Steel forming straightness control method for engineering machinery suspension arm and engineering machinery suspension arm

Abstract

The invention discloses a steel forming straightness control method for an engineering machinery suspension arm and the engineering machinery suspension arm, a direct installation mode is adopted in a hot rolling heating stage, the temperature of a high heat section is 1300 + / -20 DEG C, and the time of the high heat section is 70-140 minutes; in the rolling stage, a front rack oversized reduction + F7 flexible micro-medium wave compensation strategy is adopted for rolling production; in the cooling stage, ultra-fast cooling and air cooling are adopted for cooling to the coiling temperature; the heat treatment process adopts a vacuum radiation heating method for tempering. The thickness of the prepared steel plate is 2.55-5.01 mm, the length of the prepared steel plate is 5.5-6.5 m, the strength grade of the prepared steel plate is 765-845 MPa, the prepared steel plate is used for manufacturing a telescopic suspension arm of an engineering machinery overhead working truck, after the steel plate is integrally bent and formed, the straightness of a part in the length direction is smaller than or equal to 3 mm / L, and the problem that the straightness of the suspension arm is out of tolerance after high-strengthening, light-weight and environment-friendly manufacturing of engineering machinery is effectively solved.

Description

Technical Field

[0001] The invention belongs to the technical field of ferrous metal manufacturing, and in particular relates to a method for controlling the forming straightness of steel for an engineering machinery boom and an engineering machinery boom. Background Art

[0002] With the implementation of the national "dual carbon" strategy and the rapid development of the construction machinery industry, competition is becoming increasingly fierce, forcing the construction machinery industry to accelerate its development in the direction of "high strength, lightweight, green, and ecological". In order to meet the development needs of the construction machinery industry, construction machinery steel must have the use properties of "high strength and thinning, green and low carbon". The increase in steel plate strength and the reduction in thickness require the same forming effect as low-strength thick specifications during the forming process, and the requirements for materials and the difficulty of forming are doubled. Because according to the forming characteristics of high-strength steel, the higher the material strength and the thinner the thickness, under the same forming conditions, the greater the forming difficulty, the more serious the forming "springback" phenomenon, and it is more difficult to ensure the dimensional standard requirements of the formed parts. Summary of the invention

[0003] The purpose of the present invention is to solve the above technical problems and to provide a method for controlling the straightness of steel forming for an engineering machinery boom and an engineering machinery boom. After the steel plate is integrally bent and formed, the straightness of the boom in the length direction is ≤3mm / L.

[0004] To achieve the above-mentioned purpose, the present invention provides a method for controlling the forming straightness of steel for engineering machinery booms, wherein a direct loading mode is adopted in the hot rolling heating stage, the high heat section temperature is 1300±20°C, and the high heat section time is 70-140min, so that the austenitization of the structure is uniform and the temperature is uniform, thereby providing favorable conditions for subsequent homogenization and low stress rolling; in the rolling stage, the front frame ultra-large pressure reduction + F7 flexible micro-wave compensation strategy is adopted for rolling production; in the cooling stage, ultra-fast cooling + air cooling is adopted for cooling to the coiling temperature; and the heat treatment process adopts vacuum radiation heating for tempering.

[0005] Furthermore, it also includes a leveling process stage, with a leveling speed of 115-145m / min, a leveling rolling force of 420-520t, and a dynamic positive bending roll for bending roll compensation leveling. It ensures that the material has sufficient plastic strain during the leveling process, the edge wave shape is fully eliminated, the material has a good apparent plate shape, and the internal stress state is evenly distributed.

[0006] Furthermore, it also includes a process of using deep bending rollers to dynamically press down as the steel coil changes during straightening and cross-cutting, and continuously applying a reverse bending moment to the steel coil to reduce or eliminate the original curvature of the steel plate.

[0007] Furthermore, during the straightening and cross-cutting: rough straightening is performed by pressing down once with a large amount of pressure, and the amount of pressure reduction is 18 to 23 mm; fine straightening is performed by segmented straightening, and fine correction bend compensation is used, and the straightening plastic strain ratio is 75 to 85%, so that the apparent plate shape unevenness of the material is ≤3 mm / m, the edge wave shape of the material is completely eliminated, and the internal stress of the material is further eliminated and the material is homogenized.

[0008] Furthermore, the direct charging temperature in the hot rolling heating stage is 725-8250° C., which improves production efficiency, reduces energy consumption, and also avoids the generation of uneven thermal stress and structural stress in the process of high temperature-cooling-reheating.

[0009] Furthermore, in the rolling stage, the front stand super-large reduction + F7 flexible micro-wave compensation strategy is used for rolling production, specifically: F1~F3 reduction is 65~75%, F4 reduction is 20~24%, F5~F6 reduction is 10~15%; F7 reduction is 6~8%; F7 flexible micro-wave compensation adopts different IU values ​​for compensation rolling according to different rolling thickness specifications, specifically 2.55~3.50mm thickness specification adopts 80m head, The IU compensation value is 60-80, the IU compensation value in the middle is 10-30, and the tail is 60m, and the IU compensation value is 30-50; the 3.51-5.01mm thickness specification adopts 80m in the head, the IU compensation value is 40-60, the IU compensation value in the middle is 0-20, and the tail is 60m, and the IU compensation value is 15-35, which compensates for the double-sided wave morphology trend of high-strength steel in the cooling process, and is also a guarantee that the original plate will not produce edge wave stress, and is the basis for good straightness of the material after forming.

[0010] Furthermore, the ultra-fast cooling rate is 120-150℃ / s to cool to 635-665℃, and then air-cooled to the coiling temperature. The ultra-fast cooling high-pressure jet water is sufficient to break the gas mold generated during high-temperature cooling, so that the cooling is converted from film boiling cooling to nucleate boiling cooling, making the cooling more uniform, and the material has better uniformity during the cooling process, thereby reducing the generation of uneven thermal stress and reducing the impact on the material forming performance. The post-air cooling further reduces the impact of cooling water on the material temperature, and ensures a uniform cooling effect in one step.

[0011] Furthermore, the tempering temperature of the heat treatment process is in the range of 561 to 582°C and the holding time is 101 to 109 minutes, ensuring that the internal structure of the material remains unchanged, and the strength of the steel plate is guaranteed by the dispersion strengthening effect of the second phase particles. The original material is based on the principles of fine grain strengthening and dispersion strengthening, while maintaining material properties, minimizing and evenly distributing the stress inside the material.

[0012] Furthermore, the steel plate prepared by the control method has a thickness of 2.55 to 5.01 mm, a length of 5.5 to 6.5 m, and a strength grade of 765 to 845 MPa.

[0013] A construction machinery boom is also provided, which is formed by bending steel prepared by the control method described above, and through the subsequent user cutting process, mold bending R angle compensation process, stamping speed, and holding time control design, it is ensured that the material meets the performance and process requirements of the boom parts, and the straightness of the boom in the length direction after bending is ≤3mm / m. The straightness of the boom in the length direction after forming is ≤3mm / L.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: the steel plate prepared by the control method of the present invention has a thickness of 2.55-5.01 mm, a length of 5.5-6.5 m, and a strength grade of 765-845 MPa, and is used to manufacture telescopic booms of engineering machinery aerial work vehicles. After the steel plate is bent as a whole, the straightness of the part in the length direction is ≤3 mm / L, which effectively solves the problem of out-of-tolerance straightness of the boom after the "high-strength, lightweight, and green" manufacturing of engineering machinery. DETAILED DESCRIPTION

[0015] The present invention will be further described below in conjunction with specific embodiments.

[0016] The main processes of the hot rolling raw steel plate rolling line are shown in Table 1.

[0017] Table 1 Main processes of rolling line

[0018]

[0019] The main processes for leveling, straightening and cross-cutting of hot-rolled raw materials are shown in Table 2.

[0020] Table 2 Flattening and straightening cross-cutting process

[0021]

[0022] The hot rolled raw steel plate is tempered according to the heat treatment process as shown in Table 3.

[0023] Table 3 Heat treatment

[0024] Example Thickness / mm Tempering temperature / ℃ Insulation time / min 1 2.57 582 101 2 3.13 581 106 3 4.02 575 109 4 4.25 577 103 5 4.78 563 105 6 5.01 561 107

[0025] After tempering, the steel plate was cooled with head and tail protection. The actual mechanical properties of the steel plate are shown in Table 4.

[0026] Table 4 Mechanical properties of original steel plate

[0027] Example Thickness / mm Length / mm <![CDATA[R eL / MPa]]> <![CDATA[R m / MPa]]> A / ％ 1 2.57 6000 778 817 24.0 2 3.13 5540 757 805 21.5 3 4.02 6000 760 798 23.5 4 4.25 5520 750 978 21.0 5 4.78 5540 804 974 26.5 6 5.01 5520 837 935 28.0

[0028] After the steel plate is cut, it is bent in multiple passes according to the process technology plan. The bending process is implemented according to Table 4, and the overall bending effect of the user is shown in Table 5.

[0029] Table 5 Bending process

[0030]

[0031] Table 6 Straightness after overall bending

[0032] Example Thickness / mm Straightness of parts after bending / mm 1 2.57 2.92 2 3.13 2.28 3 4.02 2.05 4 4.25 2.58 5 4.78 1.65 6 5.01 1.28 Comparative Example 1 2.57 7.88 Comparative Example 2 4.02 6.98 Comparative Example 3 5.01 6.93 .

Claims

1. A method for controlling the straightness of steel forming for an engineering machinery boom, characterized in that: The control method is as follows: the direct loading mode is adopted in the hot rolling heating stage, the high heat section temperature is 1300±20℃, and the high heat section time is 70-140min; the front frame ultra-large pressure reduction + F7 flexible micro-wave compensation strategy is adopted for rolling production in the rolling stage; ultra-fast cooling + air cooling is adopted in the cooling stage to cool to the coiling temperature; the heat treatment process adopts vacuum radiation heating for tempering.

2. The method for controlling the straightness of steel forming for a construction machinery boom according to claim 1 is characterized in that: It also includes a leveling process stage, with a leveling speed of 115 to 145 m / min, a leveling rolling force of 420 to 520 t, and the use of dynamic positive bending rolls for roll bending compensation leveling.

3. The method for controlling the straightness of steel forming for a construction machinery boom according to claim 1 is characterized in that: It also includes the use of deep bending rollers to dynamically press down as the steel coil changes during straightening and cross-cutting, and continuously applying a reverse bending moment to the steel coil.

4. The method for controlling the straightness of steel forming for a construction machinery boom according to claim 3 is characterized in that: During the straightening and crosscutting, rough straightening is performed by pressing down once with a large amount of 18 to 23 mm; fine straightening is performed by segmented straightening and fine correction bending compensation is adopted, and the straightening plastic strain ratio is 75 to 85%, so that the apparent plate shape unevenness of the material is ≤3 mm / m.

5. The method for controlling the straightness of steel forming for a construction machinery boom according to claim 1 is characterized in that: The direct charging temperature in the hot rolling heating stage is 725-8250°C.

6. The method for controlling the straightness of steel forming for a construction machinery boom according to claim 1, characterized in that: The rolling stage adopts the front stand super large pressure reduction + F7 flexible micro wave compensation strategy for rolling production. The specifics are: The reduction of F1~F3 is 65~75%, the reduction of F4 is 20~24%, and the reduction of F5~F6 is 10~15%; the reduction of F7 is 6~8%; the F7 flexible micro-wave compensation adopts different IU values ​​for compensatory rolling according to different rolling thickness specifications, specifically, the thickness specification of 2.55~3.50mm adopts 80m for the head, the IU compensation value is 60~80, the IU compensation value in the middle is 10~30, the tail is 60m, and the IU compensation value is 30~50; the thickness specification of 3.51~5.01mm adopts 80m for the head, the IU compensation value is 40~60, the IU compensation value in the middle is 0~20, the tail is 60m, and the IU compensation value is 15~35.

7. The method for controlling the straightness of steel forming for a construction machinery boom according to claim 1, characterized in that: The ultra-fast cooling rate is 120-150°C / s to cool to a temperature of 635-665°C, and then air-cooled to the coiling temperature.

8. The method for controlling the straightness of steel forming for a construction machinery boom according to claim 1, characterized in that: The tempering temperature of the heat treatment process is in the range of 561 to 582° C., and the holding time is 101 to 109 minutes.

9. The method for controlling the straightness of steel forming for a construction machinery boom according to claim 1, characterized in that: The steel plate prepared by the control method has a thickness of 2.55 to 5.01 mm, a length of 5.5 to 6.5 m, and a strength grade of 765 to 845 MPa.

10. An engineering machinery boom, characterized in that: The engineering machinery boom is formed by bending steel prepared by the control method of claim 1, and the straightness of the boom in the length direction after forming is ≤3mm / L.

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