Analysis of processing technology characteristics of stainless steel sanitary butterfly valve

1. The depth of the hardened layer of the stainless steel sanitary butterfly valve can reach 1/3 or more of the cutting depth; the hardness of the hardened layer is 1.4 to 2.2 times higher than the original one. Due to the large plasticity of stainless steel, the plasticity is tense and twisted, the strengthening coefficient is very large; and the austenite is not stable enough, under the action of cutting stress, the local austenite transforms into martensite; plus the compound impurities in the cutting heat Under the action of the body, it is easy to synthesize in a diffuse dispersion, so that the hardening layer is produced during the cutting process. The work hardening phenomenon caused by the previous feed or the previous process seriously affects the smooth stop of the subsequent process. The increase of sσs; the progress of σb in the austenitic stainless steel in the annealed state, the yield limit σb reaches 1470～1960MPa, and it is severe with work hardening: in stainless steel, the work hardening phenomenon of austenite and austenite + ferritic stainless steel Most prominent. Such as the strength of austenitic stainless steel after hardening;

2. Large cutting force: stainless steel has large plastic deformation during cutting, especially austenitic stainless steel (the elongation exceeds 1.5 times of 45 steel), which increases the cutting force. At the same time, stainless steel has severe work hardening and high heat strength, which further increases the cutting resistance, and the winding back of the chips is also difficult. Therefore, the cutting force of the processed stainless steel is large, such as the unit cutting force of turning 1Cr18Ni9Ti is 2,450 MPa, which is 25% higher than that of the 45 steel.

3. High cutting temperature: plastic deformation during cutting and friction with the tool are very large, resulting in more cutting heat; plus the thermal conductivity of stainless steel is about 45 steel, ~ a large amount of cutting heat is concentrated in the cutting area The interface with the knife-chip contact has poor heat dissipation conditions. Under the same conditions, the cutting temperature of 1Cr18Ni9Ti is about 200 °C higher than that of 45 steel.

4. Chips are not easy to break and easy to bond: stainless steel has great plasticity and toughness. When the car is processed, the chips are continuously from time to time, which not only affects the smooth stop of operation, but also smashes the processed surface. Under high temperature and high pressure, stainless steel has strong affinity with other metals, which is easy to cause adhesion and constitutes built-up edge, which not only aggravates the wear of the tool, but also presents a tearing phenomenon and deteriorates the processed appearance. This property is more pronounced in martensitic stainless steels with lower carbon content.

5. The tool is easy to wear: the affinity function in the process of cutting stainless steel, so that the knife-chip will bond and spread, so that the tool will produce bond wear and diffusion wear, resulting in a crescent in the rake face of the tool, and the cutting edge will also It forms tiny spalling and gaps; coupled with the high hardness of carbides in stainless steel (such as TiC), direct contact with the tool during cutting, friction, scratching the tool, and work hardening, the tool wear will be intensified.

6. The coefficient of linear shrinkage is large: the coefficient of linear shrinkage of stainless steel is about 1.5 times that of carbon steel. Under the action of cutting temperature, the workpiece is prone to thermal deformation, and the dimensional accuracy is difficult to control.