JP2003290977A - SOLID WIRE FOR Ar-CO2 MIXED GAS SHIELDED ARC WELDING - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid wire for Ar-CO<SB>2</SB>mixed gas shielded arc welding which is good in welding workability and is excellent in the strength and stable toughness of weld metal even if high-efficiency welding is performed under welding conditions of a high electric current, high heat input and high interpass temperature. <P>SOLUTION: The solid wire for Ar-CO<SB>2</SB>mixed gas shielded arc welding which performs welding by using gaseous Ar containing 5 to 40% CO<SB>2</SB>contains, by weight %, 0.01 to 0.1% C, 0.3 to 0.65% Si, 1.35 to 1.95% Mn, and 1.85 to 2.45% Si+Mn, 0.02 to 0.15% Ti, 0.1 to 0.3% Mo, ≥0.006% O, ≤0.005% N, and if necessary, 0.005 to 0.05% one or two kinds of Al or Zr, and the balance iron and inevitable impurities. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention mainly relates to 490N.
/ Mm ² class solid wire for gas shield arc welding used for high-strength steel, ensuring strength and stable toughness of weld metal even in multi-pass welding under conditions of high current, high heat input, and high pass temperature Ar-CO ₂ capable of ensuring good welding workability and capable of producing extremely small amount of spatter
The present invention relates to a solid wire for mixed gas shielded arc welding.

[0002]

2. Description of the Related Art In recent years, gas shielded arc welding has been widely used as a welding construction method in the field of steel frames and construction. For the purpose of improving the efficiency of the welding method, the welding conditions applied are those of high current and high heat input welding. Moreover, since each welding pass continuously performs the next welding pass in a short time, welding is performed at a high interpass temperature. The current state of welding under the condition of such high heat input and high interpass temperature is shifting to the high interpass temperature side on the higher heat input side. Then, the required strength characteristics and toughness characteristics of the weld metal tend to be advanced. The weld metal welded under the conditions of such high current, high heat input, and high temperature between passes tends to deteriorate in strength and toughness, and it may not be possible to secure a sound welded joint. for that reason,
There is a strong demand for a welding material capable of obtaining an excellent weld metal even under such circumstances. In a general welding method, a Ti-B-based welding material has been studied as a means for improving toughness, and some proposals have been made.

For example, Japanese Unexamined Patent Publication (Kokai) No. 10-230387 discloses a Ti-B-based component as a carbon dioxide welding wire for welding mild steel or 490 N / mm ² class high-strength steel under conditions of high heat input and high pass temperature. And the parameter PBT (B /
Wires that regulate Ti) and PBS (B × S) have been proposed. This wire can obtain toughness under welding conditions of high heat input and high interpass temperature. However, its toughness varies and is not sufficient. Further, since carbon dioxide shield arc welding is used, a large amount of spatter and slag are produced, and the welding workability and welding efficiency such as cleaning the welding torch and removing slag from the bead surface are poor.

Further, in JP-A-54-40250, the parameter (Pa = Ti × B × 10 ⁴ ) is set to 1 to 25.
There is a proposal for a high-efficiency gas shielded arc welding wire regulated by. This technique is Ar-CO ₂ mixed gas shielded arc welding, in which welding heat input for the purpose of low-temperature toughness enhancement of double-sided one-layer welding in order up to 40 kJ / cm.

In Japanese Patent Laid-Open No. 63-157795, there are 6
The purpose of low-temperature toughness improvement after PWHT in the mixed gas welding, such 0 kg class steels or more Ar-CO _2, wherein the technique for improving the low temperature toughness by the addition of Ni up to 6% Ti-B system There is. However, when these gas shielded arc welding wires are used for welding under conditions of high current, high heat input, and high interpass temperature, sufficient toughness cannot be obtained.

As described above, various Ti-B-based welding wires have been proposed as a welding material as a method for increasing the toughness of the weld metal. Under the actual conditions, the toughness has not been increased under the welding conditions of high interpass temperature, nor has the welding workability and welding efficiency been satisfied.

[0007]

DISCLOSURE OF THE INVENTION The present invention can secure the strength and stable toughness of the weld metal even when multi-pass welding is performed particularly under the conditions of high current, high heat input, and high temperature between passes, and spatter is generated. An object of the present invention is to provide a solid wire for Ar—CO ₂ mixed gas shielded arc welding which can secure good welding workability and welding efficiency such as extremely small amount and slag generation amount.

[0008]

The gist of the present invention is CO ₂
-CO welding with Ar gas containing 5-40%
_{2 In} mixed gas shielded arc welding solid wire, in mass%, C: 0.01 to 0.1%, Si: 0.3
~ 0.65%, Mn: 1.35 to 1.95%, and S
i + Mn: 1.85 to 2.45%, Ti: 0.02 to
0.15%, Mo: 0.1-0.3%, O: ≧ 0.00
6%, N: contains ≦ 0.005%, in Ar-CO ₂ mixed gas shielded arc welding solid wire and the balance being iron and unavoidable impurities.

Further, it is characterized by containing 0.005 to 0.05% of one or two of Al or Zr.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.

The most important issue under the welding conditions of high current, high heat input, and high interpass temperature is to reduce the toughness of the weld metal. As a means for ensuring this toughness, the gas used is mainly Ar. As low oxygen content of weld metal and Si
And addition of Mn are specified, and addition of Ti is effective. Further, it is particularly effective to add an appropriate amount of Mo from the viewpoint of securing stable strength and toughness, and Mo acts as an element for increasing hardenability, and is an important element for refining the weld metal to improve the toughness of the weld metal. I understood. Furthermore, it is effective to lower the N content of the weld metal to stabilize toughness, but when welding is performed using Ar-based shield gas under welding conditions of high current, high heat input, and high interpass temperature, melting The pool has low heat input,
Compared to welding conditions of low interpass temperature, it is much heated and the molten pool is large. Therefore, although the shielding property to the molten pool is deteriorated and N penetrates from the atmosphere to nitride the weld metal to lower the toughness, addition of a trace amount of Al and Zr has an effect of suppressing the toughness reduction by N. I found out that.

The amount of spatter generated is reduced by mainly using Ti and shield gas in the wire component as Ar, and the amount of slag generated is suppressed by mainly using the shield gas as Ar and the sum of Si and Mn. It is effective to specify the Ti amount.

The present invention has been made on the basis of the above-mentioned findings, and these effects can be achieved by a single and synergistic effect due to the coexistence of the shielding gas composition and each component of the wire. The reason for adding each element element of the wire and the reason for limitation will be described in detail.

(C: 0.01 to 0.1% by mass) C is an element necessary for securing the strength of the weld metal by solid solution strengthening, but on the other hand, it tends to cause an increase in hardness and a decrease in toughness due to strain aging. The upper limit of the wire is limited in consideration of these. Under welding conditions of high current, high heat input, and high temperature between passes, addition of more than 0.1 mass% (hereinafter referred to as%) excessively increases the strength and limits the toughness to 0.1% or less. . On the other hand, if it is less than 0.01%, it becomes difficult to secure the strength.

(Si: 0.3 to 0.65% by mass) Si is a main deoxidizer, and is an element necessary for improving the toughness by lowering the oxygen content of the weld metal. In particular, since the consumption of Si is large in the high welding current region, a higher addition than usual is required. S
When i is less than 0.3%, deoxidation becomes insufficient and the toughness is rapidly lowered. On the other hand, if it exceeds 0.65%, the weld metal base is hardened and the adverse effect on the toughness becomes remarkable.

(Mn: 1.35 to 1.95 mass%) Mn
Is a main deoxidizer together with Si, and is added for the purpose of securing the strength of the weld metal and stabilizing austenite to improve the toughness. Similar to Si, it is necessary to add it in consideration of oxidation consumption under high current conditions, and there is a tradeoff with the amount of Si, but if it is less than 1.35%, toughness cannot be secured and 1.95.
If the addition amount exceeds%, the strength becomes high and the toughness decreases.

Further, the above Si and Mn are Si + Mn and are set to 1.85 to 2.45%. Si + Mn is 1.85%
If it is less than 2, the toughness is reduced and Si + Mn is 2.45%.
If it exceeds, the amount of slag is increased, and if welding is continuously performed, a slag inclusion defect occurs. Therefore, it is necessary to remove the slag adhering to the bead surface after every several passes, resulting in poor work efficiency.

(Ti: 0.02 to 0.15% by mass) Ti
Is an element essential for improving the toughness by refining the structure of the weld metal. The amount of Ti required to secure the toughness varies depending on the amount of oxygen in the weld metal, and in the case of Ar-CO ₂ gas shielded arc welding where oxygen is low, about 0.02 to 0.15% is appropriate.

If the Ti content is less than 0.02%, the toughness is lowered and the spatter generation amount is slightly increased. Also, 0.2%
Excessive Sol. When Ti is solid-dissolved, the weld metal is significantly hardened, the toughness is remarkably reduced, and the amount of slag is increased, resulting in poor work efficiency.

(Mo: 0.1 to 0.3% by mass) Mo is effective in lowering the transformation temperature and refining the structure to improve toughness.
Particularly, it effectively works to improve the toughness under the conditions of high current, high heat input, and high temperature between passes. The effect is exhibited by the addition of 0.1% or more, and if it exceeds 0.3%, the effect on the toughness due to the increase in strength becomes small.

(O: ≧ 0.006% by mass) Oxygen is added for the purpose different from other elements. Under welding conditions of high current, high heat input, and high temperature between passes, the molten pool is large and high in temperature, so it was found that the droplet transfer state deteriorates compared to normal welding even in Ar-based gas shielded arc welding. did. That is, the droplets are increased in size, the amount of spatter is increased, the arc becomes unstable, and the welding workability is deteriorated. As a result of studying the improvement of the welding workability, it was found that increasing the oxygen content of the wire reduces the droplet size and reduces the spatter generation amount. The effect of this oxygen is 0.00
It becomes remarkable with the addition of 6% or more. The oxygen of the wire may be added at the time of melting or may give a grain boundary oxide layer to the wire surface base material. The upper limit of the amount of oxygen is also not particularly limited, but 0.05% or less is preferable in terms of wire feedability and manufacturing cost.

(N: ≤ 0.005% by mass) In order to stably improve the impact toughness of the weld metal, it is essential to reduce the amount of N, but the limit amount is 0.005% or less.

(One or two of Al or Zr is 0.
(005-0.05% mass) In gas shielded arc welding under welding conditions of high current, high heat input, and high temperature between passes, the molten pool becomes large, and in some cases sufficient shielding cannot be obtained, resulting in weld metal. Nitrogen in the atmosphere may enter. Thus, when the shielding property is impaired and nitrogen penetrates, the toughness of the weld metal deteriorates significantly. However, by adding Al and Zr, it is possible to suppress variation and deterioration of toughness due to a slight amount of nitrogen intrusion. It is considered that this is because Al and Zr have a strong harmony with N and fix the solid solution N to reduce the influence of strain aging. The effect appears from the addition of 0.005% or more in total of one kind or two kinds of Al or Zr, but the addition exceeding 0.05% rather lowers the toughness.

It should be noted that V and Nb can be added in the range of 0.005% or less in order to adjust the strength and toughness other than the above-mentioned components. In addition, the unavoidable impurity P is 0.
It is preferable that the content is 015% or less and the content of S is 0.01% or less.

The gas shielded arc welding wire according to the present invention, welding using Ar-CO ₂ mixed gas of CO ₂ mainly of Ar mixed 5-40%. If the CO ₂ gas content in the mixed gas is less than 5%, brohol occurs in the weld metal. If it exceeds 40%, the droplets become large and the amount of spatter generated increases, and the arc becomes unstable. In addition, the amount of slag produced increases and work efficiency deteriorates.

The effects of the present invention will be described in more detail below with reference to examples.

[0027]

EXAMPLE First, a raw material steel is melted in a vacuum, forged, rolled, drawn and plated, and then drawn to a diameter of 1.4 mm to 20 mm.
It was a spool winding wire of kg winding. Table 1 shows the chemical composition of the prototype wire.

[0028]

[Table 1]

Using the wires in Table 1, the high currents shown in Table 2,
Welding metal test by changing the amount of CO ₂ mixed under welding conditions of high heat input and high temperature between passes (groove shape, test piece sampling position is JIS
According to Z3312) was performed.

[0030]

[Table 2]

The weld metal was evaluated to have a tensile strength of 490 N /
mm ² or more was determined to be acceptable, and toughness was subjected to an impact test of 5 pieces each at 0 ° C., and a minimum value of impact absorption energy was 100 J or greater.

The amount of spatter generated was welded three times under the conditions shown in Table 2 by bead-on-plate welding using a copper collection box separately from the deposited metal test (one welding time of 1.5 min).
Then, the amount of spatter collected was converted into the amount of sputter generated per minute.
When the amount of spatter is 2 g / min or less, the arc is stable and workability is good.

Further, the amount of slag formed was visually observed, and it was shown that a small amount of slag could be welded to the final layer without removing the slag. The results are summarized in Table 3.

[0034]

[Table 3]

In Table 3, the test No. 1 to 11 are examples of the present invention,
Test No. 12 to 26 are comparative examples.

Test No. which is an example of the present invention. In Nos. 1 to 11, since the CO ₂ mixing amount of the shield gas and the components of the wire symbols W1 to 11 are appropriate, both the strength of the weld metal and the impact absorption energy are good, and the slag generation amount and spatter generation amount during welding are small. The arc was stable and the result was extremely satisfactory.

Test No. in the comparative example. 12 is a wire symbol W
C of 12 is high and the test No. No. 16 has a high Mn of wire symbol W16, and the test No. 21 is Mo with wire symbol W21
In all cases, the tensile strength of the weld metal was high and the impact absorption energy was low.

Test No. No. 13 had a low C in the wire symbol W13, so the tensile strength of the weld metal was low, and the total amount of Al and Zr was high, so the impact absorption energy was low.

Test No. 14 is Si of wire symbol W14
The test No. 15 is the wire symbol W15 Si
Is low, the test No. 17 is Mn of wire symbol W17
Is low, the test No. 19 is Si of wire symbol W19
Since + Mn is low, the test No. 22 is a wire symbol W22
Since the Mo content is low, the impact absorption energy is low.

Test No. 18 is the wire symbol W18 Si
Since + Mn is high, a large amount of slag is generated, and since Ti is low, a large amount of spatter is generated, and the impact absorption energy of the weld metal is also low.

Test No. 20 is Ti with wire symbol W20
, The impact absorption energy was low and the amount of slag produced was also slightly high.

Test No. 23 is Al with wire symbol W23
Since the total amount of Zr and Zr is low, the variation in shock absorption energy is large, and since oxygen is low, the amount of spatter generated is large.

Test No. In No. 24, since the wire symbol W24 has a high N, the variation in the impact absorption energy is large.

Test No. 25 is CO ₂ in the shield gas
Due to the small amount, brohol was generated in the weld metal. Therefore, the mechanical test was discontinued.

Test No. 26 is CO ₂ in the shield gas
Since the amount is large, the spatter generation amount and the slag generation amount are large.

[0046]

As described above in detail, the Ar-C of the present invention
According to the solid wire for O ₂ mixed gas shielded arc welding, under the welding conditions of high current, high heat input and high pass temperature, it is possible to secure the weld metal with excellent tensile strength and stable toughness, and the spatter generation amount. Further, it is possible to provide a solid wire for Ar—CO ₂ mixed gas shielded arc welding which can secure good welding workability and welding efficiency such as an extremely small amount of slag generation.

Claims (2)

[Claims] 1. A solid wire for Ar-CO ₂ mixed gas shielded arc welding for welding using Ar gas CO ₂ and containing 5-40%, by mass% C: 0.01 to
0.1%, Si: 0.3 to 0.65%, Mn: 1.35
˜1.95%, and Si + Mn: 1.85-2.45
%, Ti: 0.02 to 0.15%, Mo: 0.1 to 0.
3%, O: ≧ 0.006% , N: contains ≦ 0.005%, Ar-CO ₂ mixed gas shielded arc welding solid wire and the balance being iron and unavoidable impurities. 2. The solid for Ar—CO ₂ mixed gas shielded arc welding according to claim 1, characterized in that it contains 0.005 to 0.05% by mass of one or two of Al or Zr. Wire.