JP3862213B2 - Welding wire for gas shielded arc welding - Google Patents

Description

【００２８】
【表２】

【００２９】
【表３】

【００３０】
得られた測定結果を表４に示す。本発明の条件を満たす場合（試験番号Ｎｏ．１〜５）、溶接金属の引張強度が高入熱高パス間温度条件で必要な５００ＭＰａを満たし、かつ溶接金属の硬さが低入熱溶接条件で必要なビッカース硬さで３２０以下であった。これにより、本発明の条件を満たせば、高入熱高パス間温度溶接を行っても、溶接部の機械的な強度を確保でき、かつ低入熱溶接を行っても、溶接部靭性の劣化あるいは割れの発生を防止できることが確認できた。
【００３１】
これに対し、本発明の条件を満たさない場合は何れも引張強度あ又はビッカース強度の必要条件を満たさない。すなわち、試験番号６、９及び１０の場合は、溶接金属の引張強度は５００ＭＰａ以上であるが、ビッカース硬さが３２０を超えている。また、試験番号７及び８の場合は、ビッカース硬さは３２０以下であるが引張強度が５００ＭＰａ以下である。
【００３２】
【表４】

【００３３】
【発明の効果】
本発明により、高入熱高パス間温度の溶接条件において十分な強度の溶接金属が得られ、また低入熱の溶接条件においても溶接金属の硬さの上昇を抑え、靭性の劣化さらにはそれに基づく割れの発生を防止できる。
【図面の簡単な説明】
【図１】 表３に示す溶接条件Ａによって溶接試験を行うときの開先形状を示す断面図である。
【図２】 表３に示す溶接条件Ｂによって溶接試験を行うときの開先形状を示す断面図である。[0001]
[Industrial application fields]
The present invention relates to a welding wire for gas shielded arc welding of mild steel, 490 and 520 N / mm grade ² high-strength steel plates, and in particular, a gas that has high strength and high toughness even when welded at high heat input and high pass-to-pass temperatures. The present invention relates to a welding wire for shielded arc welding.
[0002]
[Prior art]
For welding steel structures, gas shielded arc welding, particularly carbon dioxide shielded arc welding, is widely used as the most common welding method. Conventionally, in the welding, a Ti-B welding material has been studied as a means for improving the toughness of weld metal. For example, Japanese Patent Publication No. 43-12258 discloses a welding wire containing C, Si, Mn and one or more of Al, Ti, Zr, and V in the welding wire and adding B. . Japanese Patent Publication No. 55-149797 proposes a welding wire containing one or more of C, Si, Mn, Ti, and Mo and having B added thereto.
[0003]
However, in recent years, in order to improve the efficiency of welding work, welding tends to be performed under conditions of high current, high heat input, and high-pass temperature conditions. Under such high heat input and high pass temperature conditions, the strength of the weld metal is reduced and the impact properties are also deteriorated. It is high. In particular, carbon dioxide shielded arc welding has recently been highly demanded, and it is required to obtain suitable mechanical characteristics under high heat input and high interpass temperature conditions.
[0004]
In order to cope with such high heat input high pass temperature conditions, Japanese Patent Application Laid-Open No. 10-230387 includes C, Si, Mn, Ti, B, S, the ratio of B to Ti, and B and S. Japanese Patent Application Laid-Open No. 11-90678 proposes a welding wire containing at least one of Ti, B, Al, and Zr, and further containing a predetermined amount of C, Si, Mn, and Mo. Yes.
[0005]
[Problems to be solved by the invention]
However, these methods are effective for improving the mechanical properties under high heat input and high pass temperature conditions, but in practice, the low heat input and high pass temperature required in the case of assembly welding and transverse welding are required. There was a problem in weldability under the conditions. In other words, since these conventional welding wires were not supposed to be welded under conditions of high heat input and high pass temperature, the practical work efficiency was not reduced, and when continuous welding work was continued, Hardness increased, causing toughness deterioration or cracking.
[0006]
An object of the present invention is to solve the above-described problems associated with conventional welding wires, and even if welding with a high heat input and high pass temperature required for improving the efficiency of welding work is performed, a weld metal machine For gas shielded arc welding, which ensures high strength and suppresses the increase in hardness of the weld metal and prevents toughness deterioration or cracking even when welding under low heat input conditions such as assembly welding or sideways welding The purpose is to propose a welding wire.
[0007]
[Means for Solving the Problems]
The present inventors have conducted a comprehensive study on the characteristics of welding under high heat input and high pass temperature conditions in gas shield welding, the chemical composition of the weld metal, and the deterioration of toughness or the occurrence of cracks under low heat input welding conditions. In order to obtain a welding wire that can be applied to both welding conditions of high heat input and high pass temperature and low heat input conditions, it is partially detached from the molten metal by a deoxidation reaction occurring in the molten metal during welding. The present invention has been completed by conceiving that it is important to separate the contribution of the element to the carbon equivalent and the contribution of the element that does not substantially leave the molten metal during welding to adjust the components.
[0008]
Specifically, the composition of the welding wire including plating is mass ratio: C: 0.005 to 0.07%, Si: 0.65 to 1.2%, Mn: 1.7 to 2.2% Ti: 0.15 to 0.30%, Mo: 0.12 to 0.22%, B: 0.0010 to 0.0025%, Cr: 0.50% or less, Cu: 0.5% or less A welding wire for gas shielded arc welding comprising: the balance being substantially made of Fe and satisfying the following formula:
DE = C% + Mn% / 6 + Si% / 24 (1)
AE = Mo% / 4 + Cr% / 5 + Ni% / 40 (2)
0.32 <(0.7 × DE + 0.8 × AE) (3)
(DE + AE) <0.50 (4)
0.1 <AE / DE (5)
Pcm = C% + Mn% / 6 + Si% / 30 + (Cr% + Cu%) / 20 + Ni% / 60 + Mo% / 15 + 5B% (6)
Pcm + 760B% <2.5 (7)
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be specifically described including reasons for limiting the composition of the welding wire.
[0010]
C: 0.005 to 0.7% (% is mass ratio, the same applies hereinafter)
C inevitably contained in the welding wire is necessary to ensure the strength of the weld metal, and also has an effect as a deoxidizing element. If it is less than 0.005%, the strength of the weld metal is insufficient, while if it exceeds 0.07%, the toughness of the weld metal is lowered. For this reason, it was made into 0.005% or more and 0.07% or less.
[0011]
Si: 0.65-1.2%
Si is an indispensable element as a deoxidizing element for welding wires used in gas shielded arc welding, particularly carbon dioxide shielded arc welding and MAG welding. If it is less than 0.65%, the deoxidation effect is insufficient and blowholes are likely to occur. On the other hand, if it exceeds 1.2%, the content in the weld metal becomes excessive, and the toughness is rather deteriorated. For this reason, it is made to contain in 0.65% or more and 1.0% or less of range.
[0012]
Mn: 1.7-2.2%
Mn is not only an essential element as a deoxidizing element together with Si, but also an essential element for ensuring the mechanical strength and toughness of the weld metal. If it is less than 1.7%, the content in the weld metal is insufficient, and sufficient mechanical strength and toughness cannot be obtained. However, if the content exceeds 2.2%, the content in the weld metal becomes excessive, and the toughness is deteriorated. For this reason, it is made to contain in 1.7% or more and 2.2% or less of range.
[0013]
Ti: 0.15 to 0.30%
Ti is used as a welding wire, and has an effect of stabilizing the arc to reduce spatter and preventing the occurrence of blowholes when performing gas shielded arc welding with relatively high heat input. Moreover, there exists an effect which improves the toughness of a weld metal. However, if it is less than 0.15%, these effects are poor. On the other hand, if it exceeds 0.30%, productivity is lowered due to a problem in melting the welding wire material. For this reason, the content shall be 0.15 or more and 0.30% or less.
[0014]
B: 0.0010 to 0.025%
B is an element effective in suppressing the formation of coarse ferrite in the weld metal structure, miniaturizing the structure, and improving toughness. If it is less than 0.0010%, the effect of improving toughness is insufficient. On the other hand, if it exceeds 0.0025%, the effect of improving toughness is poor, and hot cracking tends to occur. For this reason, the content is made 0.0010 or more and 0.025% or less.
[0015]
Mo: 0.12-0.22%
Mo is an indispensable element for improving the toughness by refining the structure of the weld metal when performing gas shield arc welding with high heat input. However, when the content is less than 0.12%, the effect is poor. On the other hand, when the content exceeds 0.22%, a low temperature transformation structure is generated in the weld metal, the weld metal is hardened, the toughness is deteriorated, and cracking is remarkable. Become. For this reason, the content is made 0.12% or more and 0.22% or less.
[0016]
Cr: 0.30% or less Cr is an indispensable element for improving the toughness by refining the structure of the weld metal when performing gas shield arc welding with high heat input. If it exceeds 0.30%, a low-temperature transformation structure is generated in the weld metal, the weld metal is hardened, the toughness is deteriorated, and cracking becomes prominent. Therefore, the content is made a range of 0.30% or less. In addition, in order to acquire sufficient effect, it is good to set it as 0.05% or more.
[0017]
Cu: 0.50% or less Cu increases the hardenability of the weld metal and is expected to ensure strength by solid solution strengthening of the microstructure. However, if contained in a large amount, Cu increases the susceptibility to solidification cracking. 5% or less.
[0018]
The balance excluding these alloy elements is substantially Fe (iron) and inevitable impurities. Inevitable impurities include Ca, N, and the like, and these are acceptable within a mass ratio of 20 ppm or less, respectively. However, in order to suppress the increase in the hardness of the weld metal at the time of low heat input, it is preferable to set it to 10 ppm or 50 ppm or less, respectively.
[0019]
In the present invention, DE and AE defined by the following formulas (1) and (2) must satisfy the following formulas (3) and (4) while satisfying the above composition conditions. Here, DE is the total amount of elements in the welding wire that are partially detached from the molten metal due to the deoxidation reaction that occurs in the molten metal during welding, and AE is an element that does not separate from the molten metal during welding. The total amount in the welding wire.
DE = C% + Mn% / 6 + Si% / 24 (1)
AE = Mo% / 4 + Cr% / 5 + Ni% / 40 (2)
0.32 <(0.7 × DE + 0.8 × AE) (3)
(DE + AE) <0.50 (4)
[0020]
Of these, equation (3) is a condition for ensuring weld metal strength when welding is performed at high heat input and high interpass temperature conditions, while equation (4) is weld metal under low heat input conditions. This is a condition for suppressing an increase in the hardness of the steel and preventing toughness deterioration or cracking. These conditions are all amounts related to the so-called carbon equivalent, but in the case of the present invention, the elements are partially separated from the molten metal by the deoxidation reaction that occurs in the molten metal during welding and decrease. It is divided into element groups that are not so, and the balance of these elements is achieved in the form represented by the above formula.
[0021]
Furthermore, in the present invention,
0.1 <AE / DE (5)
It is necessary to satisfy. Thereby, weld metal intensity | strength is securable on the high heat input and the temperature conditions between high passes. Under high heat input and high pass temperature conditions, depending on conditions such as laminating method and waving width, the group of elements partially desorbed from the molten metal due to the deoxidation reaction that occurs in the molten metal is reduced, which stabilizes the weld metal strength. It becomes difficult to secure.
[0022]
Therefore, by satisfying the equation (5), AE, which is an index of the carbon equivalent of the element group that does not depart from the molten metal during welding, is replaced with DE, which is an index of the carbon equivalent of the element group that partially desorbs from the molten metal. Therefore, the strength of the weld metal is secured stably. In this case, if the value of AE / DE is less than 0.2, an increase in weld metal hardness can be suppressed in the case of low heat input conditions, and deterioration of toughness or accompanying cracking can be prevented. preferable.
[0023]
Furthermore, in the present invention, in order to ensure weldability at low heat input such as assembly welding or sideways welding, the content of B that raises the hardness of the weld metal particularly during low heat input welding is expressed by equation (6). And it restrict | limits so that (7) Formula may be satisfy | filled.
Pcm = C% + Mn% / 6 + Si% / 30 + (Cr% + Cu%) / 20 + Ni% / 60 + Mo% / 15 + 5B% (6)
Pcm + 760B% <2.5 (7)
[0024]
In general, the effect of chemical composition on the hardness of the weld metal is evaluated by Pcm, but when performing welding with low heat input using a welding wire corresponding to the high heat input high pass temperature as in the present invention, The influence of B becomes remarkable. Therefore, the condition defined by the equation (7) is provided to suppress the increase in the hardness of the weld metal that occurs when the heat input is low, and to avoid the deterioration of toughness and the cracks derived therefrom.
[0025]
【Example】
Steel having the chemical composition shown in Table 1 was melted, and a steel wire for welding was manufactured through forging, rolling, plating, and winding processes. Using these wires, carbon dioxide shielded arc welding was performed on the steel sheet having the composition shown in Table 2 and having a tensile strength of 500 MPa class under the welding conditions shown in Table 3 to obtain a welded joint. The groove shape was as shown in FIG. 1 (welding condition A: high heat input high pass temperature condition) and FIG. 2 (welding condition B: low heat input welding).
[0026]
A test piece containing a weld metal was taken from the welded portion of the welded joint obtained as described above, and the tensile strength and Vickers hardness Hv were measured. In addition, the test piece for measuring the tensile strength is an A1 round bar test piece defined in JIS Z 2201 processed from a welded joint, and the Vickers hardness is 98 N with a load of 98 mm and the weld metal part is continuously provided at intervals of 0.5 mm. Five points were measured and the average value was taken.
[0027]
[Table 1]

[0028]
[Table 2]

[0029]
[Table 3]

[0030]
The obtained measurement results are shown in Table 4. When the conditions of the present invention are satisfied (test numbers No. 1 to 5), the tensile strength of the weld metal satisfies 500 MPa required under high heat input and high pass temperature conditions, and the weld metal has low heat input welding conditions. The required Vickers hardness was 320 or less. As a result, if the conditions of the present invention are satisfied, the mechanical strength of the welded portion can be ensured even if high heat input high-pass temperature welding is performed, and even if low heat input welding is performed, the toughness of the welded portion deteriorates. Or it has been confirmed that the occurrence of cracks can be prevented.
[0031]
On the other hand, when the conditions of the present invention are not satisfied, none of the requirements for tensile strength or Vickers strength is satisfied. That is, in the case of test numbers 6, 9, and 10, the tensile strength of the weld metal is 500 MPa or more, but the Vickers hardness is over 320. In the case of test numbers 7 and 8, the Vickers hardness is 320 or less, but the tensile strength is 500 MPa or less.
[0032]
[Table 4]

[0033]
【The invention's effect】
According to the present invention, a weld metal having a sufficient strength can be obtained under welding conditions of high heat input and high pass temperature, and an increase in weld metal hardness can be suppressed even under low heat input welding conditions, toughness deterioration and further. The generation of cracks based on this can be prevented.
[Brief description of the drawings]
1 is a cross-sectional view showing a groove shape when a welding test is performed under welding conditions A shown in Table 3. FIG.
2 is a cross-sectional view showing a groove shape when a welding test is performed under welding conditions B shown in Table 3. FIG.

Claims (1)

The composition of the welding wire including plating is C: 0.005-0.07%, Si: 0.65-1.2%, Mn: 1.7-2.2%, Ti: 0.15 by mass ratio. -0.30%, Mo: 0.12-0.22%, B: 0.0010-0.0025%, Cr: 0.30% or less, Cu: 0.5% or less, the balance being substantially A welding wire for gas shielded arc welding characterized by comprising Fe and satisfying the following formulas (1) to (7).
DE = C% + Mn% / 6 + Si% / 24 (1)
AE = Mo% / 4 + Cr% / 5 + Ni% / 40 (2)
0.32 <(0.7 × DE + 0.8 × AE) (3)
(DE + AE) <0.50 (4)
0.1 <AE / DE (5)
Pcm = C% + Mn% / 6 + Si% / 30 + (Cr% + Cu%) / 20 + Ni% / 60 + Mo% / 15 + 5B% (6)
Pcm + 760B% <2.5 (7)

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