KR20060107380A - Solid wire for gas shield arc welding - Google Patents

Abstract

Provided is a gas shielded arc welding wire which is excellent in strength and toughness of a weld metal and excellent in low temperature crack resistance against low heat input welding even under high heat input and high pass temperature welding conditions.

The solid wire for gas shielded arc welding of the present invention is, in mass%, C: 0 to 0.011%, Si: 0.5 to 1.0%, Mn: more than 1.8 and 2.5% or less, Cu: 0.1 to 1.0%, Mo: 0.10 to 0.50 %, Ti: made of, contain 0.0040 to 0.0150%, and also to the general formula 1 P _MP is more than 10%, the balance being Fe and inevitable impurities: 0.1 to 0.3%, B: 0.001 to 0.005%, N:

P _MP = 4 [Mn] + ([Cu] + [Ni] + [Cr]) + 6000 ([Mo] + [V] + [Nb] + [Zr] + [Ta] + [Hf] + [W ]) * [B]

Where

[Elemental Name] shows the content mass% of the said element.

Description

SOLID WIRE FOR GAS SHIELD ARC WELDING}

BRIEF DESCRIPTION OF THE DRAWINGS It is a perspective view which shows the structure of the base material test body used for the restraint fillet welding test.

* Explanation of symbols for the main parts of the drawings

1: substrate 2: stand

3: square constraint plate 4: triangle constraint plate

6: welding bead

TECHNICAL FIELD The present invention relates to a solid wire for gas shielded arc welding, which is excellent in weldability at high heat input and high interpass temperature, and also excellent in low temperature crack resistance at low heat input.

The gas shielded arc welding method using carbon dioxide gas as a shield gas has high welding efficiency and can be welded in all postures. Therefore, the gas shielded arc welding method can be used in the construction, construction, and construction of steel structures in the construction, bridge, and shipbuilding fields. It is used. In recent years, in order to improve work efficiency, welding is required at high heat input and high interpass temperature. However, conventional welding using the welding wire cannot obtain the strength and toughness of the deposited metal. Mechanical properties were not obtained.

Therefore, there have been various proposals for weldable wires even at such high heat input and high interpass temperatures. For example, Japanese Patent Application Laid-Open No. 1998-230387 discloses, in mass%, C: 0.02 to 0.10%, Si: 0.65 to 1.10%, Mn: 1.75 to 2.50%, Ti: 0.16 to 0.45%, and B: 0.003 to 0.010. The wire which contains% and S: 0.020% or less, remainder consists of Fe and an unavoidable impurity, and regulates B amount, Ti amount, B amount, and S amount under predetermined relationship is described. In addition, Japanese Patent Laid-Open No. 1999-90678 and Japanese Patent Laid-Open No. 1999-239892 also include wires in which Ti, B, N, Al, and / or Zr are added in predetermined amounts, furthermore, C, Si, Mn, P, The wire which added predetermined amount of S, Mo, V and / or Nb, O, or regulated the upper limit of addition amount is described.

The wire was made to cope with high heat input welding, and sufficient characteristics were not obtained under welding conditions in which the interpass temperature exceeded 500 ° C. On the other hand, recently, the wire which can be welded even in the interpass temperature exceeding 500 degreeC is proposed by Unexamined-Japanese-Patent No. 2004-98143. The wire contains a predetermined amount of C, Si, Mn, Mo, Ti, B, V and / or Nb, and furthermore, the addition amount of the component so that the toughness of the weld metal is ensured under welding conditions of high heat input and high interpass temperature. Is regulated by the variable Pts, and the relationship between Mn, Mo, Si, Ti is regulated by the variable Vcq.

In addition, Japanese Patent Application Laid-Open No. 2004-202572 proposes a wire which ensures high heat input weldability and also improves weldability in low heat input welding such as assembly welding and lateral welding.

Although the high heat input welding characteristic is improved by the wire described in the above-described Japanese Patent Application Laid-Open No. 2004-98143, and the wire of the Japanese Patent Laid-Open No. 2004-202572 further improves to some extent, the low input heat welding characteristic is also improved. Since the low temperature crack resistance of city is not enough, improvement of low temperature crack resistance is calculated | required.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and is excellent in strength and toughness of weld metal in welding conditions with high heat input and high interpass temperature, and moreover, for gas shielded arc welding with excellent low temperature crack resistance against low heat input welding. It is an object to provide a wire.

The solid wire for gas shielded arc welding of this invention is C: 0 to 0.011%, Si: 0.5 to 1.0%, Mn: more than 1.8 and 2.5% or less by mass% (Hereinafter, it expresses only "%"), Cu and 0.0040 to include 0.0150%, and also to the P _MP is at least 10% the formula (1): 0.1 to 1.0%, Mo: 0.10 to 0.50%, Ti: 0.1 to 0.3%, B: 0.0010 to 0.0050%, N The balance consists of Fe and unavoidable impurities:

Formula 1

P _MP = 4 [Mn] + ([Cu] + [Ni] + [Cr]) + 6000 ([Mo + [V] + [Nb] + [Zr] + [Ta] + [Hf] + [W]) * [B]

Where

[Elemental Name] shows the content mass% of the said element.

The wire composition of the present invention is designed to exhibit excellent low temperature crack resistance while ensuring high tensile heat and toughness under welding conditions of high heat input and interpass temperatures of more than 500 ° C. In other words, while mainly suppressing the amount of C as much as possible, the amount of Si is added to reduce the amount of C in the weld metal to improve the low temperature crack resistance, and to compensate for the decrease in the amount of C so as to secure the strength and toughness of the high heat input welding. the amount of the ferrite suppression element optimization by introducing indicators that P _MP and further by the addition of N to actively improve the toughness by refining the texture of the deposited metal, substituted thermal welding characteristic, low-temperature of the low heat input welding The crackability is improved.

In the wire, instead of a part of Fe, (1) 0.1 to 2.0% in total of one or two of Cr and Ni, and (2) one or two of V, Nb, Zr, Ta, Hf, and W. In total, one or more elements selected from the group consisting of 0.001 to 0.1%, (3) Al: 0.001 to 0.1%, and (4) REM: 0.001 to 0.2% can be added alone or in combination. Thereby, the mechanical characteristic of a weld metal can be improved more.

According to the solid wire for gas shielded arc welding of this invention, since the weld metal which is excellent in the intensity | strength and toughness of a weld metal in welding in a high heat input and high interpass temperature, and also excellent in toughness in low heat input welding is obtained, The low temperature crack resistance at the time of low heat input welding is also excellent.

Solid wire for gas shielded arc welding of the present invention is C: 0 to 0.011%, Si: 0.5 to 1.0%, Mn: more than 1.8 and 2.5% or less, Cu: 0.1 to 1.0%, Mo: 0.10 to 0.50%, Ti: 0.1 to 0.3%, B: 0.001 to 0.005%, N: 0.0040 to 0.0150% and including, but an addition to the general formula 1 P _MP is more than 10%, the balance being Fe and inevitable impurities:

Formula 1

P _MP = 4 [Mn] + ([Cu] + [Ni] + [Cr]) + 6000 ([Mo] + [V] + [Nb] + [Zr] + [Ta] + [Hf] + [W ]) * [B]

Where

[Elemental Name] shows the content mass% of the said element.

Hereinafter, the reason for component limitation is demonstrated.

C: 0 to 0.011%

C acts to improve the strength of the weld metal, but in order to ensure excellent low temperature crack resistance, the lower one is preferable, and in the present invention, no addition is satisfactory. However, in order to reduce C concentration excessively, since manufacturing cost becomes high, it is preferable to set it as about 0.001% or more. On the other hand, if it exceeds 0.011%, the strength becomes excessive, the toughness of the weld metal deteriorates, and in particular, the deterioration of low temperature crack resistance becomes remarkable. For this reason, C amount is 0.011% or less, Preferably you may be 0.010% or less.

Si: 0.5 to 1.0%

Si is a deoxidation element and reduces the amount of dissolved oxygen in the weld metal. In addition, by suppressing the amount of Si in the above range, it is possible to suppress the reduction of CO _{2 in} the atmosphere, to lower the amount of C in the weld metal, and to improve the low temperature crack resistance. If it is less than 0.5%, the amount of dissolved oxygen is not sufficiently reduced, and the toughness of the deposited metal deteriorates. For this reason, the minimum of Si amount shall be 0.5%, Preferably it shall be 0.6%. On the other hand, when it adds excessively, strength will become excessive by solid solution strengthening, and the toughness and low temperature crack resistance of a weld metal will deteriorate. For this reason, the upper limit is made into 1.0%, Preferably it is good to set it as 0.9%.

Mn: more than 1.8 and less than 2.5%

Since Mn acts as a deoxidation element and suppresses generation of grain boundary ferrite, it has the effect of improving strength and toughness. When the amount of Mn is too small, the mechanical properties during high heat input welding deteriorate, so the amount of Mn is more than 1.8%, preferably 1.9% or more. On the other hand, when excessive, the strength at the time of low heat input welding will become excessive, and the low temperature crack resistance will deteriorate. For this reason, the upper limit is made into 2.5%, Preferably it is good to set it as 2.4%.

Cu: 0.1 to 1.0% (including the amount given as a conductive plating film)

Cu has an effect of improving the toughness of the weld metal and is inevitably contained as a conductive plating film of a core wire. If it is less than 0.1%, electroconductivity cannot be ensured and welding workability will deteriorate. On the other hand, when it exceeds 1.0%, Cu will precipitate finely, and the intensity | strength and toughness grade will deteriorate. For this reason, the minimum of Cu amount is made into 0.1%, Preferably it is 0.15%, and the upper limit is made into 1.0%, Preferably it is 0.8%.

Mo: 0.10 to 0.50%

Mo is added in combination with B to suppress the formation of grain boundary ferrite and to improve the degree of strength toughness at the time of high heat input welding. If it is less than 0.10%, this action is underestimated, while if it exceeds 0.50%, the strength is excessively high and the low temperature crack resistance deteriorates. For this reason, the minimum of Mo amount is made into 0.10%, Preferably it is 0.15%, The upper limit is made into 0.50%, Preferably it is 0.42%, More preferably, it is 0.40%.

Ti: 0.1 to 0.3%

Ti forms an oxide, which acts as a nucleus of intramolecular transformation, thereby improving the microstructure and toughness of the tissue. If it is less than 0.1%, this action is excessive. If it exceeds 0.3%, Ti carbide is formed and the toughness of the weld metal is deteriorated. For this reason, the minimum of Ti amount is made into 0.1%, Preferably it is 0.15%, and the upper limit is made into 0.3%, Preferably it is 0.25%.

B: 0.0010 to 0.0050%

B suppresses the formation of grain boundary ferrite, thereby improving the strength toughness. If it is less than 0.0010%, such an action will be insignificant, whereas if it exceeds 0.0050%, the strength of the weld metal at the time of low heat input welding will become excessive, and the low temperature crack resistance will deteriorate. For this reason, the lower limit of the amount of B is made 0.0010%, preferably 0.0015%, and the upper limit is made 0.0050%, preferably 0.0040%.

N: 0.0040 to 0.0150%

N reacts with Ti to form TiN, and serves to improve toughness by miniaturizing the γ particle size. If less than 0.0040% of TiN is not formed, a sufficient amount of TiN is not formed. On the other hand, if it exceeds 0.0150%, solid solution N is present, and thus toughness deteriorates. For this reason, the minimum of N amount is made into 0.0040%, Preferably it is 0.0050%, On the other hand, the upper limit is made into 0.0150%, Preferably it is 0.0120%.

P _MP : over 10

P _MP is an index that quantitatively evaluates the effect of the addition amount of the ferrite generation inhibitory element on the strength and toughness of the weld metal during the high heat input welding, and when this value is less than 10%, the desired high strength and high toughness under the extremely low C content Cannot be secured. For this reason, the amount of the ferrite element to inhibit _MP P 10% or more.

Although the wire of this invention is typically formed with remainder Fe other than the said basic component, instead of a part of Fe, (1) 0.1 to 2.0% in total of 1 or 2 types of Cr and Ni, (2) V , Nb, Zr, Ta, Hf, W, one or two or more in total from 0.001 to 0.1%, (3) Al: 0.001 to 0.1%, (4) REM: from 0.001 to 0.2% The selected elements may be added alone or in combination. Hereinafter, the reason for addition of these elements is demonstrated.

Cr, Ni: 0.01-2.0% in total

These elements act to suppress the formation of grain boundary ferrite and to refine the structure, and improve the degree of strength toughness. If the amount is less than 0.01%, such an effect becomes less. On the other hand, if it exceeds 2.0%, MA (Martensite-Austenite Constituent: a mixture of martensite and austenite) is formed in the deposited metal during the high heat input welding. For this reason, the lower limit is made into 0.01% and the upper limit is made into 2.0% by 1 or 2 types of total amounts.

V, Nb, Zr, Ta, Hf, W: 0.001 to 0.1% in total

These elements are added together with Mo and B to increase the effect of suppressing the formation of grain boundary ferrite, thereby improving the strength and toughness. However, when excessively added, the strength becomes excessive, and the degree of strength toughness deteriorates. Therefore, the lower limit is 0.001% and the upper limit is 0.1% based on one kind or two or more kinds of these elements.

Al: 0.001-0.1%

Al fixes solid solution N as AlN, thereby acting to improve the base material toughness. At less than 0001%, this action is underestimated, while an excess of more than 0.1% causes excessive solid solution strengthening and toughness. For this reason, the minimum of Al amount is made into 0.001%, and the upper limit is made into 0.1%, Preferably it is 0.05%.

REM: 0.001 to 0.2%

The REM functions to refine the inclusions and thereby to refine the weld metal structure to improve strength toughness. On the other hand, when excessively added, these effects are lost and rather the strength toughness is deteriorated. For this reason, in this invention, the minimum of REM amount shall be 0.001%, and the upper limit shall be 0.2%.

When manufacturing the welding wire of this invention, special manufacturing conditions are not necessary and can be manufactured by a conventional method. That is, the steel of the said component is melted and an ingot is obtained. In this case, regarding the amount of Cu added, the steel component is considered in consideration of the amount given by copper plating carried out after drawing (which varies depending on the wire wire diameter but is usually about 0.1 to 0.3% of the wire mass). Decide The ingot is subjected to hot forging or the like as needed, followed by hot rolling, and further cold drawn to form an element wire. An element wire is annealed at the temperature of about 500-900 degreeC as needed, and after pickling, copper plating is performed, Furthermore, finishing drawing is performed as needed, and it is set as a target wire diameter. After that, a lubricant is applied as necessary to form a welding wire.

Hereinafter, although an Example is given and this invention is demonstrated concretely, this invention is not interpreted limitedly by these Examples.

Example

150 kg of steel of a predetermined component is melted under vacuum in a VIF (vacuum induction furnace) so as to have a target wire composition (does not contain Cu), and the ingot is hot-forged at 155 mm angle, and then 1000 It heated to 50 degreeC, rolled to 5.5 mm (phi) by hot rolling, and was fresh, and obtained 1.4 mm% of wire. Furthermore, after pickling this element wire, copper plating was performed. Copper plating consisted of Cu and an unavoidable impurity, and the plating amount was adjusted so that the amount of Cu was about 0.2% with respect to the wire weight. The composition of the welding wire manufactured in this way is shown in Table 1.

The welding test was performed on the following welding conditions using the welding wire manufactured as mentioned above, and the strength and toughness of the weld metal at the time of high heat input welding were investigated.

Welding current: 420A

Welding voltage: 43V

Wire dispensing speed: 28 cm / min

Heat input amount: 38.7 kJ / cm

Preheat: None

Interpass management conditions: continuous, last interpass temperature 500 to 550 ℃

Base material steel plate: SM490, shape 22 mm thickness × 100 mm width × 200 mm length

Groove shape: 35 ° レ groove, gap 7 mm

Shield gas: CO ₂ , flow rate 25 L / min

After welding, the test piece was taken from the weld metal, the tensile test and the impact test were performed according to JISZ3111, and the tensile strength (TS) and the impact value (vE 0 degreeC) were measured. In the case of TS: 540 MPa or more and vE 0 ° C: 80 J or more, the degree of strength toughness at the time of high heat input welding is good and can be evaluated at the pass level. The measurement results are shown in Table 2.

Next, the restraint fillet welding test was performed under the following welding conditions, and the low temperature crack resistance at the time of quench heat welding was investigated.

Welding current: 200A

Welding voltage: 26V

Wire dispensing speed: 50cm / min

Heat input amount: 6.24 kJ / cm

Preheat: None

Base material steel plate: SM490

Structure of the base material test specimen: FIG. 1

Test temperature: 0 ℃

Shield gas: CO ₂ , flow rate 25 L / min

As shown in Fig. 1, the test body is provided with a standing plate 2 at the center in the width direction of the substrate 1, a triangular restraint plate 4 is bonded thereto, and a rectangular restraint plate on the bottom surface of the substrate 1. Three pieces of (3) were joined, and these joints were welded with a restraint fillet leg length of 6 mm or more (refer to Document (published by the Japan Welding Association, "Study of Welding", No. 40 (2002) p203). ]. The board | substrate 1 and the board 2 were welded using the said welding wire in six places avoiding the upper part of the restraining board 3, as shown in the figure, and the welding bead 6 was investigated at low temperature cracking property. . After 24 hours passed after welding, the low-temperature cracking property color-checked the bead surface and visually observed the presence of a crack. The observation results are shown in Table 2 together. In Table 2, ○ in the evaluation column indicates that the acceptance criteria are satisfied, and × indicates that the evaluation criteria are not satisfied.

Sample Nos. 1, 7, 8, 15, 17 to 26 according to Inventive Example from Table 2 are excellent in mechanical properties during high heat input welding and low temperature crack resistance at low heat input welding.

On the other hand, in the comparative example, since the amount of C was too high, the sample number 2 was excessively high in the strength of the high heat input welding, the impact characteristic of the weld metal was deteriorated, and the low temperature crack resistance was also deteriorated. In addition, with respect to Si, deoxidation is insufficient at the number 3 in which the amount of Si is too low, and toughness is deteriorated because of solid solution oxygen. On the other hand, in the number 4 in which the amount of Si is excessive, the strength is excessively increased due to solid solution strengthening. Significantly degraded. In addition, with respect to Mn, the number 5 indicates that the amount of Mn is too low to suppress the formation of grain boundary ferrite, and the toughness at the time of high heat input welding deteriorates. The low temperature crack resistance deteriorated. In addition, with respect to Cu, since the amount of Cu was too high in sample No. 9, although the strength improved by precipitation of Cu, toughness deteriorated. In addition, with respect to Mo, the formation of grain boundary ferrite cannot be suppressed at the number 10 where Mo is too low, and the high heat input welding characteristic is deteriorated. On the other hand, at the excessively high number Mo, the strength at low heat input welding is excessively increased. Low temperature crack resistance could not be secured. Further, with respect to Ti, in number 12 where the Ti amount is excessively 0.54%, Ti carbide is formed in the weld metal, and the deterioration of toughness is remarkable. In addition, in the case where the amount of B is too small with respect to B, formation of grain boundary ferrite cannot be suppressed, toughness at the time of high heat input welding cannot be secured, while in the case of excessive number B, the strength at the time of low heat input welding is high. Since it became excessively high, the low temperature crack resistance was not secured. In addition, numeral 16, each of the alloy components, but within the scope of the present invention, when the assessment ferrite suppression element amount because P _MP is under 8.6, is not obtained a sufficient assignment thermal welding characteristics. In addition, No. 27 had a high C content and a low N content, so that the toughness of the weld metal was lowered and low temperature crack resistance was not secured.

According to the solid wire for gas shielded arc welding of this invention, it is excellent in the intensity | strength and toughness of a weld metal in high heat input and high interpass temperature welding, and also excellent in toughness and low temperature crack resistance in low heat input welding. .

Claims (9)

By mass%, C: 0 to 0.011%, Si: 0.5 to 1.0%, Mn: more than 1.8 and 2.5% or less, Cu: 0.1 to 1.0%, Mo: 0.10 to 0.50%, Ti: 0.1 to 0.3%, B: 0.0010 to 0.0050%, N: 0.0040 to contain 0.0150%, and also to the general formula 1 P _MP is more than 10%, the balance being Fe and unavoidable impurities, substituted thermal characteristics and low-temperature-cracking resistance is excellent gas shielded arc welding Solid wire: Formula 1 P _MP = 4 [Mn] + ([Cu] + [Ni] + [Cr]) + 6000 ([Mo] + [V] + [Nb] + [Zr] + [Ta] + [Hf] + [W ]) * [B] Where [Elemental Name] shows the content mass% of the said element. The method of claim 1, A solid wire for gas shielded arc welding comprising 0.1 to 2.0% in total of l or 2 species of Cr, Ni, instead of a part of Fe. The method of claim 1, A solid wire for gas shielded arc welding, comprising 0.001 to 0.1% of one, two or more of V, Nb, Zr, Ta, Hf, and W in total instead of a part of Fe. The method of claim 2, A solid wire for gas shielded arc welding, comprising 0.001 to 0.1% of one, two or more of V, Nb, Zr, Ta, Hf, and W in total instead of a part of Fe. The method of claim 1, A solid wire for gas shielded arc welding comprising 0.001 to 0.1% Al, instead of a portion of Fe. The method of claim 2, A solid wire for gas shielded arc welding, comprising 0.001 to 0.1% of Al, instead of a portion of Fe. The method of claim 3, wherein A solid wire for gas shielded arc welding comprising 0.001 to 0.1% Al, instead of a portion of Fe. The method of claim 4, wherein A solid wire for gas shielded arc welding comprising 0.001 to 0.1% Al, instead of a portion of Fe. The method according to any one of claims 1 to 8, Solid wire for gas shielded arc welding comprising 0.001 to 0.2% REM instead of a portion of Fe.

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