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Heat treatment technology for stainless steel valve casting

网站编辑:admin │ 发表时间:2018-05-29 
Due to the wide variety of specifications of stainless steel valves, they are used in various fields of the national economy, and their use occasions vary widely, such as high temperature and high pressure, low temperature cryogenic, flammable and explosive, highly toxic, strong corrosive medium and other working conditions, the material of stainless steel valves Demanding requirements are raised.Stainless steel valves produced by valve manufacturers use CrNi stainless steel, CrMoAl nitrided steel, CrMoV heat resistant steel, CrMnN acid resistant steel, precipitation hardened steel, duplex stainless steel, low temperature steel, titanium alloy, Monel alloy, Inconel, Hastelloy and G0CrW cemented carbide. The casting, welding and processing properties of these high-alloy materials are very poor, which brings great difficulty to the manufacturing process, and the heat treatment of various stainless steel materials is also difficult. The following analysis of how the foundry handles.

(1)Ma Tian loose iron stainless steel: This kind of stainless steel body-centered cubic structure (BCC) can attract magnets and get it from Osda temperature, which has the best corrosion resistance, but the material is hard and brittle, then it is returned. Fire can increase ductility, but corrosion resistance will decrease, especially tempering between 450 and 650 degrees Celsius, causing carbon atoms in the crystal lattice gap to diffuse and chromium to form a network of chromium carbide causing adjacent areas. The consumption of chromium element causes the chromium component to be lowered, the protective film cannot be formed, and the corrosion resistance is lost, so special care is required.

(a)The temperature of 403, 410, 416se is between 650 and 750 °C.

(b)The temperature of 414 is between 650 and 730 °C.

(c)The temperature of 431 is 6. (d) 440-A, 440-B, 440-C, 420 and the temperature is 680-750 °C.

(2)Fermented iron stainless steel: This stainless steel body-centered cubic structure (BCC) can attract magnets and is usually used in the automotive industry or chemical industry. The strength is not changed by heat treatment, but it can be increased in cold work.

(3)Austin ferrous stainless steel: This stainless steel face-centered cubic structure (FCC) does not work on magnets. As discussed above, such materials are easy to process, so they can be subjected to different heat treatments after eliminating the residual stress of the material after processing.

(4)Precipitation hardening stainless steel: This kind of stainless steel is heat treated at low temperature after high temperature quenching. The strength of aluminum or copper in the material can be increased along the slip surface or inter-metallic compounds. hardness. Commonly used precipitation hardened stainless steel 17-4PH, others have 17-7PH, PH15-7MO, AM-350, AM-355 and so on.

(5)Post-weld heat treatment of all kinds of stainless steel: the chromium element contained in the stainless steel, after welding, tends to diffuse and precipitate in the high temperature region (heat-affected zone) to form chromium carbide, which causes local chromium content to decrease and cannot form a protective film. Corrosion conditions such as perforation often occur in these heat-affected zones, and it is possible to remedy the situation. The manufacturer often heats the object after welding, and the effect is to diffuse the chromium element in other regions to the missing region of the chromium. Protective effects.