Welding material for submerged arc welding

Abstract

The purpose of one aspect of the present invention is to provide a welding material for submerged arc welding. A preferred aspect of the present invention provides a welding material for submerged arc welding, the material being capable of providing a welding joint portion with high strength as well as excellent hydrogen embrittlement resistance and stress corrosion resistance.

Description

Welding materials for submerged arc welding

[0001] The present invention relates to a welding material for submerged arc welding.

[0002] Austenitic high-strength steel sheets or strips exhibit excellent resistance to hydrogen embrittlement and stress corrosion cracking due to their high hydrogen solubility and low hydrogen diffusion rate. Furthermore, their austenitic structure provides excellent non-magnetic properties, making them suitable for use in power generation equipment and components requiring stealth capabilities.

[0003] However, conventional materials with austenitic microstructures have limitations in terms of strength enhancement, limiting their application and competiveness. In particular, while their non-magnetic properties offer superior stealth performance compared to conventional carbon steels, their relatively low strength limits their application.

[0004] Therefore, there is a need to develop a welding material for submerged arc welding that can be applied to steel sheets and strips that have both an austenitic microstructure and high strength.

[0005] One aspect of the present invention is to provide a welding material for submerged arc welding.

[0006] A preferred aspect of the present invention is to provide a welding material for submerged arc welding that can impart high strength along with excellent hydrogen embrittlement resistance and stress corrosion resistance to a weld joint.

[0007] One embodiment of the present invention provides a welding material for submerged arc welding, comprising, in wt%, C: 0.150 to 0.60%, Si: 0.10 to 1.0%, Mn: 15.0 to 25.0%, Cr: 1.0 to 5.0%, Mo: 0.050 to 3.0%, V: 0.050 to 4.0%, Ni: 5.0% or less (including 0%), P: 0.020% or less (excluding 0%), S: 0.0070% or less (excluding 0%), N: 0.15% or less (including 0%), CaF2: 0.10 to 1.0%, and the remainder being Fe and other unavoidable impurities.

[0008] The above welding material may have a microstructure composed of austenite.

[0009] According to one aspect of the present invention, a welding material for submerged arc welding can be provided.

[0010] According to a preferred aspect of the present invention, a welding material for submerged arc welding can be provided that can impart high strength to a weld joint along with excellent hydrogen embrittlement resistance and stress corrosion resistance.

[0011] Figure 1 is a photograph of invention example 1 observed with a scanning electron microscope, (a) is a photograph observed at 100x magnification, and (b) is a photograph observed at 1000x magnification.

[0012] The present inventors have confirmed that austenitic stability can be secured by using manganese and carbon instead of expensive nickel among the alloying components of a welding material for submerged arc welding of austenitic high-strength steel, and that strength can be improved by additionally including alloying elements, and thus completed the present invention.

[0013] Hereinafter, a welding material for submerged arc welding according to one embodiment of the present invention will be described. First, the alloy composition will be described. The contents of the alloy composition described below are in weight percent.

[0014] C: 0.150~0.60%

[0015] The above C is an essential element that must be included as an economical element that effectively secures the strength of the weld joint and stabilizes the austenite microstructure. If the content of the C is less than 0.150%, it may be difficult to sufficiently secure the austenite stabilization and strength improvement effects described above. If the content of the C exceeds 0.60%, it may cause welding cracks. Therefore, the content of the C is preferably in the range of 0.150 to 0.60%. The lower limit of the C content is more advantageously 0.20%, more advantageously 0.250%, and most advantageously 0.30%. The upper limit of the C content is more advantageously 0.550%, more advantageously 0.50%, and most advantageously 0.450%.

[0016] Si: 0.10~1.0%

[0017] The above Si is an element that improves strength through solid solution strengthening. In addition, it has the effect of reducing welding defects by improving the fluidity of the molten metal. If the Si content is less than 0.10%, it may be difficult to sufficiently obtain the above-described effect. If the Si content exceeds 1.0%, the formability at high and low temperatures may be reduced and the austenite stability may be reduced. Therefore, the Si content is preferably in the range of 0.10 to 1.0%. The lower limit of the Si content is more advantageously 0.150%, more advantageously 0.20%, and most advantageously 0.250%. The upper limit of the Si content is more advantageously 0.950%, more advantageously 0.90%, and most advantageously 0.850%.

[0018] Mn: 15.0~25.0%

[0019] Mn is a strong austenite stabilizing element and is an element that helps maintain non-magnetic properties. It also plays a role in increasing the work hardening degree while improving strength and impact toughness. In addition, it also has the effect of removing S, which is an impurity, through the formation of MnS. If the Mn content is less than 15.0%, it may be difficult to sufficiently obtain the above-mentioned effect. If the Mn content exceeds 25.0%, there may be disadvantages such as increased difficulty of the manufacturing process, increased manufacturing cost, and decreased corrosion resistance. Therefore, the Mn content is preferably in the range of 15.0 to 25.0%. The lower limit of the Mn content is more advantageously 16.0%, 17.0% is more advantageously 18.0%, and the upper limit of the Mn content is more advantageously 24.0%, 23.0% is more advantageously 22.0%, and the upper limit of the Mn content is most advantageously 24.0%, 23.0% is more advantageously 22.0%.

[0020] Cr: 1.0~5.0%

[0021] Cr is MC, M 23 It acts as a key component in the formation of carbides such as C6, and these microcarbides improve the strength through the precipitation strengthening effect. In addition, Cr has the advantage of increasing the oxidation resistance in response to the external oxidizing atmosphere as an antioxidant element. If the content of Cr is less than 1.0%, it may be difficult to sufficiently obtain the above-mentioned effect. If the content of Cr exceeds 5.0%, the austenite stability may be reduced, and the impact toughness may be reduced due to the excessive formation of precipitates. Therefore, the content of Cr is preferably in the range of 1.0 to 5.0%. The lower limit of the Cr content is more advantageously 1.50%, more advantageously 2.0%, and most advantageously 2.50%. The upper limit of the Cr content is more advantageously 4.50%, more advantageously 4.0%, and most advantageously 3.50%.

[0022] Mo: 0.050~3.0%

[0023] Mo has the effect of improving strength through the solid solution strengthening effect. In addition, it can prevent the deterioration of impact toughness due to excessive carbide precipitation by suppressing the formation and coarsening of precipitates in the matrix structure. If the content of Mo is less than 0.050%, it may be difficult to sufficiently obtain the above-mentioned effect. If the content of Mo exceeds 3.0%, it may not only reduce economic feasibility because it is an expensive element, but also reduce toughness. Therefore, the content of Mo is preferably in the range of 0.050 to 3.0%. The lower limit of the Mo content is more advantageously 0.10%, more advantageously 0.20%, and most advantageously 0.30%. The Mo content is more advantageously 2.50% or less, more advantageously 2.0% or less, and most advantageously 1.50% or less.

[0024] V: 0.050~4.0%

[0025] V plays a role in improving strength through precipitation of fine carbides. If the content of V is less than 0.050%, it may be difficult to sufficiently obtain the above-described effect. If the content of V exceeds 4.0%, it may cause precipitation of coarse carbides, which may lower the impact toughness. Therefore, the content of V is preferably in the range of 0.050 to 4.0%. The lower limit of the V content is more advantageously 0.10%, more advantageously 0.30%, and most advantageously 0.50%. The upper limit of the V content is more advantageously 3.50%, more advantageously 3.0%, and most advantageously 2.50%.

[0026] Ni: 5.0% or less (including 0%)

[0027] Ni is a strong austenite stabilizing element and helps improve impact toughness. It is also an element that helps improve the corrosion resistance of welded joints. If the Ni content exceeds 5.0%, it may cause a decrease in strength due to changes in deformation behavior and may also reduce economic efficiency. Therefore, it is preferable that the Ni content be within the range of 5.0% or less (including 0%). The upper limit of the Ni content is more advantageously 4.0%, more advantageously 3.0%, and most advantageously 2.0%.

[0028] P: 0.020% or less (excluding 0%)

[0029] P is an impurity element, and when the content of P exceeds 0.020%, there is a concern that embrittlement may occur, and there may also be a problem that impact toughness may rapidly decrease. Theoretically, it is preferable that P is 0%, but since it is an element that is inevitably contained in the manufacturing process, 0% is excluded. Therefore, the content of P is preferably in the range of 0.020% or less (excluding 0%). The P content is more advantageous when it is 0.0150% or less, even more advantageous when it is 0.010% or less, and most advantageous when it is 0.0050% or less.

[0030] S: 0.0070% or less (excluding 0%)

[0031] S is an impurity element, and when the content of S exceeds 0.0070%, it may form low-melting-point compounds such as iron sulfide (FeS) during welding, which may cause high-temperature cracks. Theoretically, it is preferable that S is 0%, but since it is an element that is inevitably included in the manufacturing process, 0% is excluded. Therefore, it is preferable that the content of S is in the range of 0.0070% or less (excluding 0%). It is more advantageous that the S content is 0.0060% or less, even more advantageous that it is 0.0050% or less, and most advantageous that it is 0.0040% or less.

[0032] N: 0.150% or less (including 0%)

[0033] Nitrogen acts as a strong austenite stabilizing element, helping to secure hydrogen embrittlement resistance and non-magnetic properties. If the content of Ni exceeds 0.150%, it may cause cracks during welding and form nitrides, thereby reducing impact toughness. Therefore, it is preferable that the content of Ni be 0.150% or less (including 0%). The upper limit of the Ni content is more advantageously 0.140%, more advantageously 0.130%, and most advantageously 0.120%.

[0034] CaF2: 0.10~1.0%

[0035] CaF2 serves as an arc stabilizer to improve welding workability. If the content of CaF2 is less than 0.10%, it may be difficult to sufficiently obtain the above-described effect. If the content of CaF2 exceeds 1.0%, there is a concern that defects such as pores may occur in the weld zone. Therefore, the content of CaF2 is preferably in the range of 0.10 to 1.0%. The lower limit of the CaF2 content is more advantageously 0.150%, more advantageously 0.20%, and most advantageously 0.250%. The upper limit of the CaF2 content is more advantageously 0.950%, more advantageously 0.90%, and most advantageously 0.850%.

[0036] The remaining component is iron (Fe). However, during the normal manufacturing process, unintended impurities from raw materials or the surrounding environment may inevitably be mixed in, and thus cannot be excluded. Since these impurities are readily apparent to anyone skilled in the normal manufacturing process, their full details are not specifically mentioned in this specification.

[0037] The submerged arc welding material of the present invention may have a microstructure composed of austenite. Accordingly, a weld joint manufactured using the submerged arc welding material may also have an austenite structure, and the weld joint may be provided with high strength, excellent hydrogen embrittlement resistance, and stress corrosion resistance. For example, the weld joint may have a yield strength of 500 to 650 MPa, and an impact toughness of 27 J or more at -196°C.

[0038] Hereinafter, the present invention will be described in more detail through examples. However, it should be noted that the following examples are intended only to illustrate and further illustrate the present invention and are not intended to limit the scope of the invention. This is because the scope of the invention is determined by the matters set forth in the patent claims and matters reasonably inferred therefrom.

[0039] (Example)

[0040] After manufacturing a welding material for submerged arc welding having an alloy composition shown in Table 1 below, a weld joint was obtained by submerged arc welding a steel plate having an austenitic structure using the same. At this time, the steel plate had an alloy composition containing, in wt%, C: 0.05 to 0.6%, Si: 0.2 to 2.0%, Mn: 15 to 24%, S: 0.02% or less, P: 0.02% or less, the remainder being Fe and other unavoidable impurities. The submerged arc welding was performed so that the maximum heat input was 4.8 kJ / mm. The yield strength, impact toughness, hydrogen embrittlement resistance and stress corrosion resistance of the weld joint were evaluated, and the results are shown in Table 1 below. Meanwhile, the microstructures of the weld joints according to Inventive Examples 1 to 3 and Comparative Examples 1 to 5 were all composed of austenite.

[0041] The above yield strength was measured using the ASTM A370 standard.

[0042] The above impact toughness was measured using the ASTM A20 standard.

[0043] The above hydrogen embrittlement was measured using the ASTM F519 standard and evaluated as good or bad.

[0044] The above stress corrosion resistance was measured using the ASTM G36 standard, and was evaluated as good if no cracks occurred, and poor if cracks occurred.

[0045] ClassificationAlloy composition(wt%)Yield strength(MPa)Impact toughness(J, @-196)Hydrogen embrittlementStress corrosion resistanceCSiMnCrMoVNiPSNCaF2Invention example10.50.5203.01.00.051.00.010.00500.152178GoodGoodInvention example20.60.5203.01.04.01.00.010.0050.10.757470GoodGoodInvention example30.31.0242.00.51.50.010.010.0050.080.450490GoodGoodComparative example10.40.3203.00 000.010.0050.050.539071GoodGoodComparisonExample20.31.0242.001.01.00.010.00500.541067GoodGoodComparisonExample30.31.0242.00.501.00.010.00500.539485GoodGoodComparisonExample40.10.12400000.010.00500.530599GoodGoodComparisonExample50.10.1244.01.03.000.010.00500.5425105GoodGood

[0046] As can be seen from Table 1 above, in the case of Inventive Examples 1 to 3 that satisfy the conditions of the present invention, it can be seen that high yield strength is secured along with good hydrogen embrittlement resistance and stress corrosion resistance. On the other hand, in the case of Comparative Examples 1 to 3 that do not satisfy the conditions of the present invention, it can be seen that the yield strength is at a low level.

[0047] Fig. 1 is a photograph of Invention Example 1 observed using a scanning electron microscope, (a) is a photograph observed at 100x magnification, and (b) is a photograph observed at 1000x magnification. As can be seen from Fig. 1, Invention Example 1 can be confirmed to have an austenite structure.

Claims

1. A welding material for submerged arc welding, comprising in wt% C: 0.150 to 0.60%, Si: 0.10 to 1.0%, Mn: 15.0 to 25.0%, Cr: 1.0 to 5.0%, Mo: 0.050 to 3.0%, V: 0.050 to 4.0%, Ni: 5.0% or less (including 0%), P: 0.020% or less (excluding 0%), S: 0.0070% or less (excluding 0%), N: 0.15% or less (including 0%), CaF2: 0.10 to 1.0%, with the remainder being Fe and other unavoidable impurities.

2. In claim 1, The above welding material is a welding material for submerged arc welding whose microstructure is composed of austenite.

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