JPH10230387A - Gas shield arc welding wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a welding wire capable of securing the strength and rigidity or the like of the welded metal and improving crack resistance even in the case of welding under a large heat input and an interpass temperature by specifying the composition of C, Si, Mn, Ti, B, S, controlling inevitable impurities to be <= a specified value and further composing B, Ti, S within the range satisfying a specified relation. SOLUTION: This wire is composed of, by wt., 0.02-0.10% C, 0.65-1.10% Si, 1.75-2.50% Mn, 0.16-0.45% Ti, 0.003-0.010% B, <=0.020% S and the balance Fe with inevitable impurities. Impurities are controlled to be, by wt., <=0.03% Al, <0.10% Cr, <=0.5% Mo, <=1.0% Cu and <=0.016% P. And when the containing quality of B, Ti, S are respectively expressed as [B], [Ti], [S], the value of PBT calculated with PBT=[B]×10<3> /[Ti] is specified to be 12-40 and the value of PBS calculated with PBS=[B]×[S]×10<5> is specified to be <=10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to mild steel or 490 (N
/ Mm ² ) class of gas shielded arc welding wire applied to carbon dioxide shielded arc welding of high strength steel, and particularly to a gas shielded arc welding wire capable of improving the mechanical performance of a welded portion. .

[0002]

2. Description of the Related Art Gas shielded arc welding using CO ₂ or the like as a shielding gas has been rapidly popularized because its welding efficiency is higher than that of covered arc welding.
It is the most used welding method. Furthermore, as for the welding apparatus, high-performance welding robots and simple robots have been developed, and the welding efficiency has been further improved. When welding using these welding devices, there is an advantage that fatigue does not occur or is alleviated to the human body, unlike manual welding. Therefore, when a welding device is used, the welding current can be increased and continuous welding can be performed.

[0003] However, at present, high-efficiency welding that makes full use of the performance of these welding devices is rarely performed. This is because, when a conventional welding wire is used, when welding is performed at a large heat input and a high inter-pass temperature, the strength and toughness of the weld metal are reduced, and the desired mechanical performance cannot be obtained. . Therefore, at the time of actual welding, it is necessary to set the heat input and the upper limit of the inter-pass temperature to be low, so that the welding efficiency cannot be sufficiently improved.

Therefore, steel wires for arc welding suitable for high-efficiency welding include C, Si, Mn, and A in the wire.
There has been disclosed one that regulates the contents of l, Ti, Zr, V, etc., and also contains a predetermined amount of B (Japanese Patent Publication No. Sho 43).
-12258). In addition, Ti, B in the wire,
There has also been proposed a wire for gas shielded arc welding in which the contents of C, Si and Mn are specified and the low-temperature toughness can be improved during high-efficiency automatic welding (Japanese Patent Laid-Open No. 54-402).
No. 50).

[0005]

However, no matter which of the above-mentioned wires is used, when the welding is performed at a large heat input and a high inter-pass temperature, the mechanical performance of the weld metal is still insufficient. There is a point. Further, when B is added to the wire, the effect of making the weld metal finer can be obtained, but on the other hand, there is a disadvantage that the hot cracking resistance becomes extremely low. Since all of the conventional wires described above contain a predetermined amount of B, when welding with large heat input,
Cracks may occur.

[0006] In addition, a wire for gas shielded arc welding has been proposed which can prevent a decrease in mechanical performance even when the heat input and the inter-pass temperature are increased (Japanese Patent Publication No. 54-32623). ). This does not contain B, which is an element that lowers hot cracking resistance. When this wire is used, even during high heat input welding, the mechanical performance of the weld metal can be slightly improved,
When welding is continuously performed at a high interpass temperature, there is a problem that toughness is extremely low.

The present invention has been made in view of such a problem, and can secure the strength and toughness of a weld metal even when welding is performed at a large heat input and a high inter-pass temperature. Another object of the present invention is to provide a gas shielded arc welding wire capable of improving crack resistance.

[0008]

The gas-shielding arc welding wire according to the present invention comprises C: 0.02 to 0.10% by weight, Si: 0.65 to 1.10% by weight, and Mn: 1.10% by weight.
75 to 2.50% by weight, Ti: 0.16 to 0.45
% By weight, B: 0.003 to 0.010% by weight and S:
0.020% by weight or less, the balance being Fe and unavoidable impurities. Of the unavoidable impurities, Al is 0.03% by weight or less, Cr is less than 0.10% by weight, and Mo is Mo.
Is regulated to 0.5 wt% or less, Cu is regulated to 1.0 wt% or less, and P is regulated to 0.016 wt% or less. The content of B is [B], and the content of Ti is [Ti]. When the content of S is [S], the equation P _BT = [B] × 10 ³ /
With P _BT is 12 to 40 calculated by [Ti], formula _{P BS = [B] × [} S] P BS is calculated by × 10 ⁵ is characterized in that it is 10 or less.

[0009] Mo in the wire is preferably 0.1% by weight or less, and more preferably 0.01% by weight or less.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to solve the above-mentioned problems, the present inventors have made various wires, welded them with a large heat input and a high inter-pass temperature, and obtained a weld metal. Was systematically evaluated for its mechanical performance. As a result, correlations between Ti and B and between S and B in the wire were found as a range that does not reduce the toughness and crack resistance of the weld metal.

FIG. 1 shows the B content in the wire on the vertical axis,
It is a graph which shows the range of B and Ti content which can obtain the weld metal which has a favorable mechanical property by taking the Ti content in a wire on a horizontal axis. In the present invention, B
And the ranges of the contents of Ti and Ti are defined, and the relationship between the two is appropriately limited. B promotes grain refinement,
It has the effect of improving toughness, but its effect is lost when B is nitride or oxide. Therefore, by coexisting Ti having a function as a strong deoxidizing agent and a strong denitrifying agent with B, B can be prevented from being oxidized or nitrided, and the effect of adding B can be sufficiently obtained. .

The present inventors have found an appropriate amount of Ti added to the amount of B added to the wire, which has not been conventionally proposed, and expressed the relationship between B and Ti as a parameter _PBT . The B content in the wire is [B], the Ti in the wire is
When the content is [Ti], P _BT (P _BT = [B] × 1
0 ³ / [Ti]) is 12 to 40, B and Ti
Is optimized, and good mechanical properties can be obtained. If P _BT exceeds 40, T
Since the amount of i added is insufficient, oxidation and nitridation of B cannot be suppressed, and the toughness of the weld metal cannot be improved. On the other hand, if P _BT is less than 12, the Ti content becomes excessive, the effect of adding B is saturated, and Ti oxides, nitrides, carbides, and the like are excessively present in the weld metal, It becomes brittle easily. Therefore, B and Ti
Is preferably proportionally added to the wire, and P
_BT (P _BT = [B] × 10 ³ / [Ti]) is 12 to 40
And That is, the range shown by the hatched lines in FIG. 1 is the range of B and Ti defined in the present invention.

FIG. 2 shows the B content in the wire on the vertical axis,
It is a graph which shows the range of B and S content which can obtain the weld metal which has excellent hot crack resistance by taking the S content in a wire on a horizontal axis. In the present invention, the ranges of the contents of B and S are defined, and the relationship between the two is appropriately limited. Generally, S is regarded as a harmful element in the weld metal. This is because S, like B, is an element that lowers the crack resistance of the weld metal and also lowers the toughness. However, S has the effect of lowering the surface tension of the molten pool, flattening the bead shape, and reducing the amount of slag. Therefore, S may be added to a wire used under conditions that do not adversely affect the crack resistance and toughness of the weld metal.

An object of the present invention is to obtain a weld metal having excellent toughness when welding at a large heat input and a high inter-pass temperature. Also, during high heat input welding, high temperature cracks such as pear-shaped cracks are likely to occur,
Excellent hot cracking resistance is also required. In general, the amount of S contained in a wire as an impurity varies depending on the method of dissolving the raw materials at the time of manufacturing the wire, but the S content may be 0.050% by weight or more. In the present invention, in order to obtain good crack resistance and toughness, the S content is regulated to 0.020% by weight or less.

[0015] However, even if the S content is strictly regulated, hot cracking may occur depending on the B content. That is, when the B content in the wire is high, the decrease in crack resistance is promoted.
It is necessary to reduce the content. The present inventors have found an appropriate S content relative to the addition amount of B in the wire, showing the relationship between B and S as parameters P _BS. When the B content in the wire is [B] and the S content in the wire is [S], P _BS (P _BS = [B] × [S] × 10
^{If 5} ) exceeds 10, it becomes impossible to prevent the occurrence of hot cracking. Therefore, the relationship between the B content and the S content is regulated such that P _BS (P _BS = [B] × [S] × 10 ⁵ ) becomes 10 or less. In the present invention, an excellent bead shape and appearance can be obtained by adding S in a range shown by oblique lines in FIG.

The chemical components contained in the gas-shielded arc welding wire of the present invention and the reasons for limiting the composition will be further described below.

Ti: 0.16 to 0.45% by weight As described above, Ti has a strong deoxidizing effect and a denitrifying effect. If the Ti content in the wire is less than 0.16% by weight, the effect cannot be sufficiently obtained, and B is oxidized or nitrided, so that the effect of improving the toughness of B is effective. Can not do. On the other hand, if the Ti content exceeds 0.45% by weight, the amount of Ti present in the crystal grains and at the grain boundaries increases excessively, and the alloy becomes brittle. In addition, the drawability as a wire is significantly deteriorated, so that the productivity is reduced. Therefore, the content of Ti in the wire is set to 0.16 to 0.45% by weight.

B: 0.003 to 0.010% by weight B is an element having an effect of refining crystal grains and improving toughness. If the B content in the wire is less than 0.003% by weight, the effect cannot be sufficiently obtained. On the other hand, B is also a component that significantly degrades hot cracking resistance. If the B content in the wire exceeds 0.010% by weight, cracks are extremely likely to occur and the soundness of the weld is lost. Therefore, the B content in the wire is set to 0.003 to 0.010% by weight.

C: 0.02 to 0.10% by weight C is an important element for securing the strength of the weld metal. When the C content in the wire is less than 0.02% by weight, a desired strength cannot be obtained at the time of welding with a large heat input and a high interpass temperature. On the other hand, if C is excessively added to the wire in excess of 0.10% by weight, the toughness is significantly reduced. Therefore, the C content in the wire is set to 0.02 to 0.10% by weight.

Si: 0.65 to 1.10% by weight Si is an element having an effect of deoxidizing and improving strength. When welding with large heat input and high inter-pass temperature, Si is consumed significantly because the area of the molten pool is enlarged as the cooling rate of the molten pool is reduced. If the Si content in the wire is less than 0.65% by weight, a sufficient deoxidizing effect cannot be obtained, and the weld metal is oxidized and blowholes are generated. Also, a desired strength cannot be obtained. On the other hand, the Si content is 1.10% by weight.
If it exceeds, the toughness of the weld metal decreases. Therefore, the Si content in the wire is set to 0.65 to 1.10% by weight.

Mn: 1.75 to 2.50% by weight Mn is an element having a deoxidizing effect and an effect of improving strength and toughness. It also has the effect of improving hot cracking resistance. If the Mn content in the wire is less than 1.75% by weight, the desired strength cannot be obtained when welding is performed with a large heat input and a high inter-pass temperature. Further, the effect of preventing hot cracking cannot be sufficiently obtained. On the other hand, when the Mn content exceeds 2.50% by weight, the drawability of the wire is reduced, and the weld is hardened, and the toughness is reduced. Therefore, the Mn content in the wire is set to 1.75 to 2.50% by weight.

S: not more than 0.020% by weight As described above, S is an element that lowers the crack resistance and also lowers the toughness, and therefore is not generally added to the wire. In the present invention, even when the B content in the wire is small, when the S content exceeds 0.020% by weight, hot cracking is extremely likely to occur. Therefore,
The S content in the wire is 0.020% by weight or less. However, as described above, when the addition amount of B is increased in order to improve the toughness, it is necessary to regulate the S content so as to be within the range of _PBS defined in the present invention. Since S has the effect of lowering the surface tension of the molten pool, flattening the bead shape, and reducing the amount of slag, S is added as necessary within the range specified in the present invention. can do.

Al: not more than 0.03% by weight Al present as an unavoidable impurity in the wire has an effect as a strong deoxidizer, but most of this Al
Oxide precipitates at the yield at the crystal grain boundaries, so that the toughness of the weld metal is significantly reduced. Therefore, Al in the wire
Is regulated to 0.03% by weight or less.

Cr: less than 0.10% by weight Cr is an element present as an unavoidable impurity in the wire. If the Cr content is 0.10% by weight or more, the toughness of the weld metal is significantly reduced. Therefore, Cr in the wire
The content is regulated to less than 0.10% by weight.

Mo: 0.5% by weight or less Mo present as an inevitable impurity in the wire has the effect of improving the strength of the weld metal, but reduces the toughness of the weld metal by hardening. Further, at the time of wire production, drawability is significantly reduced. When the Mo content in the wire exceeds 0.5% by weight, such a phenomenon occurs remarkably. Therefore, the Mo content in the wire is restricted to 0.5% by weight or less. In addition, it is preferable that 0.
1% by weight or less, more preferably 0.01% by weight
It is as follows.

Cu: 1.0 wt% or less Cu present as an unavoidable impurity in the wire is an element that embrittles the weld metal and reduces the hot cracking resistance. When the Cu content in the wire exceeds 1.0% by weight, such a phenomenon occurs remarkably. Therefore, the Cu content in the wire is set to 1.0% by weight or less. When the wire is plated with Cu, the total content of the Cu content in the core wire and the Cu content of the plating is defined.

P: 0.016% by weight or less P present as an unavoidable impurity in the wire is an element which, like S, significantly reduces the crack resistance of the weld metal. Further, since P has no effective effect due to the addition of P, it is preferable to reduce the P content in the wire as much as possible. If the P content in the wire exceeds 0.016% by weight, the reduction in crack resistance becomes significant. Therefore, the P content in the wire is restricted to 0.016% by weight or less.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the gas shielded arc welding wire according to the present invention will be specifically described in comparison with comparative examples.

First, a steel sheet was welded under the welding conditions shown in Table 5 below using wires having the compositions shown in Tables 1 to 4 below. In addition, since the ceramic backing material used at the time of welding uses a glass tape containing B, B is mixed into the weld metal at the time of welding.
The conditions are such that cracks in the weld metal are likely to occur. Also,
With respect to other welding conditions, the heat input amount and the inter-pass temperature were set high, so that it was difficult to obtain a weld metal having excellent mechanical properties.

Next, the obtained weld metal was evaluated for mechanical properties such as strength and toughness, and examined for the presence of cracks and blowholes by an X-ray transmission test. The evaluation results are shown in Tables 6 and 7 below. The strength and toughness were evaluated by measuring 0.2% proof stress, tensile strength and Charpy absorbed energy at 0 ° C.
Those having a 0.2% proof stress of 390 (N / mm ² ) or more, a tensile strength of 490 (N / mm ² ) or more, and a Charpy absorbed energy of 47 J or more were judged as acceptable.

[0031]

[Table 1]

[0032]

[Table 2]

[0033]

[Table 3]

[0034]

[Table 4]

[0035]

[Table 5]

[0036]

[Table 6]

[0037]

[Table 7]

As shown in Tables 1 to 4, 6 and 7,
Example No. Nos. 1 to 14 indicate that the chemical composition of the wire is within the scope of the present invention and that the relationship between B and Ti is P _BT and B and S
The relation P _BS is within the prescribed range of the even welding conditions at high heat input and high interpass temperature, it was able to strength and toughness obtain weld metal is good. In addition, although welding was performed under conditions where cracks were easily generated, no crack was generated and a weld metal having excellent crack resistance was obtained.

In particular, in Example No. In Examples Nos. 2, 5, 6 and 13, the content of Mo in the wire was within the preferred range of the present invention. As compared with Examples 7 to 10, a higher Charpy absorbed energy can be obtained. 1,
In Nos. 3, 4, 11, 12, and 14, the Mo content in the wire was more strictly controlled, so that the Charpy absorbed energy could be further increased.

On the other hand, in Comparative Example No. No. 15 shows that the content of C and Ti in the wire exceeds the upper limit of the range of the present invention,
Since excess by P _BT content is less than the lower limit of the range of the present invention, the toughness is lowered by embrittlement. In addition, S in the wire
Content exceeds the upper limit of the range of the present invention, since the P _BS exceeds the upper limit of the range of the present invention an excess of the S content, hot cracking occurred. Comparative Example No. No. 16 shows that the Si content exceeds the upper limit of the present invention range, the Ti content is less than the lower limit of the present invention range, and P is insufficient due to insufficient Ti content.
_{Since BT} exceeded the upper limit of the range of the present invention, the toughness was low. Although B and S content is within the scope of the present invention, since the P _BS defining these relationships is greater than the upper limit of the range of the present invention, with reduced resistance to cracking of the weld metal,
Cracks occurred. Furthermore, since the Ti content was less than the lower limit of the range of the present invention, the stability of the arc was lowered, and a large amount of spatter was generated.

Comparative Example No. In No. 17, since the Mn and Ti contents were less than the lower limits of the range of the present invention, the strength and toughness were reduced. Also, in Comparative Example No. As in the case of No. 16, a large amount of spatter occurred due to insufficient Ti content. Furthermore, since the S content exceeded the upper limit of the range of the present invention, cracks occurred. Comparative Example No. In No. 18, since the B content was less than the lower limit of the range of the present invention, the effect of refining the crystal grains could not be sufficiently obtained, and the toughness was low. Moreover, since the P content exceeded the upper limit of the range of the present invention, cracking occurred. Comparative Example No. 19 together with the B content is less than the lower limit of the range of the present invention, Al content exceeds the upper limit of the range of the present invention, since the P _BT by the lack of B content is less than the lower limit of the range of the present invention, oxide The deposition of the material embrittled the weld metal and lowered the toughness. Also, since the arc stability was reduced by Al, a large amount of spatter was generated.

Comparative Example No. In No. 20, hot cracking occurred because the B content exceeded the upper limit of the range of the present invention. Also,
Since the Cr content also exceeded the upper limit of the range of the present invention, the toughness of the weld metal was reduced. Comparative Example No. 21 is Ti and M
Since each of the contents of o exceeded the upper limit of the range of the present invention, the structure was hardened, and carbides and oxides were precipitated to lower the toughness. Comparative Example No. In No. 22, since both the contents of B and Cu exceeded the upper limit of the range of the present invention, the hot cracking resistance was reduced, cracking occurred, and the toughness was lowered.

Comparative Example No. In No. 23, the desired strength could not be obtained because the C content was less than the lower limit of the range of the present invention. Further, the contents of B and Ti are within the range of the present invention, but _PBT, which defines these relationships, is less than the lower limit of the range of the present invention, so that Ti becomes excessive and the toughness could not be improved. . Comparative Example No. 24 is Comparative Example No. 24.
Similarly to _No. 23, the toughness was low because PBT was less than the lower limit of the range of the present invention. Further, since the Si content is less than the lower limit of the range of the present invention, the strength is insufficient, and
Insufficient deoxidation caused blowholes.

Comparative Example No. 25 B, and Ti and S content is within the scope of the present invention, to define these relationships P _BT
And since P _BS exceeds the upper limit of the range of the present invention, the toughness is decreased, cracks also occurred. Comparative Example No. 26 together with the C content exceeds the upper limit of the range of the present invention, since the P _BT exceeds the upper limit of the range of the present invention, the toughness is lowered. Comparative Example No. 27 is the B content exceeds the upper limit of the range of the present invention, since the P _BS exceeds the upper limit of the range of the present invention an excess of B content, resistance to hot cracking is reduced, cracks occurred.

Comparative Example No. In No. 28, since the contents of Si and Cr exceeded the upper limit of the range of the present invention, the weld metal was embrittled and the toughness was reduced. Although the content of B and S are within the scope of the present invention, since the P _BS defining these relationships is greater than the upper limit of the range of the present invention, hot cracking occurred. Comparative Example No. 29 is Comparative Example No. 29. Similar to 28, since the P _BS exceeds the upper limit of the range of the present invention, hot cracking occurred. Comparative Example No. In No. 30, cracks occurred because S exceeded the upper limit of the range of the present invention. The content of Mn and B is less than the lower limit of the range of the present invention, since the P _BT has become less than the lower limit of the range of the present invention by the lack of B content, the strength and toughness is lowered.

Comparative Example No. 31 together with the Mn content exceeds the upper limit of the range of the present invention, the Ti content is less than the lower limit of the range of the present invention, since the P _BT exceeds the upper limit of the range of the present invention due to insufficient Ti content , Toughness decreased. In addition, arc stability is reduced due to insufficient Ti content,
A large amount of spatter occurred. Comparative Example No. 32 S content exceeds the upper limit of the range of the present invention, since the P _BS exceeds the upper limit of the range of the present invention an excess of the S content, the crack resistance is decreased, hot cracking occurred.

[0047]

As described in detail above, according to the present invention,
Since the composition of the wire is properly defined, and the relationship between the B content and the Ti content and the relationship between the B content and the S content are properly defined, large heat input and high interpass temperature are obtained. In this case, it is possible to secure sufficient strength and toughness as a 490 (N / mm ² ) class high-tensile steel and obtain a weld metal having excellent crack resistance. Further, when the Mo content in the wire is strictly defined, the toughness of the weld metal can be further improved. This makes it possible to reduce the number of welding passes by large heat input welding, and by welding at high interpass temperatures,
Since the cooling waiting time of the weld metal can be reduced, the efficiency of the welding process can be significantly improved, and a great industrial value can be obtained.

[Brief description of the drawings]

FIG. 1 is a graph showing the B content in a wire on the vertical axis and the Ti content in the wire on the horizontal axis, and the range of the B and Ti contents from which a weld metal having good mechanical properties can be obtained. FIG.

FIG. 2 shows the B content in the wire on the vertical axis and the S content in the wire on the horizontal axis to obtain the B and S content from which a weld metal having excellent hot crack resistance can be obtained. It is a graph which shows a range.

Claims (3)

[Claims] 1. C: 0.02 to 0.10% by weight, S
i: 0.65 to 1.10% by weight, Mn: 1.75 to 2.50% by weight, Ti: 0.16 to 0.45% by weight,
B: 0.003 to 0.010% by weight and S: 0.02
0% by weight or less, with the balance being Fe and unavoidable impurities.
Wt% or less, Cr is less than 0.10 wt%, Mo is 0.5
Wt% or less, Cu is 1.0 wt% or less, P is 0.016
% By weight, and the content of B is [B] and the content of Ti is [T
i], when the content of S is [S], the equation P _BT =
[B] × 10 P _BT calculated by the ³ / [Ti] is 1
2 to 40 and the equation P _BS = [B] × [S] ×
Gas shielded arc welding wire, characterized in that P _BS is calculated by ¹⁰⁵ is 10 or less. 2. The gas shielded arc welding wire according to claim 1, wherein said Mo is 0.1% by weight or less. 3. The gas shielded arc welding wire according to claim 1, wherein the Mo is 0.01% by weight or less.