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Rolling method for low carbon twisted steel bar

A technology of threaded steel bar and low carbon steel, applied in the field of metal rolling, can solve the problem that the strength-to-yield ratio cannot be reached, and the tensile strength of grade III steel bar cannot be fully satisfied.

Inactive Publication Date: 2005-03-02
CENT IRON & STEEL RES INST
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0002] In the prior art, the inventor of this patent has obtained the authorized invention patent on May 14, 2003. The patent number is 00109495.5. This patent is based on the chemical composition of ordinary carbon steel Q235 and the rolling process formulated by the inventor of this patent. The production of ultra-fine grain steel bars, but its finished products cannot fully meet the tensile strength σ of grade III steel bars specified in GB1499-1998 b Greater than 570Mpa and the requirement that the tensile strength of grade IV steel bars is greater than 630MPa, and the measured strength-to-yield ratio cannot reach the requirement greater than 1.25

Method used

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  • Rolling method for low carbon twisted steel bar
  • Rolling method for low carbon twisted steel bar

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Embodiment 1

[0019] The composition of the selected steel grade is 0.21%C-0.40%Si-0.79%Mn, the starting rolling temperature is 950°C, the temperature is controlled by water cooling between the intermediate and finishing rolling units and between the racks, the temperature of the finishing rolling mill is 840°C, and then the temperature is ≥10°C / The cooling rate of S is cooled to 600°C. The average yield strength obtained is σ s =460Mpa, tensile strength σ b = 630Mpa, elongation = 22.5%, strength ratio σ b / σ s =1.36, the structure is ferrite + pearlite, the ferrite grain size is 10 μm, and the pearlite grain size is 7 μm. The performance reaches the national standard of grade III steel bar.

Embodiment 2

[0021] The composition of the selected steel grade is 0.22%C-0.35%Si-0.60%Mn, the starting rolling temperature is 950°C, the temperature is controlled by water cooling between the intermediate and finishing rolling units and between the racks, the temperature of the finishing rolling mill is 850°C, and then the temperature is ≥10°C / The cooling rate of S is cooled to 550°C. The average yield strength obtained is σ s =450Mpa, tensile strength σ b = 610Mpa, elongation = 25%, strength ratio σ b / σ s =1.35, the structure is ferrite + pearlite, the ferrite grain size is 8 μm, and the pearlite grain size is 5 μm. The performance reaches the national standard of grade III steel bar.

Embodiment 3

[0023] The composition of the selected steel grade is 0.21%C-0.53%Si-0.8%Mn, the starting rolling temperature is 920°C, the temperature is controlled by water cooling between the intermediate and finishing mills and between the racks, the temperature of the finishing mill is 830°C, and then the temperature is ≥10°C / The cooling rate of S is cooled to 500°C. The average yield strength obtained is σ s =520Mpa, tensile strength σ b = 660Mpa, elongation = 22%, strength ratio σ b / σ s =1.26, the structure is ferrite + pearlite, the ferrite grain size is 7.5 μm, and the pearlite grain size is 5 μm. The performance reaches the national standard of grade IV steel bar.

[0024] batch

[0025]

[0026]

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Abstract

The present invention relates to metal rolling technology, and especially the rolling process of twisted low carbon steel bar. The twisted low carbon steel bar has the chemical components of: C 0.17-0.23 wt%, Si 0.20-0.80 wt%, Mn 0.50-1.50 wt%, S not more than 0.035 wt% and P not more than 0.035 wt%. The rolling process with complete or patial temperature control includes the following steps: initial rolling with low temperature cogging at 850-950 deg.c, middle rolling at 750-850 deg.c with accumulated deformation over 50 %, finish rolling at 750-900 deg.c, and subsequent water cooling at lower than 600 deg.c with cooling speed greater than 10 deg.c / sec. Compared with available technology, the present invention has superfine crystal grain structure and high steel bar performance.

Description

technical field [0001] The invention belongs to the field of metal rolling, and mainly relates to a rolling method of low-carbon steel threaded steel bars. Background technique [0002] In the prior art, the inventor of this patent has obtained the authorized invention patent on May 14, 2003. The patent number is 00109495.5. This patent is based on the chemical composition of ordinary carbon steel Q235 and the rolling process formulated by the inventor of this patent. The production of ultra-fine grain steel bars, but its finished products cannot fully meet the tensile strength σ of grade III steel bars specified in GB1499-1998 b The tensile strength of steel bars greater than 570Mpa and grade IV is greater than 630MPa, and the measured strength-to-yield ratio cannot reach the requirement of greater than 1.25. Therefore, in the face of the need to upgrade the types of steel bars, it is necessary to establish a new chemical composition system and rolling process system for s...

Claims

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Application Information

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IPC IPC(8): B21B1/16B21H3/02C22C38/00
Inventor 杨忠民陈其安陈颖车彦民白埃民
Owner CENT IRON & STEEL RES INST
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