Dynamic soft reduction technologies for bloom continuous casting of heavy rail

Abstract

The invention discloses a process of continuous casting dynamic with less reduction heavy rail steel cogged ingot, the process is applied in the continuous casting of high carbon steel cogged ingot, which can not only evidently alleviate center segregation, center porosity, center line shrinkage, center crack and so on defects and prevent the casting ingot center crack, middle crack and so on underbead crack, but also can improve component homogenization of rail rolled by the casting ingot, stabilize and improve mechanical property and functional performance of the rail and reach technical requirements of the high speed rail. The technical measure as follows: controlling continuous casting pulling rate and molten steel temperature of the heavy rail steel, the continuous casting pulling rate is 0.60-0.80m / min, the molten steel superheating temperature is 15-40 DEG C; adopting even and assuasive control mode in the secondary cooling zone, the continuous casting ratio water amount is 0.25-0.30L / kg, the casting ingot surface temperature on the area with less reduction is 900-1020 DEG C; the reduction is controlled on the area with less reduction, the casting ingot solidification rate on the area with less reduction fs=30%-100%, total reduction is 1.6-7.0 mm.

Description

technical field [0001] The invention relates to a continuous casting process, in particular to a dynamic soft reduction process for high-carbon steel blooms such as heavy rail steel, so as to eliminate central segregation, central porosity, central shrinkage cavity, and central cracks of the bloom. Background technique [0002] Heavy rail steel belongs to high-carbon steel. During the solidification process, the dendrites are developed, and it is easy to form a dendrite "bridge" in the core of the slab. In addition, the effect of selective crystallization during the solidification process enriches a large amount of solutes with low melting points between the dendrites. , at the end of solidification, the strong suction force generated by the solidification and contraction of the solid-liquid two-phase region at the end of the solidification of the slab causes the residual liquid enriched in impurities between the dendrites to flow to the center and fill it, resulting in centr...

AI Technical Summary

Problems solved by technology

[0004] In the above research, the "static soft reduction" process has not been combined with the continuous casting steel type, continuous casting casting speed, molten steel superheat, continuous casting cooling intensity and other factors that affect the solidification end position of the slab. The soft reduction process, For example, the light reduction position, light reduction amount, and reduction rate are fixed during the continuous casting process, and the solidification end position of the slab is an important parameter to determine whether the light reduction process is reasonable. Therefore, in continuous casting steel When the type, continuous casting casting speed, superheat degree, cooling intensity, etc. change, it is difficult to successfully reduce and eliminate the center defects such as center segregation and center porosity of the continuous casting slab by using the static light reduction process.

At the same time, if the light reduction process is unreasonable, it will cause internal crack defects in the slab, and the compression ratio (generally 10-14) of the continuous casting slab rolling heavy rail is small, and the internal cracks of the slab are difficult to be welded during the rolling process. Therefore, foreign bloom continuous casting light reduction technology is only applied to hard wire steel and other steels with relatively large compression ratio. The types of steel to be pressed are hard wire steel and tire core wire steel. According to the report of "Special Steel" magazine in December 2002, the steel types used by Xinxing Casting Pipe Company using light reduction technology are 20MnSi and Q235 steel for wire rods. The above steel cast The compression ratio of the slab and the rolled material is very large, and the internal cracks of the slab can be welded during the rolling process, while the compression ratio of the heavy rail steel slab and the rail is small, and the internal cracks of the slab are difficult to weld during the rolling process. Therefore, the risk of applying light reduction technology to heavy rail steel continuous casting is relatively high, and there is no report on the application of light reduction technology to heavy rail steel

It can be seen from the above research that the light reduction process of billet continuous casting studied at present belongs to the static light reduction process, and it is only used for steel types with relatively large compression such as hard wire steel and tire core wire steel. It is difficult to play a greater role in the control of center defects such as slab center segregation, center porosity, and center shrinkage cavity

Images