Development of stainless steel pipe fittings:
First, China's steel production mainly adopts the old-fashioned blast-furnace converter process, and the output of electric furnace steel only accounts for 15% of the total output of crude steel. In order to improve the energy structure of iron and steel production and get rid of the fetters of coking coal resources to the development of iron and steel production, the development of direct reduced iron is an important way.
Second, the upgrading of stainless steel elbow products and the adjustment of product structure require net iron source materials, and direct reduced iron is an important raw material for the production of excellent steel and net steel.
Third, the equipment manufacturing industry is in urgent need of fine net steel casting and forging blanks, and the lack of production and supply of fine net steel casting and forging blanks is an important factor affecting the rapid development of China's equipment manufacturing industry. The development of direct reduced iron, using direct reduced iron as raw material to produce fine net steel casting and forging blanks, will promote the development of China's equipment manufacturing industry.
The development of direct reduced iron is an important way to achieve energy conservation and emission reduction in the iron and steel industry.
The shortage of scrap steel is an important factor affecting the development of China's iron and steel industry, reducing energy consumption per ton of steel, and adjusting the structure of steel products. China's self-produced scrap can not meet the needs of iron and steel production in a short period of time, the inlet scrap is not only expensive, but also its quantity and quality are difficult to meet the production needs. Developing direct reduced iron and replacing scrap steel with direct reduced iron is the best way to solve the problem of insufficient supply of scrap steel in China.
Carbon steel elbow preheating is beneficial to reduce the heat affected zone of carbon steel and prevent cold cracks, which is the main process measure of welding carbon steel, preheating can also improve the joint plasticity and reduce the residual stress after welding. Usually, the preheating temperature of 35 and 45 steel is 150~250℃, and the carbon content is higher or the thickness and stiffness are large, and the crack tendency is large, the preheating temperature can be increased to 250~400℃. If the weldment is too large and the overall preheating is difficult, local preheating can be performed, and the heating range of local preheating is 150~200mm on both sides of the welding joint. When the electrode conditions permit, the basic electrode is preferred.
If stress removal heat treatment cannot be performed after welding, post-heat treatment should be performed immediately. In terms of design stress alone, the pressure resistance of carbon steel elbows is better. However, due to various factors, the actual wall thickness of the floor heating pipe is usually all kinds of pipes under this wall thickness can meet the requirements of floor heating, and the pressure advantages of the national standard carbon steel elbow pipe can not be reflected; Thermal conductivity: The pipe used for floor heating needs to have good thermal conductivity, low temperature heat shock resistance to low temperature impact performance. Carbon steel needs to be careful in the welding process, used in the appropriate environment, constantly achieve important properties, welding in an important environment, and determine quality. Groove form Open the weldment into U-shaped groove type as far as possible for welding. If it is a casting defect, the shape of the groove dug out by the shovel should be smooth, and the purpose is to reduce the proportion of the base metal into the weld metal to reduce the carbon content in the weld and prevent cracks.
