Raw material of seamless carbon steel pipe

Posted by zora li on November 1st, 2022

Raw material of seamless carbon steel pipe

manufacturing process

Carbon steel smelting is usually carried out in converters and open hearths. BOF can generally smelt ordinary carbon steel, and can also smelt various high-quality open hearth steel. BOF steelmaking technology has developed rapidly and has a tendency to replace open hearth steelmaking. Refined steel ingots are molded to obtain various steel ingots. Ingots are forged or rolled into steel, steel bars and steels of various cross-sectional shapes. Carbon steel is generally used directly in the hot rolled state. When used in the manufacture of tools and various mechanical parts, heat treatment is required as required; as for steel castings, most of them should be heat treated.

chemical composition

Chemical composition properties are highly dependent on carbon steel and carbon steel microstructure. In the annealed or hot rolled condition, as the carbon content of the steel increases, strength and hardness increase, while ductility and toughness decrease. Weldability and cold bendability deteriorate. Therefore, steel works tend to limit the carbon content. Carbon steel elements and residual impurity elements such as manganese, silicon, nickel, phosphorus, sulfur, oxygen, nitrogen, carbon steel also affect properties. Sometimes these effects reinforce each other, sometimes they cancel each other out. For example: ①Sulfur, oxygen and nitrogen can increase the hot brittleness of steel, and can reduce the amount of manganese or partially offset the hot brittleness. ②Residual elements manganese and nickel reduce the impact toughness of steel and increase cold brittleness. ③Low strength Except for sulfur and oxygen, other impurity elements increase the strength of steel to varying degrees. ④ Almost all impurity elements reduce ductility and weldability. Hydrogen in steel can cause many serious defects, such as white spots, point segregation, hydrogen embrittlement, cracks and other surface bubbling and weld heat affected zone. To maintain the quality of the steel, the hydrogen content in the steel must be kept as low as possible (see Stress Corrosion Cracking and Hydrogen Embrittlement). Deoxidation into residual elements such as aluminum can reduce the aging tendency of low-carbon steel, and refinement of grains can also improve the low-temperature toughness of steel, but the allowance should not be too large. The residual elements brought into the charge such as nickel, chromium, molybdenum, copper, etc., although high content can improve the hardenability of the steel, but it is not good for special steels with high plasticity requirements, such as deep-drawing steels.

Processing performance

Most carbon steel smelting furnaces use oxygen converters, and high-quality carbon steels are also produced using electric arc furnaces. According to the degree of deoxidation in the steelmaking process, carbon steel can be divided into killed steel between boiling steel and semi-killed steel. The main factor affecting the performance of the steelmaking process is the purity of the steel mill. People have obtained steel with higher purity through vacuum treatment and blowing technology, thereby significantly improving the quality of carbon steel. The plastic working process of carbon steel is usually hot and cold working. After the steel ingot is heat treated, the defects such as small bubbles and osteoporosis in the steel ingot are welded together to make the steel structure dense. At the same time, heat treatment can destroy the structure of the casting and refine the grains. So forged steel has better mechanical properties than cast steel. For cold steel, cold plastic deformation increases with strength and hardness, while ductility and toughness decrease. In order to improve the yield, it is widely used in the continuous casting process.

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