Method for controlling linear defects on the surface of a cold heading steel wire

Abstract

A kind of control method of cold heading steel wire surface linear defect, the chemical composition of steel is as follows: C=0.38-0.43, Si=0.10-0.30, Mn=0.60-0.90, P≤0.020, S≤0.020, Cr=0.90-1.20, Mo=0.15-0.30, the rest is Fe and essential impurities;Key process steps include: (1) continuous casting: produce 150mm×150mm section billet, the chamfer of crystallizer R=11-14mm, the water volume of crystallizer is 1951-2050L / min, and the drawing speed is 2.51-2.6m / min;(2) pass: the inner round corner radius of the first pass of rough rolling is R16mm-R22mm;The inner round corner radius of the second pass of rough rolling is R=18-25mm;The first pass and the second pass of rough rolling entrance inducer is changed from sliding guide plate to rolling guide guard.The present application solves the problem that linear defects appear in the form of cluster on the surface of the rolled piece during the rough rolling process of the billet.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of steel product development, and relates to a control method for linear defects on the surface of cold heading steel wire rods. BACKGROUND

[0002] Linear defects are a kind of defects on the surface of cold heading steel wire rods, and are one of the main reasons causing cold heading cracking. When cold heading steel is used to produce wire rods by using 150mm*150mm small square billets, straight linear surface quality defects in a cluster often appear on the surface of the wire rods. After the semi-finished products and the continuous casting billets in the production process are immersed in industrial hydrochloric acid, the surface quality of the continuous casting billets is normal, fine crack defects appear on the corner of the rolled piece in the first rack of rough rolling, a plurality of parallel short linear defects in a cluster appear on the corner of the rolled piece in the second rack of rough rolling, and a plurality of parallel straight linear defects in a cluster appear on the surface of the round rolled piece in the sixth rack of rough rolling.

[0003] The prior art produces 150mm*150mm section small square billets by using a continuous casting machine, the chamfer of the crystallizer is R8mm, the water volume of the crystallizer is 2050-3000L / min, the specific water volume of the second cooling is 0.8L / kg, the drawing speed is 2.6-2.7m / min, the round corner radius of the small square billet is small, the small square billet is subjected to strong cooling at a high speed, the round corner of the small square billet is rapidly cooled and blackened, and sometimes transverse drawing cracks appear. The small square billet needs to be subjected to high-pressure water phosphorus removal to remove the iron oxide scale on the surface of the billet before being heated and rolled in the heating furnace, the round corner radius of the small square billet is small, the round corner of the billet is seriously blackened after being subjected to high-pressure water phosphorus removal, and abnormal quenching structures easily appear at the corner of the billet. The round corner radius of the box-type hole of the first and second racks of rough rolling is R15mm, the blackening of the corner of the billet is not obviously improved during rolling, the surface layer of the corner of the billet is deformed greatly during rolling, a part of the surface layer flows forward and extends, a part of the surface layer flows horizontally to form a wide spread, the part of the surface layer that is difficult to deform is torn into cracks in the process of forming the wide spread, and the cracks are extended into linear defects on the surface of the wire rod through subsequent rolling.

[0004] Therefore, it is of great significance to study the production technology for controlling the linear defects in a cluster on the surface of the cold heading steel wire rod. SUMMARY

[0005] The application aims to provide a control method for linear defects on the surface of cold heading steel wire rods, and solve the problem of linear defects in a cluster on the surface of the cold heading steel wire rod.

[0006] The technical scheme of the application is as follows.

[0007] A kind of control method of cold heading steel wire surface linear defect, production process flow includes molten iron pretreatment-refining-continuous casting-heating-rolling-finished product inspection-warehouse.The chemical composition of steel is as follows by weight percentage: C=0.38~0.43, Si=0.10~0.30, Mn=0.60~0.90, P≤0.020, S≤0.020, Cr=0.90~1.20, Mo=0.15~0.30, the rest is Fe and a small amount of impurities.Key process steps include:

[0008] (1) continuous casting: produce 150mm×150mm section small billet, the bevel of crystallizer R=11~14mm, the water volume of crystallizer is 1951~2050L / min, and the drawing speed is 2.51~2.6m / min;

[0009] (2) pass: the inner round corner radius of rough rolling 1 roller box pass is R16mm~R22mm;The inner round corner radius of rough rolling 2 roller box pass is R=18~25mm;The entrance guide device of rough rolling 1st, 2nd frame is changed from sliding guide plate to rolling guide.

[0010] The beneficial effects of the present application are: the key of the present application is to use large bevel crystallizer, weak cold slow speed, which can increase the round corner radius of continuous casting billet, improve the sharp cooling of billet corner, and also can improve the transverse splitting crack of billet;The round corner size of billet produced by large bevel crystallizer is large, and the corner rapid cooling is improved after high-pressure water dephosphorization, eliminating the blackening and abnormal structure of billet corner;Increase the inner round corner radius R of rough rolling 1 and 2 box pass, improve the corner cooling of rolled piece, and there is no blackening in the corner of rolled piece, change the transverse deformation of rolled piece corner, and eliminate the tearing crack in the rolling process;The entrance guide plate of rough rolling 1st, 2nd frame is replaced by rolling guide, which is stable and prevents the twisting of rolled piece.The present application solves the problem of linear defects in the form of clusters on the surface of rolled piece during the rough rolling process of small billet. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 It is the surface graph of the semi-finished product rolled piece after acid immersion of rough rolling 6th frame of embodiment 1 of the present application;

[0012] Figure 2 It is the surface graph of the semi-finished product rolled piece after acid immersion of rough rolling 6th frame of embodiment 2 of the present application. DETAILED DESCRIPTION

[0013] The content of the present application will be further described below in combination with examples.

[0014] Example 1:

[0015] A method for controlling linear defects on the surface of cold heading steel wire rod, the casting blank specification is 150mm*150mm, and a Φ32.0mm specification wire rod is rolled. The chemical composition of the steel is as follows: C=0.41, Si=0.18, Mn=0.68, P=0.012, S=0.008, Cr=0.99, Mo=0.16, and the rest is Fe and inevitable impurities. Key process steps include

[0016] (1) continuous casting: rectangular blank 150mm*150mm, mould chamfer R12mm, mould water quantity 1960L / min, and drawing speed 2.55m / min;

[0017] (2) pass: the inner corner radius of the pass of the rough rolling 1 roller box type is R18mm; the inner corner radius of the pass of the rough rolling 2 roller box type is R20mm; the entrances of the rough rolling 1 and 2 are rolling guide;

[0018] (3) rolling: high-pressure water descaling is started, and improved roller and improved entrance rolling guide are used for rolling production.

[0019] The semi-finished product rolled piece after the rough rolling 6 is taken, and the surface quality is checked by industrial hydrochloric acid pickling. The surface is free of linear defects in cluster distribution. The surface of the semi-finished product rolled piece after the rough rolling 6 is seen Figure 1 .

[0020] Example 2

[0021] A method for controlling linear defects on the surface of cold heading steel wire rod, the casting blank specification is 150mm*150mm, and a Φ24.0mm specification wire rod is rolled. The chemical composition of the steel is as follows: C=0.39, Si=0.20, Mn=0.70, P=0.012, S=0.010, Cr=1.02, Mo=0.16, and the rest is Fe and inevitable impurities. Key process steps include

[0022] (1) continuous casting: rectangular blank 150mm*150mm, mould chamfer R12mm, mould water quantity 1960L / min, and drawing speed 2.55m / min;

[0023] (2) pass: the inner corner radius of the pass of the rough rolling 1 roller box type is R18mm; the inner corner radius of the pass of the rough rolling 2 roller box type is R20mm; the entrances of the rough rolling 1 and 2 are rolling guide;

[0024] (3) rolling: high-pressure water descaling is started, and improved roller and improved entrance rolling guide are used for rolling production.

[0025] The semi-finished product rolled piece after the rough rolling 6 is taken, and the surface quality is checked by industrial hydrochloric acid pickling. The surface is free of linear defects in cluster distribution. The surface of the semi-finished product rolled piece after the rough rolling 6 is seenFigure 2 。

Claims

1. A method for controlling surface linear defects of cold heading steel wire rod, the production process flow comprising molten iron pretreatment - refining - continuous casting - heating - rolling - finished product inspection - warehousing, characterized in that: The steel has a chemical composition in weight percent of C=0.38-0.43, Si=0.10-0.30, Mn=0.60-0.90, P≤0.020, S≤0.020, Cr=0.90-1.20, Mo=0.15-0.30, and the balance being Fe and inevitable impurities; The key process steps include: (1) Continuous casting: producing 150mm×150mm section billets, the mould chamfer R=12mm, the mould water quantity is 1960L / min, and the drawing speed is 2.55m / min; (2) Pass: the inner corner radius R=18mm in the pass of the first rough rolling roller box type; the inner corner radius R=20mm in the pass of the second rough rolling roller box type; the entrance inducer of the first and second passes is changed from sliding guide plate to rolling guide.

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