JPH02217172A - Steel welding method - Google Patents

Abstract

PURPOSE:To obtain a welded structure excellent in safety with a long service life by specifying Ni in welding metal of a welding zone at the time of welding steel of specific C equivalent. CONSTITUTION:Steel adjusted to 0.30-0.38% C equivalent obtained by equation I is subjected to heating, control rolling and acceleration cooling. By this method, the rolled steel is adjusted to structure containing bainite phase. The steel is then welded. Welding is performed so that the Ni quantity in the weld metal of the welding zone attains a value to satisfy inequality II. In equation I, the C quantity, Si quantity, Mn quantity, Ni quantity, Ni quantity and V quantity are all shown with the values of wt.%. In inequality II, Ni (D) and Ni (M) denote the Ni quantity (%) in the welding metal and the Ni quantity (%) in the steel of base metal, respectively. By this method, resistance to groove- shape corrosion of the welding zone of the steel is improved.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for welding steel materials, and more particularly, to marine structures and ships in which steel materials are used as structural members, particularly marine structures operated in icy waters. The present invention relates to a method for welding steel materials, which is applied when welding and joining steel materials during the construction of structures and ships, or when repairing steel material parts during operation.

(Prior Art) Marine structures and ships are painted and operated, but the paint may peel off due to collisions with driftwood or the like during operation. especially,
In the case of ships such as marine structures and icebreakers operated in icy waters, the paint tends to peel off due to ice collisions.

Once the paint is removed, the steel is exposed to seawater and begins to corrode. In particular, if the paint peels off on the welded parts of steel,
Deep spiral localized corrosion (hereinafter referred to as groove corrosion) occurs in the weld metal part (hereinafter referred to as the Depo part) or the weld heat affected zone (hereinafter referred to as the IIAZ part), and damage caused by this corrosion has become a serious problem. Therefore, preventive measures are required.

For example, [Tetsu to Hagane, 31266 (1986) J] states that when ferrite/pearlite steel is welded with a low welding heat input, groove-like corrosion occurs in the tIAZ part.

Regarding methods for preventing such corrosion, rscandinavia
mJournal of Metallurgy, v
ol, 7 (197B) + P, 11 J is a normalized high tensile strength steel with a ferrite/pearlite structure: H
When welding T~50, the Mn amount in the steel is kept below 1.1χ to prevent corrosion of the IIAZ part, and the welding heat input is increased to prevent the HAZ part from becoming a low-temperature transformed structure,
Cu-N is added to the welding material to prevent groove-like corrosion at the Depo part.
It is stated that it is sufficient to use an i-containing material (hereinafter, such method will be referred to as conventional method A).

Further, Japanese Patent Application Laid-open No. 60-228618 proposes a method (hereinafter referred to as conventional method B) in which after welding quenched and tempered steel materials, the surface layer of the welded portion is locally tempered.

(Problems to be Solved by the Invention) However, in the conventional method A, it is necessary to reduce the Mn content in the steel to less than 1.1χ, which makes it difficult to ensure the strength of the steel material.
Another problem is that ordinary manual welding cannot be applied because it is necessary to increase the welding heat input.

Conventional method B requires heat treatment both before and after welding, resulting in high manufacturing costs and a long construction period.In addition, the local tempering treatment after welding is complicated, resulting in a decrease in workability, and the reliability of tempering is low. The problem is that it lacks.

The present invention has been made in view of these circumstances, and its purpose is to solve the above-mentioned problems of conventional corporations and conventional method B, and to solve the problems of increasing manufacturing cost and construction time and decreasing workability. The purpose of the present invention is to provide a method for welding steel materials that can secure the required high strength without causing corrosion, can obtain a steel welded part with excellent groove corrosion resistance, and can also be applied to manual welding. .

(Means for Solving the Problems) In order to achieve the above object, the method for welding steel materials according to the present invention has the following configuration.

That is, the method described in the first claim heats the steel whose C equivalent determined by the following equation 0 is adjusted to 0.30=0.38wtχ, performs controlled rolling, and accelerates cooling. A method for welding steel materials in which the structure of the steel material is adjusted to a heenite phase-containing structure, and then the steel material with the adjusted structure is welded, the amount of Ni in the weld metal at the welding zone being a value that satisfies the following formula 0. This is a method for welding steel materials, characterized in that the welding is performed as described above.

C equivalent=Ci+Si amount/24+Mn amount/6+Ni amount/4
01■ amount/14---■ However, in formula 0, the amount of C, the amount of Si, the amount of Mn1l,
The amount of Ni and the amount of Ni are all the same as wtχ.

0.3≦Ni(D) −Ni(M)≦0.8---■
However, in formula (■), N1(D) is the amount of Ni in the weld metal (
χL Ni (M) is the amount of Ni ('1) in the base steel material.

The method according to claim 2 is characterized in that the steel has a C: 0.02 to 0.
．． 12wt%, Si: 0.05-0.50wt%
, Mn: 1.10~2, OOwtZ So
l. Al: 0.005~0.05htχ, Ni:
0.01-5.00wt%, Nb: :0.00
5-0.100wt%, Ti: 0.005-0.02
0wt%, N: 0.0020-0.0060t
The method of welding a steel material according to claim 1, wherein the steel material has a composition in which the steel material contains .chi. and the remainder consists of iron and unavoidable impurities.

The method according to claim 3 is characterized in that the steel has a carbon content of 0.02 to 0.
．． 12wt%, Si: 0.05 ~ 0.50wtχ
, Mn: 1.10 ~ 2, OOwtX, So
l, Al: 0.005-0.050wt%, N
i: 0.01-5.00wt%, Nt+: :0.
005~O, lOOwtX, Ti:0.005~0
．． 020iyt%, N: 0.0020-0.00
Contains 60% x and further Cu: 0.05 to 1.00
wt%, V: 0.005-0.100 wt”A,
B: 0.0005 to 0.0030 wtχ The method of welding steel materials according to claim 1, wherein the composition contains one or more selected from 0.0005 to 0.0030 wtχ, and the remainder is iron and unavoidable impurities.

The method according to claim 4 is characterized in that the steel has a C: 0.02 to 0.
．． 12wtχ Si: 0.05-0.50wt5X
Mn: 1.10-2.00wt%, Sol, Al
:0.005-0.050wt%, Ni:0.0
1-5.00wt%, Nb: 0.005-0.
100%
, N: 0.0020 to 0.0060 ivtχ, and Ca: 0.0005 to 0.0030 wt.
%, rare earth element = 0.005 to 0.030 %, rare earth element = 0.005 to 0.030 %, rare earth element = 0.005 to 0.030 %, rare earth element = 0.005 to 0.030 %, the method for welding a steel material according to the first claim, which has a composition consisting of iron and inevitable impurities. It is.

The method according to claim 5 is characterized in that the steel has C: 0.02 to O.
, 12wtχ, Si: 0.05 ~ 0.50wtχ
Mn: 1.10 ~ 2, OOwtX, Sol, ^l
:o, 005-0.050wtχ Ni: 0.01
~5. OOwt%, Nb: :0.005~0.
100% Ti: 0.005~0.020wt
%, N: 0.0020 to 0.0060, and Cu: 0.05 to 1. OOwt%, V
:o, oo5~0.100%, B:0.0005
- One or two or more selected from 0.0030 tχ, Ca: 0.0005 to 0.0030 wt%, rare earth element: one or two selected from 0.005 to 0.030 tχ The method of welding a steel material according to claim 1, wherein the steel material has a composition in which the remainder is iron and unavoidable impurities.

(Function) The present invention uses hot rolled steel manufactured under various conditions as a base material, welds and joins the base materials using various welding materials to obtain a welded joint, and conducts various tests on the joint. This work was completed based on the findings obtained through a thorough investigation of the effects of component structures on groove corrosion resistance 1 strength. The action will be explained below based on this knowledge.

That is, regarding corrosion of welded joints, when the base steel has a ferrite-pearlite structure, groove-like corrosion occurs at the 11^Z portion.

This is because the HAZ part has a low-temperature transformation structure (martensite and/or bainite structure) that is very different from the base metal structure, so the potential difference between the base metal and the 11AZ part becomes large and corrosion is promoted. On the other hand, if the base metal steel has a structure containing a bainite phase, both the base metal and the HAZ part will have a low-temperature transformed structure, and the potential difference between the base metal HAZ parts will be relatively small, so it is likely that only the HAZ part will be particularly corroded. Instead, mild general corrosion occurs, which reduces the corrosion depth. Therefore, if the base metal structure is made to have a low-temperature transformed structure that is almost the same as the IAZ part structure, groove-like corrosion in the HAZ part can be prevented.

Therefore, in the method for welding steel materials according to the present invention, the structure of the steel material is made into a bainite phase-containing structure in advance, and welding is performed.

For example, when a welded joint is immersed in seawater for 4 months and the base steel has a ferrite-pearlite structure, groove-like corrosion (4) occurs in the HAZ portion (2) as shown in FIG. On the other hand, when the base steel has a bainitic phase-containing structure, the second
As shown in the figure, the corrosion occurs from the HAZ part (2) to the base metal part (1) in a manner similar to that shown in FIG. still,
The welding material in both cases is the same and is high in NiN, so no corrosion occurs in the Depo part (3). In FIG. 2, (5) shows the surface position of the welded joint before immersion in seawater.

Corrosion of welded joints is caused not only by the potential difference between the base metal and the HAZ section as described above, but also due to the potential difference between the base metal (including the IIAZ section) and the Dep.
It also occurs due to the potential difference between the o parts. Corrosion caused by a potential difference between the base material Depo parts is often caused by a difference in composition. Welding materials are strong.

Since toughness etc. are also taken into account when using the welding material, the composition of the Depo part changes depending on the type of welding material.

By the way, the composition of the steel material according to the method of welding steel materials of the present invention is set mainly from the viewpoint of ensuring strength, although the details will be described later, and the composition is as described above. Among the components of such steel materials, Ni has the greatest effect on the corrosion, and the larger the difference in the amount of Ni between the base metal and the Depo part, the more likely groove-like corrosion will occur due to the potential difference between the base metal and the Depo part. Become. Note that groove-like corrosion occurs on the side where the Ni content is low.

As for the groove-like corrosion based on the difference in the amount of Ni, when the difference in the amount of Ni is made smaller, the groove-like corrosion becomes less likely to occur. Here, the amount of Ni in the base steel (χ): Ni (M) and the amount of Ni in the Depo part (χ
)=Ni(D), that is, Ni(D)−Ni(M
) is set to -0.3 to 0.8, groove-like corrosion can be prevented.

Therefore, in the method for welding steel materials according to the present invention, N in the weld metal is
i amount (i.e. Ni(M)) is -0,3≦Ni(D)
Welding is performed so that Ni(M)≦0.8 is satisfied. Such adjustment of the Ni content is possible by selecting the welding material based on the Ni content in the base steel.

For example, when welded joints with various Ni content differences are immersed in seawater for 4 months, as shown in Figure 3, Ni([1)≦
When using Ni (M), only the Depo part corrodes;
) When Ni(D) becomes large, groove-like corrosion occurs. N1(D
)≧Ni(M), only the HAZ part corrodes, and N1(D
) - When Ni(M) becomes large, groove-like corrosion occurs. still,
In FIG. 3, * indicates the results when the base steel has a bainitic phase-containing structure, and ○ indicates the results when the base steel has a ferrite-pearlite structure.

Furthermore, as can be seen from Fig. 3, in order to substantially prevent groove-like corrosion in the IIAZ section, if the base steel has a bainitic phase-containing structure, Ni(D)-Ni(M)≦0.8. However, in the case of ferrite/pearlite structure, N1(D)
It is necessary to satisfy Ni(M)≦0.2. Therefore, in the former case, the range of N1(D)Ni(M) is wide, which is good, but in the latter case, the range of Ni(D)-Ni(M) is narrow, making welding work extremely difficult. remain.

Considering actual welding workability as described above, the base steel needs to have a structure containing a bainite phase.

Here too, there is a reason why the steel structure is made into a bainite phase-containing structure in advance. That is, in order to prevent groove corrosion, it is necessary to make the steel material into a bainite phase-containing structure before welding, and after welding, -0.3≦Ni(D)Ni(M)≦0.8
Both of these effects make it a practical method for preventing groove-like corrosion.

In order to make a steel material having such a bainitic phase-containing structure,
In the present invention, the steel material has C equivalent (=CiJ+Sl amount/24
+Mn amount/6 +Ni'It/40+V amount/14) to 0
．． Steel adjusted to 30 to 0.38 w1χ is used, and the steel material is subjected to controlled rolling and accelerated cooling. Here, controlled rolling/accelerated cooling refers to hot rolling at a lower finish rolling temperature than in normal hot rolling, and cooling after the hot rolling is performed by rapid cooling, which tends to cause heenite transformation. It is something to do.

The reason for setting the upper and lower limits of C equivalent will be described below. C equivalent is 0
．． If it is less than 30wtχ, the steel structure will become a ferrite/pearlite structure, making it difficult to cause haenite transformation, and sufficient strength will not be obtained; if it exceeds 0.38wtχ, weld cracking will easily occur when the restraint is large or when preheating is not performed. or,
This is because when low heat input welding such as manual welding is applied, the IIAZ part becomes a martensitic structure, which is different from the base metal structure and causes groove-like corrosion.

The finishing rolling temperature is preferably 700 to 850°C. This is because if the temperature exceeds 850°C, the toughness deteriorates, and if the temperature is lower than 700°C, heenite transformation becomes difficult to occur.

Further, the cooling rate after hot rolling is preferably 2 to 20°C/min. This is because at less than 2°C/min, heenite transformation is difficult to occur, and at more than 20°C/min, martensitic transformation occurs, resulting in a decrease in ductility and deformation of the steel material.

Regarding the composition of the steel, C: 0.02 to O, 12 wt%,
Si: 0.05-0.50wt%, Mn: 1.1
0-2.00wt%, Sol, Al: 0.005-0
．． 050wt%, Ni: 0.01-5. OOwt
X, Nb: 0.005-0.100wt%, Ti
:0.005~0.020wt%, N:0.0020~
It is desirable to contain 0.006 htχ, with the remainder consisting of iron and unavoidable impurities. This is because the steel material can be reliably made into a bainitic phase-containing structure, and can be made to have high strength and toughness, and can be made to have good weldability. The reason for setting the upper and lower limits in this case will be described below.

Although C is effective in improving strength, if it is less than 0.02 wtχ, sufficient strength cannot be obtained, and if it exceeds 0.12 wtχ, weldability and IIAZ section toughness will decrease.

Si is effective in deoxidizing and improving strength, but at 0.05w
If it is less than tχ, sufficient deoxidizing effect cannot be obtained, and 0.50wt
This is because if it exceeds χ, weldability deteriorates.

Although Mn is effective in improving strength, 1.10wt% or more is required to ensure sufficient strength, and if it exceeds 2.0htχ, weldability deteriorates.

This is because AI needs to be at least 0.005wt″A for deoxidation, and if it exceeds 0.050wtχ, the toughness of the HAZ part will decrease.

Ni is effective in improving strength and low-temperature toughness, but 0.0
This is because if it is less than 1 wtχ, there is no effect, and if it exceeds 5.00 wtχ, the ratio of strength to the amount of expensive Ni added (ie, the economic effect index) becomes poor.

Nb is effective in improving toughness through microstructural refinement, improving strength through the hardenability increasing effect of solid solution Nb and precipitation of Nb(C,N), and introducing a bainitic phase-containing structure, but 0.0
This is because if it is less than 0.05 wtχ, the effect will be small, and if it exceeds 0.100 wtχ, the HAZ toughness will decrease.

Ti is effective in improving the toughness of steel materials because it precipitates finely as TiN and prevents coarsening of austenite grains.Also, since TiN becomes ferrolite transformation nuclei in the HAZ part during cooling after welding, it improves the toughness of the IIAZ part. Furthermore, since it suppresses martensitic transformation, it has the effect of making the 11AZ part a bainite phase-containing structure even when low heat input welding such as manual welding is applied.
Below 0.05 wtχ, these effects are small, and 0.02
This is because if it exceeds 0 wtχ, the amount of hard TiN precipitated becomes too large and the ductility and toughness of the steel material decreases.

N is necessary to combine with Ti to form the above-mentioned TiN, but if it is less than 0.0020wtχ, the above effect cannot be obtained, and if it exceeds 0.0060wtχ, the amount of TiN becomes too large and the ductility of the steel material decreases. Because it does.

If even higher strength and high elongation toughness are required, in addition to the above elements, Cu, V, B, Ca + rare earth elements (hereinafter referred to as R) may be added.
E) One or more types selected from I) are 0.
．． It is preferable to contain 0005 to 1.00wtχ. In addition, at this time, Cu is 0.05 to 1.0 (ht%, ■ is 0.00
5-0.100wtχB is 0.0005-0.0030
wt%, Ca is 0.0005 to 0.0030 χ R
EFI is preferably in the range of 0.005 to 0.030 wtχ. The reason for setting the upper and lower limits when one or more types are contained will be described below.

This is because Cu has the effect of improving the strength without reducing the toughness of the IIAZ portion, but if it is less than 0.05 wtχ, this effect cannot be obtained, and if it exceeds 1.00 wtχ, weldability deteriorates.

(2) is effective in improving strength, but if it is less than 0.00511tχ, the effect cannot be obtained, and if it exceeds 0.100wtχ, weldability deteriorates.

Ca and REM have the effect of controlling the morphology of MnS inclusions and are effective in improving ductility and cracking resistance, but Ca:
The effect cannot be obtained with less than O,0005wtχ, REM: less than 0.005wtχ, and Ca:0.0030wtχ
REM: If it exceeds 0.030 wtχ, the inclusions will increase, and the ductility and cracking resistance will deteriorate.

The method of the present invention is a method of welding steel materials that have been subjected to controlled rolling and accelerated cooling in terms of the manufacturing process, so unlike conventional method B, the number of steps is not increased and it can be carried out on a rolling line. Therefore, it does not cause an increase in manufacturing cost and construction period, or a decrease in workability.

(Example) Steels having various compositions were heated to 1150°C, then rolled under control 7, and accelerated cooled to obtain rolled steel materials having a thickness of 30 mm and having a bainitic phase-containing structure. Here, the rolling rate of controlled rolling was 87%, the finishing temperature of rolling was 750° C., and the cooling rate after hot rolling was 10° C./min.

For comparison, instead of the accelerated cooling described above, natural cooling was performed using air cooling. Furthermore, instead of the above-mentioned controlled rolling and accelerated cooling, rolling and air cooling were performed using a conventional method.

Welded joints were obtained by welding the above rolled steel materials using various welding materials. Here, welding is done by manual welding method or SIV (
The welding heat input was varied using the submerged arc automatic welding method (submerged arc automatic welding method). Furthermore, the amount of Ni in the Depo part was varied to vary the difference in the amount of Ni between the base material and the 0epo part. Before obtaining the welded joint, a diagonal Y-shaped weld cracking test was conducted to determine the preheating temperature for preventing cracking.

Regarding the above welded joints, confirmation of Ni content difference, tensile test,
■A notch impact test, microstructural observation, and a corrosion resistance test by immersion in seawater for 4 months were conducted.

Tables 1 to 3 show the steel composition, C equivalent, and rolling/cooling method. Table 4 shows the strength of the base material (0,2″y, yield strength, tensile strength)
and impact fracture surface transition temperature, weld crack prevention preheating temperature, and impact value of the HAZ part. Table 5 shows the types of welding materials and welding methods, the amount of welding heat input, and the amount of Ni in the Depo part.
Shows the difference in Ni content and corrosion resistance.

Note that the corrosion resistance was expressed as a value obtained by subtracting the thickness of the HAZ section from the thickness of the Depo section.

As can be seen from these tables, Experiment Nos. 2.3 and 10
The welded joint according to the above has good properties of the base steel. However, since the amount of Ni in the Depo part is excessive, the value obtained by subtracting the HAZ part plate thickness from the Depo part plate thickness after the corrosion resistance test is large, and the HAZ part is deeply corroded.

This indicates that groove-like corrosion has occurred in the HAZ.

The welded joints according to Experiment Nos. 15 and 17 were, on the contrary, Dep.
.

Since the amount of Ni in the part is too small, the Depo part is deeply corroded, which indicates that groove-like corrosion has occurred in the Depo part.

The welded joints related to Experiment No. 7.8+ 12 and 13 are:
This is a case where rolled steel obtained by air cooling after controlled rolling or normal rolling and air cooling is used. In either case, accelerated cooling is not performed, so the steel structure does not become a bainitic phase-containing structure, but instead changes to a ferrite/pearlite structure. Therefore, the strength of the steel material is low, and the 11AZ section is deeply corroded.

The reason why groove-like corrosion occurred in the HAZ part is because the above-mentioned steel structure is a ferrite/pearlite structure, but this is because the amount of Ni in the Depo part is excessive and the difference in the amount of NiN in the HAZ part is large. This accelerates the growth of groove corrosion.

The welded joint according to Experiment No. 18 had a steel composition different from the composition according to the present invention, and in particular contained a lot of C. Therefore, the preheating temperature for preventing cracking is high, resulting in poor weldability and poor IIAZ toughness. Furthermore, rolling and post-rolling cooling are performed using normal rolling and rolling.
Because air cooling is used, the steel structure does not become a bainite phase-containing structure, but instead becomes a ferrite/pearlite structure.
Therefore, the strength of the steel material is low, and the 11AZ section is deeply corroded.

In contrast, experiment No. 1.4.5.6.9.11.
The welded joints according to Nos. 14 and 16 have good properties of the base steel, weldability, and HAZ toughness. Also, the steel structure is the first
Table (hereinafter, margin) Table (hereinafter, margin) Table (hereinafter, margin) Table (hereinafter, margin) Table (hereinafter, margin) Table (hereinafter, margin) Haenite phase-containing structure, Depo part Ni amount and H rudder part The difference with the amount of Ni is small, and therefore the difference between the thickness of the Depo portion and the thickness of the HAZ portion after the corrosion resistance test is small.

This shows that groove-like corrosion did not occur in either the IIAZ part or the Depo part.

(Effects of the Invention) According to the method for welding steel materials according to the present invention, the required high strength of the steel materials can be ensured without increasing production costs, construction time, or reducing workability, and the groove-resistant shape of the welded portions of the steel materials can be maintained. Can have excellent corrosive properties. Furthermore, such effects can be obtained even when a welding method that requires a low amount of heat by the welder, such as a manual welding method, is applied. Therefore, welded steel structures such as marine structures and ships that have a long life and excellent safety can be obtained without reducing economic efficiency and workability.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a welded joint where the base material steel structure is a ferrite/pearlite structure and shows the groove-like corrosion after immersing the welded joint in seawater for 4 months. Figure 3 shows the groove-like corrosion state after immersing a welded joint in seawater for 4 months in the case of a heenite phase-containing structure.
Fig. 3 is a diagram showing the relationship between the corrosion rate (value obtained by subtracting the thickness of the IIAZ section from the thickness of the Depo section) of a welded joint after being immersed in seawater for 4 months. Furthermore, the third
In the figure, . indicates the result when the base material steel structure is a structure containing a heenite phase, and ○ indicates the result when the base material steel structure is a ferrite/pearlite structure.

Claims (5)

[Claims] (1) C equivalent determined by the following formula [1] is 0.30 to 0
．． By heating the steel adjusted to 38%, controlled rolling, and accelerated cooling, the structure of the rolled steel material is adjusted to a bainite phase-containing structure, and then the steel material with the adjusted structure is welded. A welding method for steel materials, characterized in that the welding is performed such that the amount of Ni in the weld metal in the welded portion satisfies the following formula [2]. C equivalent = C amount + Si amount / 24 + Mn amount / 6 + Ni amount / 4
0+V amount/14...[1] However, in formula [1], C amount, Si amount, Mn amount, Ni
All amounts and amounts are in wt%. -0.3≦Ni(D)-Ni(M)≦0.8...[2
] However, in formula [2], Ni (D) is N in the weld metal.
i amount (%), Ni (M) is the Ni amount (%) in the base steel material
It is. (2) The steel contains C: 0.02 to 0.12 wt%, Si
:0.05~0.50wt%, Mn:1.10~2.0
0 wt%, Sol. Al: 0.005~0.050wt
%, Ni: 0.01-5.00wt%, Nb::0.0
05-0.100wt%, Ti: 0.005-0.02
0 wt%, N: 0.0020 to 0.0060 wt%, and the remainder is iron and unavoidable impurities. (3) The steel contains C: 0.02 to 0.12 wt%, Si
:0.05~0.50wt%, Mn:1.10~2.0
0 wt%, Sol. Al: 0.005~0.050wt
%, Ni: 0.01-5.00wt%, Nb::0.0
05-0.100wt%, Ti: 0.005-0.02
0 wt%, N: 0.0020 to 0.0060 wt%, further Cu: 0.05 to 1.00 wt%, V: 0
．． 005-0.100wt%, B: 0.0005-0.
The method for welding steel materials according to claim 1, having a composition containing one or more selected from 0,030 wt %, and the remainder consisting of iron and inevitable impurities. (4) The steel contains C: 0.02 to 0.12 wt%, Si
:0.05~0.50wt%, Mn:1.10~2.
00wt%, Sol. Al: 0.005~0.050w
t%, Ni: 0.01-5.00wt%, Nb: 0.0
05-0.100wt%, Ti: 0.005-0.02
0 wt%, N: 0.0020 to 0.0060 wt%, and further Ca: 0.0005 to 0.0030 wt%.
, rare earth elements: 0.005 to 0.030 wt%, and the remainder is iron and unavoidable impurities. (5) The steel contains C: 0.02 to 0.12 wt%, Si
:0.05~0.50wt%, Mn:1.10~2.0
0 wt%, Sol. Al: 0.005~0.050wt
%, Ni: 0.01-5.00wt%, Nb: 0.00
5-0.100wt%, Ti: 0.005-0.020
wt%, N: 0.0020 to 0.0060 wt%, Cu: 0.05 to 1.00 wt%, V: 0.
005-0.100wt%, B: 0.0005-0.0
One or more selected from 030wt%, Ca
:0.0005-0.0030wt%, rare earth element: 0
．． The method for welding steel materials according to claim 1, having a composition containing one or two selected from 0.005 to 0.030 wt%, and the remainder consisting of iron and unavoidable impurities.