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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  • 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, s

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
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Example Embodiment

[0033] Example 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 margin.

[0035] 2) Hot-rolling the cast slab after conventional heating, the rolling specification is Φ20mm, the billet heating temperature is 1150°C, the tapping temperature is 1100°C, the opening 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 rapidly cooled for 2s, and the average cooling speed is V cooling ≥100℃ / s; adopts the stepwise stepped control cooling method of fast cooling-returning-rapid cooling-returning temperature cycle to control the upper cooling bed's returning temperature of 600~680℃;

[0037] 4) All the hot-rolled high-strength steel bars that adopt the stepped cooling process have no red Fe on the surface after the cooling bed 2 O 3 Rust layer.

[0038] 5) When pl...

Example Embodiment

[0039] Example 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 the cast slab after conventional heating, the rolling specification is Φ25mm, and the final rolling temperature is controlled at 1050℃;

[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 rapidly cooled for 2s, and the average cooling speed is V cooling ≥100℃ / s; adopts the stepped stepped control cooling method of fast cooling-returning-rapid cooling-returning temperature cycle to control the upper cooling bed's return temperature to 770~980℃;

[0043] 4) No surface red Fe appeared after being put on the cooling bed 2 O 3 Rust layer.

Example Embodiment

[0044] Example 3:

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

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

[0047] 3) After finishing rolling, the steel bar runs at a speed of 11.5m / s, and the surface of the steel bar is rapidly cooled for 2s, and the average cooling speed is V cooling ≥100℃ / s; adopts the stepped stepped control cooling method of fast cooling-returning-rapid cooling-returning cycle to control the upper cooling bed's return temperature of 680~770℃;

[0048] 4) All the hot-rolled high-strength steel bars that adopt the stepped cooling process have no red Fe on the surface after the cooling bed 2 O 3 Rust layer.

[0049] 5) When placed in the open air for 1 month, the rusted area is equivalent to 50% of the rusted area of ​​the forced water cooling process.

[0050] Table 1 Su...

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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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