Stainless Steel Pipe Fittings production enterprises, to take into account the production costs of pipe fittings, but also to take into account the prevention of corrosion and improve product quality factors, therefore, Stainless Steel Pipe Fittings production process to take solid solution process, to enhance the safety of pipe is very necessary, heat treatment process on the pipe Quality and safety plays a vital role. It is understood that a small number of enterprises in the production of pipe fittings to save costs, did not take the solution treatment, only polishing and other methods to deal with, cover up the defects and lack of pipe, which will bring the use of permanent damage to the pipe.
To this end, this article on the importance of Stainless Steel Pipe Fittings solid solution process, methods and rules to share, so that more people understand the knowledge and the need for solid solution of pipe to ensure that the quality of Stainless Steel Pipe Fittings fittings and the use of security.
Stainless steel by heat treatment to soften the stainless steel heated to 950 ~ 1150 ℃ or so, heat for a certain time, so that carbide and a variety of alloying elements dissolved in austenite, known as the solution treatment.
First, the role of Stainless Steel Pipe Fittings heat treatment
We all know, Stainless Steel Pipe Fittings after forming, welding and other processing technology, the metal molecular structure, magnetic and physical properties have changed. Through the atmosphere to protect the solid solution process can be restored after processing in the impact of corrosion resistance, while the hardness required to obtain stainless steel to ensure the best use of stainless steel performance. After the solution treatment of Stainless Steel Pipe Fittings fittings, has a good role in improving:
1, to eliminate the Stainless Steel Pipe Fittings in the process of modification of the phenomenon, so that the hardness of stainless steel reduced to 220HV below to improve the plasticity and toughness of stainless steel, the pipe fittings in the installation more convenient and safe.
2, to restore the Stainless Steel Pipe Fittings production process stress and intergranular changes, reduce the intergranular corrosion and stress corrosion of stainless steel, enhanced corrosion resistance.
3, remove the stainless steel due to the process of production of magnetic, stable austenite.
4, restore the natural light of the surface of stainless steel (natural bright and polished bright different).
Second, the characteristics of Stainless Steel Pipe Fittings solid solution
Stainless steel is a special kind of steel, due to the presence of nickel, chromium and other alloying elements, the heat treatment and ordinary steel heat treatment has different characteristics:
1, the thermal conductivity of stainless steel is low, the thermal conductivity at room temperature is only 27% of carbon steel, and with the heating temperature increases, the thermal conductivity of stainless steel, the difference gradually reduced. Therefore, the stainless steel heating at low temperatures, the heating process should be slow.
2, austenitic stainless steel by solid solution heating to 1100 ℃ or so, can inhibit the generation of carbides, and then quickly cooled to room temperature, so that carbon to supersaturated state, can greatly improve the corrosion resistance of stainless steel.
3, the pipe in the process of solid solution used (hydrogen) gas protection, to avoid the surface of stainless steel viscous iron oxide generation, restore the surface of stainless steel bright, improve the appearance of the reputation.
Third, the three elements of solid solution of stainless steel tube
Stainless Steel Pipe Fittings solid solution of the advantages and disadvantages of stainless steel corrosion resistance, the appearance of brightness has a great impact, but also on the processing performance of stainless steel, plays a decisive role. Therefore, the stainless steel heat treatment process, in the production of Stainless Steel Pipe Fittings is in a very important position.
1, solution temperature. According to the characteristics of stainless steel chemical composition, stainless steel solution temperature to 950-1150 degrees Celsius, in order to achieve softening effect, so that the hardness of stainless steel reduced to 220HV or less, to meet the quality requirements of pipeline installation. If the temperature control is unreasonable, prone to various quality defects.
2, the solution time. Austenitic stainless steel in the heating process, the residual ferrite content in steel with the heating time to reduce. Therefore, the solution treatment of Stainless Steel Pipe Fittings should be controlled at about 1050 ℃, so that carbon saturation, improve corrosion resistance. And then quickly cooled in the air to achieve solid solution effect.
3, solid solution speed and insulation. Stainless steel thermal conductivity is low, at room temperature when the thermal conductivity is only 27% of carbon steel, therefore, stainless steel heating process at low temperatures should be slow. If the heating speed is too fast, prone to deformation, in the solution should be controlled stainless steel heating rate, and pay attention to the holding time. Such as 316L steel at about 1100 ℃, holding a long time, the residual ferrite content will continue to decrease.
We in the solid solution production, stainless steel tube solid solution to go through the heating - insulation - cooling process, the whole takes about 40 minutes.
Fourth, the pipe solid solution process operation and use
Shandong Jinli Special Industry Co., Ltd. in the production process, attaches great importance to solution treatment to enhance the corrosion resistance of Stainless Steel Pipe Fittings fittings to improve the safety factor; attention to the production process and equipment improvements to ensure product quality.
1, the company produced all the pipe, pipe fittings all through the solution process. The pipe is annealed by solid solution furnace, and the pipe is solid solution by pipe-line solid solution. To improve product quality, meet the requirements of national standards.
2, the cost of solid solution. The use of a solid solution process will bring a greater cost to the pipe. The main costs are: electricity costs, gas costs, labor costs.
3, the protection of gas (hydrogen) selection. Pipe solid solution of the gas in the production of hydrogen, there are liquid ammonia cracked after the hydrogen (mixed gas) as a protective gas, the two gases as a solution to protect the gas is no different.
The principle is: per kilogram of liquid ammonia by cracking, can be made 2.64Nm3 (Nm3 = standard cubic meters) mixed gas, a standard cubic meter containing 75% hydrogen and 25% nitrogen; the second is obtained after cleavage Of the mixed gas impurities less (water vapor about 2 grams / cubic meter, residual ammonia 1000PPM); Third, the mixed gas through the molecular sieve (UOP) adsorption purification, residual ammonia can be reduced to 3PPM (3PPM = ), The nitrogen content is very small, nitrogen under normal conditions is inert gas, the solution will not be affected.
1, solid solution can increase the ability to resist corrosion.
2, so that the hardness of stainless steel reduced to 220HV or less, to improve the quality requirements of pipeline installation.
3, when the solid solution to do the temperature, time to master, to prevent the solution temperature, time control unreasonable, resulting in quality defects.
4, the use of solid solution process, the cost per ton will increase the cost of 2600-3000 yuan.