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Method for controlling iron scale structures of hot-rolled steel bars by stepped cooling

A technology of iron oxide scale and cooling control, which is applied in rolling mill control devices, metal rolling, temperature control, etc., and can solve the problems of steel bar corrosion speed and serious corrosion degree

Active Publication Date: 2016-05-18
CENT IRON & STEEL RES INST
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0005] The purpose of the present invention is to provide a stepwise cooling method for hot-rolled steel bars to control the scale structure, and to obtain a dense scale structure through the optimization of rolling and cooling processes, so as to solve the problem of strong water penetration after rolling. The corrosion rate and degree of corrosion of steel bars in the atmosphere are serious, and the goal of alleviating rust within a period of time (sales cycle) is achieved

Method used

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  • Method for controlling iron scale structures of hot-rolled steel bars by stepped cooling
  • Method for controlling iron scale structures of hot-rolled steel bars by stepped cooling
  • Method for controlling iron scale structures of hot-rolled steel bars by stepped cooling

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Experimental program
Comparison scheme
Effect test

Embodiment 1

[0034] 1) The internal control chemical composition of test steel bar 1: C0.22%, Si0.41%, Mn1.18%, P0.033%, S0.018%, Cr0.011%, Ni0.006%, V0.002%, Fe balance.

[0035] 2) Hot rolling is carried out after conventional heating of the billet, the rolling specification is Φ20mm, the billet heating temperature is 1150°C, the furnace temperature is 1100°C, the rolling start temperature is 1070°C, and the final rolling temperature is 1050°C;

[0036] 3) After the final rolling, the steel bar runs at a speed of 14.0m / s, and the surface of the steel bar is subjected to rapid cooling treatment for 2s, and the average cooling rate V cooling ≥100°C / s; using the step-by-step controlled cooling method of fast cooling-return temperature-quick cooling-return temperature cycle, the return temperature of the upper cooling bed is controlled at 600-680°C;

[0037] 4) For all the hot-rolled high-strength steel bars that adopt the staged cooling process, there is no red Fe on the surface after the co...

Embodiment 2

[0040] 1) The chemical composition of industrial test steel bars: C0.23%, Si0.44%, Mn1.39%, P0.035%, S0.030%, V0.032%, Fe balance.

[0041] 2) Hot rolling is performed on the slab after conventional heating, the rolling specification is Φ25mm, and the final rolling temperature is controlled at 1050°C;

[0042] 3) After the final rolling, the steel bar runs at a speed of 11.5m / s, and the surface of the steel bar is subjected to rapid cooling treatment for 2s, and the average cooling rate V cooling ≥100°C / s; using the staged controlled cooling method of fast cooling-return temperature-fast cooling-return temperature cycle, the return temperature of the upper cooling bed is controlled to be 770-980°C;

[0043] 4) There is no surface red Fe after the cooling bed 2 o 3 rust layer.

Embodiment 3

[0045] 1) Chemical composition of test steel bar 1: C0.25%, Si0.34%, Mn1.44%, P0.031%, S0.031%, Cr0.037%, Fe balance.

[0046] 2) Hot rolling is performed on the slab after conventional heating, the rolling specification is Φ20mm, and the final rolling temperature is controlled at: 1050°C;

[0047] 3) After the final rolling, the steel bar runs at a speed of 11.5m / s, and the surface of the steel bar is subjected to rapid cooling treatment for 2s, and the average cooling rate V cooling ≥100°C / s; using the step-by-step controlled cooling method of fast cooling-return temperature-quick cooling-return temperature cycle, the return temperature of the upper cooling bed is controlled at 680-770°C;

[0048] 4) For all the hot-rolled high-strength steel bars that adopt the staged cooling process, there is no red Fe on the surface after the cooling bed 2 o 3 rust layer.

[0049] 5) Placed in the open air for 1 month, the corrosion area is equivalent to 50% of the corrosion area of ​​...

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Abstract

A method for controlling iron scale structures of hot-rolled steel bars by stepped cooling belongs to the technical field of steel rolling. Compact iron scale structures are obtained through optimization of a rolling and cooling process, so that a problem that steel bars produced by a post-rolling forceful through-water process are fast in corrosion rate and serious in corrosion degree in atmosphere is solved, and a goal that rust is relieved within a period of time is achieved. By adopting a stepped cooling process and the method for controlling the iron scale structures, provided by the invention, a traditional through-water cooling process can be replaced, so that mechanical property of an HRB400 (hot-rolled ribbed bar)-grade steel bar with phi 20 to 25 mm of a typical specification meets requirements of various technical indexes of GB 1499.2-2007; meanwhile, when being delivered to a cooling bed, each of all hot-rolled high-strength steel bars produced by adopting the stepped cooling process does not have a surface red Fe2O3 rust layer; shown by SEM (scanning electron microscope) analysis, iron scale is 10 to 30 [mu]m thick; after staying for one month in the open air, corrosion area of a sample is reduced by 50 percent in comparison with that of a steel bar produced by a traditional forceful through-water process.

Description

technical field [0001] The invention belongs to the technical field of steel rolling, and in particular relates to a method for stepwise cooling of hot-rolled steel bars to control the oxide scale structure. Background technique [0002] At present, the production process of domestic hot-rolled ribbed steel bars is basically divided into two types, one is the traditional natural cooling process after hot rolling, and the other is the forced water cooling process after hot rolling. The former needs to add a certain amount of Strengthening alloy elements, the ribbed steel bar has better corrosion resistance, but the alloy cost is higher; the steel bar produced by the latter process saves the alloy cost, and the alloy addition is greatly reduced, but the existing martensitic ring welding softens and The problem of red rust on the surface after water penetration, and its poor anti-corrosion performance have seriously affected subsequent use. Users even asked for returns or reduc...

Claims

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Application Information

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IPC IPC(8): B21B37/00B21B37/74B21B45/02C22C38/02C22C38/04C22C38/12C22C38/18
CPCB21B37/00B21B37/74B21B45/0203C22C38/02C22C38/04C22C38/12C22C38/18
Inventor 王卫卫李光瀛肖金福张江玲白宇
Owner CENT IRON & STEEL RES INST
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