The Harm of Hydrogen in Steelmaking
Hydrogen is a common harmful gas in steel. Its content exceeds the safety content will bring the harmful influence to the steel performance. The harmful effect of hydrogen on steel is mainly manifested in the following points.
1.Hydrogen embrittlement in steel
Hydrogen embrittlement mainly shows that the elongation and section shrinkage of steel are obviously decreased. Usually, the higher the tensile strength, the greater the hydrogen embrittlement sensitivity of the steel. Hydrogen embrittlement is the most harmful to martensite steel, and austenitic steel is insensitive to hydrogen embrittlement. The hydrogen embrittlement of steel occurs under certain stress. After a period of time, the steel suddenly breaks.
2.Make the steel white spot
Excessive hydrogen content in steel will show round or elliptical silver bright and glossy spots along the fracture of steel cross section. The essence of the white spot is the extremely fine microcracks caused by hydrogen, which destroy the continuity of the metal, make its transverse tensile strength, section shrinkage and elongation decrease, and finally lead to the scrap of steel.
3.Causes the ingot to produce the bubble ingot
Because the solubility of hydrogen in molten steel is greater than that in solid steel, when the hydrogen content of molten steel is too high, a large amount of hydrogen precipitates during the solidification of ingot will cause ingot to rise and form pores and cracks inside ingot. Finally, the ingot is scrapped. Most of these defects occur in the smelting of nickel-based alloys in atmospheric induction furnaces.
4.Make weld heat affect area produce crack.
During the welding process, the weld metal absorbs a large amount of hydrogen from the humid welding material, and when the weld metal is cooled, it precipitates from it and forms a crack in the heat affected zone. With the cooling shrinkage of the metal in the weld zone, cracks continue to grow and produce cracks.
Because the harm of hydrogen in steel is many and serious, the content of hydrogen in steel should be reduced as far as possible in medium frequency smelting process.