Manufacturing method of corrosion-resistant coating high-strength part

Abstract

The invention relates to a manufacturing method of a corrosion-resistant coating high-strength part. The manufacturing method comprises the working procedures of coating steel plate heating, high-pressure gas injection, mold entering, forming and cooling, laser shaping and coating welding. In the plating steel plate heating process, the plating steel plate is heated to be completely austenitized, the temperature range is 850-910 DEG C, the heating time is 200-400 s, and meanwhile the heating rate is required to be larger than or equal to 50 DEG C / s in the process of 350-520 DEG C. The high-strength automobile part produced by the method has enough mechanical properties to ensure the safety of an automobile, has corrosion resistance the same as that of an aluminum-silicon coating and pure zinc indirect hot forming, and meanwhile, due to the adoption of direct hot forming, the working procedures of pre-forming, shot blasting and the like are omitted, so that the manufacturing period of the part can be shortened, and the production cost of the part can be reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of hot-formed high-strength automobile parts, and particularly relates to a method for manufacturing high-strength parts with corrosion-resistant coatings. Background Art

[0002] With the increasing demand for lightweight and safety performance in automobiles, hot forming technology is becoming more and more widely used. It is mainly used in the production of automotive safety components. It can solve the springback problem of cold-formed ultra-high-strength steel and the high requirements for cold-formed stamping equipment.

[0003] The current hot forming technologies mainly include direct hot forming and indirect hot forming. The raw materials used for hot forming are bare plates and coated steel plates. Although the raw material cost of bare plate hot formed products is low, a large amount of iron oxide scale will be generated during the hot forming process, which requires increased costs for cleaning the mold and shot blasting. The current mainstream application technology for zinc-based coating products is indirect hot forming technology. Indirect hot forming generally requires pre-forming of parts, and shot blasting is still required after the hot forming is completed, which results in higher production costs. The present invention improves the hot forming process to achieve direct hot forming of zinc-based coating hot-formed steel, which can shorten the production cycle and reduce production costs. Summary of the Invention

[0004] The present invention provides a method for manufacturing high-strength parts with corrosion-resistant coatings, which can solve the problems of long production cycle and high cost of indirect hot forming of zinc-based coatings.

[0005] To address the above technical issues, the present invention provides the following technical solution: a method for manufacturing high-strength components with corrosion-resistant coatings, comprising heating the coated steel plate, injecting high-pressure gas, molding and cooling, laser shaping, and coating and welding. The coated steel plate heating step involves heating the coated steel plate to complete austenitization within a temperature range of 850-910°C for 200-400 seconds, with a heating rate of ≥50°C / s between 350°C and 520°C. Direct heating of the coated steel plate is performed without pre-forming.

[0006] The coating steel plate heating process described in the present invention has the following requirements for the heating furnace: the heating furnace ensures positive pressure during the entire production process, with a pressure ≥0.5 bar, and the pressure is maintained by introducing pure nitrogen or nitrogen-hydrogen protective gas. There are nitrogen air knives or sealing rollers at the heating furnace inlet and outlet to prevent oxygen in the air from entering the furnace and causing excessive oxidation of the coating.

[0007] The high-pressure gas injection process described herein involves spraying the loose oxide layer on the steel plate after heating and exiting the furnace. The gas used is high-pressure nitrogen or a nitrogen-hydrogen mixture, with a pressure >20 bar, ensuring a cooling rate of ≥35°C / s. The hydrogen volume fraction (H2) in the nitrogen-hydrogen mixture is ≤1.5%. This step primarily removes the brittle oxide layer on the coating and prevents the transformation of austenite to ferrite.

[0008] The die-entry cooling process described in this invention requires a die entry temperature of 400-440°C, a cooling rate of ≥25°C / s during stamping, and a holding pressure of at least 12 seconds. The die exit temperature is ≤80°C to further ensure the post-formed performance of the part. Steel plates undergo austenite-to-martensite transformation below 400°C, so cooling rate requirements are imposed on the die-following cooling zone. Generally, martensite transformation is completed at 100°C, so the die exit temperature is required.

[0009] In the manufacturing method of the present invention, the material of the coated steel plate is 22MnB5, and the thickness range of the steel plate is: 0.8-3.0mm.

[0010] In the manufacturing method of the present invention, the coating of the coated steel plate is pure zinc, zinc-iron alloy and zinc-aluminum-magnesium coating, and in the zinc-aluminum-magnesium coating, aluminum ≤1.1% and magnesium ≤1.0%.

[0011] The tensile strength of the parts obtained by the method of the present invention is: 1350-1650MPa, yield strength: 950-1250MPa, elongation A 80% ≥4.5%.

[0012] Under neutral salt spray conditions, the red rust area of ​​the parts obtained by the method of the present invention is ≤5% and the time is ≥8 hours, and the corrosion resistance is good.

[0013] Design ideas of the present invention: 1) The present invention requires a certain heating temperature and time to achieve full austenitization of the steel plate, so as to obtain ideal physical properties subsequently.

[0014] 2) The coated steel plate is heated in a furnace, initially within the 350-520°C temperature range, at a heating rate of ≥50°C. The coating rapidly alloys during heating, so a specific heating rate is required within a certain temperature range to prevent liquefaction or even volatilization of the coating during subsequent heating at higher temperatures. After alloying, the coated steel plate is continuously heated to above the AC3 temperature. To ensure the speed and proportion of austenitization, the heating temperature is increased to 850-910°C for 200-400 seconds.

[0015] 3) During the heating process of the coated steel plate, the pressure of the furnace itself and the sealing conditions of the entrance and exit are restricted, mainly to prevent the air in the workshop from entering the furnace during the heating process, causing excessive oxidation of the coating surface. The oxidized coating structure is easy to fall off and powder.

[0016] 4) After the heated coated steel plate is taken out of the furnace, it is clamped and sprayed with high-pressure nitrogen or nitrogen-hydrogen protective gas. On the one hand, this is to remove the loose oxide layer on the surface, and on the other hand, the cooling rate is to prevent the transformation of austenite to ferrite.

[0017] 5) The cooling process of entering the mold to form the coated steel plate still maintains the full austenite into the mold to form, and the mold is required to cool at a constant speed to ensure the transformation of austenite into martensite.

[0018] The beneficial effects of the above technical solution are: the high-strength automobile parts produced by the present invention have sufficient mechanical properties to ensure the safety of the automobile, with tensile strength: 1350-1650MPa, yield strength: 950-1250MPa, elongation A 80% ≥4.5%, with the same corrosion resistance as aluminum silicon coating and pure zinc indirect hot forming. Under neutral salt spray conditions, the red rust area is ≤5% and the time is ≥8 hours. At the same time, due to the use of direct hot forming, the pre-forming, shot blasting and other processes are omitted, which can shorten the production cycle and production cost of parts. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. Example 1

[0020] A method for manufacturing corrosion-resistant coated high-strength parts, comprising the steps of heating the coated steel plate, blowing high-pressure gas, molding and cooling, laser shaping, coating and welding; Heating of coated steel plate: Heat the coated steel plate to complete austenitization in the temperature range of 850℃ and the heating time of 200s. At the same time, the heating rate is required to be 67℃ / s in the process of 350-520℃.

[0021] The following requirements are placed on the heating furnace: the heating furnace must ensure positive pressure during the entire production process, with a pressure of 0.56 bar. The pressure is maintained by introducing pure nitrogen or nitrogen-hydrogen protective gas. There are nitrogen air knives or sealing rollers at the inlet and outlet of the heating furnace to prevent oxygen in the air from entering the furnace and causing excessive oxidation of the coating.

[0022] 2) High-pressure gas blowing: After heating is completed, the steel plate is subjected to high-pressure blowing on the loose surface oxide layer under clamping conditions. The high-pressure blowing gas is high-pressure nitrogen or nitrogen-hydrogen mixed gas. The blowing pressure is 20 bar, the cooling rate is 57 ℃ / s, and the volume fraction of hydrogen in the nitrogen-hydrogen mixed gas is 1.0%.

[0023] 3) Mould forming cooling: The temperature requirement for moulding is 400-440 ℃. The cold speed during stamping is 36 ℃ / s, and the pressure is maintained for 15 s. The temperature after moulding is 80 ℃, further ensuring the performance of the formed part.

[0024] 4) Laser shaping and coating welding: After laser shaping and coating welding, a corrosion-resistant plated high-strength part is obtained.

[0025] The plated steel plate material used in this embodiment is 22MnB5, and the thickness of the steel plate is 0.8 mm. The plated layer of the plated steel plate is pure zinc, zinc-iron alloy, and zinc-aluminum-magnesium plated layer. In the zinc-aluminum-magnesium plated layer, the aluminum content is 1.1%, and the magnesium content is 0.9%.

[0026] The mechanical properties of the corrosion-resistant plated high-strength part obtained in this embodiment are as follows: tensile strength: 1540 MPa, yield strength: 1058 MPa, elongation A 80 : 5.0%, corrosion resistance: red rust time under neutral salt spray condition is 10 hours. Embodiment 2

[0027] A method for manufacturing a corrosion-resistant plated high-strength part, comprising the steps of plated steel plate heating, high-pressure gas blowing, mould forming cooling, laser shaping, and coating welding; 1) Plated steel plate heating: The plated steel plate is heated to complete austenitization, and the temperature range is 867 ℃. The heating time is 270 s, and the heating rate during 350-520 ℃ is required to be 62 ℃ / s.

[0028] The following requirements are placed on the heating furnace: The heating furnace ensures positive pressure during the overall production process, the pressure is 0.57 bar, the pressure maintaining mode is to introduce pure nitrogen or nitrogen-hydrogen protective gas, there are nitrogen air knives or sealing rollers at the inlet and outlet of the heating furnace to prevent oxygen in the air from entering the furnace and causing excessive oxidation of the plated layer.

[0029] 2) High-pressure gas blowing: After heating is completed, the steel plate is subjected to high-pressure blowing on the loose surface oxide layer under clamping conditions. The high-pressure blowing gas is high-pressure nitrogen or nitrogen-hydrogen mixed gas. The blowing pressure is 20 bar, the cooling rate is 57 ℃ / s, and the volume fraction of hydrogen in the nitrogen-hydrogen mixed gas is 1.0%.

[0030] 3) Cooling of the mold: the temperature of the mold is required to be 400-440℃, the cooling rate is required to be 25℃ / s during stamping, the pressure is kept for 16s, the temperature of the mold is 58℃, and the performance of the part after forming is further ensured.

[0031] 4) Laser shaping and coating welding: after the laser shaping and coating welding process, the corrosion-resistant plated high-strength part is obtained.

[0032] The plated steel plate material used in the embodiment is 22MnB5, and the thickness of the steel plate is 1.4mm; the plated layer of the plated steel plate is pure zinc, zinc-iron alloy and zinc-aluminum-magnesium plated layer, and in the zinc-aluminum-magnesium plated layer, aluminum is 1.0%, and magnesium is 1.0%.

[0033] The mechanical properties of the corrosion-resistant plated high-strength part obtained in the embodiment are: tensile strength: 1487MPa, yield strength: 1135MPa, elongation A 80 : 5.5%, corrosion resistance: red rust time under neutral salt spray condition is 12 hours. Example 3

[0034] A method for manufacturing a corrosion-resistant plated high-strength part, comprising the steps of heating a plated steel plate, high-pressure gas blowing, mold forming cooling, laser shaping, and coating welding. 1) Heating of the plated steel plate: heat the plated steel plate to complete austenitization, the temperature range is 882℃, the heating time is 320s, and the heating rate is required to be 56℃ / s during 350-520℃.

[0035] The heating furnace has the following requirements: the heating furnace ensures positive pressure during the whole production process, the pressure is 0.55bar, the pressure maintaining mode is to introduce pure nitrogen or nitrogen-hydrogen protective gas, there are nitrogen air knives or sealing rollers at the inlet and outlet of the heating furnace to prevent oxygen in the air from entering the furnace and causing excessive oxidation of the plated layer.

[0036] 2) High-pressure gas blowing: after heating and discharging, the loose oxide layer on the surface of the steel plate is blown with high-pressure gas under clamping conditions, the high-pressure gas is high-pressure nitrogen or nitrogen-hydrogen mixed gas, the blowing pressure is 35bar, the cooling rate is ensured to be 48℃ / s, and the volume fraction of hydrogen in the nitrogen-hydrogen mixed gas is 1.3%.

[0037] 3) Cooling of the mold: the temperature of the mold is required to be 400-440℃, the cooling rate is required to be 32℃ / s during stamping, the pressure is kept for 15s, the temperature of the mold is 62℃, and the performance of the part after forming is further ensured.

[0038] 4) Laser shaping and coating welding: after the laser shaping and coating welding process, the corrosion-resistant plated high-strength part is obtained.

[0039] The material of the coated steel plate used in this embodiment is 22MnB5, and the thickness of the steel plate ranges from 1.8 mm. The coating of the coated steel plate is pure zinc, zinc-iron alloy, and zinc-aluminum-magnesium coating, and the zinc-aluminum-magnesium coating contains 1.05% aluminum and 0.85% magnesium.

[0040] The mechanical properties of the corrosion-resistant coating high-strength parts obtained in this embodiment are: tensile strength: 1630MPa, yield strength: 1120MPa, elongation A 80 : 5.0%, corrosion resistance: red rust time under neutral salt spray conditions is 11 hours. Example 4

[0041] A method for manufacturing corrosion-resistant coated high-strength parts, comprising the steps of heating the coated steel plate, blowing high-pressure gas, molding and cooling, laser shaping, coating and welding; 1) Heating of coated steel plate: Heat the coated steel plate to complete austenitization in the temperature range of 895℃ and the heating time of 350s. At the same time, the heating rate is required to be 50℃ / s in the process of 350-520℃.

[0042] The following requirements are placed on the heating furnace: the heating furnace must ensure positive pressure during the entire production process, with a pressure of 0.65 bar. The pressure is maintained by introducing pure nitrogen or nitrogen-hydrogen protective gas. There are nitrogen air knives or sealing rollers at the inlet and outlet of the heating furnace to prevent oxygen in the air from entering the furnace and causing excessive oxidation of the coating.

[0043] 2) High-pressure gas injection: After heating is completed and the steel plate is taken out of the furnace, high-pressure gas injection is performed on the loose oxide layer on the surface under clamping conditions. The high-pressure injection gas is high-pressure nitrogen or nitrogen-hydrogen mixed gas. The injection pressure is 47 bar, ensuring a cooling rate of 42°C / s. The volume proportion of hydrogen in the nitrogen-hydrogen mixed gas is 1.4%.

[0044] 3) Cooling during mold forming: The mold temperature is required to be 400-440℃, the cooling rate is required to be 34℃ / s during the stamping process, and the pressure is maintained for 17s. The mold exit temperature is 71℃ to further ensure the performance of the part after forming.

[0045] 4) Laser shaping, coating and welding: After laser shaping, coating and welding processes, high-strength components with corrosion-resistant coatings are obtained.

[0046] The material of the coated steel plate used in this embodiment is 22MnB5, and the thickness range of the steel plate is: 2.5mm; the coating of the coated steel plate is pure zinc, zinc-iron alloy and zinc-aluminum-magnesium coating, and the zinc-aluminum-magnesium coating contains aluminum: 0.94% and magnesium: 0.87%.

[0047] The mechanical properties of the corrosion-resistant coating high-strength parts obtained in this embodiment are as follows: tensile strength: 1570MPa, yield strength: 1023MPa, elongation A 80: 5.0%, corrosion resistance: red rust time under neutral salt spray conditions is 10 hours. Example 5

[0048] A method for manufacturing corrosion-resistant coated high-strength parts, comprising the steps of heating the coated steel plate, blowing high-pressure gas, molding and cooling, laser shaping, coating and welding; 1) Heating of coated steel plate: Heat the coated steel plate to complete austenitization in the temperature range of 910℃ and the heating time of 400s. At the same time, the heating rate is required to be 54℃ / s in the process of 350-520℃.

[0049] The following requirements are placed on the heating furnace: the heating furnace must ensure positive pressure during the entire production process, with a pressure of 0.50 bar. The pressure is maintained by introducing pure nitrogen or nitrogen-hydrogen protective gas. There are nitrogen air knives or sealing rollers at the inlet and outlet of the heating furnace to prevent oxygen in the air from entering the furnace and causing excessive oxidation of the coating.

[0050] 2) High-pressure gas injection: After heating is completed and the steel plate is taken out of the furnace, high-pressure gas injection is performed on the loose oxide layer on the surface under clamping conditions. The high-pressure injection gas is high-pressure nitrogen or nitrogen-hydrogen mixed gas. The injection pressure is greater than 49 bar, and the cooling rate is guaranteed to be ≥39℃ / s. The volume proportion of hydrogen in the nitrogen-hydrogen mixed gas is 1.5%.

[0051] 3) Mold forming cooling: The mold temperature is required to be 400-440℃, the cooling rate is required to be 29℃ / s during the stamping process, and the pressure is maintained for 15s. The mold exit temperature is 77℃ to further ensure the performance of the part after forming.

[0052] 4) Laser shaping, coating and welding: After laser shaping, coating and welding processes, high-strength components with corrosion-resistant coatings are obtained.

[0053] The material of the coated steel plate used in this embodiment is 22MnB5, and the thickness range of the steel plate is: 3.0mm; the coating of the coated steel plate is pure zinc, zinc-iron alloy and zinc-aluminum-magnesium coating, and the zinc-aluminum-magnesium coating contains aluminum: 0.83% and magnesium: 0.77%.

[0054] The mechanical properties of the corrosion-resistant coating high-strength parts obtained in this embodiment are: tensile strength: 1490MPa, yield strength 970MPa: elongation A 80 : 5.5%, corrosion resistance: red rust time under neutral salt spray conditions is 13 hours.

[0055] The above embodiments are only used to illustrate rather than limit the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the present invention can still be modified or replaced by equivalents. Any modification or partial replacement that does not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A method for manufacturing high-strength components with corrosion-resistant coatings, characterized in that: The manufacturing method includes the following steps: heating the coated steel plate, blowing high-pressure gas, molding and cooling, laser shaping, coating and welding; in the coating steel plate heating step, the coated steel plate is heated to be completely austenitized, the temperature range is 850-910°C, the heating time is 200-400s, and the heating rate is required to be ≥50°C / s during the process of 350-520°C.

2. The method for manufacturing a high-strength component with corrosion-resistant coating according to claim 1, characterized in that: The coating steel plate heating process has the following requirements for the heating furnace: the heating furnace ensures positive pressure during the entire production process, with a pressure ≥0.5 bar, and the pressure is maintained by introducing pure nitrogen or nitrogen-hydrogen protective gas. There are nitrogen air knives or sealing rollers at the heating furnace inlet and outlet to prevent oxygen in the air from entering the furnace.

3. The method for manufacturing a high-strength component with corrosion-resistant coating according to claim 1, characterized in that: In the high-pressure gas blowing process of the present invention, after the heating is completed and the steel plate is taken out of the furnace, the loose oxide layer on the surface is subjected to high-pressure blowing under clamping conditions. The high-pressure blowing gas is high-pressure nitrogen or a nitrogen-hydrogen mixed gas. The blowing pressure is greater than 20 bar, and the cooling rate is ensured to be ≥35°C / s. The volume proportion of hydrogen in the nitrogen-hydrogen mixed gas is H2≤1.5%.

4. The method for manufacturing a high-strength component with corrosion-resistant coating according to claim 1, characterized in that: The mold entering and cooling process requires that the mold entering temperature be 400-440°C, the cooling rate be ≥25°C / s during the stamping process, the pressure be maintained for more than 12s, and the mold exit temperature be ≤80°C.

5. The method for manufacturing a high-strength component with a corrosion-resistant coating according to any one of claims 1 to 4, characterized in that: In the manufacturing method, the material of the coated steel plate is 22MnB5.

6. The method for manufacturing a high-strength component with a corrosion-resistant coating according to any one of claims 1 to 4, characterized in that: In the manufacturing method, the thickness range of the coated steel plate is 0.8-3.0 mm.

7. A method for manufacturing a high-strength component with a corrosion-resistant coating according to any one of claims 1 to 4, characterized in that: In the manufacturing method, the coating of the coated steel plate is pure zinc, zinc-iron alloy and zinc-aluminum-magnesium coating, and in the zinc-aluminum-magnesium coating, aluminum ≤1.1% and magnesium ≤1.0%.

8. The method for manufacturing a high-strength component with a corrosion-resistant coating according to any one of claims 1 to 4, characterized in that: The parts obtained by the method have a tensile strength of 1350-1650 MPa, a yield strength of 950-1250 MPa, and an elongation of A 80% ≥4.5%.

9. The method for manufacturing a high-strength component with a corrosion-resistant coating according to any one of claims 1 to 4, characterized in that: The red rust area of ​​the parts obtained by the method is ≤5% under neutral salt spray conditions and the time is ≥8 hours.