In 2019, the output of pig iron in the world was 1.265 billion tons, with China accounting for 64%; the overseas output accounted for 36% (460 million tons), ranking 86.982 million tons of EU 28 countries, 74.907 million tons of Japan, 74.099 million tons of India, 73.264 million tons of CIS, and A283 grade D mild steel coil 47.521 million tons of South Korea. In the first quarter, the global output was 311 million tons, with a year-on-year decrease of 0.5%, with China A283 grade D mild steel coil increasing by 2.4%; the overseas output decreased by 5.4%, Among them, EU decreased by 9.2%, Japan increased by 1.3%, India decreased by 7.7%, CIS increased by 2.1%, and South Korea decreased by 4%.
Hydrogen (H) is the most harmful element in general steel such as A283 grade D mild steel coil. Hydrogen dissolved in steel will cause hydrogen embrittlement, white spots and other defects. Hydrogen, like oxygen and nitrogen, has very little solubility in solid steel. It dissolves into liquid steel at high temperature, and accumulates in the structure without time to escape when cooling, forming high-pressure micro pores, which greatly reduce the plasticity, toughness and fatigue strength of steel, and even cause cracks and brittle fracture in severe cases. "Hydrogen embrittlement" mainly occurs in martensitic steel, but not very prominent in ferrite steel, and generally increases with hardness and carbon content.
The chemical composition of 20CrMo steel pipe is 0.17-0.24, Si: 0.17-0.37, Mn: 0.40-0.70, Cr: 0.80-1.10, Mo: 0.15-0.25. Mechanical properties of 20CrMo steel pipe: tensile strength 410 Mpa; yield strength: 265mpa; elongation after fracture: 24; reduction of area: 60; impact absorption energy: 110J. 20CrMo steel pipe belongs to alloy structure steel pipe, which has high thermal strength, good high-temperature strength, good machinability, medium cold bending plasticity, high hardenability and good welding performance at 500-520℃. A283 grade D mild steel coil, 20CrMo steel pipe is generally used in quenching and tempering state.
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