Method for effectively controlling generation of central cracks in medium-carbon steel plate

A center crack and steel plate technology, applied in the field of effectively controlling the generation of center cracks in medium carbon steel plates, can solve the problems of unstable mechanical properties, center cracks in steel plates, unqualified flaw detection, etc., to improve internal quality, ensure cooling, and improve performance qualifications rate effect

Inactive Publication Date: 2014-02-26
NANJING IRON & STEEL CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, production practice has found that medium-carbon series steel plates are prone to flaw detection failures and unstable mechanical properties. Metallographic testing and scanning electron microscopy-energy spectrum analysis have found that the main defect causing such problems is serious cracks in the center of steel plates, cracks There may be type A or type B inclusions occasionally, and there are severe bainite or martensite segregation on both sides of the crack

Method used

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Examples

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Effect test

Embodiment 1

[0013] A method for effectively controlling the occurrence of cracks in the center of medium carbon steel plates. This method effectively controls the occurrence of cracks in the center of steel plates by controlling the purity of molten steel, the superheat of molten steel in a tundish, the slow cooling time of billet stacking, and the cooling rate of steel plates after rolling. For production, a group of 11 furnaces of Q345R container steel was selected for steelmaking. The casting slab size was 220mm*2060mm*long, the total weight of the casting slab was 1666.296t, the rolled steel grade was Q345R, the thickness of the steel plate was 16~50mm, and the total weight of the steel plate was 1501.881t. Specific requirements are as follows:

[0014] Control the purity of molten steel. The molten iron needs to be pre-desulfurized, and the sulfur content of the molten iron entering the converter is controlled to be ≤0.015%, and the slag is fully removed; the top-bottom composite blo...

Embodiment 2

[0020] A method for effectively controlling cracks in the center of medium-carbon steel plates. In this embodiment, a group of 10 furnaces of S355J-2 medium-carbon alloy steel is selected for steelmaking. The size of the billet is 260mm*2260mm*long. The grades are Q345BZ15, Q345BZ25 and Q345R, the thickness of the steel plate is 16~45mm, and the total weight of the steel plate is 1375.142t. Specific requirements are as follows:

[0021] Mainly through the pre-desulfurization treatment of molten iron, control the sulfur content of molten iron entering the converter to ≤0.015%, and fully remove slag; top-bottom composite blowing converter smelting, ensure that the phosphorus content of the tapping is ≤0.015%, strictly avoid the slag of the converter, and use Deoxidize pure aluminum blocks to ensure that the refined aluminum content is 0.010-0.050%; LF refining furnace produces white slag, uses aluminum wire to deoxidize the slag, and adds 20~30kg / furnace in batches, each batch 5...

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Abstract

The invention discloses a method for effectively controlling generation of central cracks in a medium-carbon steel plate. Molten iron pretreatment, converter tapping pure aluminum block deoxidation, LF (ladle furnace) white slag refinement, RH vacuum treatment and other techniques are mainly utilized to control the molten steel purity and the continuous casting frequency, so that the tundish molten steel superheating temperature is controlled at 5-20 DEG C, the casting blank stacking slow cooling time is controlled to at least 45 hours, and the cooling speed of the rolled steel plate is controlled by an ultra-fast cooling system and a head/tail masking technique, thereby effectively controlling the generation of central cracks in the steel plate. The method improves the internal quality of the steel plate, enhances the performance qualification rate and the flaw detection qualification rate of flaw detection steel, and has favorable economical and social benefits.

Description

technical field [0001] The invention belongs to the field of metallurgy, and relates to a method for controlling the generation of cracks in the center of a steel plate, in particular to a method for effectively controlling the generation of cracks in the center of a medium carbon steel plate. technical background [0002] Medium carbon series (mainly including Q345 series, S355 series and A709Gr50 series, etc.) steel plates are currently the most widely used and most used steel types in the fields of boilers and pressure vessels, engineering structures and construction machinery because of their good comprehensive mechanical properties and process properties. One of the series. However, production practice has found that medium-carbon series steel plates are prone to flaw detection failures and unstable mechanical properties. Metallographic testing and scanning electron microscopy-energy spectrum analysis have found that the main defect causing such problems is serious crac...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C21C5/28C21C7/00C21C1/02C21D8/02
Inventor 刘军楚觉非王端军何烈云王攀峰侯彩霞
Owner NANJING IRON & STEEL CO LTD
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