JPS6057953B2 - Steel wire for gas shield arc welding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a steel wire for gas-shielded arc welding, and more particularly to a steel wire for gas-shielded arc welding that provides weld metal with high strength and high toughness.

As structures become larger and more sophisticated, the demand for high tensile strength steel, particularly high tensile strength steel of grade 60 to 9/1 or higher, tends to increase more and more.

Submerged arc welding, covered arc welding, gas-shielded arc welding, etc. have been put into practical use as welding methods for these high-strength steel materials, but submerged arc welding method and gas shielded arc welding method have been widely used. In the latter type of welding, alloy components such as C, Si, Mn, Cr, Mo, and Ni are added to the welding steel wire in order to ensure a weld metal with a strength comparable to that of the target base metal. The objective of ensuring this has been fully achieved. Regarding cal toughness,
Merely adding the above alloying elements is not sufficient, and especially when performing hot welding with the aim of improving welding efficiency, the toughness of the welded part decreases due to coarsening of the crystal grains, etc., and the joint performance is not sufficiently improved. cannot be increased. In order to deal with these problems, attempts have been made to improve toughness by adding trace amounts of grain refining elements such as A], Ti, and B, but there are problems with the method of adding these trace elements. Even if the crystal grains can be made finer, it is not possible to sufficiently reduce the solid solution nitrogen and solid solution oxygen in the weld metal. As a result, the transition temperature of the weld metal increases and nonmetallic inclusions (trace element carbides, nitrides,
The amount of oxides, etc.) increases, and these act as notches, which negatively affects toughness. As described above, it is difficult to obtain a weld metal that satisfies toughness with conventional gas-shielded arc welding steel wires, and this is an important issue to be solved in the field of welding high-strength steel materials.

The inventors of the present invention have focused on the above-mentioned circumstances and have conducted intensive research with the aim of developing a steel wire for gas-shielded arc welding that satisfies both strength and toughness.

As a result, by determining the type and content of the main alloying elements, high strength can be ensured, and by adding appropriate amounts of acid-soluble and acid-insoluble A1 and Ti, the toughness of the weld metal can be greatly improved. After confirming this and conducting further studies, the present invention was completed. That is, the configuration of the present invention is C:0
．． Contains 15% (weight %: the same hereinafter) or less, Mn: 2.5% or less, and Sl: 0.8% or less as essential components, as well as Ni: 5% or less, Cr: 1.5% or less, and MO:
In a steel wire for gas-shielded arc welding containing 1.5% or less of one or more types, and the remainder consisting of iron and unavoidable impurities, acid-soluble (SOI) Ti: 0.2% or less and acid-soluble (SOI) A1: 0.02% or less, and acid-insoluble (InsOl) Ti: 0.2% or less and acid-insoluble (I
nsOl) A1: 0.02% or less, (IrlsOlT
i/SOITi) weight ratio: 30 or less, (InsOlA
The gist is that the weight ratio of 1/SOIAl): 1@) is added within a range that satisfies the following conditions. The reasons for setting the component composition in the present invention will be explained below.

C: 0.15% or less It is an essential element for giving weld metal the strength necessary for welding high-strength steel, but if it exceeds 0.15%, cracking susceptibility increases and low-temperature toughness decreases.

Mn: 2.5% or less Mainly acts as a deoxidizing agent and has the effect of increasing strength and toughness. However, if it exceeds 2.5%, welding workability decreases, hardenability sharply increases, and toughness deteriorates. .

Si: 0.8% or less is a ferrite structure forming element; if it exceeds 0.8%, the pro-eutectoid ferrite grains become coarse, the toughness decreases, and the bending performance also deteriorates.

Ni: 5% or less has the effect of increasing the toughness of the weld metal, but if it exceeds 5%, hot cracking resistance deteriorates.

Cr: 1.5% or less, MO: 1.5% or less These elements are effective for increasing the strength of weld metal, but if both exceed 1.5%, toughness decreases.

By determining the above amount of alloying elements, it is possible to obtain sufficient strength for welding high-strength steel, but the toughness is still insufficient. On the other hand, a method of increasing toughness by adding a small amount of A1 or Ti, which are grain refiners, can be considered. That is, appropriate amounts of InsOlTi and I are added to the weld metal.
In the presence of nsOlAl, (a) InsOl during solidification
Ti crystallizes and dendrites become finer. (b) During cooling, Ir)SOlTi precipitates in the austenite region, suppressing the growth of austenite grains.

(c) During the transformation from austenite to ferrite, InsOI,A] is precipitated at austenite grain boundaries, and pro-eutectoid ferrite grains become finer. With these effects, the purpose of grain refinement is achieved.

However, InsOlTi and InsOl are present in the welding wire.
If a large amount of N is contained, (1) N, O, and C are not fixed, and SOIN, O, and C remain in the weld metal.

(Ii) The effect of suppressing pro-eutectoid ferrite grain coarsening by InsOlAl is that SOlAl is Irls near the AC3 transformation point.
InsOlN in the welding wire, which exists at high temperatures, does not contribute much to grain refinement.

(Iii) As mentioned above, SOIAI in the welding wire is Aq
Since it precipitates as InsOlAl near the transformation, the amount of 1nsOIA1 in the weld metal increases, and the toughness significantly decreases due to their notch effect.

Problems such as this occur.

Moreover, if a large amount of SOlAI and Ti are present in the welding wire, the amounts of SOlAl and Ti in the weld metal will also increase, the reduction temperature will increase, and the toughness will become poor. As is clear from the above, the amounts of Al and Ti in the welding wire are
sOlAl and Ti. ．． It is necessary to specify the appropriate content separately for sOIAl and Ti, and furthermore, it is necessary to specify the appropriate content for sOIAl and Ti.
Conversion from Al and Ti to InsOlAl and Ti also needs to be taken into account.

Based on these findings, we determined the content of Ni and Ti that would satisfy all of the requirements of grain refinement, prevention of transition temperature rise, suppression of notch effect, and fixation of N, O, and C. , InsOIA]: 0. Below 屹, SOlAl: 0.02
% or less, InsOlTi: 0.2% or less, SOlTi:
0.2% or less, and 1r1S01A1/S
The weight ratio of OlAl is 10 or less, InsOITi/SOI
It has been found that the above object can be achieved by setting the weight ratio of Ti to 30 or less.

The reason for setting the upper limits for Ti and Ti<5sOlAI and Ti is clear from the advantages and disadvantages of each component described above, but the (InsOlAl/SOlAl) ratio and the
The reason for determining the ratio (OlTi/SOlTi) is that SOlAl→InsOlN and SOlTi→Ins that occur during welding
It takes into account the conversion of OlTi, and (InsOlA
l/SOlAl) ratio exceeds 10 or (InsOl
If the ratio (Ti/SOlTi) exceeds 30, soluble N, O and C in the weld metal will not be sufficiently fixed, resulting in
Toughness decreases together with an increase in OIN and Ti content.
In this specification, IrlsOlAl●Ti, sOlA
I●Ti is produced by performing constant potential electrolysis in a methanol solution containing 10% acetylacetone and 1% tetramethylammonium chloride, and converting the eluted N and Ti (i.e., A1 and T1 dissolved in the metal) into SOAI and SOL
Ti and also A1 and Ti in the residue (i.e. A1 in the metal
compound and Ti compound) to IrlsOlAl and Ins
It is called OlTi.

As described above, in the present invention, toughness is greatly improved by dividing Al and Ti, which have the strongest bonding strength with oxygen, nitrogen, carbon, etc. in the weld metal, into acid-soluble components and acid-insoluble components. can be increased to

In addition to N and T1, there are trace elements (Zr, Be, Nb, V, Ta, etc.) that form oxides, nitrides, and carbides, but their influence on toughness is not as great as that of A1 and Ti. However, even with regard to these trace elements, it is effective to suppress the content of their compounds as low as possible in improving toughness.
In addition, InsOI oxygen in the welding wire is not as effective as InsOI nitrogen in refining grains, promoting notch action and deteriorating toughness, and SOI oxygen coarsens grains and increases transition temperature. It is preferable to suppress the oxygen content to 0.015% or less.

In addition, a small amount of B has the effect of suppressing the coarsening of pro-eutectoid ferrite grains, but JO. When OO exceeds 3%, it becomes easy to be adsorbed at austenite grain boundaries, causing segregation and impairing toughness. The present invention is roughly constructed as described above, and it ensures high strength by specifying the types and amounts of the main alloying elements, and separates N and Ti into acid-soluble and acid-insoluble components, respectively. By specifying the amount of addition of , the toughness can be significantly increased, and it has become possible to provide a gas-shielded arc welding wire that is ideal as a welding material for high-strength steel, especially 60k9/Tnlt class or higher. Next, the configuration and effects of the present invention will be explained with reference to Examples.

Experimental Example 1 Test wires (1.67nφ) with various amounts of InsOlTi and SOlTi were prepared using gas-shielded arc welding wires with the basic compositions shown in Table 1, and when welded under the following conditions: The impact strength (absorbed energy at -40°C) of the weld metal was investigated.

[Test conditions] Base material: HT-801 thickness 30m Shield gas Ni 80%K+20%CO2, 28e/min Welding method: MIG method Welding conditions: (310-350) AX (3
1 to 33) ■×(17 to 24) Cln/min, average heat input 32.3 KJ/Cm Groove shape/layer method: Figure 1 The results are shown in Figures 2 A, B, and C.

As is clear from this result, in order to obtain a high-toughness weld metal, it is necessary to keep InsOlTi below 0.2% and SOLTi below 0.2% (InsOlTi/SOIT
i) The ratio should be below 30.

Experimental Example 2 Using gas-shielded arc welding wires with the basic composition shown in Table 2, test wires (1.6W!7j!φ) with various amounts of IrlsOlAI and SOlAl were produced,
The impact strength of the weld metal (same as above) when welded under the following conditions was investigated.

〔Test conditions〕

Base material: HT-80, thickness 40Tn Shield gas Ni CO2, 25e/min Welding method: MAG method Welding conditions: (300-380) A x (30-35) V x
(22-34) Cm/min, average heat input 28.3KJ/
Cm groove shape/layering method: Fig. 3 The results are shown in Fig. 4 A, B, and C.

As is clear from this result, in order to obtain a weld metal with high toughness, InsOlAl should be 0.0 or less and SOIN should be 0.0 or less.
It is necessary to make the InsOlAl/SOlA ratio 10 or less.

Experimental Example 3 Using gas-shielded arc welding wires with the basic composition shown in Table 3, test wires (
A 1.6mm diameter) was prepared and welded under the following conditions, and the impact strength of the resulting weld metal was examined.

[Test conditions] Base material: HT-601 thickness 25 order Shield gas Ni Ar''+2%02, 25e/min Welding method:
Pulse MIG welding conditions: (155-175) A x 21
■×(3.8 to 7.7) Ctt/min, average heat input 3
7.8KJ/α) Groove shape/layer method: The results in Figure 5 are shown in Figure 6.
Shown in Figures A and B.

As is clear from this result, in order to obtain a weld metal with high toughness, the amount of B should be 0.015% or less, and the amount of B should be 0.003%.
% or less.

[Brief explanation of the drawing]

Figures 1, 3, and 5 are diagrams showing the groove shape and layering method adopted in the experimental examples, and Figures 2, 4, and 6 are graphs showing the experimental results.

Claims (1)

[Claims] 1 C: 0.15% (weight %: same below) or less, Mn:
Contains 2.5% or less, Si: 0.8% or less as an essential component, and contains one or more of Ni: 5% or less, Cr: 1.5% or less, and Mo: 1.5% or less, In a steel wire for gas shielded arc welding, the balance of which is iron and unavoidable impurities, acid-soluble Ti: 0.2% or less, acid-soluble Al: 0.02% or less, and acid-insoluble Ti: 0.2%.
% or less and acid-insoluble Al: 0.02% or less, the weight ratio of (acid-insoluble Ti/acid-soluble Ti): 30 or less, and the weight ratio of (acid-insoluble Al/acid-soluble Al): 10 or less. A steel wire for gas-shielded arc welding, characterized in that it is made by adding each of the following: