阅读说明：本技术 由先共析铁素体引发的铸坯表面裂纹的控制方法 (Method for controlling surface crack of casting blank initiated by proeutectoid ferrite ) 是由 陈波涛 邢立东 蒋凌枫 曾凡政 包燕平 王敏 于 2019-11-06 设计创作，主要内容包括：由先共析铁素体引发的铸坯表面裂纹的控制方法,提供一种控制由先共析铁素体引发的铸坯表面裂纹的工艺方法,通过在连铸机矫直段前增加一排小喷射角冷却水喷嘴,提供一个窄区域表面冷却带,以小区域通过表面强冷来消除表面先共析铁素体的存在而不影响内部组织来达到控制表面裂纹的目的。本发明方法可规模化生产,能有效地控制亚共析钢铸坯表面先共析铁素体的产生,进而使得该钢种由表面先共析铁素体而引起的裂纹得到有效的控制。(A method for controlling the surface crack of casting blank caused by proeutectoid ferrite features that a row of cooling water nozzles with small spray angle is additionally arranged before the straightening segment of conticaster to provide a narrow-area surface cooling zone, which can eliminate the proeutectoid ferrite in small area without influence on internal structure. The method can realize large-scale production, and can effectively control the generation of the proeutectoid ferrite on the surface of the hypoeutectoid steel casting blank, so that the cracks of the steel caused by the proeutectoid ferrite on the surface can be effectively controlled.)

1. The method for controlling the surface crack of the casting blank initiated by the proeutectoid ferrite is characterized by comprising the following steps of:

(1) the casting blank drawing speed is 0.5 ~ 0.7.7 m/min, the superheat degree of molten steel is controlled at 15 ~ 25 ℃, and the alloy structure steel casting blank is produced by an arc continuous casting machine with crystallizer electric stirring and tail end stirring;

(2) continuously measuring the surface temperature of the casting blank after the casting blank is discharged from a crystallizer to a straightening section by using an infrared thermometer, and then selecting the casting blank with the surface temperature interval of 700 ~ 800 ℃;

(3) after the temperature range of the casting blank is determined, a row of small spray angle cooling water nozzles are arranged in the area, the cooling width of the small spray angle nozzles is controlled to be 10 ~ 50mm, the surface of the casting blank is subjected to strong cooling, and other technological parameters of a continuous casting machine are not changed;

(4) the casting process is further controlled, the cooling water amount is controlled to be 1 ~ 6L/min, and the cooling water pressure is controlled to be 0.4 ~ 2.0.0 MPa.

Technical Field

The invention belongs to the technical field of metallurgy, and particularly relates to a control method for controlling surface cracks of a casting blank caused by the existence of proeutectoid ferrite on the surface of the casting blank during continuous casting production.

Background

With the rapid development of the metallurgical industry, the continuous casting and rolling, hot charging and hot delivery and other processes are greatly developed, so that the quality requirement on the continuous casting billet is more strict, and although a plurality of continuous casting new technologies and a series of optimization measures are widely used at present, the surface crack of the casting billet still serves as a bottleneck problem limiting the connection of steel making and steel rolling. The surface crack of the casting blank is one of the biggest problems which troubles the quality improvement of the casting blank, the quality of the surface quality of the casting blank directly affects the quality of rolled materials, the yield of products and the cost, and the systematic prevention and control technology of the surface crack of the casting blank is very important.

For hypoeutectoid steel, eutectoid transformation occurs at high temperature and slow cooling to form proeutectoid ferrite. It is known that proeutectoid ferrite is likely to be preferentially precipitated at grain boundaries, and the strength of proeutectoid ferrite is much lower than the matrix strength, so that the presence of proeutectoid ferrite increases the crack sensitivity of the material, decreases the continuity of the material, and tends to cause cracks in the region where proeutectoid ferrite is present during the straightening of the cast slab. The surface of the casting blank has a temperature return phenomenon in the continuous casting production, and when the surface temperature is increased to Ar₃The proeutectoid ferrite is generated when the steel is slowly cooled above the line, and the invention provides a method for eliminating the proeutectoid ferrite on the surface of hypoeutectoid steel in order to solve the surface crack caused by the proeutectoid ferrite.

Disclosure of Invention

The invention aims to provide a method for controlling surface cracks of a casting blank caused by proeutectoid ferrite, which can effectively control the generation of the proeutectoid ferrite on the surface of a hypoeutectoid steel casting blank so as to effectively control the cracks of the steel grade caused by the proeutectoid ferrite on the surface.

The invention adopts the following technical scheme:

a method for controlling surface cracks of an ingot blank initiated by proeutectoid ferrite comprises the following steps:

(1) the casting blank drawing speed is 0.5 ~ 0.7.7 m/min, the superheat degree of molten steel is controlled at 15 ~ 25 ℃, and the alloy structure steel casting blank is produced by an arc continuous casting machine with crystallizer electric stirring and tail end stirring;

(2) continuously measuring the surface temperature of the casting blank after the casting blank is discharged from a crystallizer to a straightening section by using an infrared thermometer, and then selecting the casting blank with the surface temperature interval of 700 ~ 800 ℃;

(3) after the temperature range of the casting blank is determined, a row of small spray angle cooling water nozzles are arranged in the area, the cooling width of the small spray angle nozzles is controlled to be 10 ~ 50mm, the surface of the casting blank is subjected to strong cooling, and other technological parameters of a continuous casting machine are not changed.

(4) The casting process is further controlled, the cooling water amount is controlled to be 1 ~ 6L/min, and the cooling water pressure is controlled to be 0.4 ~ 2.0.0 MPa.

The invention provides a narrow-area surface cooling zone by adding a row of small spray angle cooling water nozzles in front of a straightening section of a continuous casting machine, and the small area eliminates the existence of surface pro-eutectoid ferrite without influencing internal tissues through surface intensive cooling to achieve the purpose of controlling surface cracks. The method is novel and can be used for large-scale production. Practice shows that the method can effectively control the generation of the proeutectoid ferrite on the surface of the hypoeutectoid steel casting blank, and further effectively control the cracks of the steel caused by the proeutectoid ferrite on the surface.

Drawings

FIG. 1 is a schematic diagram of the process of the present invention.

FIG. 2 shows a microstructure of a prior art ingot near a surface crack.

FIG. 3 shows a microstructure of a prior art ingot surface in the vicinity of a non-crack.

FIG. 4 shows the microstructure of the surface of the cast slab of the present invention.

Detailed Description