Production method of low-carbon low-silicon cold heading steel

Abstract

The invention discloses a production method of low-carbon low-silicon cold heading steel. The steel comprises the following chemical components including, by weight, 0.02%-0.20% of C, less than or equal to 0.06% of Si, 0.25%-0.60% of Mn, less than or equal to 0.020% of P, less than or equal to 0.005% of S, more than or equal to 0.020% of Al and the balance Fe and inevitable impurities. A smeltingprocess includes converter-LF furnace-VD furnace-square billet continuous casting. In the converter working procedure, the Si in molten steel is less than 0.01%, and the Al is equal to 0.015%-0.040%;in the LF working procedure, the Al is equal to 0.015%-0.040%, in final slag components, CaO is equal to 54%-62%, Al2O3 is equal to 31%-38%, SiO2 is less than or equal to 2.0%, MgO is equal to 3%-7%,and TFe is less than or equal to 0.8%; the Al is increased to 0.055%-0.070% before leaving a station, and the Si in the molten steel leaving the station is smaller than 0.04%; the VD is kept in vacuumfor 5-7 min, soft blowing is carried out for more than or equal to 18 min after vacuum breaking for coming to the station, and the Ca in the molten steel leaving the station is equal to 0.0015%-0.0030%; in the continuous casting working procedure, tundish gas driving is conducted after a tundish car is in place before large ladle casting, and gas driving operation continues to be conducted afterlarge ladle casting; when the liquid level of the molten steel in a tundish reaches 280-320 mm, a covering agent starts to be rapidly put into the tundish till the molten steel surface is completely covered; and after the liquid level of the molten steel in the tundish reaches 650 mm, tundish casting is organized. According to the production method, the castability of the molten steel of a castingfurnace for producing the low-carbon low-silicon cold heading steel by a billet caster can be greatly improved.

Description

technical field [0001] The invention belongs to the technical field of metallurgy and relates to a production method of low-carbon and low-silicon cold heading steel. Background technique [0002] Type A cold heading steel wire rod is used for cold heading forming to manufacture various mechanical standard parts and fasteners such as bolts, nuts, screws, etc. The cold heading process requires the steel to have high cleanliness and high cold heading performance, and requires the control of molten steel inclusions at a low level, and at the same time requires control of the Si and Al content in the steel. Some customers require the silicon content of the finished steel to be ≤0.06%, and the Al content to be ≥0.02%. The current main difficulty in smelting cold heading steel is to control the Si content of molten steel at a low level. At the same time, in order to ensure the purity of molten steel, aluminum deoxidation is used in the smelting process, and the grains can also be...

AI Technical Summary

Problems solved by technology

[0003] At present, most steel mills use converter ~ LF furnace ~ continuous casting process to produce cold heading steel. Because aluminum deoxidation is used, it is easy to cause nodulation at the nozzle, fluctuations in the liquid level of the crystallizer, and unstable control of the pouring furnace. Some steel mills first furnace The use of molten steel with low Al content to start pouring solves the problem of low success rate of casting, but at the same time, it leads to high output products such as joint billets, and when there are steel grades with carbon content <0.06%, it also leads to joint cast billets The issue of invalidation