JPH04313488A - Tig welding wire for high tension steel - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a welding wire for high-strength steel that essentially uses Ar gas as a shielding gas.
Specifically, it relates to TIG welding wire for high-strength steel that is used for TIG welding of high-strength steel with a 0.2% yield strength of 80 kgf/mm2 class to obtain a weld metal with excellent low-temperature toughness especially in large welding amounts. It is.

0002

2. Description of the Related Art In recent years, as steel structures have become larger, high-strength steel has been widely used to reduce weight. In addition, technological advances in steel materials have been remarkable, and the weldability of high-strength steel has been improved, and in particular, the cold cracking susceptibility, which had been a problem in welding high-strength steel, has been significantly improved. Therefore, the demand for high-strength steel of 60 kg class or more is increasing more and more. These 6
When manufacturing structures using high-strength steel of 0 kg class or higher, TIG welding is used because it has low oxygen content, low hydrogen content, and excellent cracking resistance.

[0003] Conventionally, Ni and Cr have been used for such applications.
High tensile strength steel wire (hereinafter referred to as wire) to which appropriate amounts of , Mo, etc. were added was used. However, in order to ensure strength and toughness, these wires use a method that uses relatively low heat input and limits the amount of welding to a low level, but this not only reduces welding efficiency but also causes weld defects in position welding. There was a problem that occurred. When this type of wire is used at a high welding speed, the yield point decreases and the toughness significantly deteriorates, so there has been a need for a wire that can maintain the yield point and toughness even under high welding conditions.

[0004] As a technique to solve some of the drawbacks of these conventional wires, for example, a TIG wire for high-strength steel disclosed in Japanese Patent Application Laid-open No. 57-159293 incorporates a technology to improve the toughness of the weld metal. , the amount of oxygen in the wire is 0.0
Although wires with increased strength of 150 to 0.0320% have been proposed, no improvement in toughness has been achieved for use under high welding conditions.

[0005]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems and is used for TIG welding of high tensile strength steel with a 0.2% yield strength of 80 kg class, particularly under conditions of high welding speed. It is an object of the present invention to provide a TIG welding wire for high-strength steel that can yield a good weld metal having appropriate strength and high toughness.

[0006]

[Means for Solving the Problems] The gist of the present invention is that, in weight %, C: 0.02 to 0.08%, Si
: 0.35% or less, Mn: 0.70 to 1.60%, P:
0.010% or less, S: 0.010% or less, Ni: 2.
0-5.0%, Cr: 0.30-1.20%, Mo: 0
．． 30-1.50%, Ti: 0.003-0.050%
, Al: 0.003-0.050%, Nb: 0.005
~0.030%, V:0.005~0.080%, N:
0.005% or less, O: 0.005% or less, and V+N
The TIG welding wire for high-strength steel is characterized in that b is in a range of 0.5 to 2.0 times that of C, and the remainder is substantially made of Fe.

[0007]

[Function] In order to solve the above-mentioned problems, the present inventors conducted various studies on elements that are effective for improving toughness even at a high welding amount. As a result, Al
, Adjusting the amount of Ti alone is insufficient under conditions of high heat input and high welding amount.
, it has been found that it is effective to add V and to maintain an appropriate ratio of V+Nb to C.

[0008] Using the wire with the composition shown in Table 1,
and 8 welded according to the welding conditions and groove shape shown in Figure 1.
Table 3 shows the results of examining the strength and toughness of 0 kg class high tensile strength steel weld metal.

[0009]

[Table 1]

0010

[Table 2]

[0011]

[Table 3]

[0012] Thus, it has been found that by adding trace amounts of Nb and V and further adjusting the ratio of V+Nb to C to an appropriate range, a good weld metal with improved strength and toughness can be obtained. . Below, the reasons for limiting the ingredients of the present invention will be explained in detail along with their effects.

C: 0.02-0.08% C is an essential component for ensuring the strength of weld metal. However, 0.02%
If it is less than 80 kg, it is difficult to obtain the strength required for welding metal of 80 kg class steel. In addition, if it exceeds 0.08%, the toughness decreases significantly under conditions of large welding amount, so 0.02 to 0.08%
And so.

Si: 0.35% or less Si is the main deoxidizing element, but in TIG welding, Si is 0.35% or less.
If it exceeds 5%, the impact toughness of the weld metal will be significantly impaired, so the limit was set at 0.35%. However, if reduced too much,
Since blowholes may occur due to insufficient deoxidation, the content is preferably in the range of 0.05 to 0.35%.

Mn: 0.70-1.60% Mn is a major deoxidizing element along with Si, and is effective in improving the impact toughness of weld metal. However, if it is less than 0.70%, there will be insufficient deoxidation, and if it exceeds 1.60%, no effect of increasing the yield strength can be expected, so it is set in the range of 0.70 to 1.60%.

[0016] P, S: 0.010% or less Both P and S are
Compounds with low melting points are generated at grain boundaries, significantly impairing toughness. This tendency is particularly strong in high-strength steels containing relatively large amounts of alloying elements, so it is necessary to keep the content to 0.010% or less.

Ni: 2.0 to 5.0% Ni is added to obtain low temperature toughness and strength, but 8% Ni is added to obtain low temperature toughness and strength.
In the case of 0 kg class steel, it is ineffective if it is less than 2.0%; 5.
If it exceeds 0%, the cracking resistance decreases, so the range is set to 2.
．． The content was set at 0 to 5.0%.

Cr: 0.30-1.20% Cr is added to ensure the strength of the weld metal, but if it is less than 0.30%, no effect will be obtained, and if it exceeds 1.20%, it will have excessive strength. Become.

Mo: 0.30 to 1.50% Mo is added for the purpose of increasing the softening resistance of the weld metal during high heat input welding and reducing the decrease in strength. If it is less than 0.30%, this effect cannot be obtained, and if it exceeds 1.50%, Mo carbide is generated, resulting in significant hardening of the weld metal and deterioration of toughness, so the upper limit was set at 1.50%.

Al: 0.003-0.050% Al is a strong deoxidizing element that reduces the amount of oxygen in the weld metal, and
It is effective in improving impact toughness by making the microstructure finer. However, this effect is absent at less than 0.003%, and 0.05%
If it exceeds 0%, Al oxide is generated, which actually has the effect of impairing toughness, so 0.050% is set as the upper limit.

[0021] Ti: 0.003 to 0.050% Ti is also A
Like 1, it is a strong deoxidizing element, and has the effect of improving the toughness by refining the microstructure of the weld metal, and this effect is enhanced by its coexistence with Al. However, 0.003
If it is less than 0.050%, no toughness improvement effect can be expected, and if it exceeds 0.050%, carbides will be generated and the toughness will be significantly impaired.
．． The upper limit was set at 0.050%.

Nb: 0.005-0.030% Nb produces fine carbides and refines the microstructure of the weld metal, thereby significantly increasing the impact toughness and reducing the yield strength in high heat input welding. It has a preventive effect. The ability to form this carbide is stronger than that of Ti, and the addition of an appropriate amount of the aforementioned Ti
It acts to suppress the formation of carbides and enhance the effect of refining the microstructure of Ti. However, if it is less than 0.005%, such an effect cannot be obtained, and if it exceeds 0.030%, the carbide becomes large and the toughness is deteriorated, so the upper limit was set at 0.030%.

V: 0.005% to 0.080% V is also a carbide forming element and has the same effect as Nb. However, as a result of the study, it was found that the effect of improving toughness is further enhanced when Nb coexists with Nb. When the amount of Nb is within the above range, no effect is obtained when V is less than 0.005%, and no effect on improving toughness is observed when it exceeds 0.080%.

Furthermore, even if the amounts of V and Nb are within their respective limited ranges, if the amount is less than 0.5 times the amount of C, good toughness cannot be obtained, and if the amount exceeds 2.0 times, the toughness is similarly poor. , the appropriate range was set from 0.8 to 2.0.

N: 0.005% or less Since addition of N significantly deteriorates low temperature toughness, it is preferable to keep the level as low as possible. However, practically 0.00
If it is 5% or less, the effect of decreasing toughness is reduced.

O: 0.005% or less O oxidizes and consumes C and deoxidizing elements, reducing the strength of the weld metal. Moreover, O coarsens the microstructure of the weld metal and impairs its toughness. Therefore, the lower the element content, the more preferable it is, but practically, such an effect can be prevented if the content is 0.005% or less.

The present invention will be specifically explained below with reference to Examples.

[0028]

[Example] A high tensile strength steel with a yield strength of 80 kg and a chemical composition shown in Table 4 was provided with the groove shown in Fig. 1, and welded using the wire shown in Table 5 under the conditions shown in Table 6. was created. From this joint, a JISAI tensile test piece and a 2mm
Table 7 shows the results of taking V-notch Charpy impact test pieces and evaluating them by mechanical tests.

Regarding impact toughness, absorption energy at -50°C of 10.0 kgf·m or more was judged to be good, and regarding elongation, 20% or more was judged to be good.

Wire No. 6 is C, Ni, Al, Ti,
Since each element of V exceeds the limited range of the present invention, the 0.2% proof stress and tensile strength are too high, and the impact toughness is also reduced. Wire No. 7 has high Mn and also N
Since both the amount of b, V and the ratio of V+Nb to C exceed the limited range of the present invention, not only the strength is high but also the toughness and elongation are significantly deteriorated. Also, wire No.
Similarly, for wire No. 11, the amounts of Al, V, and Nb and the (V+Nb)/C value are out of the range. You can only get the same performance as 7.

Wire No. In No. 8, although the amounts of all elements are within the limited range, the ratio of V+Nb to C amount is below the range, so the impact toughness is low. Also, wire No. 9
Not only does (V+Nb)/C have a low value, but also the amounts of C and Cr are too large, making it impossible to obtain good results in terms of toughness, strength, and elongation. Wire No. In No. 10, the amount of each element of C, Al, and V is less than the range of the present invention, and the toughness is decreased. Wire No. No. 12 has a low Ni content, Ti, Nb content and (V
Since the +Nb)/C value is high, the strength is low and the toughness is also unsatisfactory. Wire No. In No. 13, the amounts of P, S, Mo, Nb, and V and the (V+Nb)/C value were too high, and all the results of strength, elongation, and toughness were poor.

[0032] Compared to these comparison wires, wire No. within the scope of the present invention. 1 to No. It is clear that each wire of No. 5 provides good values in all items.

[0033]

[Table 4]

[0034]

[Table 5]

[0035]

[Table 6]

[0036]

[Table 7]

[0037]

As described above, in the wire of the present invention, by specifying the amount of alloy addition and the ratio of (V+Nb/C), it is possible to ensure the yield strength and strength of TIG weld metal with a large amount of welding, and to achieve high impact resistance. It became possible to obtain toughness.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the groove shape of a test plate.

Claims (1)

[Claims] Claim 1: In weight%, C: 0.02 to 0.08%, Si: 0.35% or less, Mn: 0.70 to 1.60%, P: 0.010% or less, S: 0 .010% or less, Ni: 2.0-5.0%, Cr: 0.30-1.20%, Mo: 0.30-1.50%, Ti: 0.003-0.050%, Al : 0.003 to 0.050%, Nb: 0.005 to 0.030%, V: 0.005 to 0.080%, N: 0.005% or less, O: 0.005% or less, and V+Nb A TIG welding wire for high-strength steel, characterized in that the amount of carbon is in a range of 0.5 to 2.0 times that of C, and the remainder is substantially made of Fe.