Development Of Stainless Steel Alloy Pipe Fittings And Preheating Welding Of Carbon Steel Elbows
Stainless Steel Weld Fitting development:
1. my country's steel production mainly adopts the conservative blast furnace-converter process, and the output of electric furnace steel accounts for only 15% of the total crude steel output. In order to improve the energy structure of steel production and get rid of the shackles of coking coal resources on the development of steel production, the development of direct reduced iron is an important way.
2. The upgrading and replacement of stainless steel elbow products and the adjustment of product structure require clean iron source materials. Direct reduced iron is an important raw material for producing high-quality steel and clean steel.
3. The equipment manufacturing industry urgently needs casting and forging billets of high-quality clean steel. The insufficient production and supply of casting and forging billets of high-quality clean steel are important factors affecting the rapid development of my country's equipment manufacturing industry. The development of direct reduced iron and the production of casting and forging billets of high-quality clean steel using direct reduced iron as raw materials will promote the development of my country's equipment manufacturing industry.
4. The development of direct reduced iron is an important way to achieve energy conservation and emission reduction in the steel industry.
5. The shortage of scrap steel is an important factor affecting the development of my country's steel industry, reducing the energy consumption per ton of steel, and adjusting the structure of steel products. my country's self-produced scrap steel cannot meet the needs of steel production in a short period of time. Imported scrap steel is not only expensive, but also difficult to meet the needs of production in terms of quantity and quality. Developing direct reduced iron and replacing scrap steel with direct reduced iron is the best way to solve the problem of insufficient scrap steel supply in my country.
Preheating of carbon steel elbows is conducive to reducing the heat affected zone of medium carbon steel and preventing cold cracks. This is the main process measure for welding medium carbon steel. Preheating can also improve the plasticity of the joint and reduce residual stress after welding. Usually, the preheating temperature of 35 and 45 steels is 150~250℃. If the carbon content is higher or the thickness and rigidity are large, the crack tendency is large, the preheating temperature can be increased to 250~400℃. If the weldment is too large and it is difficult to preheat the whole piece, local preheating can be performed. The heating range of local preheating is 150~200mm on both sides of the weld. Alkaline welding rods are preferred when welding rod conditions permit.
If stress relief heat treatment cannot be performed after welding, post-heat treatment should be performed immediately. From the design stress alone, the pressure resistance of carbon steel elbows is better. However, due to various factors, the actual wall thickness of floor heating pipes is usually , and under this wall thickness, all kinds of pipes can meet the requirements of floor heating, and the pressure resistance advantage of national standard carbon steel elbow pipes cannot be reflected; thermal conductivity: pipes used for floor heating need to have good thermal conductivity, low temperature heat shock resistance, and low temperature impact resistance. Carbon steel needs to be cautious during the welding process, used in appropriate environments, and continuously achieve important performance. Welding in important environments determines the quality. Bevel form The weldment is opened into a U-shaped bevel for welding as much as possible. If it is a casting defect, the shape of the bevel dug out by the shovel should be smooth. The purpose is to reduce the proportion of the parent material melted into the weld metal to reduce the carbon content in the weld and prevent cracks.
