Cr-Mo alloyed steel round billet produced by arc continuous casting machine and technique thereof

Abstract

The present invention relates to one kind of round Cr-Mo alloy steel billet produced in a bow-type continuous casting machine and its production process. The molten steel for the round Cr-Mo alloy steel billet contains P not more than 0.012 wt% and S not more than 0.002 wt%, and has Mn/S weight ratio not smaller than 200. The present invention features that the continuous casting process has the second cooling with specific cooling water amount of 0.47-0.53, the first region cooling water amount accounting for 35-45 %, the second region cooling water amount accounting for 22-32 %, the third region cooling water amount accounting for 14-24 %, the fourth region cooling water amount accounting for 9-19 %, and Mn/S content ratio in steel not smaller than 200. The present invention can produce continuously cast round low carbon alloy steel billet without crack, shrinkage hole and other defects.

Description

technical field [0001] The invention relates to an alloy steel and a process method thereof, in particular to a Cr-Mo alloy steel round billet produced by an arc continuous casting machine and a process method thereof. Background technique [0002] The Baosteel electric furnace was put into operation in December 1996. Since the corresponding smelting and casting technology was not introduced, it mainly produced carbon steel, manganese steel and low alloy steel in the 7 years before the start of operation. During this period, Cr-Mo series alloy steels with an alloy content of 2.5-5.5% were also trial-manufactured. However, due to failure to master the key technology of alloy steel smelting and casting, steel breakouts and internal Defects are mainly central cracks and shrinkage cavities that exceed the standard. Due to Baosteel electric furnace continuous casting production The 178mm round billet is mainly used for rolling steel pipes by Baosteel Steel Pipe Branch. Baoste...

AI Technical Summary

Problems solved by technology

[0007] The purpose of continuous casting secondary cooling is to directly and continuously cool the billet shell with liquid core pulled out from the crystallizer by supplying a sufficient amount of spray water to promote its rapid and complete solidification. The secondary cooling system must be set so that it can evenly reduce the billet temperature to avoid sharp changes in the surface temperature of the billet. In the prior art, the specific water volume of 0.35L / kg is likely to cause the length of the liquid phase hole to be too long, resulting in straightening with a liquid core, which is prone to defects such as cracks. In addition, the prior art four The area adopts "fluctuating" water distribution, resulting in a large temperature difference between the slabs in the sector, which makes the slab prone to "reheating" during the solidification process, which can cause local thermal stress and cause defects in the slab