Rust steel pipe and flange production enterprises, to consider the fitting production cost, but should consider more factors to prevent the corrosion and improve the quality of products, therefore, stainless steel pipe flange production process adopts the solution process, enhance the pipe security is very necessary, heat treatment process on pipe quality and safety plays an important role. It is known that there are a few enterprises in the production of pipe fittings, in order to save costs, do not take solid solution treatment, only use the method of polishing sandblasting treatment, covered up the defects and shortcomings of pipe fittings, which will bring permanent hidden trouble to the use of pipe fittings.
Austenitic stainless steel with heat treatment to soften, the stainless steel is heated to a temperature of about 950 ~ 1150 ℃, the heat preservation time, make the carbide and various alloy elements evenly dissolved in austenite, called solid solution treatment.
The effect of heat treatment on stainless steel pipe fittings
he metal molecular structure, magnetic properties and physical properties of stainless steel pipe fittings changed after forming and welding. The corrosion resistance of the stainless steel can be restored through the atmosphere protection solid solution process, and the required hardness of the stainless steel can be obtained to ensure the best performance of the stainless steel. Stainless steel pipe fittings after solid solution treatment have a good improvement effect:
1. Eliminate the modification phenomenon of stainless steel pipe fittings during processing, reduce the hardness of stainless steel below 220HV, improve the plasticity and toughness of stainless steel, and make pipe fittings more convenient and safe in installation.
2. Restore the stress and intercrystalline changes in the production process of stainless steel pipe fittings, reduce intercrystalline corrosion and stress corrosion of stainless steel pipes, and enhance corrosion resistance.
3. Remove the magnetism of stainless steel caused by the processing process and stabilize the austenite structure.
4. Restore the natural brightness of stainless steel material surface (the natural brightness is different from that of polishing).
Characteristics of solid solution of stainless steel pipe fittings：
Stainless steel is a special kind of steel. Due to the presence of alloying elements such as nickel and chromium, its heat treatment is different from that of ordinary steel.
1.The thermal conductivity of stainless steel is low, which is only 27% of carbon steel at room temperature. With the increase of heating temperature, the thermal conductivity of stainless steel decreases gradually. Therefore, when stainless steel is heated at low temperature, the heating process should be carried out slowly.
2, austenitic stainless steel after solid solution heated to 1100 ℃, can inhibit the production of carbide, and then rapidly cooling to room temperature, carbon supersaturation state, can greatly improve the corrosion resistance of stainless steel.
3. The pipe fittings are protected by (hydrogen) gas in the process of solid solution to avoid the formation of sticky ferric oxide on the stainless steel surface, restore the brightness of the stainless steel surface, and improve the appearance reputation.
Three elements of solid solution of stainless steel pipe fittings：
The advantages and disadvantages of stainless steel pipe fitting solid solution technology have great influence on the corrosion resistance and appearance brightness of stainless steel, and play a decisive role in the processing performance of stainless steel. Therefore, the heat treatment process of stainless steel is very important in the production of stainless steel pipe fittings.
1. Solid solution temperature. According to the characteristics of the chemical composition of stainless steel, the solid solution temperature of stainless steel should be between 950 and 1150 degrees Celsius, so as to achieve the softening effect, so that the hardness of stainless steel can be reduced to 220HV, and meet the quality requirements of piping installation clamping. If the temperature control is not reasonable, various quality defects are likely to occur.
2. Solid solution time. The residual ferrite content in austenitic stainless steel decreases with the increase of heating time. Therefore, stainless steel pipe fittings solid solution treatment should be controlled at about 1050 ℃, the carbon saturated state, improve the corrosion resistance. It is then cooled rapidly in the air to achieve a solid solution effect.
3. Solid solution speed and heat preservation. The thermal conductivity of stainless steel is low, and it is only 27% of carbon steel at room temperature. Therefore, the heating process of stainless steel at low temperature should be carried out slowly. If the heating speed is too fast and deformation is easy to occur, the heating speed of stainless steel should be controlled in solid solution, and the heat preservation time should be paid attention to. Such as 316 l steel at 1100 ℃, holding time is long, the residual content of ferrite is reduced.In our solid solution production, the solid solution of stainless steel pipe fittings should go through the process of heating, heat preservation and time cooling. The whole process takes about 40 minutes.
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