Preparation method of air bag restraint system pipe and air bag restraint system pipe

Abstract

The invention discloses a preparation method of a safety airbag tube. The method comprises the following steps: S01, sawing a steel bar to form a blank; s02, the blank is heated, perforated and hot-rolled to form a tubular billet; s03, the tubular billet is subjected to annealing treatment; s04, carrying out large-deformation drawing on the annealed tubular billet; s05, normalizing treatment is conducted on the pipe subjected to large-deformation drawing, and then rapid cooling is conducted; s06, small-deformation drawing is conducted on the pipe treated in the step S05; and S07, the pipe obtained after small-deformation drawing is tempered, and the safety air bag pipe is obtained. The safety air bag pipe prepared through the method achieves the design strength and low-temperature toughness needed by high hydraulic blasting, the design safety margin is improved, the failure risk in the low-temperature environment is eradicated, and therefore the stability of an air bag assembly and the personnel safety are guaranteed.

Description

Technical Field

[0001] This invention relates to a method for preparing an airbag tube and the airbag tube itself, belonging to the technical field of airbag steel tube preparation. Background Technology

[0002] Currently, airbag tubes are a key component of automotive safety systems, primarily used to connect the gas generator to the airbag body, undertaking the crucial function of gas delivery. Airbag tubes need to meet requirements such as high strength, resistance to high and low temperatures, and precise airflow control to ensure rapid and reliable airbag deployment during a collision. Most cold-drawn airbag steel tubes on the market currently have a fine-grained (grain size grade 8) microstructure of pearlite + ferrite. Such airbag tubes cannot meet the pressure requirements for room-temperature liquid explosion, and exhibit significant brittleness at -40°C. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide a method for preparing airbag tubes. The airbag tubes prepared by this method achieve the design strength and low-temperature toughness required for high hydraulic bursting, improve the design safety margin, eliminate the risk of failure in low-temperature environments, and thus ensure the stability of airbag components and personnel safety.

[0004] To solve the above-mentioned technical problems, the technical solution of the present invention is: a method for preparing an airbag tube, the method comprising the following steps: S01: Sawing the steel bar to form a blank; S02: Heating, piercing, and hot rolling the blank to form a tube; S03: Annealing treatment of the capillary tube; S04: The annealed tube undergoes large deformation drawing; S05: Normalize the pipe after large deformation drawing, and then rapidly cool it; S06: Perform small deformation drawing on the pipe after the treatment in step S05; S07: Temper the tube after small deformation drawing to obtain the airbag tube.

[0005] Furthermore, the chemical composition and mass percentage of the chemical composition of the steel bar are as follows: C: 0.15~0.25%; Si≤0.50%; Mn: 1.0~2.0%; P≤0.030%; S≤0.030%; V≤0.20%; Nb≤0.080%; Ti≤0.060%; Al≥0.020%, with the remainder being Fe and other unavoidable impurities, totaling 100%.

[0006] Furthermore, in large deformation drawing, the reduction of deformation area is ≥50%; In small deformation drawing, the reduction of deformation area is ≤25%.

[0007] Furthermore, in step S05, sub-temperature normalizing is used, with a normalizing temperature of 780℃~880℃.

[0008] Furthermore, in step S05, the cooling rate of rapid cooling is ≥5℃ / s.

[0009] Furthermore, the tempering adopts a medium-temperature tempering method, with a tempering temperature of 350~500℃.

[0010] The present invention also provides an airbag tube, which is prepared by the above-described preparation method.

[0011] By adopting the above technical solution, the method of the present invention, through adjusting the production method and using large deformation drawing, normalizing, small deformation drawing and then tempering, can improve the design strength and low temperature toughness required for high hydraulic bursting of steel pipes while keeping the steel bar material unchanged, enhance the design safety margin, eliminate the risk of failure in low temperature environment, and thus ensure the stability of airbag components and personnel safety. Attached Figure Description

[0012] Figure 1 This is a metallographic image of the airbag tube in Embodiment 1 of the present invention under a 500X microscope; Figure 2 This is a metallographic image of the airbag tube in Comparative Example 1 of the present invention under a 500X microscope; Figure 3 This is a diagram of the airbag tube in Embodiment 1 of the present invention after a hydraulic burst test; Figure 4 The image shows the airbag tube of Comparative Example 1 of this invention after a hydraulic burst test. Detailed Implementation

[0013] This invention provides a method for preparing an airbag tube and the airbag tube itself. Those skilled in the art can refer to the content of this document and appropriately modify the process parameters to achieve the desired result. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and fall within the scope of protection of this invention. The method and application of this invention have been described through preferred embodiments. Those skilled in the art can clearly modify or appropriately change and combine the method and application described herein without departing from the content, spirit, and scope of this invention to realize and apply the technology of this invention.

[0014] A method for preparing an airbag tube, the method comprising the following steps: S01: Sawing the steel bar to form a blank; S02: Heating, piercing, and hot rolling the blank to form a tube; S03: Annealing treatment of the capillary tube; S04: The annealed tube undergoes large deformation drawing (two consecutive drawing processes). S05: Normalize the pipe after large deformation drawing, and then rapidly cool it; S06: Perform small deformation drawing on the pipe after the treatment in step S05; S07: Temper the tube after small deformation drawing to obtain the airbag tube.

[0015] Specifically, the chemical composition and mass percentage of the chemical composition of the steel bar are as follows: C: 0.15~0.25%; Si≤0.50%; Mn: 1.0~2.0%; P≤0.030%; S≤0.030%; V≤0.20%; Nb≤0.080%; Ti≤0.060%; Al≥0.020%, with the remainder being Fe and other unavoidable impurities, totaling 100%.

[0016] Specifically, in large deformation drawing, the deformation area reduction rate is ≥50%; large deformation drawing causes high-density dislocations and other crystal defects to form on the microscopic level of the airbag tube, and thermodynamically stores a large amount of distortion energy, which increases the nucleation rate for subsequent normalizing, thereby refining the grains; In small deformation drawing, the reduction of area is ≤25%; small deformation drawing can make the airbag tube reach the design strength required for high hydraulic burst, but does not produce obvious deformation texture, thus reducing low temperature toughness.

[0017] Specifically, in step S05, the cooling rate of rapid cooling is ≥5℃ / s.

[0018] Specifically, in step S05, normalizing effectively refines the grain size of the alloy carbides by controlling the amount of microalloy remelting. A sub-temperature normalizing heating method is used, with a normalizing temperature of 780~880℃, followed by a rapid cooling method with a cooling rate ≥5℃ / s, forming an ultrafine-grained structure (grain size ≥11). The sub-temperature heated incomplete austenite, after supercooling, consists of ferrite + bainite + MA islands, resulting in a significantly improved strength compared to a ferrite + pearlite matrix. Furthermore, the ductile-brittle transition temperature of the airbag tube structure of this invention is relatively low.

[0019] Specifically, the tempering process employs a medium-temperature tempering method, with a tempering temperature of 350~500℃. Tempering serves two purposes: firstly, it eliminates some deformation stress and improves elongation; secondly, it causes carbides to precipitate in the MA islands, eliminating low-temperature brittleness, ultimately enhancing strength and improving elongation.

[0020] The present invention also provides an airbag tube, which is prepared by the above-described preparation method.

[0021] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0022] Example 1: A method for preparing an airbag tube, the method comprising the following steps: S01: Sawing the steel bar to form a blank; S02: Heating, piercing, and hot rolling the blank to form a tube; S03: Anneal the tube; the annealing process shall be adopted using existing annealing technology; S04: The annealed tube undergoes large deformation drawing; S05: Normalize the pipe after large deformation drawing, and then rapidly cool it; S06: Perform small deformation drawing on the pipe after the treatment in step S05; S07: Temper the tube after small deformation drawing to obtain the airbag tube.

[0023] The chemical composition and mass percentage of the chemical composition of the steel bar are as follows: C: 0.15%; Si: 0.3%; Mn: 1.0%; P: 0.020%; S: 0.020%; V: 0.10%; Nb: 0.050%; Ti: 0.050%; Al: 0.020%, with the remainder being Fe and other unavoidable impurities, totaling 100%.

[0024] In step S05, sub-temperature normalizing is used, and the normalizing temperature is 790℃±5℃.

[0025] In step S05, the cooling rate of rapid cooling is 6 ± 0.5℃ / s.

[0026] The tempering process is carried out at a medium temperature of 400℃.

[0027] The metallographic structure of the airbag tube prepared in this embodiment under a 500X microscope is shown in the following figure. Figure 1 As shown in the figure, the airbag tube prepared in this embodiment was tested after hydraulic bursting at room temperature and hydraulic bursting at -40℃. Figure 3 As shown, it can be seen that the hydraulic blasting vents after both ambient temperature hydraulic blasting and -40℃ hydraulic blasting exhibit ductile openings. The strength of the ambient temperature hydraulic blasting is 163.1 MPa, and the strength of the -40℃ hydraulic blasting is 165.2 MPa, both meeting the design requirements (above 160 MPa).

[0028] Example 2: The preparation method in this example is basically the same as that in Example 1, except that: The chemical composition and mass percentage of the chemical composition of the steel bar are as follows: C: 0.25%; Si: 0.50%; Mn: 2.0%; P: 0.030%; S: 0.030%; V: 0.20%; Nb: 0.080%; Ti: 0.060%; Al: 0.020%, with the remainder being Fe and other unavoidable impurities, totaling 100%.

[0029] In step S05, sub-temperature normalizing is used, and the normalizing temperature is 870±5℃.

[0030] In step S05, the cooling rate of rapid cooling is 6 ± 0.5℃ / s.

[0031] The tempering process is carried out at a medium temperature of 500℃.

[0032] Example 3: The preparation method in this example is basically the same as that in Example 1, except that: The chemical composition and mass percentage of the chemical composition of the steel bar are as follows: C: 0.2%; Si: 0.40%; Mn: 1.5%; P: 0.010%; S: 0.010%; V: 0.10%; Nb: 0.040%; Ti: 0.030%; Al: 0.010%, with the remainder being Fe and other unavoidable impurities, totaling 100%.

[0033] In step S05, sub-temperature normalizing is used, and the normalizing temperature is 830±5℃.

[0034] In step S05, the cooling rate of rapid cooling is 8 ± 0.5℃ / s.

[0035] The tempering process is carried out at a medium temperature of 400℃.

[0036] Comparative Example 1: A method for preparing an airbag tube, the method comprising the following steps: S01: Sawing the steel bar to form a blank; S02: Heating, piercing, and hot rolling the blank to form a tube; S03: Anneal the tube; the annealing process shall be adopted using existing annealing technology; S04: The annealed tube is then drawn normally. S05: The drawn tube is subjected to stress-relief annealing to obtain the airbag tube.

[0037] The chemical composition and mass percentage of the chemical composition of the steel bar are as follows: C: 0.15%; Si: 0.3%; Mn: 1.0%; P: 0.020%; S: 0.020%; V: 0.10%; Nb: 0.050%; Ti: 0.050%; Al: 0.020%, with the remainder being Fe and other unavoidable impurities, totaling 100%.

[0038] The metallographic structure of the airbag tube prepared in this comparative example under a 500X microscope is shown in the following figure. Figure 2 As shown in the figure, the airbag tube prepared in this comparative example was tested under hydraulic burst conditions at -40℃. Figure 4 As shown, the hydraulic rupture opening after hydraulic rupture at -40℃ exhibits a brittle opening, with the crack extending a long distance towards both ends of the pipe. The opening is normal at room temperature. The strength after hydraulic rupture at room temperature is 150.8 MPa, while the strength after hydraulic rupture at -40℃ is 161.4 MPa. The strength after hydraulic rupture at room temperature does not meet the design requirements. Although the strength value at low temperature is satisfactory, brittleness is evident, with a significant difference between room temperature and low temperature values. This is mainly due to the substantial increase in brittleness at low temperatures caused by this unfavorable microstructure.

[0039] The specific embodiments described above further illustrate the technical problems, technical solutions, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing an airbag tube, characterized in that, The steps of the method include: S01: Sawing the steel bar to form a blank; S02: Heating, piercing, and hot rolling the blank to form a tube; S03: Annealing treatment of the capillary tube; S04: The annealed tube undergoes large deformation drawing; S05: Normalize the pipe after large deformation drawing, and then rapidly cool it; S06: Perform small deformation drawing on the pipe after the treatment in step S05; S07: Temper the tube after small deformation drawing to obtain the airbag tube.

2. The preparation method according to claim 1, characterized in that, The chemical composition and mass percentage of the chemical composition of the steel bar are as follows: C: 0.15~0.25%; Si≤0.50%; Mn: 1.0~2.0%; P≤0.030%; S≤0.030%; V≤0.20%; Nb≤0.080%; Ti≤0.060%; Al≥0.020%, with the remainder being Fe and other unavoidable impurities, totaling 100%.

3. The preparation method according to claim 1, characterized in that, In large deformation drawing, the reduction of deformation area is ≥50%; In small deformation drawing, the reduction of deformation area is ≤25%.

4. The preparation method according to claim 1, characterized in that, In step S05, sub-temperature normalizing is used, with a normalizing temperature of 780℃~880℃.

5. The preparation method according to claim 1, characterized in that, In step S05, the cooling rate of rapid cooling is ≥5℃ / s.

6. The preparation method according to claim 1, characterized in that, Tempering is performed at a medium temperature of 350~500℃.

7. An airbag tube, characterized in that, It is prepared by the preparation method as described in any one of claims 1 to 6.

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