650mpa grade multi-wire submerged arc welding pad wire and welding wire suitable for large heat input welding

Abstract

The application discloses a 650MPa grade multi-wire submerged-arc welding disc bar suitable for large heat input welding and belongs to the technical field of welding materials. The chemical components of the disc bar include the following in percentage by mass: C: 0.04-0.10, Si: 0.09, Mn: 2.3-2.55, P: 0.012, S: 0.005, Cr: 0.10-0.25, Ni: 0.75-1.05, Mo: 0.4-0.58, Ti: 0.11-0.24, Ca: 0.0015-0.030, Re: 0.030, and the balance of Fe and inevitable impurities. The application further discloses a welding wire based on the disc bar. The welding wire is designed rationally in chemical components, and the deposited metal obtained under the heat input of 50-100kJ / cm has excellent comprehensive performance, high tensile strength and low-temperature impact toughness.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of welding materials, and particularly relates to a 650MPa-grade multi-wire submerged-arc welding pad wire suitable for large heat input welding. BACKGROUND

[0002] In the field of bridge manufacturing, with the large-scale and high-strengthening of steel components, in order to improve the welding efficiency of medium-thick plates and reduce production costs, large heat input welding technology is usually used. Multi-wire submerged arc automatic welding has the characteristics of high welding metal deposition efficiency, good quality performance, fast welding speed and automatic welding process, and is widely used in engineering. At present, the application of welding metal with a tensile strength below 590MPa is the most common, which is mainly through the toughening method of Ti-B composite addition to ensure the strength while improving the impact toughness of the welding seam, but as the required strength of steel structure continues to increase, in order to realize the strength matching of the welded joint, the required welding material strength also increases, and at present, most of the high-strength welding materials used in large heat input are imported from abroad, which is expensive and seriously restricts the rapid development of China's large bridge manufacturing industry. Therefore, the development and research of high-strength multi-wire submerged arc welding wire are of great significance.

[0003] In the prior art, for example, the invention patent with the application publication number CN104476008A “Large heat input submerged arc welding wire”, which obtains composite oxide inclusions and manganese sulfide by the nucleation effect of Ti and N elements and adding a certain amount of rare earth element Ce, promotes the nucleation of acicular ferrite, and the-40℃ impact energy of the welding seam metal can be between 48J and 118J in the heat input range of 60kJ / cm to 160kJ / cm, but it is not suitable for low-alloy high-strength steel with a strength level above 500MPa.

[0004] The invention patent with the application publication number CN107984112A “High-strength submerged arc welding wire with good low-temperature toughness”, which selects Mn-Mo-Ni as the main alloy system, adopts the design concept of Ti and B micro-alloying, controls the content ratio of Ti and B to be 6-10, the total content of Cr+Mn≤2.1%, the total content of Cr+Ni≤2.1%, the total content of Cr+Mo≤1.0%, and adds a small amount of rare earth elements such as Y or Ce, and the tensile strength of the deposited metal can reach 740MPa, but the-40℃ impact toughness is low, only≥47J, and the welding heat input is only 20kJ / cm, and it is not suitable for large heat input welding.

[0005] The invention patent with the application publication number CN107984114A "Low-alloy high-strength high-toughness submerged arc welding wire suitable for large heat input welding" controls 7.0≤Ti / B≤9.0 and 1.0≤B / N≤2.0 to inhibit the generation of proeutectoid ferrite and promote the generation of acicular ferrite. The-40℃ impact toughness of the weld metal and the welded joint reaches 130J under a large heat input of 100-200kJ / cm, but the tensile strength thereof is not mentioned.

[0006] The invention patent with the application publication number CN108247234A "Submerged arc welding wire for high-strength steel and preparation method thereof" controls Ti / B: 9-11 and Ni / Cu>1 to refine acicular ferrite and make the weld have good strength and toughness, but the welding heat input thereof is only 70kJ / cm, the welded structure needs to be tempered at high temperature to obtain a high tensile strength of 700MPa, and only-20℃ impact test is performed, which cannot guarantee the safety in use in colder areas.

[0007] The invention patent with the application publication number CN13878500A "Submerged arc welding solid core welding wire with excellent low-temperature toughness for large heat input welding" adopts the Mn-Ni-Ti-B alloy system, the ratio of Ti / B is 7.0-10.0, and is matched with domestic SJ101 flux. The toughness of the weld metal can still reach 120J under the condition of-40℃ under a welding heat input of 60kJ / cm-120kJ / cm, but the tensile strength thereof is only 650MPa, which cannot meet the requirements of the base material with higher strength on welding materials.

[0008] Therefore, under the requirements of the mechanical properties of the welded joint in the relevant standards, specifications and the like, in order to improve the welding manufacturing efficiency of large steel structures of bridge and other steel structure manufacturing enterprises and guarantee the safety in use, a domestic submerged arc automatic welding wire suitable for bridge steel with a tensile strength of not less than 650MPa under large welding heat input needs to be developed, which is an important way to further improve the welding efficiency, reduce the cost, improve the mechanical properties of the welded joint and replace imported products. SUMMARY

[0009] The problem to be solved by the present application is to provide a 650MPa multi-wire submerged arc welding rod and wire suitable for large heat input welding, which is matched with Fe powder-MgO-SiO2-CaF2-Al2O3 basic sintered flux in the heat input range of 50-100kJ / cm, has high deposition efficiency, excellent low-temperature toughness, strong adaptability to the welding heat input range, and is suitable for efficient welding manufacturing of large steel structures in the fields of bridges, ships and buildings.

[0010] To solve the above technical problems, the technical scheme adopted by the present application is: a 650MPa grade multi-wire submerged arc welding pad wire suitable for large heat input welding, the chemical components in the wire include, in terms of mass percentage: C: 0.04-0.10, Si≤0.09, Mn: 2.3-2.55, P≤0.012, S≤0.005, Cr: 0.10-0.25, Ni: 0.75-1.05, Mo: 0.4-0.58, Ti: 0.11-0.24, Ca: 0.0015-0.030, Re: ≤0.030, and the balance is Fe and inevitable impurities.

[0011] Further, the chemical components in the wire satisfy, in terms of mass percentage: 550≤Bs≤630, Bs=830-270(0.82W C )-90(0.73W Mn )-37(0.73W Ni )-70(0.90W Cr )-83(0.9W Mo ), wherein W C is the content of C in the wire, W Mn is the content of Mn in the wire, W Ni is the content of Ni in the wire, W Cr is the content of Cr in the wire, and W Mo is the content of Mo in the wire.

[0012] Further, the chemical components in the wire satisfy, in terms of mass percentage: 670.9≤θ≤799.9; the strength factor θ=9.8×{36.69+220(0.82W C )+8.0(0.73W Mn )+14(0.90W Cr )+3.4(0.73W Ni )+8.1(0.9W Mo )+8(0.17W Ti )}, wherein W C is the content of C in the wire, W Mn is the content of Mn in the wire, W Ni is the content of Ni in the wire, W Cr is the content of Cr in the wire, W Mo is the content of Mo in the wire, and W Ti is the content of Ti in the wire.

[0013] Further, the chemical components in the wire satisfy, in terms of mass percentage: 0.043≤α≤0.056, wherein α=W Si / 14+W Mn / 55+WTi / 24, wherein W Si is the content of Si in the wire rod, W Mn is the content of Mn in the wire rod, W Ti is the content of Ti in the wire rod.

[0014] Further, the chemical composition of the wire rod satisfies: 17%≤β≤31%, in terms of mass percentage, wherein β=W Ni / (W Mn +W Ni ) * 100%, W Mn is the content of Mn in the wire rod, W Ni is the content of Ni in the wire rod.

[0015] The application further provides a 650MPa grade multi-wire submerged arc welding wire suitable for large heat input welding, which is made by drawing the wire rod.

[0016] Further, a copper plating layer is arranged outside the welding wire, and the thickness of the copper plating layer is 0.19~0.23um.

[0017] Further, under the heat input of 50~100kJ / cm, the yield strength Rp 0.2 of the welding wire deposited metal is 529~577MPa, the tensile strength Rm is 681~737MPa, the elongation A is 22~24.5%, and the-40℃ impact absorption energy Akv-40℃ is 80~112J.

[0018] Further, the welding wire deposited metal is mainly composed of complex phase structure of acicular ferrite and granular bainite, and the content of the acicular ferrite is 65~74%.

[0019] The application has the following beneficial effects: (1) the welding wire of the application has excellent comprehensive performance, higher tensile strength and low temperature impact toughness by reasonable design of the chemical composition under the heat input of 50~100kJ / cm; and (2) the welding wire deposited metal has the following mechanical properties: yield strength Rp 0.2 / MPa: 529~577 MPa, tensile strength Rm / MPa: 681~737 MPa, elongation A / %: 22~24.5%, impact energy Akv-40℃ / J: 80~112 J at-40℃, and the content of acicular ferrite in the weld structure is between 65~74%.(2) The welding wire is suitable for multi-wire fusion pool large heat input welding operation of submerged arc welding, flux copper backing method and the like, the welding parameter range is adjusted widely, the welding process performance is stable under 50~100 kJ / cm heat input, the molten pool fluidity is good, the deposited metal is formed beautiful, and the crack resistance is excellent.(3) The welding wire alloy system is reasonably regulated, the wire rod smelting, rolling and welding wire drawing process is easy to realize, the quality is stable, and is suitable for large-scale popularization and application.

[0020] The application will be described in detail below with reference to the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The metallographic structure chart of Example 3;

[0022] Figure 2 The metallographic structure chart of Comparative Example 2. DETAILED DESCRIPTION

[0023] The application provides a 650 MPa grade multi-wire submerged arc welding wire rod suitable for large heat input welding, and the chemical components in the wire rod include the following in percentage by mass: C: 0.04~0.10, Si≤0.09, Mn: 2.3~2.55, P≤0.012, S≤0.005, Cr: 0.10~0.25, Ni: 0.75~1.05, Mo: 0.4~0.58, Ti: 0.11~0.24, Ca: 0.0015~0.030, Re: ≤0.030, and the balance is Fe and inevitable impurities.

[0024] The design of each chemical component in the application is based on the following.

[0025] C: C is the most important alloying element in the weld metal, has the effect of improving the strength of the deposited metal, and can increase the tensile strength by 190 MPa and the yield strength by 230 MPa for each addition of 0.1% C, a small amount of C in the weld can increase the acicular ferrite, while reducing the amount of proeutectoid ferrite, but the increase of carbon content will significantly increase the welding crack sensitivity of the deposited metal, and reduce the elongation. The content of C in the application is 0.04~0.10%, preferably 0.08~0.10%.

[0026] Si: Si is a deoxidizing element and a solid solution strengthening element, and its oxide can act as a nucleating agent for acicular ferrite; when Mn and Si coexist, with the increase of the content, the continuous cooling transformation temperature gradually decreases, the structure is refined, thereby affecting the structure and performance of the weld metal. However, too high content of Si will affect the toughness of the metal, increase the brittleness, and make the weldability worse. Since a large amount of silicates are contained in the flux, the Si content of the deposited metal is often increased, and the Si content needs to be limited. In the present application, the Si content is ≤0.09%, preferably 0.04-0.09%, and more preferably 0.06-0.08%.

[0027] Mn: Mn is one of the main elements for improving strength and toughness, and Mn increases the stability of the undercooled austenite, so that the austenite transformation moves to a lower temperature, the eutectoid reaction occurs at a lower carbon concentration, and the formation temperature of martensite is reduced. Adding an appropriate amount of Mn can increase the content of acicular ferrite in the weld, but excessive Mn will result in too high strength and increased hardness of the weld, and when the content of Mn is more than 2.6%, a large amount of M / A components will be generated in the weld, which will deteriorate the toughness, and therefore, the content of Mn needs to be reasonably matched with the content of Ni. In the present application, the content of Mn is 2.3-2.55%, preferably 2.31-2.54%, and more preferably 2.35-2.5%.

[0028] Cr: Cr is one of the important strengthening elements, and a certain amount of Cr can refine the grains and increase the strength of the metal. However, if the content of Cr is too high, it will cause carbide segregation, increase the weld crack sensitivity, and reduce the toughness and plasticity of the deposited metal. In the present application, the content of Cr is 0.1-0.25%, preferably 0.12-0.24%, and more preferably 0.14-0.22%.

[0029] Ni: Ni is an important element for ensuring the low-temperature impact toughness of the weld, and can inhibit the formation of large-size granular bainite. When the content of Ni is more than 1.0%, low-temperature cracks are prone to occur. The joint action of Mn and Ni can change the solidification dynamics of the weld, reduce the austenite transformation temperature, and make the CCT curve move to the right, which is beneficial to the formation of acicular ferrite. However, if the content of Mn is high, increasing the content of Ni will easily increase the content of M-A components, and the cost of Ni is high. Therefore, under the premise that the content of Mn and Ni does not exceed the martensite formation line (Ms line), the content of the alloy can be matched by adding Mn and reducing Ni. In the present application, the content of Ni is 0.75-1.05%, preferably 0.76-1.00%, and more preferably 0.79-0.89%.

[0030] Mo: Mo is dissolved in austenite or exists in the form of carbide in the weld, delays the pro-eutectoid ferrite transformation, refines the weld metal structure, and at the same time expands the temperature interval of acicular ferrite and bainite formation, which can significantly improve the strength and low temperature impact toughness of the weld metal, Mo is an expensive alloying element, and needs to be controlled to control the alloy cost. In the present application, the content of Mo is 0.4-0.58%, preferably 0.42-0.56%, more preferably 0.48-0.55%.

[0031] Ti: The dispersed distribution of oxides formed with the addition of Ti in the weld effectively prevents the growth of austenite grains. There is a strong interaction between Ti and Mn, when the content of Mn is high, a small amount of Ti can promote the rapid increase of the number of acicular ferrite. At the same time, the composite oxide inclusions of Ti and Si, Mn, Al g are beneficial to the nucleation and growth of acicular ferrite, and improve the low temperature toughness of the deposited metal under high heat input. In the high heat input welding, the burning loss of Ti is serious, so the addition amount of Ti should be increased, therefore, the preferred range of Ti in the present technical solution is 0.11-0.24%, preferably 0.16-0.23%, more preferably 0.17-0.21%.

[0032] Ca: Adding an appropriate amount of Ca can spheroidize the original strip-shaped MnS inclusions, promote the nucleation and growth of AF; at the same time, Ca forms CaS or CaO with other inclusions, induces the formation of AF, thereby improving the toughness of the deposited metal. However, the content of Ca should not exceed 0.030%, otherwise coarse inclusions will be formed, and excessive addition will not be easy to oxidize and reduce in the molten pool, which will reduce the toughness of the weld metal, therefore, the preferred range of Ca in the present technical solution is Ca: 0.0015-0.030%, preferably 0.004-0.01%, more preferably 0.006-0.008%.

[0033] Re: Adding a small amount of rare earth elements in the welding wire can effectively reduce the content of oxide, nitride, sulfide and other inclusions, and change the morphology of inclusions. At the same time, rare earth elements can improve the fluidity of the welding pool, further reduce the gas and inclusion content in the weld, and improve the metallurgical quality of the deposited metal. In the present application, the content of Re is ≤0.03%, preferably 0.02-0.03%.

[0034] S and P: S and P have a harmful effect on the toughness of the weld metal, and excessive content can easily cause cracks in the weld, so their content should be reduced as much as possible, especially the content of P element. Because the use of flux in the submerged arc welding process can increase the content of P element in the weld metal. The content of S element is required to be not more than 0.005%, and the content of P element is required to be not more than 0.012%.

[0035] The welding wire of the present application is matched with the Fe powder-MgO-SiO2-CaF2-Al2O3 series basic sintered flux, and can be used for high-efficiency welding of steel plates with tensile strength not less than 650 MPa under welding heat input of 50-100 kJ / cm. The welding wire of the present application adopts C-Mn-Cr-Ni-Mo-Ti system, and appropriately adds Ca and Re elements, and strictly controls the contents of S and P. The present application uses higher C content to compensate for the large loss of C in the process of large heat input welding, so as to keep the C in the deposited metal or weld metal within a reasonable range and improve the toughness of the weld; through the cooperation of C, Mn, Mo and Cr, on the one hand, the deoxidizing effect is achieved to reduce the oxygen content in the deposited metal or weld metal, and on the other hand, the dispersed strong carbides Cr23C6 and Cr7C3 are generated to improve the strength and hardness of the deposited metal and weld metal, and the crack resistance and low-temperature impact toughness of the deposited metal are improved, and the fluidity of the weld metal pool is improved. In addition, higher Mo can increase the hardenability and impact toughness of the material; Ti is added to the submerged arc welding wire as a trace element, the size of the oxide formed by Ti can be refined, and the volume content is significantly increased, so as to significantly promote the generation of acicular ferrite in the weld metal; appropriate addition of Ni element can toughen the ferrite matrix, reduce the ductile-brittle transition temperature, and improve the stability of the low-temperature toughness of the weld metal; the main effects of adding Re during smelting are: first, the inclusions such as S and P are spheroidized, and then melt into the slag together with the inclusions, so as to purify the weld metal and improve the low-temperature toughness thereof; second, part of Re enters the weld metal to reduce the hydrogen-induced crack sensitivity of the weld metal. In addition, appropriate addition of Ca element can achieve the effect of sulfide modification. In addition to the above-mentioned need to reasonably control the chemical composition range of each element, the following innovative technical requirements must be set to accurately control the relative addition amount of part of key elements.

[0036] (1) 550≤B s ≤630, B s =830-270(0.82W C )-90(0.73W Mn )-37(0.73W Ni )-70(0.90W Cr )-83(0.9W Mo), by controlling the proportion of C, Mn, Ni, Cr, Mo five elements, the weld metal bainite transformation temperature is controlled in 570-630℃ under 50-100kJ / cm heat input, because acicular ferrite as a kind of bainite-like structure, is formed in slightly higher than bainite transformation temperature range, through the mixed phase change mechanism of shear and diffusion, high heat input welding due to high energy, slow cooling rate, in high temperature residence time is longer, and higher bainite transformation temperature interval is conducive to the formation of acicular ferrite in high heat input welding, and B s too high, easy to form coarse granular bainite structure, B s too low, easy to form a large number of pearlite and proeutectoid ferrite, affect the low temperature impact toughness.

[0037] (2) by regulating the formula 0.043≤α≤0.056, α=W Si / 14+W Mn / 55+W Ti / 24, control the addition of Si, Mn, Ti, effectively reduce the O content in the weld, at the same time generate SiO2, MnO, TiO2 oxide, which under the condition of high temperature in high heat input, preferentially form, in the subsequent cooling process to promote sulfide, carbide, nitride, etc. on its surface precipitation, form 2-3μm effective complex inclusions, these inclusions have the characteristics of high melting point, good thermal stability, etc. effectively induce acicular ferrite nucleation, refine the austenite intracrystalline organization, so that the weld metal obtains good low temperature impact toughness. α too high, will lead to the number of inclusions increases, size increases, instead of the continuity of the matrix, causing stress concentration in the surrounding local area, so that the micro crack is easy to form, grow on the two phase interface, and then expand. α too low, will cause more CaO, Al2O3 and other invalid inclusions in the weld, resulting in the deterioration of weld metal properties.

[0038] (3) by regulating the formula 17%≤β≤31%, β=(W Ni / W Mn +W Ni) 100%, control Ni, Mn element content ratio, increase quenching, make CCT curve right shift, restrain eutectoid ferrite growth, change weld solidification dynamics, be favorable to form acicular ferrite, because Mn element promotes acicular ferrite formation simultaneously, also increase the precipitation of brittle second phase pearlite in recrystallization zone, and the distribution trend of pearlite is directional long strip through reheating zone with the increase of Mn, harden structure, deteriorate weld joint toughness, and add appropriate amount of Ni element can make the structure generate more boundary irregular quasi-polygonal ferrite, hinder pearlite along strip grain boundary growth, and inhibit the generation of large size granular bainite.But simultaneously, the proportion of Ni, Mn element content should not be more than 31%, if more than 31%, although a large amount of acicular ferrite will be produced, but will exceed martensite formation line (M s Line), lead to martensite or other low temperature phase change product formation, reduce its weld joint toughness, if β is less than 17%, then Mn element content is excessive, easy to increase the segregation tendency of structure.

[0039] (4) by regulating formula 670.9≤θ≤799.9, θ=9.8×{36.69+220(0.82W C ) +8.0(0.73W Mn ) +14(0.90W Cr ) +3.4(0.73W Ni ) +8.1(0.9W Mo ) +8(0.17W Ti )}, control solid solution strengthening element Mn, Si, Ni and Mo content and precipitated strengthening element Ti, also consider the element burning loss problem caused by large heat input welding when considering the effect of alloying elements on weld metal strength and toughness, combine the transition allowance of each alloying element after large heat input welding with the strength increment caused by chemical composition, so that the tensile strength of the wire deposit metal is not less than 650MPa.

[0040] The wire manufacturing technology of the application is the same as the prior art. According to the alloy composition of the wire of the application, the wire is smelted and cast into an ingot, then forged, rolled into a rod, drawn into a wire of a corresponding size, plated with copper and polished, wherein the copper plating thickness is controlled to be 0.19-0.23um, and finally packaged into finished products.

[0041] The wire of the application has a yield strength Rp 0.2 of the wire deposit metal of 529-577MPa, a tensile strength Rm of 681-737MPa, an elongation A of 22-24.5%, and an impact absorption energy Akv-40℃ of 80-112J at a heat input of 50-100kJ / cm. The microstructure of the wire deposit metal comprises acicular ferrite and granular bainite, and the content of acicular ferrite is 65-74%.

[0042] The multi-wire submerged arc welding wire of the present application will be further explained and described in connection with specific examples.

[0043] The chemical composition ratio (mass percentage) (balance is Fe) of the submerged arc welding wires of Examples 1-8 and Comparative Examples 1-8 of the present application is shown in the following table.

[0044] .

[0045] According to the precisely calculated composition ratio of the welding wire, raw materials with low P, S, gas and inclusion contents are selected, the addition amount of the alloy is calculated, the welding wire steel is smelted by using a 75 kg vacuum induction furnace, after charging, melting, refining, the steel ingot is cast after the composition is qualified. After the steel ingot is forged into a bloom, it is heated, rough rolled, finished, reduced in diameter, wire drawing, Stelmor wire controlled cooling, coiling, inspection, packaging, and the finished product is 8.5 mm wire rod; the wire rod is pretreated by rough drawing (pickling), rough drawing, fine drawing, degreasing, chemical copper plating, precision layer winding, and packaging to make 5.0 mm submerged arc welding solid core welding wire, and the copper plating thickness is controlled at 0.19-0.23 mm.

[0046] Examples 1-4 and Comparative Examples 1-4 were subjected to deposited metal single wire deposited metal test according to the welding process parameters shown in the following table, the welding heat input was 50 kJ / cm, and Fe powder-MgO-SiO2-CaF2-Al2O3 system alkaline sintered flux was selected for welding, and the layer temperature was controlled at not more than 160℃.

[0047] Welding process parameters of Examples 1-4 and Comparative Examples 1-4

[0048] .

[0049] Examples 5-8 and Comparative Examples 5-8 were subjected to deposited metal single wire deposited metal test according to the welding process parameters shown in the following table, the welding heat input was 100 kJ / cm, and Fe powder-MgO-SiO2-CaF2-Al2O3 system alkaline sintered flux was selected for welding, and the layer temperature was controlled at not more than 160℃.

[0050] Welding process parameters of Examples 5-8 and Comparative Examples 5-8

[0051] .

[0052] The sample was taken from the welded metal, ensuring that the parallel length was entirely composed of the welded metal, and the sample size and test method were in accordance with GB / T 228. The impact sample was taken from the center of the welded metal, the longitudinal axis of the impact sample was perpendicular to the length direction of the welded metal, the notch surface was perpendicular to the surface of the welded metal, and the notch axis was located at the center of the welded metal. The sample size was 10*10*55mm, and the impact test method was in accordance with GB / T 229. The tensile test and impact test results of the welded metal are shown in the following table, and the average values are in the brackets.

[0053] Tensile test and impact test results of the welded metal

[0054] .

[0055] Figure 1 The welded metal of the welding wire of Example 3 of the present application is mainly composed of fine and uniform acicular ferrite and granular bainite, and has excellent low-temperature impact toughness, which is not affected even under large heat input conditions. Figure 2 The welded metal of the welding wire of Example 3 of the present application is mainly composed of fine and uniform acicular ferrite and granular bainite, and has excellent low-temperature impact toughness, which is not affected even under large heat input conditions.

[0056] As can be seen from the test results of the above examples, the submerged arc welding solid core welding wire of the present application has mechanical properties of the welded metal that meet the requirements of various specifications in the range of 50-100kJ / cm of heat input, that is, good strength and plasticity are obtained, and the welded metal also has excellent low-temperature impact toughness, with an impact absorption energy of 80-112J at-40℃. It can be applied to the production and efficient welding manufacturing of large welded structural parts in the industries of bridges, ships and buildings.

[0057] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application and not to limit them; although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the specific embodiments of the present application can be modified or some technical features can be replaced by equivalent ones; without departing from the spirit of the technical solutions of the present application, they should be covered in the technical solution range of the present application.

Claims

1. A 650 MPa grade multi-wire submerged arc welding pad wire suitable for high heat input welding, characterized in that, The chemical composition in the wire rod includes, in mass percentage: C: 0.04~0.10, Si≤0.09, Mn: 2.3~2.55, P≤0.012, S≤0.005, Cr: 0.10~0.25, Ni: 0.75~1.05, Mo: 0.4~0.58, Ti: 0.11~0.24, Ca: 0.0015~0.030, Re: ≤0.030, the balance being Fe and inevitable impurities, The chemical composition in the wire rod satisfies: 550≤Bs≤630, Bs=830-270(0.82W C )-90(0.73W Mn )-37(0.73W Ni )-70(0.90W Cr )-83(0.9W Mo ) in mass percentage wherein W C is the content of C in the wire rod, W Mn is the content of Mn in the wire rod, W Ni is the content of Ni in the wire rod, W Cr is the content of Cr in the wire rod, W Mo is the content of Mo in the wire rod; 670.9 < θ < 799.9; strength factor θ = 9.8 x {36.69 + 220(0.82W C ) + 8.0(0.73W Mn ) + 14(0.90W Cr ) + 3.4(0.73W Ni ) + 8.1(0.9W Mo ) + 8(0.17W Ti )}, wherein W C is the content of C in the wire rod, W Mn is the content of Mn in the wire rod, W Ni is the content of Ni in the wire rod, W Cr is the content of Cr in the wire rod, W Mo is the content of Mo in the wire rod, W Ti is the content of Ti in the wire rod; The chemical composition in the wire rod satisfies: 0.043≤a≤0.056, wherein, a=W Si / 14+W Mn / 55+W Ti / 24, W Si is the content of Si in the wire rod Mn is the content of Mn in the wire rod Ti is the content of Ti in the wire rod The chemical composition in the wire rod satisfies: 17%≤β≤31%, in mass percentage, wherein, β=W Ni / (W Mn +W Ni ) * 100%, W Mn is the content of Mn in the wire rod, and W Ni is the content of Ni in the wire rod.

2. A 650 MPa grade multi-wire submerged arc welding wire suitable for high heat input welding, characterized in that, The wire rod is drawn to form the welding wire.

3. The 650 MPa grade multi-wire submerged arc welding wire suitable for large heat input welding according to claim 2, characterized in that, A copper plating layer is arranged outside the welding wire, and the thickness of the copper plating layer is 0.19~0.23um.

4. The 650 MPa grade multi-wire submerged arc welding wire suitable for large heat input welding according to claim 2, characterized by, Under a heat input of 50~100kJ / cm, the yield strength Rp of the weld metal deposited by the welding wire 0.2 The tensile strength is 529~577MPa, the tensile strength Rm is 681~737MPa, the elongation A is 22~24.5%, and the impact absorption energy Akv at -40℃ is 80~112J.

5. The 650 MPa grade multi-wire submerged arc welding wire suitable for large heat input welding according to claim 4, characterized in that, The welding wire deposited metal is mainly composed of acicular ferrite and granular bainite.

6. The 650 MPa grade multi-wire submerged arc welding wire suitable for large heat input welding according to claim 5, characterized in that, The content of the acicular ferrite is 65~74%.

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