JPH09308987A - Submerged arc welding wire excellent in low temperature toughness - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide stable low temperature toughness without being affected by Al to be mixed in the weld metal through the base metal dilution by containing C, Si, Mn, Mg and Al at the prescribed composition. SOLUTION: A submerged arc welding wire has a composition consisting of, by weight, 0.01-0.10% C, 0.01-0.50% Si, 0.50-2.50% Mn, 0.10-1.0% Mg, and 0.001-0.50% Al, and the balance Fe with inevitable impurities. The structure most excellent in the low temperature toughness is acicular ferrite AF. In order to stably obtain AF without being affected by the Al quantity in steel, it is effected to use the oxide of the element whose affinity with oxygen is stronger than that of Al as a core of transformation. It is necessary that the oxide which can be the core in generating AF is excellent in matching with α iron. For example, because Mg is stronger than Al in the affinity with oxygen, MgO- Al2 O3 can be stably generated even when the Al quantity in steel is fluctuated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welding wire having excellent low temperature toughness, and specifically discloses a welding wire capable of ensuring stable low temperature toughness without being affected by the amount of Al in a steel material.

[0002]

2. Description of the Related Art Studies for improving the low temperature toughness of low alloy steel weld metal have been conducted for a long time and it is known that the toughness largely depends on the metal structure. According to these findings, many studies report that the microstructure with the best low-temperature toughness is acicular ferrite (hereinafter referred to as AF) (for example, the microstructure and toughness of welds Yukihiko Horii 128th Nishiyama Memorial Lecture).

An oxide which is a nucleus of transformation is indispensable for the formation of AF, and a Ti oxide has been mainly used conventionally. However, since Ti has a lower affinity for oxygen than Al, the formation of Ti oxide is always affected by the amount of Al. That is, when the amount of Al is excessive, all oxygen in the weld metal is consumed by Al and Ti oxide is not formed. Therefore,
In this case, AF is not generated and a weld metal having high toughness cannot be obtained. On the other hand, when Al is insufficient, oxides of Si and Mn, which cannot be nuclei for AF formation, are generated, and the required hardenability is reduced. Therefore, it has been shown that high toughness cannot be obtained even when Al is insufficient (for example, O. Gron
g. International Metal Re
views 1986 Vol. 31, p. 27).
For example, ordinary low temperature steel and Ti
In the case of steel materials having different Al contents such as deoxidized steel, it was difficult to share the welding material due to the influence of Al mixed by the dilution of the base metal.

[0004]

As described above, when welding steel materials having different Al contents, the affinity for oxygen is Al.
It is considered that it is effective to use an oxide of a stronger element as a nucleus of transformation, and in the present invention, a welding wire that can obtain stable low temperature toughness without being affected by Al mixed in the weld metal by dilution of the base material is provided. It is intended to be disclosed.

[0005]

DISCLOSURE OF THE INVENTION The present invention is to solve the above-mentioned problems, and in a submerged arc welding wire, the weight% (hereinafter the same) based on the total weight of the wire, C:
0.01 to 0.10%, Si: 0.01 to 0.50%,
Mn: 0.50 to 2.50%, Mg: 0.10 to 1.0
%, Al: 0.01 to 0.50%, and if necessary, Ti: 0.01 to 0.50%, Mo: 0.0
1 to 0.50%, Ni: 0.01 to 6.0% of one or more kinds, and the balance consisting of Fe and unavoidable impurities, a submerged arc welding wire excellent in low temperature toughness. .

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION In order to stably obtain AF without being affected by the amount of Al in steel, it is effective to use an oxide of an element having a stronger affinity for oxygen than Al as a nucleus for transformation. Therefore, the inventors of the present invention have focused their attention on Mg oxide and have proceeded with research. Table 1 shows the compatibility between various oxides and α iron.
It is necessary that the oxide that can be the nucleus of AF formation has good compatibility with α iron, but MgO—Al ₂ O ₃ has very good compatibility with α iron. Further, since Mg has a stronger affinity with oxygen than Al, MgO-Al ₂ O ₃ is stably generated even when the Al content of the steel material fluctuates.

[0007]

[Table 1]

Next, the reasons for limiting the various chemical components specified in the present invention will be described. C: An extremely low C amount of less than 0.01% increases the wire manufacturing cost, and C of more than 0.10% lowers the toughness of the welded portion. Therefore, C is set to 0.01 to 0.10%.

Si: Si is added as a deoxidizer and a strengthening element, but if it is less than 0.01%, its effect is not sufficient, while if it exceeds 0.50%, the impact toughness of the welded portion deteriorates. Therefore, Si is set to 0.01 to 0.5%.

Mn: Mn is an important element for functioning as a deoxidizing agent and ensuring the necessary hardenability, but 0.5
If it is less than 0%, its effect is small, and if it exceeds 2.50%, the productivity of the welding wire is lowered. Therefore, Mn is 0.50
˜2.50%.

Mg: Mg not only acts as a deoxidizing agent, but also forms a complex oxide in the presence of Al and plays an important role in the generation of α iron transformation. From the results of experiments using various alloy components, it is the addition amount of 0.10% or more that is effective in increasing the toughness of the welded portion, but if it exceeds 1.0%, there is a problem in welding workability. Therefore, Mg is set to 0.10 to 1.0%.

Al: Al is also a deoxidizing agent and AF similarly to Mg.
Is an important element for the transformation formation, but if it is less than 0.01%, the effect is small, and if it exceeds 0.50%, the toughness of the welded part decreases. Therefore, Al is set to 0.01 to 0.50%.

Ti: Ti also acts as a deoxidizing agent and a Ti oxide, which is advantageous for AF formation, and thus may be added.
However, if the addition amount is 0.01% or less, the effect is small, and conversely, if it exceeds 0.50%, TiC is generated and the toughness of the welded portion is deteriorated. Therefore, Ti is set to 0.01 to 0.50%.

Mo: Mo is an element that suppresses post-weld heat treatment (PWHT) embrittlement and can be added as a substitute for Mn. However, if it is less than 0.01%, the effect of adding Mo is small, and if it exceeds 0.50%, the toughness of the welded portion deteriorates. Therefore, Mo is set to 0.01 to 0.50%.

Ni: Ni is a typical element that improves the low temperature toughness and is added as necessary. However, if it is less than 0.01%, the effect of addition is small, and if it exceeds 6.0%, hot cracking occurs in the weld. Cause Therefore, Ni is set to 0.01 to 6.0%.

[0016]

EXAMPLES The effects of the present invention will be described below based on examples.
Ten types of welding wires shown in Table 2 were used for the test. In the table, No. 1 to No. 5 is a wire of the present invention, N
o. 6-No. 10 is a wire for comparison.

[0017]

[Table 2]

These welding wires and JIS Z33
52 FS-BN1 equivalent flux is used for SM4
90B was subjected to submerged arc welding. Table 3 shows the welding conditions. The groove used was in accordance with the total welding test specified in JIS. Then, a JIS No. 4 Charpy test piece was sampled from the weld metal to evaluate the toughness. The results are shown in Table 4. Here, those having an absorbed energy of 50 J or more at -50 ° C were regarded as acceptable. As shown in Table 4, all of the present inventions have good low temperature toughness.

[0019]

[Table 3]

[0020]

[Table 4]

[0021]

As described above, according to the welding wire of the present invention, stable low temperature toughness can be obtained without being affected by Al mixed in the weld metal by diluting the base metal. Also, the welding material can be shared, and the advantage is great.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masao Fuji, 20-1 Shintomi, Futtsu City, Chiba Shin Nippon Steel Co., Ltd.

Claims (2)

[Claims] 1. A submerged arc welding wire comprising:
% By weight based on the total weight of the wire, C: 0.01 to 0.10%, Si: 0.01 to 0.50%, Mn: 0.50 to 2.50%, Mg: 0.10 to 1 0.0%, Al: 0.01 to 0.50%, and the balance consisting of Fe and inevitable impurities, a submerged arc welding wire excellent in low-temperature toughness. 2. Further, at least one of Ti: 0.01 to 0.50%, Mo: 0.01 to 0.50% and Ni: 0.01 to 6.0% is contained. The submerged arc welding wire according to claim 1.