JPH10140238A - Manufacturing method of steel tube for high strength and high toughness air bag - Google Patents

Abstract

(57) [Summary] [Problem] To manufacture a seamless steel pipe having excellent workability and weldability, high strength and high toughness for an accumulator of an air bag system. SOLUTION: C: 0.01 to less than 0.20%, Si:
0.50% or less, Mn: 0.30% to 2.00%, P:
0.020% or less, S: 0.020% or less, Al: 0.
Steel containing 10% or less, with the balance being Fe and unavoidable impurities, being hot-formed so as to have a final finishing temperature of 750 ° C. or higher, or stress relief annealing, normalizing and normalizing after hot-forming. By performing annealing, as-quenched or quenching and tempering, a seamless and high-strength, high-toughness steel pipe having excellent workability and weldability can be manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a high-strength, high-toughness steel pipe which is excellent in workability and weldability and is suitable for airbag parts requiring high strength and high toughness of 590 N / mm ² or more. About.

[0002]

2. Description of the Related Art In recent years, the automobile industry has been actively introducing devices that pursue safety. Among them, before an occupant collides with a steering wheel, an instrument panel, or the like at the time of a collision, the occupant is required to carry out the same. An airbag system that deploys an airbag between the occupant with gas or the like and absorbs the kinetic energy of the occupant to reduce injuries has been developed and installed.

Conventionally, a system using explosive chemicals has been adopted as an air bag system. However, in recent years, a system using an accumulator made of a steel pipe filled with argon gas has been developed because of its high cost, environmental problems and recycling problems. . The steel pipe used for accumulators such as argon gas always keeps 300 kgf / cm ² of inert gas and the like blown into the air bag at the time of collision, and then adds a small amount of gas at the time of collision to ignite the explosive, so that the gas is blown at once. Since it is ejected, stress is applied at a large strain rate in a very short time, and unlike conventional structures such as pressure cylinders and line pipes, high strength, high toughness, workability and weldability are required. .

[0004]

The steel pipe used in the new field for the accumulator is required to have high strength, high toughness, workability and weldability. Therefore, in the conventional combination of cold drawing and stress relief annealing, On the other hand, the toughness is reduced due to the high strength, and the above requirements cannot be satisfied.

An object of the present invention is to provide a high-strength, high-toughness airbag which is excellent in workability and weldability, and is suitable for airbag parts which require high strength and high toughness as a new field without any prior art. An object of the present invention is to provide a method for manufacturing a steel pipe.

[0006]

Means for Solving the Problems The present inventors have intensively studied and studied to achieve the above object. As a result, the steel of a predetermined component is hot-formed so that the final finishing temperature is 750 ° C. or higher, or the steel of a predetermined component is hot-formed,
The stress relief annealing, annealing, normalizing, as-quenched or by quenching and tempering treatment, it is possible to obtain a high-strength, high-toughness steel pipe with excellent workability and weldability, and to the present invention. Reached.

The method for producing a steel pipe for a high-strength, high-toughness air bag according to claim 1 of the present invention is characterized in that C: 0.05% or more and 0.15% or more.
%, Si: 0.50% or less, Mn: 0.30% or more
2.00%, P: 0.020% or less, S: 0.020%
Hereinafter, a steel containing Al: 0.10% or less, with the balance being Fe and inevitable impurities, having a final finishing temperature of 750
Hot pipe production is to be carried out at a temperature of at least ℃. As described above, by limiting the chemical components in the steel to the above component composition, it is possible to obtain sufficient strength, toughness, high workability, and weldability for an accumulator of an airbag.
In addition, the above steel is subjected to hot pipe making so that the final finishing temperature is 750 ° C. or more, so that a steel pipe for an air bag having high strength, high toughness, excellent in workability and weldability suitable for the properties of the final purpose. Can be obtained.

The method for producing a steel pipe for a high-strength, high-toughness air bag according to claim 2 of the present invention is characterized in that C: 0.01% to 0.1%.
20%, Si: 0.50% or less, Mn: 0.30% or more
2.00%, P: 0.020% or less, S: 0.020%
Hereinafter, a steel containing Al: 0.10% or less, with the balance being Fe and inevitable impurities, having a final finishing temperature of 750
Hot pipe production is to be carried out at a temperature of at least ℃. As described above, by limiting the chemical components in the steel to the above component composition, it is possible to obtain sufficient strength, toughness, high workability, and weldability for an accumulator of an airbag.
In addition, the above steel is subjected to hot pipe making so that the final finishing temperature is 750 ° C. or more, so that a steel pipe for an air bag having high strength, high toughness, excellent in workability and weldability suitable for the properties of the final purpose. Can be obtained.

Further, the method for producing a steel pipe for a high-strength high-toughness air bag according to claim 3 of the present invention is as follows: C: 0.05% or more and less than 0.15%; Si: 0.50% or less; 3
0% to 2.00%, P: 0.020% or less, S: 0.0
20% or less, Al: 0.10% or less, Mo: 0.
50% or less, V: 0.10% or less, Ni: 0.50% or less, Cr: 1.00% or less, Cu: 0.50% or less, T
i: 0.10% or less, Nb: 0.10% or less, B: 0.
005% or less, the balance being Fe and unavoidable impurities.
Hot pipe production is to be carried out at a temperature of at least ℃. As described above, by limiting the chemical components in the steel to the above component composition, it is possible to obtain high strength, high toughness, high workability, and weldability sufficient for an accumulator of an airbag. In addition, the above steel is subjected to hot pipe making so that the final finishing temperature is 750 ° C. or more, so that a steel pipe for an air bag having high strength, high toughness, excellent in workability and weldability suitable for the properties of the final purpose. Can be obtained.

Further, the method for producing a steel pipe for a high-strength high-toughness air bag according to claim 4 of the present invention is characterized in that C: 0.01%
0.20%, Si: 0.50% or less, Mn: 0.30
% To 2.00%, P: 0.020% or less, S: 0.02
0% or less, Al: 0.10% or less, Mo: 0.5
0% or less, V: 0.10% or less, Ni: 0.50% or less, Cr: 1.00% or less, Cu: 0.50% or less, T
i: 0.10% or less, Nb: 0.10% or less, B: 0.
005% or less, the balance being Fe and unavoidable impurities.
Hot pipe production is to be carried out at a temperature of at least ℃. As described above, by limiting the chemical components in the steel to the above component composition, it is possible to obtain high strength, high toughness, high workability, and weldability sufficient for an accumulator of an airbag. In addition, the above steel is subjected to hot pipe making so that the final finishing temperature is 750 ° C. or more, so that a steel pipe for an air bag having high strength, high toughness, excellent in workability and weldability suitable for the properties of the final purpose. Can be obtained.

Further, the method for manufacturing a steel pipe for a high-strength and tough airbag according to claim 5 of the present invention is characterized in that: C: 0.05%
Not less than 0.15%, Si: 0.50% or less, Mn:
0.30% to 2.00%, P: 0.020% or less, S:
A steel containing 0.020% or less, Al: 0.10% or less, the balance being Fe and unavoidable impurities, after hot pipe making, stress relief annealing, annealing, normalizing, as-quenched or Quenching and tempering are performed. As described above, by limiting the chemical components in the steel to the above component composition, it is possible to obtain high strength, high toughness, high workability, and weldability sufficient for an accumulator of an airbag. In addition, after the above steel pipe is hot-formed, stress relief annealing, annealing, normalizing, by performing quenching or tempering as it is, high strength suitable for the properties of the final purpose,
It is possible to obtain a steel pipe for an airbag which has high toughness and excellent workability and weldability.

Further, the method for producing a steel pipe for a high-strength and tough airbag according to claim 6 of the present invention is characterized in that: C: 0.01%
0.20%, Si: 0.50% or less, Mn: 0.30
% To 2.00%, P: 0.020% or less, S: 0.02
0% or less, Al: 0.10% or less, the balance being Fe
After hot-forming the steel containing inevitable impurities, the steel is subjected to stress relief annealing, annealing, normalizing, quenching, or quenching and tempering. Thus, by limiting the chemical components in the steel to the above component composition,
High enough strength for air bag accumulator,
High toughness, high workability, and weldability can be obtained. Also,
After hot forming the above steel, stress relief annealing, annealing, normalizing, by quenching or quenching and tempering, high strength, high toughness and workability suitable for the properties of the final purpose A steel pipe for an air bag having excellent weldability can be obtained.

Further, the method for producing a steel pipe for a high-strength, high-toughness airbag according to claim 7 of the present invention is as follows.
Not less than 0.15%, Si: 0.50% or less, Mn:
0.30% to 2.00%, P: 0.020% or less, S:
0.020% or less, Al: 0.10% or less, M
o: 0.50% or less, V: 0.10% or less, Ni: 0.
50% or less, Cr: 1.00% or less, Cu: 0.50%
Hereinafter, Ti: 0.10% or less, Nb: 0.10% or less,
B: Steel containing at least one of 0.005% or less, the balance being Fe and unavoidable impurities, after hot pipe making, stress relief annealing, annealing, normalizing, as-quenched or as-quenched Tempering treatment is to be performed. As described above, by limiting the chemical components in the steel to the above component composition, it is possible to obtain high strength, high toughness, high workability, and weldability sufficient for an accumulator of an airbag.
In addition, after hot-forming the above steel, stress relief annealing, annealing,
By performing normalizing, quenching, or quenching and tempering, a steel pipe for an air bag having high strength, high toughness, and excellent workability and weldability suitable for the properties of the final purpose can be obtained.

Further, the method for producing a steel pipe for a high-strength, high-toughness airbag according to claim 8 of the present invention is characterized in that: C: 0.01%
0.20%, Si: 0.50% or less, Mn: 0.30
% To 2.00%, P: 0.020% or less, S: 0.02
0% or less, Al: 0.10% or less, Mo: 0.5
0% or less, V: 0.10% or less, Ni: 0.50% or less, Cr: 1.00% or less, Cu: 0.50% or less, T
i: 0.10% or less, Nb: 0.10% or less, B: 0.
005% or less, the balance being Fe and unavoidable impurities, after hot pipe making, stress relief annealing, annealing, normalizing, as-quenched or quenched and tempered. I have to do that. As described above, by limiting the chemical components in the steel to the above component composition, it is possible to obtain high strength, high toughness, high workability, and weldability sufficient for an accumulator of an airbag. In addition, after the above steel pipe was hot-formed, stress relief annealing, annealing, normalizing,
As-quenched or quenched and tempered, it is possible to obtain a steel pipe for an air bag having high strength, high toughness, excellent in workability and weldability, which is suitable for the properties of the final purpose.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the reasons for limiting the chemical components of the steel used in the present invention are as follows. C is an element added to obtain the necessary strength of steel at low cost.
If it is less than 0.01%, sufficient strength cannot be obtained.
If it exceeds 20%, workability and weldability are deteriorated and toughness is reduced. Therefore, the content is set to 0.01 to 0.20%. A particularly preferable range is 0.05% or more and less than 0.15%. .

Si is an element that inhibits the cold workability of steel. If the content exceeds 0.50%, the workability deteriorates.
50% or less.

Mn is an effective element for improving the strength and toughness of steel. However, if it is less than 0.30%, sufficient strength and toughness cannot be obtained, and if it exceeds 2.00%, the weldability becomes poor. Due to deterioration, the content was set to 0.30 to 2.00%.

P is set to 0.020% or less because P causes a decrease in toughness due to grain boundary segregation. S is combined with Mn in steel to form inclusions due to MnS, thereby deteriorating workability and decreasing toughness.

Al has an element effective for improving the workability, but when the content exceeds 0.10%, the effect is reduced. Therefore, the content is set to 0.10% or less.

By limiting the above chemical components in steel, it is possible to obtain sufficient strength, toughness, high workability and weldability for accumulators for airbags. It is effective to further add Mo, V, Ni, Cr, Cu, Ti, Nb, and B to the components. The reasons for limiting the contents of these additional components are as follows.

Mo has the effect of increasing the strength by solid solution strengthening and improving the quenchability. However, if it exceeds 0.50%, the weld is hardened and the toughness is reduced.
% Or less.

V has the effect of forming precipitates and improving the strength, but if it exceeds 0.10%, the toughness of the weld decreases, so V is set to 0.10% or less.

Ni is an element effective for improving hardenability and toughness. However, if it exceeds 0.50%, it is not expected to have an effect for an air bag, and it is an expensive element. 0.50% or less.

Cr is an element effective for improving the strength and corrosion resistance of steel. However, if it exceeds 1.00%, the workability and the toughness of the welded portion are reduced.

Although Cu is an effective element for improving the corrosion resistance of steel, if it exceeds 0.50%, the hot workability is deteriorated.

Ti is effective in improving the toughness by making the structure finer, but when it exceeds 0.10%, the toughness is adversely deteriorated. Therefore, the content of Ti is set to 0.10% or less.

Like Nb, Nb is effective in improving the toughness by making the structure finer, but when it exceeds 0.10%, it deteriorates the toughness. Therefore, Nb is made 0.10% or less.

B is an element effective for improving the hardenability, but if it exceeds 0.005%, the toughness is reduced, so that the content is made 0.005% or less.

In the present invention, a steel pipe whose chemical composition is adjusted as described above is used as a raw material to perform hot pipe production. Toughness is imparted by setting the final finishing temperature during hot pipe production to 750 ° C. or higher. On the other hand, if the final finishing temperature during hot pipe making is lower than 750 ° C., uniform austenite grains cannot be obtained, and high toughness cannot be obtained. Therefore, in the present invention, when the final finishing temperature at the time of hot pipe production is less than 750 ° C.
If toughness and workability cannot be obtained, after hot pipe making, high strength, high toughness, and by performing stress relief annealing, annealing, normalizing, quenching or quenching and tempering treatment A steel pipe for an air bag having excellent workability and weldability can be obtained.

[0030]

EXAMPLE Using a billet of the steel of the present invention having the chemical components shown in Table 1 and a comparative steel having the chemical components shown in Table 2, piercing and rolling were performed by the Mannesmann-mandrel mill method.
It was finished with a reducer at a final finishing temperature of 700 to 850 ° C. to an outer diameter of 76.2 mm and a wall thickness of 4.0 mm. Thereafter, stress relief annealing is performed at 500 ° C. as it is in a hot tube or 900 ° C.
Normalizing treatment at 600 ℃, annealing treatment at 600 ℃, 900 ℃
Quenched at 900 ° C. or tempered at 500 ° C. to evaluate various characteristics. The results are shown in Tables 3 and 4.

The evaluation of the properties was carried out for strength, toughness and workability. Regarding the strength, the specified JIS Z2201 metal material tensile test piece was used as specified in JIS Z2201.
A tensile test was performed according to the metal material tensile test method of Z2241. As for the toughness, as shown in FIG. 1, the seamless steel pipe 1 was cut in half as shown by a dashed line, and a half test piece 2 having a length of 10 mm was collected and placed on the table 3 of the drop test apparatus shown in FIG. The half-specimen 2 was placed on the table, and a weight 4 having a weight of 5 kg was dropped from a position of 2000 mm from the upper surface of the placing table 3 to check for cracks. The drop weight test was repeated 10 times at −40 ° C. and evaluated by the crack rate. Workability was evaluated in terms of flatness. As shown in FIG. 3, the flatness of the V-block (60 mm
°) using the pressing tools 5 and 5 to flatten the seamless steel pipe 1 until it comes into close contact, and evaluate the presence or absence of cracks in the shoulder 6 of the largest flat part. Existence was evaluated as ×.

[0032]

[Table 1]

[0033]

[Table 2]

[0034]

[Table 3]

[0035]

[Table 4]

As shown in Tables 1 and 3, the steel No. 1 to 1
9 using the steel of the present invention. The inventive examples of Nos. 1 to 26 have a tensile strength of 5
High strength of 90 N / mm ² or more, and 0% cracking rate in the drop test, no cracking of the shoulder after flattening,
It had good workability.

On the other hand, as shown in Tables 2 and 4, steel No. Comparative steels Nos. 20 to 27 and steel Nos. Test No. 18 using the steel of the present invention. The comparative examples of Nos. 27 to 35 are steel Nos.
Test Nos. 20 and 23 were used. Nos. 27 and 30 have a tensile strength of 590 N / mm ² or less and have insufficient strength. 2
Test Nos. 1, 22, 24 to 27, 18 28,
Nos. 29 and 31 to 35 have a crack rate of 10% or more in a drop load test, and a crack in a shoulder after flattening of adhesion occurs, resulting in insufficient toughness and workability.

[0038]

According to the present invention, there is provided a method for producing a steel tube for a high-strength, high-toughness airbag according to claims 1 to 4, wherein the steel having a chemical composition adjusted is hot-rolled so that the final finishing temperature is 750 ° C or higher. By carrying out, excellent workability and weldability suitable for applications such as accumulators for air bags, and high strength,
High toughness steel pipe can be obtained.

The method of manufacturing a steel pipe for a high-strength, high-toughness air bag according to claims 5 to 8 of the present invention is a method for hot-forming steel having a chemical composition adjusted, followed by stress relief annealing, annealing, and normalizing. , As-quenched or by quenching and tempering, high strength, high toughness and workability suitable for the final target properties
A steel pipe for an accumulator of an air bag having excellent weldability can be manufactured.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory view of a drop weight test piece in an embodiment, and FIG.
The figure is a perspective view of the half-split method, and the figure (b) is a perspective view of a drop weight test piece.

FIG. 2 is a schematic explanatory view for explaining a drop weight test method in an example.

FIG. 3 is a schematic explanatory view for explaining an adhesion flatness test method in an example.

[Explanation of symbols]

 Reference Signs List 1 seamless steel pipe 2 half test piece 3 table 4 weight 5 pressing tool 6 shoulder

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C22C 38/06 C22C 38/06 38/58 38/58

Claims (8)

[Claims] 1. C: 0.05% or more and less than 0.15%, S
i: 0.50% or less, Mn: 0.30% to 2.00%,
P: 0.020% or less, S: 0.020% or less, Al:
A steel pipe for high-strength high-toughness airbags, wherein a steel pipe containing 0.10% or less, and the balance being Fe and inevitable impurities, is subjected to hot pipe making so that the final finishing temperature is 750 ° C. or more. Manufacturing method. 2. C: 0.01% to 0.20%, Si:
0.50% or less, Mn: 0.30% to 2.00%, P:
0.020% or less, S: 0.020% or less, Al: 0.
Manufacture of a steel tube for a high-strength and toughness airbag, characterized in that a steel tube containing 10% or less and the balance being Fe and unavoidable impurities is subjected to hot pipe making so that the final finishing temperature is 750 ° C. or more. Method. 3. C: 0.05% or more and less than 0.15%, S
i: 0.50% or less, Mn: 0.30% to 2.00%,
P: 0.020% or less, S: 0.020% or less, Al:
0.10% or less, Mo: 0.50% or less, V:
0.10% or less, Ni: 0.50% or less, Cr: 1.0
0% or less, Cu: 0.50% or less, Ti: 0.10% or less, Nb: 0.10% or less, B: 0.005% or less, the balance being Fe and inevitable A method for producing a steel pipe for a high-strength and tough airbag, wherein a steel pipe made of impurities is subjected to hot pipe making so that a final finishing temperature is 750 ° C. or more. 4. C: 0.01% to 0.20%, Si:
0.50% or less, Mn: 0.30% to 2.00%, P:
0.020% or less, S: 0.020% or less, Al: 0.
Including 10% or less, Mo: 0.50% or less, V: 0.1
0% or less, Ni: 0.50% or less, Cr: 1.00% or less, Cu: 0.50% or less, Ti: 0.10% or less, N
b: 0.10% or less, B: 0.005% or less of steel containing at least one of the following, the balance being Fe and unavoidable impurities, hot-rolled steel such that the final finishing temperature is 750 ° C or more. A method for producing a steel pipe for a high-strength, high-toughness airbag, comprising: 5. C: 0.05% or more and less than 0.15%, S
i: 0.50% or less, Mn: 0.30% to 2.00%,
P: 0.020% or less, S: 0.020% or less, Al:
A steel containing 0.10% or less, with the balance being Fe and unavoidable impurities, is subjected to stress relief annealing, annealing, normalizing, quenched or quenched and tempered after hot pipe making. A method for manufacturing a steel pipe for a high-strength, high-toughness airbag. 6. C: 0.01% to 0.20%, Si:
0.50% or less, Mn: 0.30% to 2.00%, P:
0.020% or less, S: 0.020% or less, Al: 0.
A steel containing 10% or less, with the balance being Fe and unavoidable impurities, being subjected to stress relief annealing, annealing, normalizing, quenched or quenched and tempered after hot pipe making. Manufacturing method of steel pipe for high strength and toughness airbag. 7. C: 0.05% or more and less than 0.15%, S
i: 0.50% or less, Mn: 0.30% to 2.00%,
P: 0.020% or less, S: 0.020% or less, Al:
0.10% or less, Mo: 0.50% or less, V:
0.10% or less, Ni: 0.50% or less, Cr: 1.0
0% or less, Cu: 0.50% or less, Ti: 0.10% or less, Nb: 0.10% or less, B: 0.005% or less, the balance being Fe and inevitable A method for producing a steel tube for a high-strength and toughness air bag, comprising: subjecting a steel tube made of impurities to hot tube production, and then subjecting the steel tube to stress relief annealing, annealing, normalizing, quenching or quenching and tempering. 8. C: 0.01% to 0.20%, Si:
0.50% or less, Mn: 0.30% to 2.00%, P:
0.020% or less, S: 0.020% or less, Al: 0.
Including 10% or less, Mo: 0.50% or less, V: 0.1
0% or less, Ni: 0.50% or less, Cr: 1.00% or less, Cu: 0.50% or less, Ti: 0.10% or less, N
b: 0.10% or less, B: 0.005% or less, the balance consisting of steel containing Fe and unavoidable impurities, after hot pipe forming, stress relief annealing, annealing, annealing A method for producing a steel pipe for a high-strength and tough airbag, wherein the pipe is subjected to a quenching process or a quenching and tempering process.