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Method for controlling martensite and grain boundary cementite at center of 82B hot-rolled wire rod

A control method and martensite technology, applied in the field of iron and steel metallurgy, which can solve problems such as affecting service performance and abnormal fracture

Active Publication Date: 2020-12-15
PANGANG GROUP RESEARCH INSTITUTE CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0003] The uniformity of the structure of the wire rod is one of the main factors leading to drawing fracture. In terms of the uniformity of the structure, in addition to requiring a high sorbite rate, "Hot Rolled Wire Rod for Prestressed Steel Wire and Steel Strand" ( GBT 24238-2017) standard requires sorbite rate ≥ 85%, The standard wire rod cementite and core martensite shall not be > 2.0, and in the actual production process, due to the temperature and cooling rate difference between the surface and core of the wire rod after rolling, as well as the influence of factors such as chemical composition segregation , so that serious abnormal structures such as martensite and grain boundary cementite appear in the core of the wire rod, which greatly affects its performance, especially for mechanical peeling users, abnormal fracture occurs during the drawing process, and many cup cone fracture

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0030] Example 1 Preparation of Specification 82B Hot Rolled Wire Rod

[0031] First, the 82B billet or square steel with a central carbon segregation of 1.20 is heated in a walking heating furnace, descaled by high-pressure water, and then rolled by a 30-stand high-speed rolling mill. The standard smooth round, the exit temperature of the finishing mill in the high-line rolling mill is 921°C, and the spinning temperature is controlled at 870-890°C through the cooling of the water cooling box, and then the spinning is carried out through the laying machine. The actual spinning temperature is 872°C, spinning speed is 30m / s.

[0032] The wire rod after spinning is controlled and cooled in the Stelmore air-cooled line. The control parameters of the Stelmore air-cooled line are as follows:

[0033] (1) The roller table speed of the first stage roller table is 0.60m / s, the roller table speed of the second stage roller table is 0.62m / s, the roller table speed of the third stage ...

Embodiment 2

[0038] Example 2 Preparation of Specification 82B Hot Rolled Wire Rod

[0039] First, the 82B billet or square steel with a central carbon segregation of 0.9 is heated in a walking heating furnace, descaled by high-pressure water, and then rolled by a 30-stand high-wire rolling unit. The standard smooth round, the exit temperature of the finishing mill in the high-line rolling mill is 928°C, and the spinning temperature is controlled at 870-890°C through the cooling of the water-cooled box, and then the spinning is carried out through the laying machine. The actual spinning temperature is 890°C, spinning speed is 35m / s.

[0040] The wire rod after spinning is controlled and cooled in the Stelmore air-cooled line. The control parameters of the Stelmore air-cooled line are as follows:

[0041] (1) The roller table speed of the first stage roller table is 0.60m / s, the roller table speed of the second stage roller table is 0.62m / s, the roller table speed of the third stage rol...

Embodiment 3

[0046] Example 3 Preparation of Specification 82B Hot Rolled Wire Rod

[0047] First, the 82B billet or square steel with a central carbon segregation of 1.12 is heated in a walking heating furnace, descaled by high-pressure water, and then rolled by a 30-stand high-speed rolling mill. The standard smooth round, the exit temperature of the finishing mill in the high-line rolling mill is 921°C, and the spinning temperature is controlled at 870-890°C through the cooling of the water cooling box, and then the spinning is carried out through the laying machine. The actual spinning temperature is 882°C, spinning speed is 35m / s.

[0048] The wire rod after spinning is controlled and cooled in the Stelmore air-cooled line. The control parameters of the Stelmore air-cooled line are as follows:

[0049] (1) The roller table speed of the first stage roller table is 0.60m / s, the roller table speed of the second stage roller table is 0.62m / s, the roller table speed of the third stage ...

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Abstract

The invention belongs to the technical field of ferrous metallurgy, and particularly relates to a method for controlling martensite and grain boundary cementite at the center of an 82B hot-rolled wirerod. The technical problem to be solved by the invention is to provide a control method for martensite and grain boundary cementite at the center of an 82B hot-rolled wire rod. The method comprises the following steps that a, a casting blank or square steel with the center carbon segregation degree of 0.90-1.20 is heated, and the wire rod is obtained through high-pressure water descaling, high-speed wire unit rolling and spinning; and b, the spun wire rod is cooled by adopting Stelmor air cooling control, and collecting, rolling and packaging are conducted. An air cooling roller way delayed slow cooling mode is adopted for Stelmor air cooling, and the speed of an air cooling roller way is controlled to range from 0.6 m / s to 0.88 m / s. The 82B hot-rolled wire rod prepared through the methodhas the advantages of being moderate in strength, good in plasticity and the like, the sorbite rate is larger than or equal to 90%, the centerless martensite and grain boundary cementite are smallerthan or equal to the 0.5 level, and good drawing performance is achieved.

Description

technical field [0001] The invention belongs to the technical field of iron and steel metallurgy, and in particular relates to a method for controlling martensite and grain boundary cementite in the center of an 82B hot-rolled wire rod. Background technique [0002] 82B hot-rolled wire rod is mainly used for the production of prestressed steel strands. In order to ensure the mechanical properties of the finished product, improve the drawing formability and production operation rate, etc., the wire breaking rate of the wire rod drawing and stranding and stranding processes is average. There are strict requirements, therefore, it is necessary for the wire rod to have the characteristics of high strength, high plasticity, and good uniformity of structure. [0003] The uniformity of the structure of the wire rod is one of the main factors leading to drawing fracture. In terms of the uniformity of the structure, in addition to requiring a high sorbite rate, "Hot Rolled Wire Rod f...

Claims

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Application Information

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IPC IPC(8): C21D8/06
CPCC21D8/065C21D2211/00
Inventor 邓通武柯晓涛唐伟张颖刚
Owner PANGANG GROUP RESEARCH INSTITUTE CO LTD