TW201144455A - Steel pipe for air bag and manufacturing method thereof - Google Patents

Abstract

The present invention provides a steel pipe for air bag, which is reduced in alloy cost and has a tensile strength of 1,000 MPa or higher and a vTrs100 of -80 DEG C or less. A process for producing the steel pipe is also provided in which the number of softening/annealing treatments in the cold drawing step can be minimized. Stable properties can be obtained even through quenching thermal treatment is conducted by mass-scale high-frequency heating. The steel pipe has a steel composition which contains, in terms of mass%, 0.05-0.20% C, 0.10-0.50% Si, 0.10-1.00% Mn, up to 0.025% P, up to 0.005% S, 0.005-0.10% Al, 0.0005-0.0050% Ca, 0.005-0.050% Nb, 0.005-0.050% Ti, 0.01-0.50% Cu, 0.01-0.50% Ni, 0.01-0.50% Cr, 0.0005-0.0050% B, 0.002-0.010% N and the remainder comprising Fe and inevitable impurities.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel pipe for an air bag having a high strength of tensile strength of 1000 MPa or more and a high toughness of vTrs 100 of -8 0 ° C or less, and a method for producing the same. More specifically, the present invention relates to a steel pipe for airbags which can be manufactured by a relatively inexpensive and simple manufacturing process, and which can be used for short-time heat-injection heat treatment by a rapid heating means such as high-frequency induction heating, and a method for producing the same. [Prior Art] In recent years, in the automotive industry, the introduction of safety-seeking devices has been actively pursued. One of such devices is, for example, development of an airbag system. It is a system in which the airbag is deployed between the passengers by gas or the like before the passenger collides with the steering wheel or the instrument panel, and the occupant's kinetic energy is absorbed to reduce the damage. In the past, the airbag system has adopted the method of using explosive drugs. However, in recent years, a system using a high-pressure gas-filled gas has been developed, which has been widely used. The above system using a high-pressure gas-filled gas maintains a constant high pressure of the gas, etc., and the high-pressure gas is instantaneously ejected in the airbag during the collision. Therefore, the steel pipe used for the high-pressure gas storage cylinder must be loaded at a large deformation speed in a very short time. stress. Therefore, the above-mentioned steel pipe is different from the conventional simple structure such as a pressure cylinder or a wire conduit, and requires high dimensional accuracy, workability, and solubility, and further requires high strength and excellent burst resistance. Recently, in the case of thinning and lightening, in order to ensure a high burst pressure, an ultra-high-strength seamless steel pipe having a tensile strength exceeding -5 - 201144455 lOO MPa is also used in an air bag system as an air reservoir. For example, when the air reservoir consisting of a seamless steel pipe with a wall thickness of 3.55 mm and an outer diameter of 60 mm is as high as about 100 MPa with respect to the burst pressure when the TS is 800 MPa, the burst pressure is increased to 130 MPa when the TS becomes 1000 MPa. . Moreover, when the outer diameter of the gas pipe of the air bag and the required burst pressure are constant, the wall can be thinned by about 20%. For example, in a cold area, the gas cylinder also needs to have excellent low temperature toughness, so that the air reservoir is collided. Brittle damage will not lead to secondary disasters. From these points of view, the seamless steel pipe used in the gas cylinder is subjected to quenching-tempering to impart high strength and high edge resistance. Specifically, in the state in which the air reservoir is subjected to the diameter reduction processing as described later, even in the temperature range of -6 (the temperature range below TC, sufficient low temperature toughness is required). However, the air reservoir for the air supply is generally After the jointless steel pipe of the pipe is cut into a specific length and becomes a short pipe, at least one end is subjected to a reduction process such as press working or spinning processing (referred to as a bottle mouth processing), and finally processed into a shape required for loading such as a blasting agent. In the action of the air reservoir for the airbag, there is a case where the toughness of the seamless steel pipe which is the material is incomplete. This is because the toughness of the bottle portion is reduced by the reduction processing of the final processing. The possibility of cracking during high-pressure load. Therefore, considering the reduction in toughness, the seamless steel pipe used for the gas storage cylinder must have a lower temperature toughness than the ambient temperature of the gas cylinder. For the jointless steel pipe constituting the gas storage cylinder, it is required to have an elongation of 10% or more and a tensile strength of 100 MPa or more at -80 ° C, preferably at -10 ° C. Xiabi Charpy) impact test, the fracture exhibits low temperature toughness of elongation (that is, vTrslOO is below -80 ° C, preferably below -100 ° C low temperature toughness). As for the high strength and high tensile strength of 1 000 ΜΡa or more A conventional technique for a seamless steel pipe for a flexible airbag system is, for example, Patent Document 1. Patent Document 1 proposes a seamless steel pipe using a steel material having a chemical composition of a specific range, and applying the seamless steel pipe to the seamless steel pipe. Cold-stretching into a steel pipe of a specific size, followed by heating to a temperature in the range of Ac3 above the transformation point and below 1 050 °C, followed by quenching, and then in the range of 450 ° C or higher and below the A c 1 transformation point The method for producing a seamless steel pipe for tempering at the temperature of the inside is obtained. According to this method, the processability and the weldability at the time of producing the air bag for an air bag (In flator) are excellent, and the air cylinder has a stretch of 900 MP a or more. The strength, and the jointless steel pipe showing the high toughness of elongation for the weight drop test of the longitudinal section of the steel pipe at -6 0 ° C. However, in order to obtain the steel of strength and toughness by this method It is necessary to contain a large amount of Cr, which is expensive. In Patent Document 2, it is shown that by high-frequency heating and quenching, by rapidly heating and fine-graining, it is possible to manufacture a high-strength and high-toughness airbag system having a tensile strength of more than 10,000 MPa. Sewed steel pipe. This technology uses a steel material of a specific range of chemical composition to form a seamless steel pipe, and then the cold-stretched steel pipe is cold-stretched into a steel pipe of a specific size, and then, at 1 〇t/sec. After the above heating rate is heated to 900 to 1 000 ° C, quenching is performed, and then 201144455 tempering is performed at a temperature below the Acl transformation point. The elongation is also exhibited in an explosion test such as below -8 0 ° C. High toughness. Although a specific example of heating for quenching at 20 ° C / sec is exemplified in Patent Document 2, it is expected that the industrial productivity is expected to be rapidly heated in a shorter period of time, and the holding time at the reaching temperature is also short. When the heat is rapidly heated in a short period of time and the heat treatment is performed in a short holding time, if the heating temperature is uneven, since the local temperature is also lower than Ac3, it is desirable to set a slightly higher heating temperature if possible. However, in the case of high-frequency heating, in order to become a rapid heating, there is a problem of heating over-shooting exceeding the set temperature. Therefore, it is necessary to consider that the high-frequency heating quenching has a temperature exceeding 1 〇〇〇 ° C. However, such a problem at the time of mass production is not described in Patent Document 2. On the contrary, when the temperature exceeds 1 〇〇〇 °C, there is a problem that the r particles are coarsened and the toughness is lowered. Patent Document 3 also shows an example in which high-frequency heating and quenching is used. However, as shown in Table 3 of the examples of the document, heating in a short time in the range of 900 to 1 000 ° C is not assumed, and the same as in Patent Document 2 The problem. In Patent Document 4, high-frequency heating quenching is also used. However, as shown in the examples, heating in the range of 920 to 940 °C has the same problem as Patent Document 2. PRIOR ART DOCUMENT Patent Document 1: JP-A-2004-76034 Patent Document 2: WO 2004/104255 A1 Patent Document 3: WO 2002/079526 A1 Patent Document 4: US 2006/0169368 A1 201144455 [Summary of the Invention] [Problems to be Solved by the Invention] In the past, although various jointless steel pipes for airbags have been proposed, in recent years, steel pipes for high-strength airbags having a tensile strength of 1 000 MP a are required to be at -60 ° C, preferably - The ductility was exhibited under the 80 °C burst test. The bursting resistance is designed to increase the degree of freedom in the design of the gas cylinder. The lower limit temperature of the 100% extensibility fracture (vTrslOO) of the Charpy impact test is below -80 °C, preferably -10 °C. the following. In the conventionally known literature, excellent low-temperature toughness and bursting performance have been confirmed by induction hardening and tempering, and it has been rapidly heated to a temperature of 900 to 1 000 °C. When the steel pipe is thinned, the heating temperature is increased in a large amount by actual high-frequency heating and quenching. In this case, the heating temperature is lowered for a while, and it is more than 100 (TC, which is not predicted by the prior art, and the stability of the product performance is lowered to lower the yield. For example, in Patent Document 1, according to the present inventors, etc. The human opinion is that the cold drawing processability is insufficient due to the large amount of Cr, and in order to ensure a large degree of processing in the cold drawing stage, intermediate softening and blunting are required several times in the middle, and there is a problem that the manufacturing cost increases. Although the elongation is shown in the drop weight test at -60 ° C, it does not mean that the elongation is necessarily exhibited in the burst test at -60 ° C. Also, in terms of efficient mass production, it is better. The manufacturing steps are simple. In the conventionally known literature, the sum of the contents of Cr and Mo as the steel composition is almost in the range of more than 0.6%. When a large amount of the Cr and Mo are contained, the seamless steel pipe is formed after heating. The air cooling also increases the strength of the strong 9 - 201144455, but due to the difficulty of cold drawing, it is necessary to soften and burn before the cold drawing process, which complicates the process and is costly. The above-mentioned patent documents are not mentioned, but many of them are examples in which a small amount of steel tubes for airbags are not contained in Cr or Mo, or a total content thereof is reduced to 0.6% or less. However, the range of known examples of the composition of the steel is described. It is not speculated that the 100% extended fracture lower limit temperature (vTrslOO) is shown to exhibit an extensible fracture at an explosion test of -8 (below TC) or at one side at -60 °C, while ensuring stability above 1 000 ΜΡ a. Examples of the tensile strength. Although there are more than 1,000 MPa in the past, in this case, it is not possible to obtain the high tensile strength and the excellent low temperature toughness at the same time. The object of the present invention is to provide an airbag. The current required performance of the gas storage cylinder, that is, the high pressure of the gas cylinder pressure and the thinning of the steel pipe, and the high quenching suitability for high-frequency induction heating by a mass production scale. The steel pipe and the method for producing the same. Here, the technical problem of the present invention is more specifically listed as follows: (I) The final product is required to have a tensile strength of 100 MPa or more, preferably 1050 MPa or more. -6 (TC also exhibits excellent low temperature toughness in the burst test, especially the 100% elongation lower limit temperature (vTrslOO) is below -80 °C, preferably below -100 °C. The steel pipe for gas is called the technical problem (I). (II) The steel pipe according to the above (I) which suppresses the cost of the alloy, in particular, is required to reduce the use of Mo which is often used for high strength in the past. (Π) (III) For the steel pipe described in (I) above, it is required to reduce the alloy design of the number of times of softening and blunting in the less cold stretching step as much as possible - 201144455. More specifically, 'required pipe In the cold drawing processing stage, the intermediate softening and blunt treatment is not performed, and the degree of processing of 40% or more can be achieved, and the alloy design with high cold workability can be realized. Called the technical topic (III). (IV) As for the better mode, it is required to manufacture the alloy in a state in which the stability of the steel pipe described in the above (I) can be obtained by quenching the steel pipe described in the above (I) by mass production scale, and more Specifically, it is required to manufacture a steel pipe for airbags of a product having a certain level or higher toughness even when the heating temperature for heating quenching exceeds 1 000 ° C (for example, 1020 to 104 (TC). Problem (IV) In order to solve the above problems, the present inventors investigated the relationship between alloying elements, strength, and low-temperature toughness in a seamless steel pipe for an airbag system subjected to quenching and tempering after cold working. As a result, unlike the current understanding, it is unexpected that the balance between the excellent strength and toughness required to determine the current requirement, even if it does not contain Mo, can be reduced by a small amount of Μη, and a large amount of Cr added so far. Addition, which is obtained by a steel containing an appropriate amount of Cu, Ni, Ti, and niobium. That is, the inventors of the present invention have developed a TS super for quenching and tempering after cold working for alloying elements. The airbag system over 100 MPa was examined for the influence of the strength and toughness of the seamless steel pipe. As a result, the following findings were obtained, and the present invention was completed. (i) It was judged that C, Si, Μη, Al, Ca, Nb, Ti were contained in an appropriate amount. ' -11 - 201144455 and B' have been added in large quantities for high strength until ^5 % or less 'does not contain Mo (according to the need to contain less than 〇1%), Cu and Ν each are 0.01~0.50 When % is substituted and the total content of Cu and Ni is {(C〇+ M〇) 2 + 0.3} or more, the above problems (I), (Π), and (III) can be effectively achieved at the same time. The heating temperature at the time of rapid heating and quenching is, for example, 10 ° C ° C, which is higher than the upper limit (1 〇〇〇 r ) of the target range of alignment, that is, 'for the above problem (IV) 'by containing Ti: The present invention is based on the above findings and is further reviewed, and the subject matter of the present invention is as follows: (1) A non-seamless steel pipe for gas, characterized by having a C: 0.05 to 0.20 %, Si: 0.10-0.50%, Μη: 0.10-1.00% ' Ρ : 0.025% or less, S: 0.005% or less, A1 : 0.005-0.10% ' Ca : 0.0005 ～ 0.0050 %, Nb : 0.005-0.050% ' Ti : 0.005 ~ 0.050 % , Cu: 0.01 ~ 0.50 %, Ni: 0.01-0.5 0% ' Cr: 0.0 1-0.5 0% ' B : 0.0005~0.0050%, N : 0.002~0.0 10%, the rest is Fe and not It is composed of impurities which are avoided, and satisfies the steel composition of the following formula (1), has a tensile strength of 100 MPa or more, and has a high toughness of vTrslOO of -80 ° C or less.

Cu + Ni ^ (M) 2 + 0.3 (1) Further, "Μ" of the formula (1) means that the Cr' element symbol means the number 値 when the content of the elements is expressed by mass%. (2) The seamless steel pipe for an airbag according to (1), wherein the content of Ti -12 to 201144455 is more than 〇 〇 2 〇 % and is 〇 · 〇 50% or less by mass%. (3) The seamless steel pipe for an airbag according to (1) or (2), which has a steel composition containing, in mass%, Mo: less than 0.10% and satisfying the following formula (1):

Cu + Ni ^ (M) 2 + 0.3 (1) Further, the "Μ" of the formula (1) means that the (Cr + Mo ) 'element symbol means the number of the elements in mass %. . When the Mo content is 0, 〇 (zero) is substituted into the formula (1). (4) The seamless steel pipe for an airbag according to any one of (1) to (3), which further comprises, by mass%, a steel composition of V: 0.02 to 0.20% (5) - for an airbag A method for producing a seamless steel pipe, characterized in that a seamless steel pipe produced by using a hot pipe is used for a billet having a steel composition according to any one of (1) to (4) The steel pipe of a specific size is processed by cold working with a degree of cold working of 40% or more, and after being corrected as necessary, it is heated to a temperature higher than the Ac3 metamorphic point by high-frequency heating and quenched by quenching, and then heated to below the Ac 1 metamorphic point. Tempering at the temperature. [Effect of the Invention] According to the present invention, it is possible to provide a seamless steel pipe having extremely high strength and excellent low-temperature bursting performance, which contributes significantly to the high pressure of the airbag storage cylinder whose end portion is reduced in diameter (1 4 5 Μ P a or more) Pressure) thin-walled lightweight (for example: seamless steel pipe with a wall thickness of 3.6 mm to 1.7 mm and a diameter of 60.3 mm to 25.0 mm - 13444445) [Embodiment] For the chemical composition and steel pipe of the steel pipe of the present invention The reason for the manufacturing method is described. (A) Chemical composition of steel "%" in the present specification means "mass % C : 0.05-0.20% c is an inexpensive element for effectively increasing steel strength unless otherwise specified. When the content is less than 0.05%, it is difficult to obtain a desired tensile strength of 100 MPa or more, and when it exceeds 0.20%, workability and weldability are lowered. Therefore, the content of c is 0.05 to 0.20%. The preferred range of 'C content is 〇 .〇7~0.17.

Si: 0.1 0 to 0.5 0 %

Si is an element which improves the hardenability and the strength of the steel in addition to the deoxidation effect, and the content is required to be 0.10% or more. However, when the content exceeds 0.50%, the toughness is lowered, so that the content of Si is 0.10 to 0.50%. Further, the preferred range of Si content is 〇.2〇~〇.50%» Μη: 0.10-1.00% Μη has a deoxidizing effect, and is an element which effectively improves the hardenability of steel and improves strength and toughness. However, when the content is less than 0.10%, sufficient strength and toughness cannot be obtained. On the other hand, when it exceeds 1.00%, the MnS is coarsened. This will delay the hot pressing and lower the toughness. In the present invention, Μη is suppressed to 1.00°/c or less, and it is necessary to ensure the tensile strength of 1 〇〇〇 MPa -14 - 201144455 or more and excellent low-temperature burst performance for the purpose, so that B is prepared as described later. Improved hardenability. 01〜〜1.00%。 According to this, the content of Μ η becomes 0. 1 0~ 1.00%. When the content of Μη becomes 〇.4〇~〇·90%, the balance between strength and toughness is preferable. Ρ : 0.0 2 5 % or less Ρ is a decrease in toughness due to grain boundary segregation, especially when the content exceeds 0.0 2 5 %. Therefore, the content of ruthenium is made 0.025% or less. Further, the content of bismuth is preferably 〇.02〇% or less, more preferably 0. 015% or less S: 0.0 0 5 % or less S is particularly perpendicular to the direction of the steel pipe, that is, perpendicular to the rolling method (longitudinal direction) of the steel pipe The toughness of the direction is reduced. In particular, when the content exceeds 0·0 0 5 %, the toughness of the steel tube in the τ direction is remarkably lowered. Therefore, the S content is 0.005% or less. Further, the content of S is preferably 0.003% or less. A1 : 0 · 0 0 5 % or more 0.1 0 % or less A1 is an element which has a deoxidizing effect and effectively improves toughness and workability. However, when the content exceeds 0.10%, a sand mark is remarkably generated. Therefore, the content of A1 is 0.10% or less. Further, in order to obtain the effect of the species A1, it is necessary to contain 0.005% or more. Further, the content of A1 in the present invention means the content of acid-soluble A1 (so-called "dissolution").

Ca : 0.000:5 〜0.00 5 0%

Ca is used to fix S in the steel as an inevitable impurity, and to improve the toughness of the toughness and to improve the toughness in the T direction of the steel pipe, thereby improving the burst resistance. This effect can be expressed by more than 0.0003%, especially -15-201144455 0.0005%. However, when the content exceeds 0.0050%, the amount of the filler increases and the toughness decreases. Therefore, the content of 〇3 is set to 〇.〇〇〇5~ 0.00 5 0% ·

Nb : 0.005-0.050%

Nb is finely dispersed in the steel by carbide, and has the effect of pinning the grain boundary. According to this, there is an effect of making the crystal grains finer and improving the toughness of the steel. In order to obtain this effect, 〇.〇〇 5 % or more is contained, but when it exceeds 0.050%, the carbide is coarsened and the toughness is lowered. Accordingly, the content of Nb is set to 0.005 to 0.050%.

Ti : 0.005-0.050%

Ti has the effect of fixing the N in the steel to improve the toughness. Further, the finely dispersed Ti nitride has the effect of strongly locking the crystal grain boundary to finely crystallize the crystal grains and to improve the toughness of the steel. Further, the fixing of N in the steel is also important for extracting the effect of B described later. Accordingly, in order to obtain such effects, 0.005% or more, but more than 0.050%, the nitride is coarsened and the toughness is lowered. Accordingly, the content of Ti is set to 0.005 to 0.05%. In particular, when quenching is performed by the rapid heating, it is easy to make the crystal grain size coarser than the heating temperature, and the toughness is easily lowered. Therefore, it is preferable to sufficiently utilize the crystal grain boundary locking effect by the Ti nitride. It means that the preferred content is more than 0.02 0%~0.03 5 % ° B : 0.0005-0.0050% B segregation at the grain boundary in steel, which significantly improves the quenching of steel and contributes to the improvement of toughness. The effect is exhibited when it contains 0.0005% or more. On the other hand, when the content exceeds 0.0050%, the boride at the crystal grain boundary is coarsely precipitated from -16 to 201144455, and the toughness is rather lowered. Accordingly, the content of B is set to be 0.0005 to 0.00 5 0%, preferably 0.0 〇 30% or less. In the present invention, since the upper limit of the amount of Μη is limited to 1.0%, the strength is improved by the improvement of the hardenability by blending. If there is no solid solution state, it is not segregated at the grain boundary. According to this, it is easy to use Ti to fix the compound, and it is preferable to use Ti to fix it. It means that the B content, the stoichiometry of B, Ti, and N preferably satisfies the relationship of the following formula (2) or (3): N - T i / 3.4 0 when B ^ 0.0005 ... (2) N- Ti/3.4 > 0 B-(N-Ti/3.4)x(10.8/14)^ 0.0005 (3) The enthalpy, N, and Ti in the formula (2) are respectively expressed by mass%. The number of times. N : 0.002 ~ 0.010% N is an impurity that cannot be avoided in steel. However, in the present invention, it is important to control the content of N by forming a nitride with Ti, utilizing the dispersion thereof, and fully utilizing the crystal grain boundary locking effect. In order to exert the effect, the content of N is made 0.002% or more. On the other hand, when N is excessively contained, the solid N increases or forms a compound with B, which causes a decrease in the amount of solid solution B. Therefore, the upper limit of the N content is set to 〇 · 〇 1 〇 % or less. Preferably, the N content ranges from 0.002 to 0.008%. Herein, the steel of the present invention can limit Mo to a very small amount even if C 、 is reduced and Μ Μ is added, and since Cu and Ni are contained, even with the addition of Β -17- 201144455, Cr and Mo can be suppressed. Since the carboride is precipitated, it is preferable in terms of improvement in strength and toughness.

Cu: 0.01 to 0.50%

Cu has the effect of improving the hardenability of steel and improving strength and toughness. If the effect is 0.001% or more, preferably 0.03% or more, it can be exhibited. However, if it contains more than 0.50%, the alloy cost is significantly increased. Accordingly, the content of Cu was set to 〇.〇1 to 0.50%. A preferred content is 0.03% or more, particularly 0.05% or more, more preferably 0.15% or more.

Ni : 0.01 to 0.50%

Ni has the effect of improving the hardenability of steel and improving strength and toughness. The effect can be exhibited if it is contained in an amount of 0.01% or more, preferably 0.03% or more. However, if the content exceeds 0.50%, the alloy cost is exceeded. Accordingly, the content of Ni is set to 0.01 to 0.50%. A preferred content is 0.03% or more, particularly 0.05% or more, more preferably 0.15% or more.

Cr : 0.01~0.50%

Cr has the effect of improving the hardenability of steel, improving the temper softening resistance, and improving strength and toughness. The effect is exhibited if each element contains 0.01% or more. However, when the content exceeds 0.5%, the strength at the time of cold stretching is exceeded, and it is not suitable due to a decrease in workability. Accordingly, the content of Cr is set to 0.01 to 0, 50%. It is preferably 0.18 to 0.40% β. Further, the balance of Cu, Ni, Cr, and Mo is as follows. The formula is defined by the formula of the content of Cu, Ni, Cr, and Mo. When Mo is added in the present invention, the contents of Cu, Ni, Cr, and Mo satisfy the following relationship from -18 to 201144455.

Cr and Mo hinder the spheroidization of cementation which is precipitated during tempering, and the steel containing B of the present invention is easy to form a B compound (boride) at the grain boundary, especially in high-strength materials. toughness. Therefore, by including Cr (and limiting Mo to a very small amount even when Mo is added), the strength is increased, and the strength is increased by the inclusion of Cu or Ni, which is also suitable for the present invention. High strength and high toughness steel pipe for airbags. Specifically, it is important that the balance of Cr, Mo, Cu, and Ni satisfies the following formula (1).

Cu + Ni ^ (M) 2 + 0.3 (1) "Μ" of the formula (1) means "Cr + Mo", and the symbol of the element is the number 値 when the content of each element is expressed by mass%. Further, when Mo is not contained, "Mo of "Cr + Mo" is substituted by 〇. The following elements may not be included, but may be included as needed. Μ 〇 : Not up to 0.01% In the present invention, Mo is not contained in principle, but may be contained in a small amount as needed. Mo has the effect of improving the hardenability of steel, improving the softening resistance of tempering, and improving strength and toughness. The effect can be seen even in a small amount, but it is preferably 0.01% or more in terms of obtaining a satisfactory effect. However, when it contains 0.10% or more, the alloy cost is exceeded. Further, when the content of the crucible is high, the jointless steel pipe tends to increase the strength during air cooling after the hot pipe, and the softening heat treatment before the cold drawing process becomes necessary, resulting in an increase in manufacturing cost. Accordingly, even if Mo is added, the content of Mo needs to be less than 0.10%. V: 0.02 to 0.20% -19- 201144455 V has an effect of increasing strength by precipitation strengthening. When the effect of these V is 0.02% or more, the effect is exhibited, but when it exceeds 0.20%, the toughness is lowered. Therefore, the V content at the time of addition is preferably set to 0. 02 to 0.20%. The V content is preferably in the range of 0.03 to 0.10%. Hereinafter, the method for producing the seamless steel pipe according to the present invention will be described with reference to the reasons for limitation. (B) Material In the present invention, there is no particular limitation on the steel block to be the material of the steel pipe. It may be a cast piece cast in a continuous casting machine having a cylindrical mold, or may be formed into a rectangular shape and then formed into a cylindrical shape by hot forging. The steel of the present invention is added to an austenite-stabilizing element such as Cu and Ni by adding an oxygenating element stabilization element such as Cr (Cr and Mo when Mo is added), so that even continuous casting is performed. When the spherical shape is used as a circular CC steel blank, the effect of preventing the center crack is also large, and it can be used as a circular CC steel embryo. The center of the circular CC steel has a large number of cracks, so that the seamless steel pipe is cold-worked, especially After the cold drawing, if the correcting process is applied, the crack is expanded and subjected to high-frequency quenching and tempering, and after the final diameter reduction process, cracks occur from the inner surface. Accordingly, the steel composition of the present invention can be suitably applied to a seamless steel pipe for an air bag in a gas cylinder, especially when a circular CC steel blank is used as a material. (C) Heat-manufactured pipe In the present invention, the pipe-making method of the steel pipe is not limited to -20-201144455 as long as the steel piece is made of the slab as described above in the chemical composition (B). For example, a Mannesmann mandrel (M a η n e s m a η η - M a n d r e 1 ) method can be employed. (D) Cold working Cold-working is carried out under the condition that the pipe-formed steel pipe of the seamless steel pipe as described above is obtained to obtain a specific dimensional accuracy and surface properties. As long as cold working can obtain specific dimensional accuracy and surface properties, this means that the specific method of cold drawing, cold rolling, etc. in cold working is not particularly limited. The degree of processing is better than the reduction ratio (the reduction rate of the section) is 3% or more. On the other hand, if it exceeds 50%, the inner surface wrinkles are significantly developed, so it is preferably less than 50. %. Further, although the number of cold working is several times, the size of the final product may be small. However, if the degree of micro-thinning is high, that is, if the degree of processing is high, the strength of the steel pipe rises due to work hardening, so cracks easily occur during processing. It is necessary to perform an intermediate heat treatment to soften it during the period. However, by using a steel having a chemical composition defined by (A), since the strength of the pipe is low, the strength is not excessively increased by cold working, and the softening heat treatment before cold working can be omitted. When the steel of the present invention is subjected to cold working, the preheating softening treatment or the intermediate softening and blunting is not performed, and the degree of reduction of the surface ratio of 40% or more, preferably more than 40%, can be achieved. In the present invention, the rate of reduction of the surface is the same as the reduction rate of the section, and is defined by the following formula. Reduction rate (%) = (S〇-Sf)xl 00/S〇 But

So: cross-sectional area of steel pipe before cold working sf: cross-sectional area of steel pipe after cold working 21 - 201144455 Also, if it is carried out without softening and burning in the middle, the total reduction area of multiple cold working can also be used as the above-mentioned reduction surface rate. However, in the present invention, it is not excluded from the cold processing in which the softening and burning are performed in the middle. (E) Correction Since the object of the present invention has a tensile strength exceeding 1,000 MPa, and has a seamless steel pipe which is necessary dimensional accuracy, surface property and low temperature toughness for use in a gas enthalpy system, the strength after cold drawing is higher than that of the conventional steel pipe. The tendency, by springback, is equal to the possibility of bending the steel tube. When the steel pipe is bent, there is a concern that the high-frequency coil cannot pass the straight steel pipe by quenching by the high-frequency heating described below. Therefore, in a preferred embodiment, in order to perform quenching by high-frequency heating, the refining process is performed after cold working (for example, cold drawing). The method of the correction processing is not particularly limited, but it is preferable to provide, for example, a four-row two-roll type calender such that the center positions of the roll gaps of the respective rows are different from each other and are shifted (i.e., offset), thereby adjusting the rolls. The gap is a method of applying bending and bending recovery by passing a steel pipe therebetween. The bending and bending recovery have a high degree of workability and a high correction effect. Therefore, the offset amount of the outer diameter of the steel pipe is preferably 1% or more of the outer diameter of the steel pipe, and the amount of the roll gap is preferably 1% or less of the outer diameter of the steel pipe. When the amount of the roll gap of 5% or more of the outer diameter of the steel pipe is less than 50% of the outer diameter of the steel pipe, there is no problem such as the occurrence of creases in the inner surface of the steel pipe. (F) Heat treatment After the above-mentioned (E) correction processing, the desired tensile strength of the steel pipe is also applied, and heat is also applied to improve the T-direction toughness and to ensure the explosive resistance. In order to make the steel pipe have high strength and explosive resistance with tensile strength of l〇〇〇MPa or more, it is heated to a temperature at least above the metamorphic point of Ac3, then quenched, and then tempered at a temperature below the A c 1 transformation point. . When the heating temperature before quenching does not reach the Ac3 transformation point of the austenite single phase, good T-direction toughness cannot be ensured (so that the explosion resistance cannot be ensured). On the other hand, when the heating temperature is too high, the austenite particles rapidly start to grow, tend to be coarse particles, and tend to lower the toughness, so that it is preferably 10.5 ° C or less. Further, after rapidly heating to a temperature higher than the A c3 transformation point in the austenite region, the austenite grain size is kept fine for a short period of time to ensure extremely high toughness. In such a rapid manner, the heating is maintained for a short period of time, and from the viewpoint of productivity, a high frequency induction heating method is preferably employed. Further, the heating rate at this time can be adjusted by the speed of the steel pipe passing through the high frequency wire, etc., but it is preferably about 25 〇C / sec or more. Better for 50. (: / / sec or more, and more preferably 1 0 0. (: / / sec or so. After heating to at least A c 3 above the temperature above the temperature of the cooling is better to be used to stabilize the desired 1 Quenching of tensile strength of 000 MPa or more or quenching by water quenching, etc. Specifically, the cooling rate between 800 ° C and 500 ° C during quenching treatment is preferably 50 ° C / sec or more. 125 ° C / sec. The steel pipe cooled by quenching to near normal temperature is tempered at a temperature below the change point of Ac 1 to impart the required tensile strength and explosive resistance at 1 MPa & If the Ac 1 metamorphic point is exceeded, it is difficult to obtain the above characteristics stably and reliably -23- 201144455. After tempering, the bending can be corrected by a suitable straight line straightening machine or the like as described in (E). Even if used (A In the pipe material composed of steel, if the heating rate or the cooling rate in the quenching stage is insufficient, there is a case where the strength and toughness of the object of the present invention cannot be stabilized and the purpose of the present invention is ensured. Cut to a specific length as previously described After the short tube is formed, at least one end is subjected to reduction processing such as press working or spinning, and finally processed into a shape required for loading such as a blasting agent, and used as an air bag. Embodiments (Example 1) This embodiment is The relationship between the steel composition and the low temperature toughness of the material produced by simulating the manufacturing conditions of the seamless steel pipe. The steel of the chemical composition of the six steel types shown in Table 1 is vacuum melted and melted, and hot rolled. Afterwards, cold rolling was used to form a sheet of 5 mm thick (40% processing degree), and then heated to 920 ° C at an average heating rate of 300 ° C / sec by high-frequency heating, while maintaining 920 ° C for x 5 seconds. The quenching treatment by water cooling is carried out, followed by tempering. From the sheet subjected to the heat treatment, a tensile test piece of 14A No. 14A (parallel portion diameter 4 mm, parallel portion length 20 mm) of JIS Z22 0 1 was taken perpendicularly to the rolling direction. The tensile test was carried out in accordance with JIS Z224 1. Also, in the same direction as the rolling direction, according to >118 22242, a V-notch Charpy test piece of a sampling size of 2.5111111 width was taken for the Charpy impact test. -24- 201144455 0.0042 0.0033 0.0045 0.0028 0.0052 0.0024 1 0.0039 0.0044 < oi/i 00 S d S ο τ~* S ο CM S Ο CM S d S 〇' CSI s Ο CM S Ο m 0.0015 0.0012 0.0006 0.0008 0.0007 0.0006 1 0.0013 0.0011 < 3 0.0022 0.0020 0.0020 0.0022 0.0023 0.0023 0.0009 0.0015 Γ- S ο <〇S § m S ο <〇S ο <〇SO a ο ο S ο S ο ο s ο ΙΟ CM Ο Ο g ο ο ο ο σ gt ; ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ΙΟ CS ο CQ CO C4 Ο 5 ο CO CNJ ο ο 5 δ in ο S ο co ca Ο LO eg ΙΟ ο Csi ο 5 ο CO S ο ο S ο ο 04 ο ο ο ο OJ ο ο S p 0.00t3 0.0013 CM ο CM CM CM CM Ο cr cr CO CM CM CM CM CM CM CM CM CM 00 00 00 00 00 00 Ο σ σ > Cs| σ > CM ο ο CQ σ> CSJ ο GO CM Ο C0 CNJ Ο Ο ττ ο CN Ο ο ο c〇5 inch ο in ο CO 5 JMJ CM C0 inch 1C CD ν 00

S -25- 201144455 Table 2 shows the tensile strength (τ S ) of each steel and the lower limit temperature of 100% calendering fracture obtained by the Charpy impact test (^1^3100). Adjusting the tempering temperature to adjust the range from 1^ to 1〇〇〇]^?3, but since the formula (1) is not satisfied, the high temperature of vTrslOO is higher than -80°c. Although it is sufficient as a material, it has sufficient toughness. If the toughness is lowered by the processing of the bottle mouth, there is a possibility that sufficient low-temperature burst performance cannot be obtained. [Table 2] Steel No. (Cu+NiHM) 2 TS (MPa) vTrslOO (°C) 1 0.15 1018 -75 2 0.15 1056 -70 3 0.12 1025 -70 4 0.36 1110 -100 5 0.41 1056 -110 6 0.49 1146 - 100 7 0.40 1024 -100 8 0.32 1033 -100 On the other hand, the steels 4 to 8 are more than 1 050 MPa or more in the TS system because the formula (1) is satisfied, and the vTrslOO is also -100 ° C or less. Predictions also ensure adequate low temperature burst performance. In Fig. 1, the total content of Cr and Mq and the total content of Cu and Ni in each steel in this example are plotted. When vTrslOO is -80 °C or more, it is represented by ▲, -1 〇〇. (The above is expressed as 〇. It can be understood from Fig. 1 that the total content of Cu and Ni is such that the total content of Cu and Ni is such that the relationship of the formula (1) is satisfied, and excellent low temperature toughness can be ensured.

Cu + Ni ^ (Cr + Mo) 2 + 〇 - 3 · (1) Further, the elemental mark of the formula (1) means the number 値 when the content of the elements is expressed by mass%. When it does not contain Mo steel, it becomes 1^^0. -26- 201144455 (Example 2) Steel having the chemical composition shown in Table 3 was dissolved in a converter, and a cylindrical steel embryo having an outer diameter of 191 mm was produced by continuous casting. The round CC steel embryos are cut into a desired length, heated at 1 250 ° C, and then perforated and calendered by a general Mannesmann-Mandrel method, thereby being modified to have an outer diameter of 70 mm. The wall thickness is 4.0 mm. The obtained seamless steel pipe was used as a pipe material, and subjected to cold drawing processing (cold drawing processing) in a usual manner, and was modified to have an outer diameter of 60.3 mm and a wall thickness of 3.6 mm. This is called steel pipe size 1. The steel pipe subjected to the cold drawing process is corrected by a linear straightening machine, and then heated to 920 ° C at an average temperature increase rate of 300 ° C / sec using a high frequency induction heating device, and maintained at 920 ° C for 5 seconds, and then water is applied. After quenching, a 30 minute soaking treatment for tempering is carried out in a usual walking beam furnace. In addition, the steel pipe size 1 is corrected by a straight line straightening machine, and a double roll type calender is provided in three rows, and the center position of the roll gap in the second row is shifted to 20 mm for the center position of the first column, and the third column is The center position of the roll gap is shifted to 3 mm for the center position of the first column, and the roll gap of the second column and the third column is adjusted to 58.8 mm (outer diameter - 1.5 mm) and 57.3 mm (outer diameter - respectively). 3.0 mm), a process of bending 'bending recovery' is applied by passing the steel pipe through. Further, in the same manner, a seamless steel pipe having an outer diameter of 51 mm and a wall thickness of 3.0 mm was subjected to perforation and rolling, and subjected to cold drawing processing (cold drawing processing) by a usual method to be modified into an outer diameter. 40.0mm wall thickness 2.6mm. This is called -27- 201144455 steel pipe size 2. The steel tubes subjected to the cold drawing process are corrected by a linear straightening machine, heated to 92 ° C for 5 seconds using a high frequency induction heating device, and then subjected to water quenching, followed by a conventional walking beam furnace. Heat treatment at tempering for 30 minutes. In addition, this steel pipe size 2 is corrected by a straight line straightening machine, and the center position of the roll gap in the second row is shifted to 1 〇mm in the center line of the first column, and the third position is the same as that of the steel pipe size 1. The center position of the roll gap of the column is shifted to 3 mm for the center position of the first column, and the roll gap of the second column and the third column is adjusted to 39.5 mm (outer diameter - 0.5 mm) and 39.2 mm (outer diameter - respectively). 0.8 mm), a process of applying bending and bending recovery by passing the steel pipe through the period. For the steel tube subjected to the induction hardening and tempering, the tensile test of the shape shown in Fig. 2 was used to investigate the strength characteristics. The figures in the figure indicate the dimensions (unit: mm). In addition, the steel tubes subjected to high-frequency quenching and tempering are cut into 6 pieces each of which is 300 mm long, and pressed at the ends of the two tubes to make the diameter of the reduced diameter portion/unshrinked. The diameter reduction portion was set to be 25 mm long so that the ratio of the diameter of the diameter portion was 0.6, and the shape of the mouth portion of the gas cylinder was created. Subsequently, the welded single end is sealed, and the other end is welded through the blocking member of the high pressure tube. The test body was immersed in ethanol in a chamber cooled to -60 ° C. Ethanol was injected into the tube from a high pressure tube and the internal pressure was increased to break the tube, and the failure mode was observed. As a result, the brittle fracture area ratio of all of the -28-201144455 of the test pieces of the steel tubes A and B of the steels A to B was less than 5%, and the full-heartedness was satisfied. performance. On the other hand, in each of the six types of the steel specimens of the steel tube sizes 1 and 2 of the steel C, three of them were destroyed early from the reduced diameter portion, and the burst pressure was remarkably lowered. Further, the brittle fracture area ratio of all the openings of the test pieces of steel D and steel E was 5% or more, and the performance was not satisfied. The above results are summarized in Table 4 together with the results of the above tensile test. Steel A to steel B in Table 4 are steels whose compositions satisfy the conditions specified in the present invention. Steel C to steel E is a steel which is satisfied in the present invention and which does not satisfy the range of Cu, Ni, Cr, and Mo, and which does not satisfy the range of the steel of the formula (1) or other components.

S 29 - 201144455

n bS 3行船S 00 卜 in co σ> o <〇00 00 名趟mo 卜jj CO JO Γ- 卜 Z soo 〇> s 〇· ? O σ 〇> soo CO CO od <3 CO o § o 3 O o C9 ooosp CM eg o § CD soo to oo CM oo 10.0002※※丨<〇ooo < lO soop CO soso CO s § co so in so to CM p to s § p > 1 § oom 伥ps 伥ps 枨ί= sp in oo co g § ΙΟ ooap ο S o o' goo 5 g § so ό 8 oso 〇sosd 2 CD CM osoo 5 CM CO o § o δ so 8 o 〇oso U) CM d in so § CO oo <〇o § <〇oosood 0U CM oo CM p to oo CM oo in O oc S \e> osogosdsw G〇CM 〇〇> CM 〇 another o σ> CM oo O CO 5 inch 5 (O 5 o inch 5 黯 黯 < mo UJ -30- 201144455 [Table 4] Steel number (C: u + Ni) - (M) 2 Tensile strength - 60 ° C burst test results Steel pipe size 1 Steel pipe size 2 A 0.40 1078 Passing through B 0.30 1160 Passing through C -0.14 1067 Failure failure D 0.32 1028 Failure failure E 0.54 1022 Failure failure (Example 3) With Table 5 The chemical composition of the steel is melted in a converter, and a cylindrical steel embryo having an outer diameter of 191 mm is produced by continuous casting. The circular CC steel embryos are cut into a desired length and heated at 1 250 °C. After that, it is perforated and calendered by a general Mannesmann mandrel method, whereby a heat-made pipe is formed into a seamless steel pipe. Subsequently, cold drawing processing (cold drawing process) is applied in a usual manner to be modified into various products. The size of the steel pipe. The size of the steel pipe at the time of the hot pipe production and the steel pipe size after the cold drawing process are shown in Table 6. The steel pipes subjected to the cold drawing process are corrected by the straight straightening machine, and the use is high. The frequency induction heating device heats the conditions shown in Table 6 at an average temperature increase rate of 300 ° C / sec, followed by water quenching. Further, the water quenching is performed by spraying a spray-like water from a nozzle arranged in a ring shape, and passing the steel pipe through the inside of the ring to cool the outer surface of the steel pipe. The aforementioned high frequency induction heating device is coupled to the water quenching device to vary the cooling rate by varying the steel tube passage speed. Then, a 30-minute soaking treatment for tempering was carried out in a usual walking beam furnace, and the tensile strength was adjusted to 1000 MPa or more. -31 - 201144455 z 0.0043 0.0050 0.0029 0.0045 0.0045 <3 0.0021 0.0018 0.0020 0.0022 0.0020 CO 0.0012 0.0015 0.0015 0.0001 0.0006 < soo σ> CM O d SO CM s § SO J3 'Z sp IO S d to <M oo &lt ;〇CM od IO s > o S ogoo O soo <〇S o IO oosp CO so 0 2 oooogooom 5 ό different o tf) c〇oooo S o 2 art o \ndgo CO CM d ID CM 〇δ aodso iO CM dc〇CJ o to 0.0024 0.0018 0.0016 0.0020 0.0020 a CM 〇o O) od CM 〇doo' CM 〇ocssosdsoso eg 00 o W 00 CM 〇CO CsJ o 〇> eg o 7 o 〇> CNi o in o CO 5 々do CSJ 5 铕m 〇X X - -32- 201144455

The steel pipes subjected to quenching and tempering as described above were cut to a certain length, and the tensile test was carried out according to the tensile test method of the metal material specified in JIS 2 2 1 using the test piece No. 11 prescribed in JIS Z 2201. Further, each steel pipe was cut to a predetermined length, and was cut and expanded at a room temperature in the longitudinal direction of the pipe. A test piece in which a 2 mm V notch was introduced into a rectangular material having a length of 5 5 mm, a height of l〇mm, and a width of the original wall thickness of the steel tube from the T-direction of the self-expanding tube was subjected to a Charpy impact test. The lower limit temperature (indicated by vTrs 1 0 0 in Table 6) which can be obtained at this time to ensure the elongation at break of 100% is shown in Table 6. In addition, the steel tubes for high-frequency quenching and tempering are cut into a length of 300 mm, and pressed at the ends of the two tubes to reduce the diameter of the reduced diameter portion/the diameter of the unreduced diameter portion to 0.6. The diameter portion is set to be 25 mm long, and is formed into the shape of the mouth portion of the gas cylinder bottle. Subsequently, the welded single end is sealed, and the other end is welded through the blocking member of the high pressure tube. The test body was immersed in ethanol in a chamber cooled to -60 ° C. Ethanol was injected into the tube from a high pressure tube and the internal pressure was increased to break the tube, and the failure mode was observed. The case where the brittle fracture area ratio of the opening portion was less than 5% was expressed as acceptable (indicated by 〇 in Table 6), and those which were 5% or more were shown as unacceptable (indicated by X in Table 6), and are shown in Table 6. 33- 201144455

[9S

-6 〇 r burst performance 〇Ο ο Ο 0 Ο ο o 0 o 〇O o 〇χ XXXXX 1 XX vTrslOO °C 〇Ο 1 S 1 S t ο 1 ο 1 ο 1 0 1 〇1 s 1 O 1 O 1 0 1 〇1 m rp 〇1 0 1 o η» 0 1 0 1 1 0 1 0 1 uJ ΙΓ) Ο) C5 C0 €6 gas <〇〇><0 cst in eg evi CO ci gas &lt ;DO) CM· o S in S sal CO r^· n {2| r*» g Ο C0 Ο r* s 〇> S σ> g ο os u> O s in S CO 〇> s in g In O to S 〇> IA O (O go S 1 in S in S CD Ο S ο <〇α> ο ο SS 〇> i 00 CO σ> eg O) 〇} <〇〇> σ&gt CO CO σ> s 05 〇〇l〇O) O) O o S Oi in 〇> oo <7) 1 r*» og 〇r&& (Ν CS4 CN - - - - - CM C4 - - o 〇> in 1 oo Cooling rate during water cooling: •c渺Ο Ο ο δ SSS o 〇〇sssssg 〇oo 1 oo Keep i time: seconds 1 €Μ ιη «Ν »» CM ΙΟ CSJ cvj in .^ eg In CM CM in CM io 1 to hO heating brewing °c Ο CO S σ> S 〇> ο ο Ο g Ο g to g 〇CO O 〇> s 〇> ooosog (〇ooosoo 〇ooo Sog 1 ooo cold drawing degree % σ> 5 σ> 3 00 ο οο ο σ> c6 00 ο Ο) to σ> 3 〇> oc〇o CO o 〇> c6 CO o σ> in CO o 〇 > CO CO o 00 o σ> 3 CO o CD o ιΐ g!f | fS Is OD30.05 χ WT2.50 OD30.05 χ WT2.50 OD25.05 χ WT2.02 OD25.05 χ WT2.02 OD30 .05 χ WT2.50 OD25.05 WT WT2.02 OD25.0xWT1.70 OD30.05 x WT2.50 OD30.05 x WT2.50 OD25.05 x WT2.02 OD25.05 x WT2.02 OD30.05 x WT2.50 OD25.05 x WT2.02 OD25.0x WT1.70 OD25.05 x WT2.02 OD30.05 x WT2.50 OD25.05 x WT2.02 OD25.05 x WT2.02 ! OD30.05 X WT2 .50 0025.05 x WT2.02 OD25,05 x WT2,〇2 OD25.05 x WT2.02* OD25.OxWT1.70** 1^| |ii as〇Weakness OD42.7xWT3.10 OD42.7xWT3.10 OD31 .8xWT2.70 OD31.8xWT2.70 OD42.7xWT3.10 OD31.8xWT2.70 OD3l.8xWT2.50 OD42.7 x WT3.10 OD42.7 x WT3.10 OD31.8x WT2.70 OD31.8xWT2.70 OD42 .7xWT3.10 OD31.8xWT2.70 OD31.8 x WT2.50 OD31.8xWT2.70 OD42.7 x WT3.10 OD31.8xWT2.70 OD31.8xWT2.70 OD42.7 x WT3.10 OD31.8xWT2.70 OD31.0xWT2.7O OD31.8 x WT2.70 OD42.7 x WT2.70 (Cu^Ni)-(H)2 1 ο ίο ο Ρ -* CO ο CO ο CO ο Γ- CO ο CO o cn CO 〇CO CO o' CO <〇o CO CO d CO CO o CO CO o CO od CO CO o CO CO o CO c〇o 〇CO O Ooo 0.06 Fine number UL U. ϋ. U. ϋ. U- IL· σ 〇σ σ 〇σ σ XXX — - - ->-> -3 Fun 黯 - σ> ιη <〇r- CO O) o - CM CO in to 卜CO 〇> s CSi 04 〇CSJ Although listening to N class - listening 1H-闺MK-Puizhou gfcHDIi^- foot fading S stupid - ΗΙ «ί -34- 201144455 Steel composition 'can be understood as a suitable range of steel F and steel G regardless of the wide range of heating conditions, can also ensure that the stability of vTrslOO is -100 °C below the excellent low temperature toughness, can also be excellent at the end of the cold processing Burst performance. On the other hand, regarding the steel bismuth in which the composition range of the steel of the present invention is such that only Ti is separated from the range, if the steel is heated at more than 1 〇〇〇 ° C, the crystal grains are remarkably coarse, and vTrs 100 rising and bursting properties are observed. reduce. Further, regarding the steel composition range of the present invention, only the steel having a B content deviating from the range is seen, and if it is heated at more than 1 ° C, the vTrslOO rise and the burst performance are lowered. Further, a steel pipe containing Mo: 0.15% is used to manufacture a steel pipe having an outer diameter of 25 mm and a wall thickness of 2.02 mm or 1_7 mm, and is carried out in a hot pipe size and a cold drawing size as in Test No. 3 or Test No. 14. After the combined processing, cracks occur in the cold drawing (Ref. No. 21). Therefore, a softening heat treatment of soaking at 62 ° C for 2 minutes was carried out before the cold drawing process in Test No. 22. Further, the drawing process was carried out twice in Test No. 2, and a softening heat treatment at 620 ° C for 20 minutes was applied between the drawing processes, so that it was not efficient. In addition to the test No. 2 1 and No. 22, the softening treatment after the heat pipe is not applied, and the cold drawing process can be modified once. It can be understood that the steel using the chemical component according to the present invention can be inexpensively and efficiently manufactured by using high-frequency quenching and tempering, and the high-strength airbag having excellent low-temperature bursting performance as the airbag member including the reduced diameter portion can be manufactured inexpensively and efficiently. Seamless seam steel pipe for the system. -35- 201144455 BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a graph showing the relationship between Cr + Mo and Cu + Ni in a preferred embodiment of the present invention. Fig. 2 is an explanatory view showing a test piece for evaluation of characteristics in the examples of the present invention. -36-

Claims (1)

201144455 VII. Scope of application for patents: 1. A seamless steel pipe for airbags, characterized in that it has a mass% consisting of the following: C: 0.05~0.20% S i : 0.1 0 〜0 _ 5 0 % Μη : 0.10 -1.00% Ρ : 0.02 5 % or less S : 0.00 5 % or less Α 1 : 0.005 to 0.10 % Ca : (Κ000 5~0·0050% Nb : 0.005~0.050% Ti : 0.005-0.050% Cu : 0.0 1 ～0.5 0 % Ni : 0.0 1 ～0.5 0% Cr : 0.01-0.50% B : 0.0005~0.0050 % N : 0 · 0 0 2 〜0.0 1 〇%, the balance is composed of Fe and unavoidable impurities and satisfies the following formula (1) The steel composition has a tensile strength of 1000 MPa or more and a high toughness of vTrs100 of -8 〇 ° C or less, Cu + Ni^(M;) 2 + 〇.3 (1) (1) "Μ" means Cr, and the element mark means the number 値 when the content of the elements is expressed by mass%. £: ' 2 . For the jointless steel pipe for airbags of the scope of the patent application ' 37- 201144455 The above Ti content is more than 0.020% by mass% and is 0.050% or less. 3. Unsealed steel pipe for airbags according to claim 1 or 2 It has a steel composition containing, in mass%, Mo: less than 0.10% and satisfying the following formula (1): Cu + Ni g (Μ) 2 + 0·3 (1) Further, the formula (1) "Μ" means (Cr + Mo ), and the element mark means the number 値 when the content of the elements is expressed by mass%. 4 · The seamless steel pipe for airbags according to claim 1 or 2, which has The % by mass further contains a steel composition of V: 0.0 2 to 0.20 ° /. 5. The seamless steel pipe for airbags according to item 3 of the patent application, which has a mass % and further contains V: 0.02 to 0.20% Steel composition. 6. A method for producing a seamless steel pipe for an air bag, which is characterized in that a billet which is made of a steel having any one of the patent claims 1 to 5 is manufactured by using a hot pipe. The seamless steel pipe is subjected to a cold working process with a working degree of 40% or more, and is cooled to a steel pipe of a specific size. After being corrected, it is heated at a high frequency to be heated above the Ac3 metamorphic point and quenched by quenching, and then heated to Tempering at a temperature below the change point of Ac 1 -38-