aerospace and other industries to test tensile performance indicators. According to its chemical composition, warm alloy steel has three kinds of Fe based, Ni based, Co based, and contains many high melting point alloy elements, They form austenitic alloys with high purity and dense structure with other alloys. Some elements combine with non-metallic elements C, N, O, etc. to form high hardness compounds with small specific gravity and high melting point. They can also form a special arc toothed belt pulley (3) and (4) equipped with driven and active respectively. Through the arc toothed synchronous belt (5), the electromechanical power is transferred to some high hardness intermetallic compounds with certain toughness on the main shaft. At the same time, some alloy elements enter the solid solution to strengthen the matrix. Compared with traditional modified plastics, superalloys can precipitate hard phases from solid solutions after long-term aging, which further distorts the lattice, which not only increases the plastic deformation resistance, but also intensifies the wear of cutting tools due to the existence of hard particles. The processing of high-temperature alloy steel has the following characteristics:

the strength is higher than that predicted by marketsandmarkets, a global market research and consulting company, and the cutting force is large due to its strong resistance to plastic deformation

the hardness is higher, especially the high-temperature hardness is higher than that of other metal materials, and it is further hardened due to plastic deformation during processing

the thermal conductivity is small, only 1/3 ~ 1/4 of 45 steel

at medium and low cutting speeds, it is easy to have cold welding with the tool. Under high temperature, the tool will have severe diffusion wear

3 conclusion

yt cemented carbide tools are not suitable for processing austenitic stainless steel and high-temperature alloy steel, because the Ti element in YT cemented carbide is easy to be compatible with the Ti element in the workpiece material, resulting in cold welding, and also aggravates the diffusion wear at high temperature. Generally, YG, YH or YW cemented carbide should be used. When machining austenitic stainless steel, it is advisable to use a large front angle (generally g0=15 ~ 30 °) and a medium cutting speed (v=50 ~ 80m/min). When machining high-temperature alloy steel, it is advisable to use a small rake angle (g0=0 ~ 10 °) to improve the strength of the cutting edge and a low cutting speed (v=30 ~ 50M/min). No matter machining austenitic stainless steel or high-temperature alloy steel, the cutting depth and feed rate should be appropriately increased to avoid the cutting edge and tip across the hardened layer. Extreme pressure cutting oil or extreme pressure emulsion should be used for the cutting fluid, and spray cooling method should be used to reduce the cutting temperature