Production method of high-strength cold-drawn steel bar

Abstract

The invention relates to a production method of a cold-drawn steel bar, in particular to a production method of a high-strength cold-drawn steel bar, which comprises the following steps: carrying out primary cold drawing on a bar to obtain a primary bar; primary aging treatment is conducted on the primary bar, and a secondary bar is obtained; performing secondary cold drawing on the secondary bar to obtain a tertiary bar; and the third-time bar is subjected to aging treatment, and the high-strength cold-drawn steel bar is obtained. According to the production method of the high-strength cold-drawn steel bar, through two times of cold drawing and two times of aging treatment, the tensile strength of the cold-drawn steel bar is stabilized at 830 MPa or above, and the high-strength cold-drawn steel bar has excellent comprehensive mechanical property indexes.

Description

Technical Field

[0001] The invention relates to a production method of a cold drawn steel bar, in particular to a production method of a high-strength cold drawn steel bar. Background Art

[0002] Q355 material is a widely used structural steel with excellent welding performance. This material cannot generally be strengthened by quenching treatment, and can only be strengthened by cold deformation strengthening mechanism. Cold drawing process is widely used as a process method to improve material strength. The cold drawing deformation has a certain nonlinear relationship with the strength, but with the increase of cold drawing deformation, the plasticity of the material reaches the limit, and the strength increase value slows down. If the drawing deformation continues to increase, a series of quality risks such as drawing fracture and internal cracks will occur due to insufficient plasticity. The original strength of the hot-rolled bar of Q355 material is about 520MPa. Taking the hot-rolled bar with a diameter of Φ42 / 45 as an example, after about 30% of the limit deformation, the strength limit is 780-800MPa, which cannot meet the use requirements in an environment where the tensile strength is greater than 830MPa. Summary of the invention

[0003] In order to solve the above problem that the tensile strength cannot be greater than 830 MPa, the present invention provides a production method of a high-strength cold-drawn steel bar, and the specific technical solution is as follows:

[0004] A production method of a high-strength cold-drawn steel bar comprises the following steps: cold drawing a bar once to obtain a primary bar; performing an aging treatment on the primary bar once to obtain a secondary bar; cold drawing the secondary bar twice to obtain a tertiary bar; and performing an aging treatment on the tertiary bar to obtain a high-strength cold-drawn steel bar.

[0005] Preferably, the deformation amount of the first cold drawing is 18-22%; the deformation amount of the second cold drawing is 15-19%.

[0006] Preferably, the primary aging temperature is 380-420° C., and the aging time is 5-6 hours; the secondary aging temperature is 230-270° C., and the aging time is 5-6 hours.

[0007] Preferably, shot blasting and film lubrication treatment are performed before the secondary cold drawing.

[0008] Compared with the prior art, the present invention has the following beneficial effects:

[0009] The invention provides a production method for a high-strength cold-drawn steel bar. Through two cold-drawing processes and two aging processes, the tensile strength of the cold-drawn steel bar is stabilized at above 830 MPa, and the steel bar has excellent comprehensive mechanical performance indicators. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is the tensile test diagram of the steel side with a diameter of 35;

[0011] Figure 2 This is the tensile test diagram of a steel bar with a diameter of 37. DETAILED DESCRIPTION

[0012] The present invention will be further described with reference to the accompanying drawings.

[0013] Example 1

[0014] like Figure 1 As shown, a method for producing a high-strength cold-drawn steel bar comprises the following steps:

[0015] Q355Φ42 hot-rolled bar material is selected. After the processes of rolling head, shot blasting, film lubrication, etc., a cold drawing is carried out, the deformation is 18.1%, and the cold drawing is carried out to Φ38. Then an aging treatment is carried out at 380℃ for 5 hours to restore the plasticity of the material and prepare for the secondary cold drawing.

[0016] After the stress is eliminated, the material is shot blasted and lubricated, and then cold drawn for the second time, with a deformation of 15.2% and cold drawn to Φ35. The hardness and strength of the material after the two drawing processes are tested, and the results are 240HV and 775MPa respectively;

[0017] Finally, the Φ35 material that has been drawn twice was subjected to a second aging treatment at a temperature of 230°C for 5 hours. The final sample test showed a hardness of 262HV, a tensile strength of 845MPa, an elongation of 12%, and a cross-sectional shrinkage of 55%.

[0018] Example 2

[0019] A method for producing a high-strength cold-drawn steel bar comprises the following steps:

[0020] Q355Φ42 hot-rolled bar material is selected. After the processes of rolling head, shot blasting, film lubrication, etc., a cold drawing is carried out, the deformation is 18.1%, and the cold drawing is carried out to Φ38. Then an aging treatment is carried out at 400℃ for 5.5h to restore the plasticity of the material and prepare for the secondary cold drawing.

[0021] After the stress is eliminated, the material is shot blasted and lubricated, and then cold drawn twice, with a deformation of 15.2% and cold drawn to Φ35. The hardness and strength of the material after the two drawing processes are tested, and the results are 245HV and 790MPa respectively;

[0022] Finally, the Φ35 material that has been drawn twice was subjected to a second aging treatment at a temperature of 250°C for 5.5 hours. The final sample test showed that the hardness was 265HV, the tensile strength was 850MPa, the elongation was 12%, and the cross-sectional shrinkage was 55%.

[0023] Example 3

[0024] A method for producing a high-strength cold-drawn steel bar comprises the following steps:

[0025] Q355Φ42 hot-rolled bar material is selected. After the processes of rolling head, shot blasting, film lubrication, etc., it is cold drawn once, with a deformation of 18.1%, cold drawn to Φ38, and then aging treatment at 420℃ for 6 hours to restore the plasticity of the material and prepare for the second cold drawing;

[0026] After the stress is eliminated, the material is shot blasted and lubricated, and then cold drawn twice, with a deformation of 15.2% and cold drawn to Φ35. The hardness and strength of the material after the two drawing processes are tested, and the results are 250HV and 786MPa respectively;

[0027] Finally, the Φ35 material that has been drawn twice was subjected to a second aging treatment at a temperature of 270°C for 6 hours. The final sample test showed a hardness of 266HV, a tensile strength of 855MPa, an elongation of 12%, and a cross-sectional shrinkage of 55%.

[0028] Example 4

[0029] like Figure 2 As shown, a method for producing a high-strength cold-drawn steel bar comprises the following steps:

[0030] Q355Φ45 hot-rolled bar material is selected. After the processes of rolling head, shot blasting, film lubrication, etc., a cold drawing is carried out with a deformation of 19% and cold drawing to Φ40.5. Then an aging treatment at 390℃ is carried out for 5.2h to restore the plasticity of the material and prepare for the secondary cold drawing.

[0031] After the stress is eliminated, the material is shot blasted and lubricated, and then cold drawn twice, with a deformation of 16.5% and cold drawn to Φ37. The hardness and strength of the material after two cold drawing are tested, and the results are 245HV and 790MPa respectively;

[0032] Finally, the Φ37 material that has been drawn twice was subjected to secondary aging treatment at a temperature of 230°C for 5 hours. The final sample test showed that the hardness was 265HV, the tensile strength was 850MPa, the elongation was 12%, and the cross-sectional shrinkage was 55%.

[0033] Example 5

[0034] A method for producing a high-strength cold-drawn steel bar comprises the following steps:

[0035] Q355Φ45 hot-rolled bar material is selected. After the processes of rolling head, shot blasting, film lubrication, etc., a cold drawing is carried out with a deformation of 19% and cold drawing to Φ40.5. Then an aging treatment at 385℃ is carried out for 5.4h to restore the plasticity of the material and prepare for the secondary cold drawing.

[0036] After the stress is eliminated, the material is shot blasted and lubricated, and then cold drawn twice, with a deformation of 16.5% and cold drawn to Φ37. The hardness and strength of the material after two cold drawing are tested, and the results are 244HV and 781MPa respectively;

[0037] Finally, the Φ37 material that has been drawn twice was subjected to secondary aging treatment at an aging temperature of 260°C and an aging time of 5 hours. The final sample test showed a hardness of 266HV, a tensile strength of 848MPa, an elongation of 12%, and a cross-sectional shrinkage of 55%.

[0038] Example 6

[0039] A method for producing a high-strength cold-drawn steel bar comprises the following steps:

[0040] Q355Φ45 hot-rolled bar material is selected. After the processes of rolling head, shot blasting, film lubrication, etc., a cold drawing is carried out with a deformation of 19% and cold drawing to Φ40.5. Then an aging treatment at 415℃ is carried out for 6 hours to restore the plasticity of the material and prepare for the secondary cold drawing.

[0041] After the stress is eliminated, the material is shot blasted and lubricated, and then cold drawn twice, with a deformation of 16.5% and cold drawn to Φ37. The hardness and strength of the material after two cold drawing are tested, and the results are 240HV and 792MPa respectively;

[0042] Finally, the Φ37 material that has been drawn twice was subjected to secondary aging treatment at a temperature of 250°C for 5 hours. The final sample test showed a hardness of 271HV, a tensile strength of 839MPa, an elongation of 12%, and a cross-sectional shrinkage of 55%.

[0043] The technical principle of the present invention is described above in conjunction with specific embodiments. These descriptions are only for explaining the principle of the present invention and cannot be interpreted as limiting the protection scope of the present invention in any way. Based on the explanations herein, those skilled in the art can associate other specific implementations of the present invention without paying creative labor, and these methods will fall within the protection scope of the claims of the present invention.

Claims

1. A method for producing a high-strength cold-drawn steel bar, characterized in that: The following steps are involved: The bar is cold drawn once to obtain a bar; Performing an aging treatment on the primary bar to obtain a secondary bar; The secondary bar is subjected to secondary cold drawing to obtain a tertiary bar; The tertiary bars are subjected to aging treatment to obtain high-strength cold-drawn steel bars.

2. The method for producing a high-strength cold-drawn steel bar according to claim 1, characterized in that: The deformation amount of the first cold drawing is 18-22%; the deformation amount of the second cold drawing is 15-19%.

3. The method for producing a high-strength cold-drawn steel bar according to claim 1, characterized in that: The temperature of the primary aging is 380-420° C., and the aging time is 5-6 hours; the temperature of the secondary aging is 230-270° C., and the aging time is 5-6 hours.

4. The method for producing a high-strength cold-drawn steel bar according to claim 1, characterized in that: Shot blasting and film lubrication are performed before the secondary cold drawing.

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