Steel forming straightness control method for engineering machinery boom and engineering machinery boom

Abstract

The present invention discloses a method for controlling the straightness of steel formed for engineering machinery booms and an engineering machinery boom. The hot rolling heating stage adopts a direct loading mode, with a high-heat section temperature of 1300±20°C and a high-heat section time of 70 to 140 minutes. The rolling stage adopts a front stand ultra-large reduction + F7 flexible micro-wave compensation strategy for rolling production. The cooling stage adopts ultra-fast cooling + air cooling to the coiling temperature. The heat treatment process adopts vacuum radiation heating for tempering. The prepared steel plate 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. It is used to manufacture telescopic booms for engineering machinery aerial work vehicles. After the steel plate is integrally bent and formed, the straightness of the part in the length direction is ≤3 mm / L, effectively solving the problem of excessive straightness of booms after the "high-strength, lightweight, and green" manufacturing of engineering machinery.

Description

Technical Field

[0001] This invention belongs to the field of ferrous metal manufacturing technology, specifically relating to a method for controlling the straightness of steel forming for engineering machinery booms and an engineering machinery boom. Background Technology

[0002] The increased strength and reduced thickness of steel plates, while requiring the same forming effect as lower-strength, thicker plates, significantly increase the material requirements and forming difficulty. This is because, according to the forming characteristics of high-strength steel, the higher the material strength and the thinner the plate, the greater the forming difficulty under the same conditions, the more severe the springback phenomenon, and the harder it is to guarantee the dimensional standards of the formed parts. Summary of the Invention

[0003] The purpose of this invention is to solve the above-mentioned technical problems and provide a method for controlling the straightness of steel forming for engineering machinery booms and an engineering machinery boom, wherein after the steel plate is bent and formed as a whole, the straightness of the boom in the length direction is ≤3mm / L.

[0004] To achieve the above objectives, this invention provides a method for controlling the straightness of steel forming for engineering machinery booms. The hot rolling heating stage employs a direct loading mode, with a high-heat zone temperature of 1300±20℃ and a high-heat zone time of 70–140 min, ensuring uniform austenitization and temperature distribution, thus providing favorable conditions for subsequent homogenization and low-stress rolling. The rolling stage utilizes a front stand with ultra-large reduction and an F7 flexible micro-wave compensation strategy for rolling production. The cooling stage employs ultra-fast cooling combined with air cooling to reach the coiling temperature. The heat treatment process uses vacuum radiation heating for tempering.

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

[0006] Furthermore, it also includes a process of using deep bending rollers to follow the changes in the steel coil 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 transverse cutting: coarse straightening is performed by a single large compression, with a compression amount of 18-23 mm; fine straightening is performed by segmented straightening and fine straightening with positive bending compensation, with a straightening plastic strain ratio of 75-85%, so that the surface flatness of the material is ≤3 mm / m, completely eliminating the edge waviness of the material, and further eliminating the internal stress and homogenizing the material.

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

[0009] Furthermore, the rolling stage employs a front-stand ultra-large reduction + F7 flexible micro-wave compensation strategy, specifically as follows: F1–F3 reductions are 65–75%, F4 reduction is 20–24%, F5–F6 reductions are 10–15%, and F7 reduction is 6–8%. The F7 flexible micro-wave compensation uses different IU values ​​for compensation rolling based on different rolling thickness specifications; specifically, for 2.55–3.50 mm thickness specifications, an 80mm head section is used. The IU compensation value is 60-80, the middle IU compensation value is 10-30, and the tail 60m IU compensation value is 30-50; for the 3.51-5.01mm thickness specification, the head 80m IU compensation value is 40-60, the middle IU compensation value is 0-20, and the tail 60m IU compensation value is 15-35. This compensates for the double-sided wave morphology trend during the cooling process of high-strength steel, and also ensures that the original plate will not generate edge wave-shaped stress, which is the basis for the good straightness of the material after forming.

[0010] Furthermore, the ultra-fast cooling process achieves a cooling rate of 120–150 °C / s to a temperature of 635–665 °C, followed by air cooling to the winding temperature. The high-pressure jet water of the ultra-fast cooling is sufficient to break up the gas mold generated during high-temperature cooling, causing the cooling to transition from film boiling cooling to nucleus boiling cooling, resulting in more uniform cooling and better material uniformity during the cooling process. This reduces the generation of uneven thermal stress and minimizes the impact on the material's forming properties. The subsequent air cooling further reduces the influence of the cooling water on the material temperature, ensuring 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 min, ensuring that there is no change in the internal structure of the material. The strength of the steel plate is guaranteed by the dispersion strengthening effect of the second phase particles. Based on the principles of fine grain strengthening and dispersion strengthening, the original material maintains its performance while minimizing and uniformly distributing the internal stress of the material.

[0012] Furthermore, the steel plate prepared by the control method 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.

[0013] Also provided is an engineering machinery boom, which is a steel bending and forming process prepared by the control method described above. Through subsequent user cutting processes, die bending R-angle compensation processes, and control design of stamping speed and holding time, the material is guaranteed to meet the performance and process requirements for boom parts manufacturing. After bending and forming, the straightness of the boom in the length direction is ≤3mm / m. The straightness of the formed boom in the length direction 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 2.55-5.01mm, a length of 5.5-6.5m, and a strength grade of 765-845MPa. When used to manufacture the telescopic boom of an aerial work platform for engineering machinery, after the steel plate is bent and formed as a whole, the straightness of the part in the length direction is ≤3mm / L, which effectively solves the problem of excessive straightness of the boom after the "high strength, lightweight, and green" manufacturing of engineering machinery. Detailed Implementation

[0015] The present invention will be further described below with reference to specific embodiments.

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

[0017] Table 1 Main processes of the rolling line

[0018]

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

[0020] Table 2. Flattening, Straightening, and Cross-cutting Processes

[0021]

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

[0023] Table 3 Heat Treatment

[0024] Example Thickness / mm Tempering temperature / °C 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 subjected to head and tail protection cooling. The actual mechanical properties of the steel plate are shown in Table 4.

[0026] Table 4 Mechanical properties of the original steel plates

[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 undergoes multiple bending processes according to the technical plan. The bending process is implemented according to Table 4, and the overall bending effect after bending is shown in Table 5.

[0029] Table 5 Bending Process

[0030]

[0031] Table 6 Straightness after overall bending

[0032] Example Thickness / mm Straightness of the bent part (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 engineering machinery booms, characterized in that: The control method is as follows: the hot rolling heating stage adopts the direct loading mode, the high-heat section temperature is 1300±20℃, and the high-heat section time is 70~140min; the rolling stage adopts the front stand ultra-large reduction + F7 flexible micro-wave compensation strategy for rolling production; the cooling stage adopts ultra-fast cooling + air cooling to cool to the coiling temperature; the heat treatment process adopts vacuum radiation heating for tempering. The rolling stage employs a front-stand ultra-large reduction + F7 flexible micro-wave compensation strategy for rolling production. Specifically, this strategy is as follows: The reduction for F1 to F3 is 65-75%, for F4 it is 20-24%, and for F5 to F6 it is 10-15%. The reduction for F7 is 6-8%. For F7 flexible micro-wave compensation, different IU values ​​are used for compensation rolling based on different rolling thickness specifications. Specifically, for thickness specifications of 2.55-3.50mm, the head section has an IU compensation value of 60-80 (80m), the middle section has an IU compensation value of 10-30, and the tail section has an IU compensation value of 30-50 (60m). For thickness specifications of 3.51-5.01mm, the head section has an IU compensation value of 40-60 (80m), the middle section has an IU compensation value of 0-20, and the tail section has an IU compensation value of 15-35 (60m).

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

3. The method for controlling the straightness of steel forming for engineering machinery booms according to claim 1, characterized in that: It also includes the straightening and cross-cutting process, in which a deep bending roller is used to press down as the steel coil changes, and a reverse bending torque is continuously applied to the steel coil.

4. The method for controlling the straightness of steel forming for engineering machinery booms according to claim 3, characterized in that: During the straightening and cross-cutting process: coarse straightening is performed by a single large compression, with a compression amount of 18-23 mm; fine straightening is performed by segmented straightening and fine straightening with positive bending compensation, with a straightening plastic strain ratio of 75-85%, so that the surface flatness of the material is ≤3 mm / m.

5. The method for controlling the straightness of steel forming for engineering machinery booms according to claim 1, characterized in that: The direct loading temperature during the hot rolling heating stage is 725–751°C.

6. The method for controlling the straightness of steel forming for engineering machinery booms according to claim 1, characterized in that: The ultra-fast cooling rate is 120-150℃ / s to a temperature of 635-665℃, followed by air cooling to the winding temperature.

7. The method for controlling the straightness of steel forming for engineering machinery booms 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 min.

8. The method for controlling the straightness of steel forming for engineering machinery booms according to claim 1, characterized in that: The steel plate prepared by the control method 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.

9. A crane boom for engineering machinery, characterized in that: The boom of the engineering machinery is made of steel bent and formed by the control method described in claim 1, and the straightness of the boom in the length direction after bending and forming is ≤3mm / m.

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