JP2001303193A - Resistance welded steel tube for structural use, excellent in hydroformability and having precipitation strengthening property, its manufacturing method, and method for manufacturing hydroformed member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for manufacturing a resistance welded steel tube for structural use, suitably used for automobile structural member, under carriage member, or the like, and particularly excellent in workability at hydroforming (hydroformability) and having precipitation strengthening property, and a member using this steel tube. SOLUTION: A hot rolled or cold rolled hoop stock, which has a composition consisting of 0.01-<0.05% C, <=1.0% Si, <=3.0% Mn, <=0.15% P, <=0.015% S, 0.01-0.1% Al, 0.5-2.5% Cu (where Cu in a state of solid solution comprises >=80%) and the balance Fe with inevitable impurities and containing, if necessary, at least one kind selected from 0.05-1.50% Ni (under the condition that the atomic ratio between Ni and Cu, Ni/Cu, is >=0.5), 0.005-0.040% Nb, 0.005-0.50% Ti, 0.0005-0.020% B, 0.02-1.0% Cr, 0.02-1.0% Mo, 0.0020-0.02% Ca and 0.0020-0.02% REM, is formed into cylindrical shape and the resultant seam is subjected to electric resistance welding, followed by sizing at 0.3-10% drawing rate of outer peripheral length.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel pipe suitable for use as a structural member or an underbody member of an automobile, and has excellent workability in hydroforming (hydroforming property) and precipitation strengthening ability. The present invention relates to a technique for manufacturing an electric resistance welded steel pipe for a structure and a member using the same.

[0002]

2. Description of the Related Art Used as structural members for automobiles,
Conventionally, to manufacture hollow members with various cross-sectional shapes,
A method has been adopted in which parts formed by pressing a steel plate are joined together by spot welding at a flange portion, which is a welding margin, but improvements are required both in terms of quality and production efficiency. On the other hand, recently, a higher impact absorption capacity at the time of collision has been required for a structural hollow member, and a steel sheet used as a material has been further strengthened. For this reason, it is becoming increasingly difficult to produce a member having no molding defects and having a good shape and dimensional accuracy of a molded product by the conventional press molding method.

As a new molding method for solving such a problem, hydroforming has recently been receiving attention. Hydroforming is a method of performing plastic working by injecting a high-pressure liquid into the inside of a steel pipe, and changing the cross-sectional dimension of the steel pipe by expanding the pipe, etc., and integrally forming complex-shaped members, while increasing strength and rigidity. It is an excellent molding method with functions. By the way, as a steel pipe to be subjected to hydroforming, in general, an electric resistance welded steel pipe made of a material made of low carbon steel in C: 0.20 to 0.10% is often used in the same manner as a normal steel pipe.

[0004]

However, even if the ERW steel pipe containing such C content is subjected to hydroforming, there is a problem that a sufficient expansion ratio cannot be obtained due to poor workability of the material itself. Was. On the other hand, in order to improve the workability of the material of the electric resistance welded steel pipe itself, it is conceivable to use ultra-low carbon steel whose carbon content is significantly reduced as the material. However, in the case of an ultra-low carbon electric resistance welded steel pipe, although the hydroforming property is good, another problem due to welding occurs. That is, in ultra low carbon ERW steel pipe,
Due to the welding heat of the seam during the production of steel pipes, the crystal grains in the heat-affected zone are coarsened and softened, and the deformation during pipe expansion is concentrated locally, and the high ductility of the material cannot be fully exhibited. When the hydroformed member is welded to another member, the same softening occurs and the member cannot have sufficient strength.

[0005] In view of the above problems of the prior art, the present invention proposes a new ERW steel pipe suitable for hydroforming. In particular, the present invention relates to an electric resistance welded steel pipe for structural use and an electric resistance welded steel pipe having so-called precipitation strengthening ability, which is excellent in hydroforming property and not only does not cause softening of welding but also strengthens precipitation by heat treatment after hydroforming. The purpose is to propose the members used. The specific target characteristics aimed at by the steel pipe of the present invention are (TS of steel pipe) ×
Hydroforming property expressed by expansion ratio (axial compression condition) is 12000 MPa ·% or more, and strain is 7%
After the hydroforming, a heat treatment at 500 ° C. for 5 minutes is performed, and the strength increase by strain aging heat treatment is 100 MPa or more. It should be noted that the strength after the strain aging heat treatment is 50 MPa higher than the strength after the hydroforming with a strain amount of 7%.
It is more preferable that it is higher than a.

[0006]

Means for Solving the Problems In order to achieve the above object, the inventors have made various studies on the component composition of the ERW steel pipe, the production method, and the like. As a result, the amount of C is 0.01 to 0.
Use semi-ultra low carbon material with a range of less than 05%, Cu
It has been found that it is effective to contain an appropriate amount of sintering, and to conduct sizing (diameter reduction) with a drawing ratio of 0.3 to 10% after forming a pipe by electric resistance welding of a joint portion. The present invention has been completed based on the above findings, and the gist configuration thereof is as follows.

(1) When the steel composition is expressed by mass% (hereinafter simply referred to as%), C: 0.01 to less than 0.05%, Si: 1.0% or less, Mn: 3.0% or less, P: 0.15% or less, S: 0.015% or less , Al: 0.01-0.
1%, Cu: 0.5-2.5%, and 80% or more of it as solid solution Cu, the remainder being an electric resistance welded steel pipe composed of a steel composition of Fe and unavoidable impurities, and having a tensile strength (MP
a) x Expansion ratio (%) is 12000 MPa ·% or more and strain amount is 7%
Excellent hydroforming properties, characterized in that the amount of increase in strength of the steel pipe is 100 MPa or more due to the strain aging treatment of performing heat treatment at 500 ° C for 5 minutes after hydroforming.
Structural ERW steel pipe with precipitation strengthening ability.

(2) In the above (1), the steel composition may be one or two selected from the following groups A to D in addition to the above components.
An electric resistance welded steel pipe for structural use having excellent hydroforming properties and a precipitation strengthening ability, characterized by containing at least one kind. Note Group A: Ni: 0.05 to 1.50%, and atomic ratio of Ni / Cu: 0.5 or more Group B: Nb: 0.005 to 0.040%, Ti: 0.005 to 0.50%,
B: One or more of 0.0005 to 0.020% C group: Cr: 0.02 to 1.0%, Mo: 0.02 to 1.0%
Species or two D group: Ca: 0.0020 to 0.02%, REM: one or two of 0.0020 to 0.02%

(3) C: 0.01 to less than 0.05%, Si: 1.0%
Mn: 3.0% or less, P: 0.15% or less, S: 0.015%
In the following, Al: 0.01 to 0.1%, Cu: 0.5 to 2.5%, and 80% or more thereof are contained as solid solution Cu, and if necessary, at least one selected from the following groups A to D is contained. The remainder is made of hot rolled or cold rolled strip material consisting of Fe and unavoidable impurities. After forming it into a cylindrical shape, the seam is welded by electric resistance, and then sizing of 0.3 to 10% by drawing ratio of the outer peripheral length. A method for producing an electric resistance welded steel pipe for a structure having excellent hydroforming properties and precipitation strengthening ability. Note Group A: Ni: 0.05 to 1.50%, and the atomic ratio of Ni / Cu: 0.5 or more Group B: Nb: 0.005 to 0.040%, Ti: 0.005 to 0.50%,
B: One or more of 0.0005 to 0.020% Group C: Cr: 0.02 to 1.0%, Mo: 0.02 to 1.0%
Species or 2 types Group D: Ca: 0.0020-0.02%, REM: 0.0020-0.02%, 1 or 2 types

(4) The electric resistance welded steel pipe obtained by the method described in the above (3) is subjected to hydroforming,
A method for producing a hydroforming member, comprising performing a heat treatment for 1 minute to 60 minutes in a temperature range of 700 ° C. to 700 ° C.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The reasons for limiting steel components in the present invention, a method for manufacturing an electric resistance welded steel pipe, and the like will be described. C: 0.01 to less than 0.05% C contributes to the strengthening of the steel, but is an element that lowers the formability. In particular, when the C content is 0.05% or more, the decrease in the formability increases. On the other hand, if the content is less than 0.01%,
Crystal grains in the heat affected zone become coarse due to resistance welding during the production of ERW steel pipes, and crystal grains also become coarse when arc welding of hydroforming members, causing a decrease in strength and uneven deformation. Become. Therefore, the amount of C is 0.01-0.05.
%.

Si: 1.0% or less Si is an element useful for strengthening steel, and is added according to desired strength. However, if it is added in excess of 1.0%, the surface properties of the hot-rolled or cold-rolled steel sheet used as the material for steel pipes deteriorate, and eventually the surface properties of the steel pipes remarkably deteriorate, resulting in burst resistance during hydroforming. 1.
Add in a range of 0% or less.

Mn: not more than 3.0% Mn is an effective element for improving the strength of the steel sheet and hence the hydroformed member without deteriorating the surface properties and weldability. To reduce the pipe expansion rate. Therefore, Mn
The content is 3.0% or less%.

P: 0.15% or less P is an element effective for improving the strength, but when added in excess of 0.15%, the weldability is remarkably deteriorated. In particular, when the strengthening action by P is not so required, or when the C content is high and there is a concern that the weldability may be reduced, it is desirable to limit the content to 0.02% or less.

S: 0.015% or less S exists as nonmetallic inclusions in steel, and there is a possibility that the S will start and break the steel pipe during hydroforming. Therefore, the lower the S content is, the more the burst resistance is improved.
If the content is 0.015% or less, the effect is exhibited. In order to further improve the burst resistance, the content is preferably limited to 0.010% or less, more preferably 0.005% or less.

Al: 0.01 to 0.1% Al has a deoxidizing effect on steel and is a useful element for suppressing the coarsening of crystal grains. Therefore, it is necessary to add 0.01% or more of Al. On the other hand, even if it is added in a large amount exceeding 0.1%, not only these effects are saturated, but also a surface defect of the steel sheet occurs. Therefore, Al is contained in the range of 0.01 to 0.1%.

Cu: 0.5 to 2.5%, 80% or more of the added amount is solid solution Cu Cu is an element useful for increasing the strength by heat treatment performed after the tube forming, sizing and hydroforming steps. . Moreover, strengthening by adding Cu
This has the advantage that the expansion ratio during hydroforming is not significantly reduced. In order to exert such an effect, it is necessary to add 0.5% or more, preferably 0.8% or more of Cu, and to make 80% or more, preferably 90% or more of the added amount exist in a solid solution state. On the other hand, 2.5
Even if Cu is added in excess of%, the effect of increasing the strength is saturated, so the upper limit is 2.5%.

Ni: 0.05-1.50% Ni is a useful element used to prevent surface defects, and particularly to prevent surface cracks, which are likely to occur in the process of manufacturing a steel sheet by hot rolling. In order to exhibit such an effect of suppressing surface defects, at least 0.05% and an atomic ratio of Ni / Cu of 0.5
It is desirable to add the above. On the other hand, over 1.50%
Even if Ni is added, such an effect is saturated and the cost is rather increased. Therefore, the upper limit is 1.50%.

Nb: 0.005 to 0.040%, Ti: 0.005 to 0.50
%, B: 0.0005 to 0.020% Nb, Ti and B are all useful elements for refining crystal grains. Such effects are obtained when Nb: 0.005% or more and Ti:
Appears when 0.005% or more and B: 0.0005% or more are added.
However, if Nb is added in excess of 0.040%, Ti: 0.50%, and B: 0.020%, not only the effect is saturated, but also the hot deformation resistance of the steel is increased and productivity is impaired. Therefore,
These elements are added in the above range.

Cr: 0.02 to 1.0%, Mo: 0.02 to 1.0% Cr and Mo are useful elements for improving the strength without impairing the ductility of the steel pipe. All of these effects can be obtained by adding 0.02% or more. However, adding more than 1.0% saturates the effect and reduces the hot workability and cold workability of steel. Therefore, these elements are added in the above range.

Ca: 0.0020-0.02%, REM: 0.0020-0.02
% Ca and REM are elements useful for making the form of nonmetallic inclusions mainly composed of S in steel into a sphere, reducing the notch action, and improving the burst resistance. These effects are:
Both Ca and REM can be obtained by adding 0.0020% or more, but 0.02%
%, The effect tends to be saturated or slightly reduced. Therefore, these elements are added in the above range. When both Ca and REM are used together,
It is preferable to add in the range of 0.03% or less.

The steel pipe of the present invention has a tensile strength (MPa) ×
The expansion ratio (%) shall be 12000 MPa ·% or more.
If the tensile strength of the steel pipe is low, a high shock absorbing capacity cannot be obtained, and if the pipe expansion rate is low, the shape that can be formed by hydroforming is limited. In the present invention,
Since it is necessary that these two properties be balanced, the tensile strength (MPa) x expansion ratio (%) is calculated as 12000 MPa
% Or more. The tensile strength is preferably 350 MPa or more, and the pipe expansion ratio is preferably 28% or more. Here, the pipe expansion ratio is defined as a steel pipe having an outer diameter do with a deformed portion length lc = 2do.
A liquid is supplied from the pipe end to the inner surface of the pipe to apply a hydraulic pressure, and a free bulge is deformed in a circular cross section.
From x, it is defined as (dmax-do) / do × 100. This expansion ratio is measured by a free bulge test. This free bulge test is, for example, shown in FIGS.
Can be carried out by expanding the dies 2a and 2b shown in FIG. 1 using a hydroforming apparatus having the configuration shown in FIG.

FIG. 1 is a perspective view of a mold, and FIG. 2 is a sectional view of the mold. Each of the molds 2a and 2b has a steel pipe holding portion 3 formed of a semi-cylindrical surface having a diameter substantially equal to the outer diameter do of the steel pipe at both ends in the length direction. d
c has a deformed portion 6 comprising a semi-cylindrical deformed portion 4 and a tapered deformed portion 5 having an inclination angle θ = 45 °, and the length lc of the deformed portion 6 is twice as long as do. It comprises a mold 2a and a lower mold 2b. The diameter dc of the semi-cylindrical deformed portion 4 may be about twice the outer diameter do of the steel pipe. As shown in FIG. 3, the steel pipe 1 is sandwiched between the upper mold 2a and the lower mold 2b such that the steel pipe 1 fits into the steel pipe holding portion 3 of each mold. In this state, when a liquid such as water is supplied from both ends of the steel pipe 1 to the inner surface side of the steel pipe 1 through the shaft pressing cylinder 7a, a hydraulic pressure P is applied, and a circular cross-section free bulge deforms and bursts. The maximum outer diameter dmax is measured. Note that FIG.
Reference numerals 8 and 9 denote a mold holder and an outer ring for holding the molds 2a and 2b with the steel tube sandwiched therebetween.

In the hydroforming, there are a case where both ends of the pipe are fixed and a case where a compressive force is applied from both ends of the pipe (referred to as axial compression). In general, the pipe end compression has a higher expansion ratio. In the present invention, a compressive force is appropriately applied from both ends of the pipe so as to obtain a high expansion rate. In FIG. 3, the compression force can be applied by applying a compression force F to the shaft pressing cylinders 7a and 7b in the axial direction.

Further, the steel pipe of the present invention has a characteristic that the tensile strength is increased by 100 MPa or more by a strain aging treatment in which a heat treatment is performed at 550 ° C. × 5 minutes after hydroforming with a strain amount of 7%. Here, the hydroforming with a distortion amount of 7% is performed by using the mold shown in FIG. 2 in which the semi-cylindrical deformed part 4 has a diameter dc of 1.07 times the outer diameter do of the steel pipe. This is performed by performing hydroforming until the portion 6 is reached. By having the above-mentioned property that the tensile strength is increased by 100 MPa or more by this strain aging treatment, if heat treatment after molding by hydroform is performed, the molded part will have high strength and will have high impact resistance. is there. The heat treatment conditions for increasing the strength applied to a part formed by hydroforming are as follows: a temperature range of 200 to 700 ° C. and a treatment for 1 to 60 minutes have an effect of increasing the strength, but a larger increase in strength is required. The most preferable condition is 500 ° C. × 5 minutes.

Next, a method of manufacturing a steel pipe according to the present invention will be described. After smelting steel according to the above composition,
The slab is formed by a continuous casting method or an ingot-bulking method.
The slab is formed into a hot-rolled steel sheet by hot rolling or a cold-rolled steel sheet by cold rolling and annealing after hot rolling. Using the hot-rolled steel sheet or cold-rolled steel sheet thus obtained as a raw material, it is formed into a substantially cylindrical shape by roll forming or bending, and a seam portion in which both width end portions are butted together is subjected to electric resistance welding. Join. Subsequent to the electric resistance welding, sizing of 0.3 to 10% is performed at a drawing ratio of the outer peripheral length. The purpose of sizing is to obtain sufficient shape accuracy and to ensure uniformity of material deformation in order to subject the ERW steel pipe to hydroforming. To achieve this goal, a draw ratio of at least 0.3% is required, but 10%
If it is carried out beyond the range, workability as a steel pipe will be reduced due to remarkable work hardening. Therefore, after the electric resistance welding, the sizing should be performed at a reduction ratio of the outer peripheral length of 0.3 to 10%.

In the present invention, it is important that 80% or more, preferably 90% or more of the added amount of Cu is present in a solid solution state in order to exert the precipitation strengthening effect of Cu in the heat treatment after hydroforming. . for that reason,
In the above-mentioned step, particularly in the hot rolling step, it is necessary to perform rapid cooling (about 20 ° C./s or more) within at least 2 seconds after the end of the rolling, and take up at a low temperature of 700 ° C. or less to prevent precipitation of Cu. In addition, cold-rolled steel sheet is 700 ° C after annealing.
It is necessary to prevent the precipitation of Cu by quenching the above region similarly (about 10 ° C./s or more). Also,
In order to exert such a precipitation strengthening effect by Cu, it is necessary to perform a heat treatment for a precipitation treatment through a sizing and a hydroforming process after a pipe forming using a steel plate. The conditions for such heat treatment are 200 ° C or more and 70
It is desirable to set the temperature at 0 ° C. or lower for 1 minute to 60 minutes.

[0028]

EXAMPLES Slabs were produced by melting steels having the chemical components shown in Table 1. After heating this slab to 1220 ° C, hot rolling
A hot-rolled steel sheet of 2.0 mm, or a sheet thickness of 2.0 mm by a process of pickling, cold rolling and continuous annealing following hot rolling.
mm cold-rolled steel sheet. Here, cooling after hot rolling is
Started within 2 seconds and wound at a temperature below 600 ° C. For cold-rolled steel sheets, after annealing at each recrystallization temperature (650-700 ° C for this steel sheet) or higher, 10 ° C /
The temperature was lowered to 500 ° C. or less at a cooling rate of s or more. After forming these hot-rolled steel sheets or cold-rolled steel sheets into a cylindrical shape, their joints are subjected to electric resistance welding to form a steel pipe having a diameter of 63.5 mm and a wall thickness of 2.0 mm. Was done.

A JIS No. 12 test piece was sampled from the obtained electric resistance welded steel pipe, and its tensile strength was determined. Further, a steel pipe was cut into a length of 500 mm to obtain a test piece for hydroforming. As shown in FIGS. 1 to 3, water was supplied to both ends of this test body, the bulge was deformed in a circular cross-section, and the tube expansion ratio when bursting was measured. Here, the die dimensions in FIG. 2 are 127.0 mm for lc, 127.0 mm for dc, and 5 m for rd.
m and lo were 550 mm and θ was 45 °. The characteristics of each ERW steel pipe were expressed not only by the expansion rate but also by the strength of the steel pipe × expansion rate in consideration of the balance with the material strength. For the strength of the steel pipe, a JIS No. 12 test piece was sampled from the ERW pipe, and the tensile strength (TS) was measured. In addition, using a sized electric resistance welded steel pipe, hydroforming is performed with a strain amount of 7%, and then a precipitation heat treatment is performed at 500 ° C. for 5 minutes, and the tensile strength (TS) after each of these steps is measured. A JIS No. 12 test piece was cut out from the deformed portion and measured.

[0030]

[Table 1]

Table 2 shows the obtained results. From Tables 1 and 2, the ERW steel pipe according to the present invention has a high material strength × expansion rate, excellent hydroforming properties,
It can be seen that the strength increase due to precipitation strengthening is large. That is, in the invention example, the value of the tensile strength of the steel pipe × expansion rate is 1200
0 MPa ·% or more, and TS after precipitation heat treatment
The difference between (D) and TS (B) of the steel pipe is 105 MPa or more,
Is obtained. On the other hand, the comparative example in which the chemical components are not appropriate has a disadvantage that either the hydroforming property is inferior or the strength increase is small, and the performance of the hydroforming member as a structural member is lacking.

[0032]

[Table 2]

Further, regarding the steel pipe of pipe No. 1 in Table 1,
When the squeezing ratio at the time of sizing was changed between 0.1 and 12%, the TS of the ERW pipe, the results of the expansion test, the TS after hydroforming with a strain amount of 7%, the TS after the precipitation heat treatment,
Table 3 shows the precipitation strengthening amount.

[0034]

[Table 3]

[0035]

As described above, according to the present invention,
It is possible to provide an electric resistance welded steel pipe for structural use having excellent hydroforming properties and having a large precipitation strengthening ability. Therefore, the present invention greatly contributes to high quality and stable production of structural members manufactured by heat treatment after hydroforming.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a mold used for a free bulge test.

FIG. 2 is a sectional view showing a mold used for a free bulge test.

FIG. 3 is a sectional view showing an example of a configuration of a hydroforming apparatus used for a free bulge test.

Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court II (Reference) C22C 38/54 C22C 38/54 (72) Inventor Yuji Hashimoto 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Corporation F term in the Technical Research Institute (reference) 4K032 AA01 AA04 AA14 AA15 AA16 AA27 AA29 AA31 BA03 CG01 CH04 4K042 AA06 BA01 CA02 CA03 CA05 CA06 CA08 CA09 CA10 CA12 CA14 DA05 DC02 DC03

Claims (4)

[Claims] The steel composition is as follows: C: 0.01 to less than 0.05% by mass, Si: 1.0% or less, Mn: 3.0% or less, P: 0.15% or less, S: 0.015% or less, Al: 0.01 to 0.1% Cu: 0.5-2.5%, and more than 80% of Cu in solid solution state
And the remainder is an ERW steel pipe composed of a steel composition of Fe and unavoidable impurities, with a tensile strength (MPa) x expansion ratio (%) of 12000 MPa ·% or more, and after hydroforming with a strain amount of 7%. An electric resistance welded structural steel pipe having excellent hydroforming properties and precipitation strengthening ability, characterized in that the strength increase of the steel pipe is 100 MPa or more due to a strain aging treatment at 500 ° C for 5 minutes. 2. The steel according to claim 1, wherein the steel composition contains one or more selected from the following groups A to D in addition to the above-mentioned components, and is excellent in hydroforming properties and precipitation strengthened. ERW steel pipe for structural use. Note Group A: Ni: 0.05 to 1.50%, and atomic ratio of Ni / Cu: 0.5 or more Group B: Nb: 0.005 to 0.040%, Ti: 0.005 to 0.50%,
B: One or more of 0.0005 to 0.020% C group: Cr: 0.02 to 1.0%, Mo: 0.02 to 1.0%
Species or two D group: Ca: 0.0020 to 0.02%, REM: one or two of 0.0020 to 0.02% 3. C: 0.01-0.05%, Si: 1.0% or less, Mn: 3.0% or less, P: 0.15% or less, S: 0.015% or less, Al: 0.01-0.1%, Cu: 0.5-0.5% 2.5% and more than 80% of solid solution Cu
And, if necessary, containing at least one selected from the following groups A to D, and the remainder consisting of Fe and unavoidable impurities. Is subjected to electrical resistance welding, and then subjected to sizing at a reduction ratio of the outer peripheral length of 0.3 to 10%, which is characterized by excellent hydroforming properties and precipitation strengthening ability. Note Group A: Ni: 0.05 to 1.50%, and the atomic ratio of Ni / Cu: 0.5 or more Group B: Nb: 0.005 to 0.040%, Ti: 0.005 to 0.50%,
B: One or more of 0.0005 to 0.020% Group C: Cr: 0.02 to 1.0%, Mo: 0.02 to 1.0%
Species or 2 types Group D: Ca: 0.0020-0.02%, REM: 0.0020-0.02%, 1 or 2 types 4. An electric resistance welded steel pipe obtained by the method according to claim 3, which is subjected to hydroforming,
A method for producing a hydroforming member, wherein a heat treatment is performed for 1 minute to 60 minutes in a temperature range of 0 ° C. or less.