A method for controlling mottle on the surface of steel plates for welded structures

A control method and technology of welding structure, applied in the direction of temperature control, workpiece surface treatment equipment, manufacturing tools, etc., can solve the problems of unsuitable elimination of surface mottle, no component design range, etc. Spot defects, dense and uniform effect of iron oxide scale

Active Publication Date: 2020-02-07
NANJING IRON & STEEL CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

Chinese patent application number 201410110279.9, titled "A Control Method for Spotting on Steel Plate Surface", provides a control method to reduce spotting on steel plate surface by reducing Si content to less than 0.20%, descaling water pressure, descaling box header design , this patent only puts forward the upper limit requirement of Si, and there is no optimal composition design range
However, the composition system of steel for welded structures is different from that of ordinary hot-rolled steel plates, and the methods of controlling mottled spots in the above-mentioned patents, such as heating, descaling, high-temperature rolling, and cooling, are not suitable for eliminating mottled spots on the surface of steel for welded structures

Method used

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  • A method for controlling mottle on the surface of steel plates for welded structures
  • A method for controlling mottle on the surface of steel plates for welded structures
  • A method for controlling mottle on the surface of steel plates for welded structures

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Embodiment 1

[0032]Example 1: Production of a 10mm thick steel for welding structures at low temperature, which requires a yield strength of 345MPa or more, a tensile strength of 470-630MPa, a longitudinal impact energy of -40°C ≥ 34J, and a carbon equivalent CEV ≤ 0.38%. It is applied to appearance structures parts, which have high requirements on the surface of the steel plate. Produce the steel plate that meets user's requirement by the method of the present invention, concrete steps are as follows:

[0033] (1) The composition weight percentage of molten steel is: C: 0.12%, Mn: 1.50%, Si: 0.12%, Nb: 0.025%, Ti: 0.010%, P: 0.009%, S: 0.002%, Cr: 0.015%, Mo: 0.003%, V: 0.003%, Ni: 0.007%, Cu: 0.013%, and the balance is iron and impurities; CEV: 0.38%. Continuous casting slab thickness is 150mm,

[0034] (2) Send the continuous casting slab into the heating furnace, the total time in the furnace is 135min, the soaking period is 25min, the temperature difference between the head and the ...

Embodiment 2

[0040] Example 2: To produce a kind of steel for welding structure for a machinery manufacturing enterprise, the thickness is 16mm and 25mm, the yield strength is required to be above 355MPa, the tensile strength is 490-610MPa, the carbon equivalent CEV is less than or equal to 0.38%, and the steel plate must not have cracks after shot peening spots, can be directly painted coating. The steel plate meeting user's requirements is produced by the method of the present invention, and concrete steps are as follows:

[0041] (1) The composition weight percentage of molten steel is: C: 0.18%, Mn: 1.00%, Si: 0.05%, Nb: 0.030%, Ti: 0.015%, P: 0.012%, S: 0.010%, Cr: 0.018%, Mo: 0.003%, V: 0.004%, Ni: 0.008%, Cu: 0.015%, the balance is iron and impurities, CEV: 0.35%. The thickness of the continuous casting slab is 220mm.

[0042] (2) Send the continuous casting slab into the heating furnace. For the slab of rolling 16mm thick steel plate, the total time in the furnace is 200min, the ...

Embodiment 3

[0049] Embodiment 3: produce a kind of 6mm thick steel plate for welding structure, carry out according to the following steps:

[0050] (1) The composition weight percentage of molten steel is: C: 0.15%, Mn: 1.20%, Si: 0.05%, Nb: 0.020%, Ti: 0.012%, P: 0.014%, S: 0.003%, Cr: 0.010%, Mo: 0.05%, V: 0.004%, Ni: 0.004%, Cu: 0.008%, the balance being iron and impurities; CEV: 0.36%. The thickness of the continuous casting slab is 150mm.

[0051] (2) Send the continuous casting slab into the heating furnace. The total time in the furnace is 120 minutes, the soaking period is 21 minutes, the temperature difference between the head and the tail of the slab is 3°C, and the furnace temperature is 1170°C.

[0052] (3) After the slab comes out of the furnace, it is descaled by high-pressure water. The pressure of the descaling system is 22.0-22.8MPa, and the iron oxide scale formed on the slab in the heating furnace is completely removed.

[0053] (4) Roll the descaled slab into a 6mm ...

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Abstract

The invention discloses a controlling method of steel plate surface spots for a welding structure. Based on a composition system of steel for the welded structure, the processes of smelting, slab heating, descaling, steel rolling and cooling of molten steel are controlled in a production process, and so that uniform iron oxide sheet is obtained in the production process; and meanwhile, on the basis of ensuring mechanical properties of a steel plate, the thickness of the iron oxide sheet for the steel for the welding structure is effectively controlled, and the damage of the iron oxide sheet isavoided. The method can enable the steel plate surface iron oxide sheet to be dense and uniform, the thickness of the iron oxide sheet is controlled within 30 [mu], and spots defects after shot blasting on the surface of the steel for the welding structure and colour difference watermark defects after spray painting are eliminated.

Description

technical field [0001] The invention relates to a production method of a steel plate, in particular to a method for controlling mottling on the surface of a steel plate for a welded structure. Background technique [0002] In the process of steel structure manufacturing, welding is a very important processing technology. Steel for welded structures is widely used in machinery manufacturing, shipbuilding, automobile manufacturing and other industries. Steel for welding structures requires low carbon equivalent, which is different from the composition system of ordinary hot-rolled medium and thick plates. Its chemical composition is different from the design idea of ​​high-carbon, high-manganese, and high-carbon The carbon equivalent of the plate is more stringent, and the carbon equivalent of the steel for welding structure is 0.06-0.20% lower than that of ordinary grades of the same steel grade. [0003] In recent years, with the deepening of my country's industrialization ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): B21B1/26B21B45/08B21B37/74C22C38/02C22C38/04C22C38/42C22C38/44C22C38/46C22C38/48C22C38/50
CPCB21B1/26B21B37/74B21B45/08C22C38/02C22C38/04C22C38/42C22C38/44C22C38/46C22C38/48C22C38/50
Inventor 李明黄灿
Owner NANJING IRON & STEEL CO LTD
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