JPH10212549A - ERW steel pipe for airbag with high toughness and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric resistance welded steel pipe excellent in workability and suitable for an airbag component requiring high toughness, and a method for producing the same. SOLUTION: C: 0.20% or less, Si: 0.50%
Hereinafter, Mn: 0.30% to 2.00%, P: 0.020
%, S: 0.010% or less, Al: 0.10% or less, with the balance being Fe and unavoidable impurities, a high toughness electric resistance welded steel tube for an airbag, excellent in workability and weldability, and High toughness can be secured. In addition, the steel is subjected to stress relieving annealing, annealing, normalizing, quenching or quenching and tempering treatment with or without the ERW pipe, thereby providing excellent workability and weldability and high toughness. Suitable for required airbag parts.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-toughness airbag steel pipe which is excellent in workability and weldability and is suitable for an airbag component requiring high toughness, and a method for producing the same.

[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 keeps the inert gas and the like blown into the air bag at the time of collision at 300 kgf / cm ² at all times, and adds a small amount of gas at the time of collision to ignite the explosive. Since the gas is ejected, stress is applied at a large strain rate in a very short time. Therefore, unlike a conventional structure such as a conventional pressure cylinder or line pipe, high toughness and workability and weldability are required. The steel pipe used for the accumulator is
Since a large number are required in automobiles, cost reduction is required.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a new field without any prior art, which has excellent workability and weldability,
It is another object of the present invention to provide a high toughness electric resistance welded steel pipe suitable for an airbag component that requires low cost as well as strength and high toughness and a method of manufacturing the same.

[0005]

Means for Solving the Problems The present inventors have intensively studied and studied to achieve the above object. As a result, a predetermined chemical component suitable for the accumulator of the air bag system was found. Further, after hot rolling the steel having the predetermined chemical composition so that the final winding temperature is 700 ° C. or lower, an ERW steel pipe is manufactured, or the steel having the predetermined chemical composition is heated to a final winding temperature of 700 ° C. After hot rolling to below ℃, after making ERW steel pipe, stress relief annealing, annealing,
By conducting normalizing, as-quenched or quenching and tempering treatment, it was determined that an ERW steel pipe having excellent workability and weldability and high toughness can be obtained at low cost, and the present invention has been achieved.

[0006] The electric resistance welded steel tube for a high toughness air bag according to the first aspect of the present invention comprises: C: 0.20% or less, Si: 0.50% or less, Mn: 0.30% to 2.00%, P: 0.020%
Hereinafter, S: 0.010% or less, Al: 0.10% or less, with the balance being Fe and unavoidable impurities. Thus, by limiting the chemical components in the steel to the above component composition, sufficient strength, toughness, high workability, and weldability for accumulators for airbags can be ensured.

The electric resistance welded steel pipe for a high toughness air bag according to claim 2 of the present invention has a C content of 0.20% or less and a Si content of 0.5%.
0% or less, Mn: 0.30% to 2.00%, P: 0.0
20% or less, S: 0.010% or less, Al: 0.10%
Mo: 0.50% or less, V: 0.10% or less, Ni: 0.50% or less, Cr: 1.00% or less, C
u: 0.50% or less, Ti: 0.10% or less, Nb:
0.10% or less, B: 0.005% or less, Ca: 0.0
It contains one or more of the elements of not more than 05%, with the balance being Fe and unavoidable impurities. Thus, by limiting the chemical components in the steel to the above component composition, sufficient strength, toughness, high workability, and weldability for accumulators for airbags can be ensured.

Further, according to a third aspect of the present invention, there is provided a method for producing an electric resistance welded steel pipe for a high toughness air bag, wherein a steel slab having the chemical composition according to the first aspect is hot-rolled and wound at a winding temperature of 700 ° C. or lower. It is to be manufactured using the hot-rolled coil taken. Thus, the above-mentioned billet is hot-rolled and the winding temperature is 700 ° C.
By manufacturing using the hot-rolled coil wound below, it is possible to obtain an electric resistance welded steel pipe for an air bag having strength, high toughness, and excellent workability and weldability suitable for the properties of the final purpose.

Further, according to a fourth aspect of the present invention, there is provided a method for producing an electric resistance welded steel pipe for a high toughness air bag, wherein the steel slab having the chemical composition according to the second aspect is hot-rolled and wound at a winding temperature of 700 ° C. or lower. It is to be manufactured using the hot-rolled coil taken. As described above, the steel slab is manufactured by using a hot-rolled coil which is hot-rolled and wound at a winding temperature of 700 ° C. or less, thereby obtaining strength, high toughness and workability suitable for the properties of the final purpose. And an electric resistance welded steel tube for an airbag having excellent weldability.

According to a fifth aspect of the present invention, there is provided a method of manufacturing an electric resistance welded steel pipe for a high toughness air bag, wherein the electric resistance welded steel pipe produced by the method of the third aspect is subjected to stress relief annealing, annealing, normalizing, and quenching. As it is or quenched and tempered.
Thus, an ERW steel pipe manufactured by using a hot-rolled coil obtained by winding a steel slab of the above chemical composition at a winding temperature of 700 ° C. or less is subjected to stress relief annealing, annealing, normalizing, as-quenched or quenched and tempered. By performing the treatment, it is possible to obtain an electric resistance welded steel pipe for an airbag having strength, high toughness, and excellent workability and weldability suitable for the properties of the final purpose.

Further, according to a sixth aspect of the present invention, there is provided a method for manufacturing an electric resistance welded steel pipe for a high toughness air bag, wherein the electric resistance welded steel pipe produced by the method according to the fourth aspect is subjected to stress relief annealing, annealing, normalizing, and quenching. As it is or quenched and tempered. In this way, the steel slab of the chemical composition is wound at a winding temperature of 700.
ERW steel pipes manufactured using hot-rolled coils wound at or below ℃ are subjected to stress relief annealing, annealing, normalizing, as-quenched or quenched and tempered to obtain strength and high strength suitable for the properties of the final purpose. An electric resistance welded steel pipe for an airbag which is tough and excellent in workability and weldability can be obtained.

[0012]

DETAILED 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
Although it is an element added to obtain the necessary strength of steel at low cost, if it exceeds 0.20%, workability and weldability deteriorate, and toughness is reduced.

[0013] Si is an element that inhibits the cold workability of steel, and if it exceeds 0.50%, the workability deteriorates.
0.50% or less.

Mn is an element effective for improving the strength and toughness of steel. However, if it is less than 0.30%, sufficient strength and toughness cannot be obtained. Is deteriorated, so the content is 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 Mn in steel
To form inclusions due to MnS, and to deteriorate the workability and reduce the weldability and toughness.
It was as follows.

Al has an element effective for improving the workability, but when the content exceeds 0.10%, the effect is reduced. Therefore, the content of Al 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 an accumulator of an air bag. It is effective to further add Mo, V, Ni, Cr, Cu, Ti, Nb, B, and Ca 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 welded portion is reduced, 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 cannot be expected to be effective 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, but 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. Therefore, Cu is set to 0.50% or less.

Ti is effective in improving toughness by making the structure finer, but if it exceeds 0.10%, on the contrary, it deteriorates toughness. Therefore, Ti is set to 0.10% or less.

Nb is effective for improving the toughness by refining the structure similarly to Ti, but when it exceeds 0.10%, on the contrary, it deteriorates the toughness.

B is an element effective for improving the hardenability, but if it exceeds 0.005%, the toughness is reduced. Therefore, B is set to 0.005% or less.

Ca is an element effective for controlling the morphology of MnS-based inclusions. In particular, Ca is effective for reducing cracks caused by inclusions near the welded portion. , The toughness is reduced, so the content is made 0.005% or less.

In the present invention, toughness is imparted by hot rolling a steel slab having a chemical composition adjusted as described above at a winding temperature of 700 ° C. or lower to form a hot rolled coil. If the winding temperature during the hot rolling exceeds 700 ° C., the crystal grains become coarse and high toughness cannot be obtained. Therefore, in the present invention, when the required temperature, toughness, and workability are not obtained when the winding temperature during hot rolling is 700 ° C. or less or in a hot-rolled state, the stress after pipe production is reduced. By performing removal annealing, annealing, normalizing, quenching or quenching and tempering, an electric resistance welded steel tube for an airbag having strength, high toughness, excellent workability and weldability can be obtained.

Among the heat treatments after the above-mentioned pipe making, stress relief annealing is applied when strength is required even if toughness is slightly lowered. The annealing treatment is applied when even toughness is required even if the strength is slightly reduced. The normalizing process is applied when workability and toughness are more important than strength. As-quenched or quenched and tempered treatment can provide high strength and high toughness.

[0029]

EXAMPLES Using a slab 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, the hot rolling finish temperature was 6 ° C.
Hot-rolled coils were formed at 00 to 750 ° C. to form hot-rolled coils. Each hot-rolled coil was formed and then subjected to ERW welding to produce an ERW steel pipe having an outer diameter of 60.0 mm and a thickness of 2.5 mm. After this, the stress-relieved annealing at 500 ° C., the annealing at 900 ° C., the annealing at 600 ° C., the quenching at 900 ° C.
Heat treatment of quenching at 900 ° C. and tempering at 500 ° C. was performed, and various characteristics were evaluated. 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 ERW steel pipe 1 was cut in half as shown by a dashed line, a half test piece 2 having a length of 10 mm was collected, and the table 3 of the drop weight test device shown in FIG.
The half-specimen 2 was placed thereon, and a weight 4 having a weight of 5 kg was dropped from a position of 2000 mm from the upper surface of the mounting table 3 to check for cracks. The drop weight test was performed at -40 ° C for 1 hour.
The test was repeated 0 times, and the crack rate was evaluated. Workability was evaluated in terms of flatness. The flatness is shown in FIG.
As shown in the figure, a V-block (60
°) using the pressing tools 5 and 5 to flatten the ERW 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 ×.

[0031]

[Table 1]

[0032]

[Table 2]

[0033]

[Table 3]

[0034]

[Table 4]

As shown in Tables 1 and 3, the steel No. 1 to 1
9 using the steel of the present invention. In all of the components and processes of the present invention examples 1 to 28, the cracking rate in the drop weight test was 0%, and there was no cracking of the shoulder after flattening, and the workability was good.

On the other hand, as shown in Tables 2 and 4, steel No. Comparative steels Nos. 20 to 26 and steel Nos. Test No. 18 using the steel of the present invention. The comparative examples 29 to 36 are steel Nos.
18, 20, 23 to 26 have a crack rate of 10 in the drop weight test.
% Or more, and cracking of the shoulder after flattening occurs,
Lack of toughness and workability.

[0037]

According to the first and second aspects of the present invention, the electric resistance welded steel pipe for a high toughness air bag is formed by subjecting an electric resistance welded pipe to a steel material whose chemical composition has been adjusted as described above. It is possible to obtain an ERW steel pipe having excellent workability and weldability suitable for applications such as accumulators for bags and high toughness.

According to a third aspect of the present invention, there is provided a method for manufacturing an electric resistance welded steel pipe for a high toughness air bag, comprising the steps of:
ERW pipes made of hot-rolled coils hot-rolled at a temperature of less than ℃ can be used to obtain ERW steel pipes with excellent workability and weldability and high toughness suitable for applications such as accumulators for airbags. it can.

The method for producing an electric resistance welded steel pipe for a high toughness air bag according to claims 5 and 6 of the present invention comprises the steps of:
High-toughness suitable for the final target properties by subjecting ERW pipes to hot-rolled coils that are hot-rolled at a temperature of less than ℃ and then subjecting them to stress relief annealing, annealing, normalizing, as-quenched or quenched and tempered. In addition, it is possible to obtain an ERW steel pipe for an accumulator of an airbag which is excellent in workability and weldability.

[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]

 DESCRIPTION OF SYMBOLS 1 ERW steel pipe 2 Half test piece 3 Stand 4 Weight 5 Push tool 6 Shoulder

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C22C 38/04 C22C 38/04

Claims (6)

[Claims] 1. C: 0.20% or less, Si: 0.50%
Hereinafter, Mn: 0.30% to 2.00%, P: 0.020
% Or less, S: 0.010% or less, Al: 0.10% or less, and an electric resistance welded steel tube for a high toughness air bag, wherein a steel containing Fe and unavoidable impurities is used as the balance. 2. C: 0.20% or less, Si: 0.50%
Hereinafter, Mn: 0.30% to 2.00%, P: 0.020
%, S: 0.010% 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, Ti: 0.10% or less, Nb: 0.1
0% or less, B: 0.005% or less, Ca: 0.005%
An electric resistance welded steel tube for a high-toughness airbag, characterized by using steel containing at least one of the following, and the balance being Fe and unavoidable impurities. 3. C: 0.20% or less, Si: 0.50%
Hereinafter, Mn: 0.30% to 2.00%, P: 0.020
%, S: 0.010% or less, Al: 0.10% or less, using a hot rolled coil obtained by winding a steel slab consisting of Fe and unavoidable impurities at a winding temperature of 700 ° C or less. A method for producing an electric resistance welded steel pipe for a high-toughness airbag, characterized by being produced by: 4. C: 0.20% or less, Si: 0.50%
Hereinafter, Mn: 0.30% to 2.00%, P: 0.020
%, S: 0.010% 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, Ti: 0.10% or less, Nb: 0.1
0% or less, B: 0.005% or less, Ca: 0.005%
A high toughness air bag comprising: producing a steel slab containing at least one of the following, with the balance being Fe and unavoidable impurities, using a hot-rolled coil wound at a winding temperature of 700 ° C or lower. For manufacturing electric resistance welded steel pipes. 5. C: 0.20% or less, Si: 0.50%
Hereinafter, Mn: 0.30% to 2.00%, P: 0.020
%, S: 0.010% or less, Al: 0.10% or less, using a hot rolled coil obtained by winding a steel slab consisting of Fe and unavoidable impurities at a winding temperature of 700 ° C or less. A method for producing an electric resistance welded steel tube for a high toughness air bag, comprising subjecting the electric resistance welded steel tube manufactured as described above to stress relief annealing, annealing, normalizing, as-quenched or quenching and tempering. 6. C: 0.20% or less, Si: 0.50%
Hereinafter, Mn: 0.30% to 2.00%, P: 0.020
%, S: 0.010% 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, Ti: 0.10% or less, Nb: 0.1
0% or less, B: 0.005% or less, Ca: 0.005%
A steel slab containing at least one of the following, the balance being Fe and unavoidable impurities, was subjected to stress relief annealing and annealing of an electric resistance welded steel pipe manufactured using a hot rolled coil wound at a winding temperature of 700 ° C. or lower. A method for producing an electric resistance welded steel pipe for a high toughness air bag, comprising annealing, normalizing, as-quenched or quenching and tempering.