阅读说明：本技术 提高轴承钢连铸坯内部质量的连铸方法 (Continuous casting method for improving internal quality of bearing steel continuous casting billet ) 是由 卫广运 李海军 李双江 刘需 董廷亮 张瑞忠 李睿昊 于 2019-11-08 设计创作，主要内容包括：一种提高轴承钢连铸坯内部质量的连铸方法,其包括浇注、拉矫和切割过程；在拉矫机与切割机之间距离拉矫机1.5～2.5m处设置热轧机对铸坯进行压下,热轧机的线速度与连铸的拉速同步；所述铸坯在表面温度为820～870℃时进行压下,单道次压下量为35～45mm。本方法通过设置热轧机在连铸坯完全凝固后,利用铸坯芯表190℃左右的温差,利用高温余热在线单道次大压下量轧制,使铸坯内部变形量大于表面；从而压合铸坯内部缩孔和疏松、破碎枝晶、细化晶粒,提高铸坯的致密度；同时铸坯处于高温塑性区,不易产生裂纹,从而整体提高铸坯的内部质量。本方法简单,可有效消除大方坯轴承钢铸坯的内部疏松和缩孔,提高铸坯内部质量。(A continuous casting method for improving the internal quality of a bearing steel continuous casting billet comprises the processes of pouring, straightening and cutting; arranging a hot rolling mill between the tension leveler and the cutting machine at a distance of 1.5-2.5 m from the tension leveler to reduce the casting blank, wherein the linear speed of the hot rolling mill is synchronous with the continuous casting pulling speed; and reducing the casting blank at the surface temperature of 820-870 ℃, wherein the single-pass reduction is 35-45 mm. The method comprises the steps that after a continuous casting blank is completely solidified, a hot rolling mill is arranged, the temperature difference of about 190 ℃ of a casting blank core surface is utilized, high-temperature waste heat is utilized for on-line single-pass large-reduction rolling, and the internal deformation of the casting blank is larger than the surface; thereby pressing shrinkage holes and looseness in the casting blank, crushing dendritic crystals, refining grains and improving the compactness of the casting blank; meanwhile, the casting blank is in a high-temperature plastic area and is not easy to crack, so that the internal quality of the casting blank is integrally improved. The method is simple, can effectively eliminate the internal looseness and shrinkage cavity of the bloom bearing steel casting blank, and improves the internal quality of the casting blank.)

1. A continuous casting method for improving the internal quality of a bearing steel continuous casting billet comprises the processes of pouring, pulling and straightening and cutting, and is characterized in that: arranging a hot rolling mill between the tension leveler and the cutting machine at a distance of 1.5-2.5 m from the tension leveler to reduce the casting blank, wherein the linear speed of the hot rolling mill is synchronous with the continuous casting pulling speed; and reducing the casting blank at the surface temperature of 820-870 ℃, wherein the single-pass reduction is 35-45 mm.

2. The continuous casting method for improving the internal quality of a bearing steel continuous casting slab according to claim 1, wherein: the molten steel is poured in a protection mode in the whole process, and the casting blank pulling speed is 0.42-0.55 m/min.

3. The continuous casting method for improving the internal quality of a bearing steel continuous casting slab according to claim 2, wherein: the superheat degree in the pouring process is controlled to be 15-40 ℃, a dynamic secondary cooling control mode is adopted, and the secondary cooling specific water quantity is 0.12-0.22L/kg.

4. The continuous casting method for improving the internal quality of a bearing steel continuous casting slab according to any one of claims 1 to 3, wherein: the bearing steel comprises the following chemical components in percentage by mass: 0.93 to 1.05 percent of C, 0.15 to 0.35 percent of Si, 0.20 to 0.45 percent of Mn0.40 to 1.65 percent of Cr, 0.010 to 0.040 percent of Al, less than or equal to 0.25 percent of Ni, less than or equal to 0.25 percent of Cu, less than or equal to 0.10 percent of Mo, less than or equal to 0.0050 percent of Ti, less than or equal to 0.0012 percent of O, less than or equal to 0.01 percent of S, and the balance of Fe and inevitable impurities.

Technical Field

The invention relates to a continuous casting method, in particular to a continuous casting method for improving the internal quality of a bearing steel continuous casting billet.

Background

In the production process of the bloom, the quality of a final product is influenced by defects of internal looseness, shrinkage cavity and the like of a casting blank. Firstly, a casting blank firstly forms a chilling layer on an outer blank shell in the solidification process, then columnar crystals grow towards the center, and bridging is caused when the columnar crystals in different directions of the casting blank touch together, so that molten steel on a bridge is prevented from flowing to the lower part of the bridge for feeding, and therefore a plurality of small pores are left below the bridge, namely the center porosity is formed; another aspect is solidification shrinkage of the cast slab, which can prevent formation of porosity if the solidification shrinkage of the cast slab can be timely supplemented by a liquid phase, and if the feeding passage is closed, the solidification shrinkage of the cast slab is easy to aggravate central porosity and shrinkage cavity. The central porosity and shrinkage cavity of the casting blank are accompanied by component segregation, and the defects can influence the mechanical property of a rolled material and the service performance of a finished product, so that the improvement of the central porosity and shrinkage cavity of the casting blank is very important.

Patent application No. 201510183899.X, entitled "a method for eliminating central porosity of casting blank and improving density of casting blank" discloses a method for improving density of casting blank, which specifically discloses: two pairs of lower rollers are arranged behind the outlet of the fan-shaped section, the linear speed of the lower rollers is synchronous with the pulling speed of the continuous casting machine, and the reduction is 15-35 mm. The invention adopts online casting blank reduction, adopts a roller press in a reduction mode, but has lower reduction rate and poorer improvement on the center quality of the casting blank.

Patent application No. 201610123821.1 entitled "method for improving center density of casting blank" discloses a method for improving density of steel casting blank for axle, which specifically discloses: and (3) utilizing a withdrawal and straightening roller of a withdrawal and straightening machine to carry out reduction on the solidification tail end of the casting blank, wherein the length of a reduction interval is 4-8 m, the number of the reduction rollers is 4-6, and the maximum reduction of a single roller is 5-6.5 mm. According to the invention, online casting blank reduction is adopted, the reduction mode adopts withdrawal and straightening roller reduction, the reduction interval is large, and the reduction force cannot be well transmitted to the center of a casting blank.

Disclosure of Invention

The invention aims to provide a continuous casting method for improving the internal quality of a bearing steel continuous casting billet with good effect.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows: the method comprises the processes of pouring, straightening and cutting; arranging a hot rolling mill between the tension leveler and the cutting machine at a distance of 1.5-2.5 m from the tension leveler to reduce the casting blank, wherein the linear speed of the hot rolling mill is synchronous with the continuous casting pulling speed; and reducing the casting blank at the surface temperature of 820-870 ℃, wherein the single-pass reduction is 35-45 mm.

The molten steel is poured in a whole-process protection manner, and the casting blank pulling speed is 0.42-0.55 m/min.

The superheat degree of the pouring process is controlled to be 15-40 ℃, a dynamic secondary cooling control mode is adopted, and the secondary cooling specific water quantity is 0.12-0.22L/kg.

The bearing steel comprises the following chemical components in percentage by mass: 0.93 to 1.05 percent of C, 0.15 to 0.35 percent of Si, 0.20 to 0.45 percent of Mn, 1.40 to 1.65 percent of Cr, 0.010 to 0.040 percent of Al, less than or equal to 0.25 percent of Ni, less than or equal to 0.25 percent of Cu, less than or equal to 0.10 percent of Mo, less than or equal to 0.0050 percent of Ti, less than or equal to 0.0012 percent of O, less than or equal to 0.01 percent of S, and the balance of Fe and inevitable impurities.

Adopt the produced beneficial effect of above-mentioned technical scheme to lie in: according to the invention, after the continuous casting billet is completely solidified, the temperature difference of about 190 ℃ on the surface of the casting billet core is utilized by the hot rolling mill, and the high-temperature waste heat is utilized for on-line single-pass large reduction rolling, so that the internal deformation of the casting billet is larger than the surface; thereby pressing shrinkage holes and looseness in the casting blank, crushing dendritic crystals, refining grains and improving the compactness of the casting blank; meanwhile, the casting blank is in a high-temperature plastic area and is not easy to crack, so that the internal quality of the casting blank is integrally improved. The method has simple process, can effectively eliminate the internal porosity and shrinkage cavity of the bloom bearing steel casting blank, and improves the internal quality of the casting blank.

Detailed Description

The present invention will be described in further detail with reference to specific embodiments.

The continuous casting method for improving the internal quality of the bearing steel continuous casting billet is used for production by adopting a continuous casting machine, wherein the continuous casting machine comprises a steel ladle, a tundish, a crystallizer, a vibration table device, a secondary cooling device, a withdrawal and straightening machine, a cutting machine and the like. The continuous casting machine is a large square billet continuous casting machine, and the section size of a casting billet is larger than 220mm multiplied by 220 mm. The method adopts the equipment that a hot rolling mill is arranged between a tension leveler and a cutting machine, and the radius of a working roll of the hot rolling mill is 600-1000 mm; the hot rolling mill is arranged 1.5-2.5 m away from the tension leveler, so that the hot rolling mill can be used for pressing (rolling) by utilizing the high-temperature waste heat of the casting blank; the advantage of placing the hot rolling mill at this place is that the casting blank can be guaranteed to have the best core surface temperature difference at the rolling mill reduction position without additionally adjusting the blank drawing speed of the casting blank, secondary cooling water distribution and extra casting blank heat supplementing measures, thereby obtaining better production effect.

The continuous casting method comprises the processes of pouring, straightening, pressing and cutting. In the pouring process, the molten steel is poured in a protection way in the whole process, and the casting blank pulling speed is 0.42-0.55 m/min; the superheat degree of the tundish is controlled between 15 ℃ and 40 ℃, a dynamic secondary cooling control mode is adopted, and the secondary cooling water ratio is 0.12-0.22L/kg. Drawing out the continuous casting billet through a withdrawal and straightening machine, wherein the continuous casting billet is completely solidified at the moment, entering a reduction process, and performing reduction rolling on the upper surface and the lower surface of the casting billet by using a hot rolling mill; in the reduction process, the linear speed of the hot rolling mill is synchronous with the continuous casting pulling speed, the surface temperature of the casting blank is 820-870 ℃ when the casting blank starts to be reduced, and the single-pass reduction is 35-45 mm; when the surface temperature of the casting blank is 820-870 ℃, the core temperature of the casting blank is 1000-1060 ℃, the core surface temperature difference of about 190 ℃ is kept, and the deformation permeability of the casting blank is good. And cutting the casting blank after the reduction process by a flame cutting machine according to the requirement of the fixed length, and conveying the cut casting blank to a steel rolling workshop for rolling a finished product.