JPH08253841A - Gas-shielded arc welding steel wire for thin sheet - Google Patents

Abstract

PURPOSE: To produce a welding steel wire for a thin sheet excellent in pore resistance, sputtering resistance and gap resistance by specifying the compsn. constituted of C, Si, Mn, P, S, O, Al, Ti, Zr, Nb, V, Ta and Fe. CONSTITUTION: This gas-shielded arc welding steel wire for a thin sheet is the one having a compsn. contg., by weight, 0.02 to 0.40% C, 0.50 to 2.0% Si, 0.20 to 3.0% Mn, 0.005 to 0.050% P, 0.005 to 0.050% S, 0.0030 to 0.050% O, one or more kinds among 0.005 to 0.20% Al, 0.005 to 0.20% Ti and 0.005 to 0.20% Zr, furthermore contg. one or more kinds among 0.05 to 1.50% Nb, 0.05 to 1.50% V and 0.05 to 1.50% Ta, and the balance substantial Fe and is used for high speed welding to a thin galvanized steel sheet.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is mainly applied to Ar--CO ₂
Regarding steel wire for thin plates that uses mixed gas as a shielding gas, in detail, for the wire to obtain excellent weldability when used for gas shielded arc welding of galvanized steel plates, non-surface treated cold rolled and hot rolled thin plates. It is related.

[0002]

2. Description of the Related Art As a means for compensating for the rust-prone defect of steel, there is a surface-treated steel sheet obtained by coating a cold-rolled or hot-rolled steel sheet with a zinc-based paint or galvanizing. These surface-treated steel sheets are used in the thin sheet field, in particular, in columns for prefabricated buildings, building materials for roofs, gasoline cans, washing machine parts, and also in automobile bodies. Gas shielded arc welding is often used for welding these surface-treated steel sheets. In the welding of thin sheets of zinc-based surface-treated steel sheets, in addition to the problems such as the occurrence of pore defects such as pits and blow holes and the increase of spatter, there are various problems such as the condition range for burn-through and gaps, that is, the gap resistance is narrow. is there. In particular, recently, with the progress of automation through the adoption of welding robots, the above problems tend to become more apparent as a factor that hinders automation, and it is strongly desired to solve these problems.

That is, the automation of thin plates is aimed at improving productivity, and higher-speed and stable welding is required.
In many cases, high speed welding with a speed of about 1 m / min or more is adopted. In high-speed welding of such thin plates, the welding heat input is small and the cooling rate is fast, so in the case of galvanized steel sheets, sufficient time is not available to float the zinc-based gas that has penetrated into the molten metal, and pore defects frequently occur. In addition to this, it is necessary to consider pore defects due to lack of shielding. Further, in high-speed welding of thin plates, the condition tolerance with respect to the groove gap is also narrowed, so it is necessary to satisfy the gap resistance at the same time.

As a technique for preventing pore defects in a galvanized steel sheet, Japanese Patent Laid-Open No. 63-56395 discloses Te and S.
e, REM and the like, or a technique of applying an inhibitor composed of an oxide, a carbonate, a fluoride or the like on the surface of a steel sheet, and Japanese Patent Application Laid-Open No. 63-108995 discloses a technique using phosphorus iron as a main component. Although agents have been proposed, these are not practical because not only it is necessary to apply the steel sheet surface in advance before welding, but also man-hours for removing the coating agent are required after welding.

Next, a steel wire is disclosed in Japanese Patent Laid-Open No. 63-72.
Japanese Patent No. 498 proposes a solid wire containing a large amount of Ni in addition to Al, Ti and Cu. However, such a composition cannot be expected to be effective for high-speed welding of galvanized steel sheet, which is the object of the present invention. Further, in Japanese Patent Laid-Open No. 1-309796, C, Si, Mn,
A solid wire for welding galvanized steel sheet is disclosed in which the addition amounts of Bi, O, and Ti are regulated. Although this technique is effective in suppressing the porosity of the galvanized steel sheet and reducing the amount of spatter generation, no consideration has been given to the gap resistance of thin plate high-speed welding.

Further, in JP-A-4-41098, C, Si, Mn and Bi are added to Nb, V and Al, Ti and Z.
There are various solid wires for surface-treated steel sheets that regulate r. This wire is also effective for the porosity resistance of the galvanized steel sheet, but cannot be expected to be effective for the spatter amount and the gap resistance.

Further, Japanese Patent Laid-Open No. 305476/1993, which targets high-speed welding of thin plates, discloses C, Si, Mn, P, S,
This is a proposal for a solid wire in which the amounts of Al, N, O and Mn / Si ratio are specified. Of these, the addition of S is intended to reduce spatter in high-speed welding of ordinary steel plates, improve bead forming properties, and improve slag peeling properties. Further, O is rather restricted because of adverse effects on the workability of the core wire and the workability of welding. Thus, this proposal is also 3.
It is intended for high-speed welding of ordinary steel plates of about 2 mm, and does not satisfy the porosity resistance of surface-treated steel plates.

[0008]

SUMMARY OF THE INVENTION The present invention solves the above problems and provides a steel wire that simultaneously satisfies the porosity resistance, the amount of spatter generation, and the gap resistance in high-speed welding of thin galvanized steel sheets. To do.

[0009]

The gist of the present invention is that C: 0.02% by weight based on the total weight of the wire.
0.40%, Si: 0.50 to 2.0%, Mn: 0.2
0-3.0%, P: 0.005-0.050%, S:
0.005-0.050%, O: 0.0030-0.0
50%, Al: 0.005-0.20%, T
i: 0.005 to 0.20%, Zr: 0.005 to 0.
20% of 1 or 2 or more, and Nb: 0.
05 to 1.50%, V: 0.05 to 1.50%, Ta:
0.05% to 1.50% of 1 type or 2 types or more,
A gas shielded arc welded steel wire for thin plates, characterized in that the balance is substantially Fe.

[0010]

In order to solve the above problems, the present inventors have made further detailed investigations on the invention of Japanese Patent Publication No. 6-47185 proposed by the present inventors in high-speed welding of thin galvanized steel sheets. The present invention has been accomplished. That is,
In the invention of Japanese Patent Publication No. 6-47185, C: 0.02
~ 0.40%, Si: 0.20 to 1.50%, Mn:
0.20 to 1.50%, P: 0.030% or less, S:
0.030% or less and Nb: 0.10 to 1.50
%, V: 0.10 to 1.50% of 1 or 2 types, and the balance is Fe and inevitable impurities. According to this structure, although it is effective in suppressing pores due to zinc in the galvanized steel plate welding and defective shielding, it cannot be said to be sufficient in reducing the gap resistance and the amount of spatter.

Therefore, further investigation was made on the above characteristics and it was found that the gap resistance can be improved by utilizing S and O. Addition of S reduces the weld penetration, increases the bead width, improves the wettability of the weld metal with the base material, improves the crosslinkability, and improves the gap resistance. However, if only S is added, the arc stability is insufficient in the high-speed welding targeted by the present invention. Addition of O is effective for improving high speed. Further, O has the same effect of improving the gap resistance as S, and coexistence of S and O is effective for ensuring the gap resistance of high-speed welding, and contributes to the reduction of spatter generation by stabilizing the arc.

The addition of Al, Ti, and Zr is effective in reducing the amount of spatter generated. Further, V, Nb and Ta change the viscosity of the molten metal and effectively act to improve the gap resistance.
Thus, coexistence of S and O, Al, Ti, Zr and T
The following studies were conducted on a and the like to obtain a new configuration.

As a result of studying the gap resistance of the galvanized steel plate weld metal welded by the welding conditions shown in Table 2 and the groove shape shown in FIG. 1 using the steel wire having the composition shown in Table 1 and having a wire diameter of 1.2 mm. Is shown in Table 3. As shown in FIG. 1, the test material is an upper plate 1 and a lower plate 2 which are stacked so that a gap G is formed in a tapered shape. The welding line 3 is the edge of the upper plate 1, and welding was performed from the closed end of the gap. The gap resistance was evaluated based on the maximum weldable gap that does not cause burn-through, and the spatter generation amount and the presence or absence of cracks were evaluated.
Gap resistance evaluation shows maximum weldable gap of 1.0 m
m or more, the amount of spatter generation was evaluated on the basis of a collection weight of 1.0 g / min or less in the copper collection box, and cracks were examined by an X-ray transmission test except for the weld bead crater.

[0014]

[Table 1]

[0015]

[Table 2]

[0016]

[Table 3]

As described above, Nb, V, and Ta are added, and A
By adjusting l, Ti, and Zr, and regulating the ranges of S and O, respectively, it became possible to weld a thin plate with improved gap resistance, spatter generation amount, and cracking.
The reasons for limiting the components of the present invention will be described in detail below together with the action.

C: 0.02 to 0.40% C has the effect of preventing pore formation in the galvanized steel sheet in the constitution of the present invention. However, if it is less than 0.02%, the effect is not recognized, and if it exceeds 0.40%, the spatter generation amount increases, and crack susceptibility becomes extremely high even in high-speed welding of thin plates, so the range is 0.02 to 0. It was set to 40%.

Si: 0.50 to 2.0% Si is added as a main deoxidizing agent, but it has the effect of improving the bead shape and the gap resistance in high speed welding. However, if it is less than 0.50%, these effects cannot be obtained, and if it exceeds 2.0%, the amount of slag generated increases, so the range was made 0.50 to 2.0%.

Mn: 0.20 to 3.0% Mn acts as a deoxidizer together with Si, and is added for the purpose of improving the bead shape. However, if it is less than 0.20%, pores caused by factors other than zinc become significant due to insufficient deoxidation, and spatter frequently occurs, so the lower limit is 0.20%.
And Further, if it exceeds 3.0%, the gap resistance is deteriorated and the hardening of the weld metal becomes remarkable, so the range was made 0.20 to 3.0%.

P: 0.005 to 0.050% P is effective in suppressing pores in the galvanized steel sheet, but excessive addition causes cracks in the weld metal. Lower limit of 0.005
% Was determined from the viewpoint of suppressing pores, and the upper limit of 0.050% was determined from the viewpoint of crackability.

S: 0.005 to 0.050% S is extremely effective as an element for improving the gap resistance together with oxygen. The effect is exhibited from about 0.005%. On the other hand, if it exceeds 0.050%, the risk of cracking increases as with P, so the range is 0.005-0.050%.
And

O: 0.0030 to 0.050% O is necessary to secure the gap resistance in high speed welding together with S. It also has the effect of reducing spatter generation. In the constitution of the present invention, the effect becomes remarkable at 0.0030% or more, but if it exceeds 0.050%, not only the effect is saturated, but also the arc becomes unstable and spatter frequently occurs. The existing form of O may be uniformly distributed in the wire as a solid solution or an oxide, but it is more preferable to exist in the surface of the wire as an internal oxide layer or a grain boundary oxide layer.

Al: 0.005-0.20% Al is a strong deoxidizing element and T as a nitrogen fixing element.
Along with i and Zr, addition of a very small amount has the effect of suppressing the generation of pores due to defective shielding. However, if it is less than 0.005%, the above effect is not observed, and if it exceeds 0.20%, the slag generation amount increases and promotes the generation of pores due to zinc, so the upper limit must be 0.20%.

Ti: 0.005 to 0.20% Ti is a strong deoxidizing agent like Al and Zr, and when added in a very small amount as a nitrogen fixing element, it has the effect of suppressing the generation of pores due to shield failure. . It also stabilizes the arc, improves high-speed weldability, and effectively acts to reduce spatter.
However, if less than 0.005%, the above effect is not observed,
If it exceeds 0.20%, the amount of slag produced increases and the encapsulation area on the bead surface of the slag increases, which promotes the generation of pores by zinc, so the upper limit must be 0.20%.

Zr: 0.005 to 0.20% Zr is a strong deoxidizing agent like Al and Ti.
Suppressing the generation of pores due to poor shielding by the combined addition of and. The effect is exhibited from 0.005%. However, if it exceeds 0.20%, the same action as Al and Ti promotes the generation of pores.

Nb: 0.05 to 1.50% Nb is a nitride-forming element, which suppresses the generation of pores due to defective shielding, and also has an effect of preventing pores due to zinc. It is added for the purpose of improving the gap resistance in welding. The effect is recognized at the addition of 0.05% or more. But 1.50%
If it exceeds, the above-mentioned effects will be saturated and the hardness of the bead will be significantly increased, so the upper limit was made 1.50%.

V: 0.05 to 1.50% V precipitates a nitride together with Nb and is added for the purpose of preventing generation of pores due to defective shield. However, if it is less than 0.05%, the effect is insufficient, and if it exceeds 1.50%, the susceptibility to cracking is rather increased, so the range was made 0.05 to 1.50%.

Ta: 0.05 to 1.50% Like Nb and V, Ta is added as a nitrogen fixing element.
The effect is recognized in the range of 0.05 to 1.50%.

[0030]

EXAMPLES The present invention will be specifically described below with reference to examples. Welding was performed under the welding conditions shown in Table 2 with the joint shown in FIG. Table 5 shows the results of evaluating the porosity resistance, maximum gap, and spatter generation amount of this joint welding.

[0031]

[Table 4]

[0032]

[Table 5]

The evaluation criteria are 1 or less by measuring the number of pits (visual inspection) for pore resistance, and 30% of total blowhole width / bead length for blowhole generation (X-ray transmission inspection). The following were accepted. For the gap resistance evaluation, the weldable gap is 1.0 mm or more, and for the spatter generation evaluation, the collection weight in the copper collection box is 1.0 g.
/ Min or less was considered to be acceptable.

Wire No. In No. 7, since the Si value is less than the range of the present invention, pits and blowholes different from the pores due to zinc are often generated, and the gap resistance and the amount of spatter are also large. Wire No. In No. 8, the Mn value exceeds the range of the present invention, and therefore, sufficient values cannot be obtained particularly for the pore resistance and the gap resistance.

Wire No. No. 9 has Mn less than the range of the present invention, and the wire No. Similar to the case of 7, there are many pores,
Sputtering occurs frequently and performance is deteriorated. Wire No.
In No. 10, although Si exceeds the limit range of the present invention, the performance of each item cannot be obtained as a whole.

Wire No. In No. 11, Nb, V, and Ta are less than the range of the present invention, the porosity resistance is particularly poor, the amount of spatter is large, and cracks occur. Wire N
o. No. 12 is a wire having a V content exceeding that of the present invention, and has poor porosity resistance.

Wire No. In No. 13, Al, Ti, and Zr do not satisfy the range of the present invention, the porosity resistance is extremely poor, and the amount of sputtering is large. Wire No. 14 is
Since Ti exceeds the range of the present invention, the gap resistance is not particularly satisfactory.

Wire No. In No. 15, since S and O are less than the range of the present invention, the gap resistance is particularly poor, and other performances are also insufficient as a whole. Wire No. 16
In the case of C, since C exceeds the range of the present invention, spatter is particularly large and cracking is observed.

Compared with these comparative wires, the wire No. 1 to No. It is clear that each wire of No. 6 gives good results in all of the items.

[0040]

As described above, the wire of the present invention has excellent porosity resistance and gap resistance in high-speed welding of surface-treated steel sheets and ordinary steel sheets, and enables welding with less spatter generation.

[Brief description of drawings]

FIG. 1 is a perspective view showing a joint shape of a test plate.

Claims (1)

[Claims] 1. C: 0.02-0.40%, Si: 0.50-2.0%, Mn: 0.20-3.0%, P: in weight% with respect to the total weight of the wire. 0.005-0.050%, S: 0.005-0.050%, O: 0.0030-0.050%, Al: 0.005-0.20%, Ti: 0.005 .About.0.20%, Zr: 0.005 to 0.20%, one or more kinds are contained, and Nb: 0.05 to 1.50%, V: 0.05 to 1.50%, Ta: 0.05-1.50% of 1 type or 2 types or more, and the balance consists essentially of Fe, The gas shielded arc welding steel wire for thin plates characterized by the above-mentioned.