A 650MPa-grade submerged arc welding material and welding method suitable for welding with a heat input of 125kJ / cm.

Abstract

This invention provides a 650MPa-grade submerged arc welding material and welding method suitable for welding with a heat input of 125kJ / cm, belonging to the technical field of welding materials. The welding material provided by this invention comprises the following elements by mass percentage: C: 0.06-0.09%, Si: ≤0.09%, Mn: 2.30-2.55%, Cr: 0.30-0.45%, Ni: 1.05-1.65%, Mo: 0.40-0.58%, V: 0.04-0.05%, Ti: 0.14-0.24%, B: 0.0005-0.006%, Als: ≤0.015%, Ce: ≤0.030%, P: ≤0.015%, S: ≤0.005%, Pb+Sn+As+Sb+Bi≤0.008%, and balance Fe.

Description

Technical Field

[0001] This invention relates to the field of welding materials technology, and in particular to a 650MPa-grade submerged arc welding material and welding method suitable for welding with a heat input of 125kJ / cm. Background Technology

[0002] In recent years, with the rapid development of the transportation industry, bridge construction has been accelerating, especially the planning and construction scale of large-span steel bridges across rivers and seas. Traditional welding methods in the bridge industry, such as single-wire submerged arc welding and gas shielded welding, have long been dominant. However, these methods are inefficient, leading to long production cycles for bridge structures. When the welding heat input of ordinary bridge steel and other equivalent steel grades exceeds 50 kJ / cm², the excessively long high-temperature dwell time will cause coarsening of the weld coarse-grained heat-affected zone (CGHAZ), resulting in larger austenite grains and a tendency for coarse-grained embrittlement. Within the grains, Widmanstätten structure, side-plate ferrite, upper bainite, and M / A components are prone to appear, causing localized embrittlement. This leads to a deterioration in the low-temperature impact toughness of the weld area, failing to meet the manufacturing requirements of high-heat-input, high-efficiency welding.

[0003] The invention patent with publication number CN104476008A discloses "a high heat input submerged arc welding wire". This welding wire obtains composite oxide inclusions and manganese sulfides through the precipitation nucleation effect of Ti and N elements and the addition of a certain amount of rare earth element Ce, which promotes the nucleation of acicular ferrite. In the heat input range of 60 to 160 kJ / cm, the impact energy of the weld metal at -40°C can be between 48 and 118 J. However, its tensile strength only reaches a maximum of 500 MPa, which is still not suitable for low alloy high strength steel with a strength level of 650 MPa or higher. The invention patent with publication number CN107984112A discloses "a high-strength submerged arc welding wire with good low-temperature toughness". This welding wire 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 to 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. Its deposited metal tensile strength can reach 740MPa, but its impact toughness at -40℃ is low, only 47-66J, and its welding heat input is only 20kJ / cm. It does not indicate that it is suitable for high heat input welding and the weld impact toughness is insufficient.

[0004] Therefore, providing a 650MPa-grade submerged arc welding material suitable for welding with a heat input of 125kJ / cm has become a technical challenge in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a 650MPa-grade submerged arc welding material and welding method suitable for welding with a heat input of 125kJ / cm. The welding material provided by this invention is suitable for welding with a high heat input of 125kJ / cm, and the tensile strength of the weld metal produced reaches 650MPa, while also exhibiting high impact toughness at -40℃.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides a 650MPa-grade submerged arc welding material suitable for welding with a heat input of 125kJ / cm, comprising the following elements by mass percentage: C: 0.06-0.09%, Si: ≤0.09%, Mn: 2.30-2.55%, Cr: 0.30-0.45%, Ni: 1.05-1.65%, Mo: 0.40-0.58%, V: 0.04-0.05%, Ti: 0.14-0.24%, B: 0.0005-0.006%, Als: ≤0.015%, Ce: ≤0.030%, P: ≤0.015%, S: ≤0.005%, Pb+Sn+As+Sb+Bi≤0.008%, and balance Fe.

[0008] Preferably, the mass percentage of elements in the 650MPa submerged arc welding material has the following relationship: 0.50≤δ≤0.63, 575≤η≤635; where δ=(1.2Cr+Ni+Mo) / (1.5Si+Mn+60Ce);

[0009] eta=885-316C-62.3Mn+40.5Si-49.4Ni-17.8Cr-63.4Mo-78.5B.

[0010] Preferably, the surface of the welding material is further coated with a copper plating layer.

[0011] Preferably, the thickness of the copper plating layer is 0.18–0.23 μm.

[0012] The present invention also provides a welding method for the welding materials described in the above technical solution, comprising: submerged arc welding of the base metal with welding materials and sintering flux under a heat input of 50-125 kJ / cm to obtain a welded part.

[0013] Preferably, the basicity of the sintering flux is B. ⅡW ≥1.9.

[0014] Preferably, the parameters of the submerged arc welding include: welding voltage of 30-40V, welding current of 620-910A, and welding speed of 30-40cm / min.

[0015] Preferably, the base metal is made of Q500qE.

[0016] Preferably, the submerged arc welding groove is a 45° V-groove.

[0017] Preferably, the submerged arc welding is performed at a horizontal position.

[0018] The 650MPa submerged arc welding material provided by this invention, suitable for welding with a heat input of 125kJ / cm, comprises the following elements by mass percentage: C: 0.06-0.09%, Si: ≤0.09%, Mn: 2.30-2.55%, Cr: 0.30-0.45%, Ni: 1.05-1.65%, Mo: 0.40-0.58%, V: 0.04-0.05%, Ti: 0.14-0.24%, B: 0.0005-0.006%, Als: ≤0.015%, Ce: ≤0.030%, P: ≤0.015%, S: ≤0.005%, Pb+Sn+As+Sb+Bi≤0.008%, and balance Fe.In this invention, carbon (C) is the main strengthening element, significantly improving the tensile strength of the weld metal. Si has excellent deoxidizing properties, deoxidizing the weld pool metal, eliminating the adverse effects of inclusions such as FeO on the weld, and simultaneously reducing the oxidation of Cr and Ni in the weld, improving the fluidity of the weld pool, and thus reducing weld inclusions. Mn also has good deoxidizing ability, not only removing FeO from steel but also forming MnS with S to eliminate the harmful effects of S. Mn also improves the hardenability of the weld metal, refines the microstructure, and enhances the mechanical properties of the weld metal through solid solution strengthening. Cr can dissolve in ferrite to produce solid solution strengthening, thereby improving the strength, hardness, and plasticity of the weld metal. Ni can refine ferrite grains. Mo can improve the low-temperature impact toughness and yield strength of weld metal; it can refine the grain size to improve the strength and hardness of weld metal, prevent temper brittleness and overheating tendency, and also improve the plasticity of weld metal, reducing the tendency to crack. At the same time, Mo can expand the bainite region and improve the strength and toughness of weld. Ti is a microalloying element that can make the microstructure of weld metal more uniform and significantly improve impact toughness. At the same time, Ti can form dispersed oxides and nitrides that hinder the growth of austenite grains. Among them, the composite oxide inclusions formed by Ti with Si, Mn, Al and Mg are conducive to the nucleation and growth of acicular ferrite, thus significantly promoting the formation of acicular ferrite in the weld metal and effectively improving the low-temperature toughness of weld metal under high heat input; V Combined with C and N elements, it can precipitate from the matrix to form diffusely distributed micron-sized V(C,N) particles. As heterogeneous nucleation particles, they can effectively promote the intragranular nucleation of acicular / blocky ferrite in the weld heat-affected zone, refine the microstructure, and greatly improve the weldability of steel plates under high heat input. B is a surface-active element with a very small atomic radius. Under the protection of Ti, it can exist freely and easily diffuses to the austenite grain boundaries at high temperatures. Boron accumulates at the austenite grain boundaries, reducing the grain boundary energy, increasing the stability of austenite, inhibiting the nucleation and growth of proeutectoid ferrite and strip ferrite, promoting the formation of acicular ferrite, and improving toughness. Als, i.e., acid-soluble aluminum, has a strong affinity for oxygen. When the weld contains a small amount of Al2O3, the resulting composite inclusions can act as AF nucleation particles. The invention effectively refines the weld grains; rare earth element Ce can improve the composition of inclusions, forming inclusions rich in Ce, S, O, and Al elements with low mismatch with acicular ferrite, which become nucleation points for acicular ferrite, thus increasing the content of acicular ferrite; rare earth element Ce can effectively refine the size of inclusions. During the oxide metallurgical process in the molten pool reaction, Ce-rich oxides combine with larger inclusions to form large inclusions. These large inclusions float to the surface and are discharged from the molten pool, thereby refining the size of inclusions and reducing the possibility of larger diameter inclusions becoming crack initiation sites, thus improving the low-temperature toughness of the weld metal; P, S, and Pb+Sn+As+Sb+Bi are all harmful elements. This invention strictly controls their content to effectively reduce their adverse effects on the weld microstructure.

[0019] The results of the embodiments show that the welding material for submerged arc welding provided by the present invention has a yield strength of 549-576 MPa, a tensile strength of 670-703 MPa, an elongation of ≥20%, and a KV2 impact absorption energy of 120-125 J at -40℃, which meets the requirements of relevant domestic standards / specifications and has sufficient impact absorption energy margin; the content of acicular ferrite in the microstructure of the welded weld metal is 69-86%, and the content of effective inclusions is 71-86%. Attached Figure Description

[0020] Figure 1 This is a SEM image of the microstructure of the welded metal in Application Example 1 of the present invention;

[0021] Figure 2 This is a SEM image of the microstructure of the welded metal in Application Example 2 of the present invention;

[0022] Figure 3 Here is a SEM image of the microstructure of the welded metal in Comparative Application Example 1 of this invention;

[0023] Figure 4 Here is a SEM image of the microstructure of the welded metal in Comparative Application Example 2 of this invention;

[0024] Figure 5 This is a SEM image of the distribution of acicular ferrite in the microstructure of the weld metal in Application Example 1 of this invention;

[0025] Figure 6 EDS diagram of elemental analysis in acicular ferrite in the microstructure of the weld metal in Example 1 of this invention;

[0026] Figure 7 This is a SEM image of the effective inclusion distribution in the microstructure of the weld metal in Example 1 of the present invention;

[0027] Figure 8 This is a SEM image showing the distribution of effective inclusions in the microstructure of the welded metal in Comparative Application Example 1 of the present invention. Detailed Implementation

[0028] This invention provides a 650MPa-grade submerged arc welding material suitable for welding with a heat input of 125kJ / cm, comprising the following elements by mass percentage: C: 0.06-0.09%, Si: ≤0.09%, Mn: 2.30-2.55%, Cr: 0.30-0.45%, Ni: 1.05-1.65%, Mo: 0.40-0.58%, V: 0.04-0.05%, Ti: 0.14-0.24%, B: 0.0005-0.006%, Als: ≤0.015%, Ce: ≤0.030%, P: ≤0.015%, S: ≤0.005%, Pb+Sn+As+Sb+Bi≤0.008%, and balance Fe.

[0029] The welding material for 650MPa submerged arc welding, suitable for welding with a heat input of 125kJ / cm, provided by this invention, comprises C: 0.06-0.09%, preferably 0.07-0.08%. By adding C and controlling its content within the above range, this invention utilizes C as a main strengthening element to significantly improve the tensile strength of the weld metal, reduce the tendency of the weld to hot crack and the tendency of the weld heat-affected zone to cold crack, thereby avoiding a decrease in the toughness of the weld metal.

[0030] The welding material for 650MPa submerged arc welding, suitable for welding with a heat input of 125kJ / cm, provided by this invention, comprises Si: ≤0.09%, preferably 0.01-0.09%, and more preferably 0.02-0.08%. This invention utilizes Si's excellent deoxidizing properties to deoxidize the weld pool metal, eliminating the adverse effects of inclusions such as FeO on the weld. Simultaneously, it reduces the oxidation of Cr and Ni in the weld, improving the fluidity of the weld pool and thus reducing weld inclusions. Furthermore, most of Si is dissolved in the ferrite matrix, improving the mechanical properties of the weld metal through solid solution strengthening. In addition, controlling the Si content within the above range avoids the problem of excessive Si leading to a significant increase in weld metal grain size and reduced toughness.

[0031] The welding material for 650MPa submerged arc welding, suitable for welding with a heat input of 125kJ / cm, provided by this invention, comprises Mn: 2.30-2.55%, preferably 2.35-2.50%, and more preferably 2.40-2.45%, by adding Mn and controlling its content within the above range. This invention utilizes Mn's excellent deoxidizing ability, which not only removes FeO from steel but also forms MnS with S to eliminate the harmful effects of S. Simultaneously, Mn can improve the hardenability of the weld metal, refine the microstructure, and enhance the mechanical properties of the weld metal through solid solution strengthening.

[0032] The welding material for 650MPa submerged arc welding, suitable for welding with a heat input of 125kJ / cm, provided by this invention, comprises Cr: 0.30-0.45%, preferably 0.32-0.42%, and more preferably 0.35-0.4%. By adding Cr and controlling its content within the above range, this invention utilizes the solid solution strengthening effect of Cr dissolved in ferrite, thereby improving the strength, hardness, and plasticity of the weld metal. In this invention, when the Cr content exceeds 0.8%, the toughness of the weld metal decreases significantly.

[0033] The welding material for 650MPa submerged arc welding, suitable for welding with a heat input of 125kJ / cm, provided by this invention, comprises Ni: 1.05-1.65%, preferably 1.10-1.60%, and more preferably 1.20-1.55% by weight percentage. By adding Ni and controlling its content within the above range, this invention can refine the ferrite grains and improve the low-temperature impact toughness and yield strength of the weld metal.

[0034] The welding material for 650MPa submerged arc welding, suitable for welding with a heat input of 125kJ / cm, provided by this invention, comprises Mo: 0.40-0.58%, preferably 0.42-0.55%, and more preferably 0.45-0.5%. By adding Mo and controlling its content within the above range, this invention can refine the grain size to improve the strength and hardness of the weld metal, prevent temper brittleness and overheating tendency, improve the plasticity of the weld metal, reduce the tendency to crack, and at the same time, Mo can expand the bainite region and improve the weld strength and toughness.

[0035] The welding material for 650MPa submerged arc welding, suitable for welding with a heat input of 125kJ / cm, provided by this invention, comprises V: 0.04-0.05%, preferably 0.041-0.049%, and more preferably 0.042-0.048%. By adding V and controlling its content within the above range, this invention enables V to combine with C and N elements, precipitating micron-sized V(C,N) particles from the matrix. These particles, acting as heterogeneous nucleation sites, effectively promote intragranular nucleation of acicular / blocky ferrite in the weld heat-affected zone, refine the microstructure, and greatly improve the welding performance of steel plates under high heat input.

[0036] The welding material for 650MPa submerged arc welding, suitable for welding with a heat input of 125kJ / cm, provided by this invention, comprises Ti: 0.14-0.24%, preferably 0.15-0.23%, and more preferably 0.16-0.2%. By adding Ti and controlling its content within the above range, this invention utilizes the microalloying effect of Ti to make the weld metal microstructure more uniform and significantly improve impact toughness. Simultaneously, the dispersed oxides and nitrides formed by Ti hinder austenite grain growth. The composite oxide inclusions formed by Ti with Si, Mn, Al, and Mg are conducive to the nucleation and growth of acicular ferrite, thereby significantly promoting the formation of acicular ferrite in the weld metal and effectively improving the low-temperature toughness of the weld metal under high heat input. In this invention, due to the use of high heat input welding, Ti burn-off is severe; therefore, controlling the Ti content within the above range ensures that Ti fully exerts its beneficial effects.

[0037] The welding material for 650MPa submerged arc welding, suitable for welding with a heat input of 125kJ / cm, provided by this invention, comprises B: 0.0005-0.006%, preferably 0.0010-0.005%, and more preferably 0.002-0.004%. This invention adds B and controls its content within the above range. B is a surface-active element with a very small atomic radius, allowing it to exist freely under the protection of Ti. At high temperatures, it readily diffuses to the austenite grain boundaries. Boron accumulates at the austenite grain boundaries, reducing grain boundary energy, increasing austenite stability, inhibiting the nucleation and growth of proeutectoid ferrite and strip ferrite, promoting the formation of acicular ferrite, and improving toughness.

[0038] The welding material for 650MPa submerged arc welding, suitable for welding with a heat input of 125kJ / cm, provided by this invention, by weight percentage, includes Als: ≤0.015%, preferably 0.0001~0.015%, more preferably 0.001~0.001%. By adding Als (acid-soluble aluminum) and controlling its content within the above range, this invention utilizes the strong affinity of Als for oxygen, allowing the composite inclusions formed when the weld contains a small amount of Al2O3 to act as nucleation sites for AF (alkaline oxidizing agents), thereby effectively refining the weld grains.

[0039] The welding material for 650MPa submerged arc welding, suitable for welding with a heat input of 125kJ / cm, provided by this invention, by weight percentage, includes Ce: ≤0.030%, preferably 0.001~0.030%, more preferably 0.005~0.025%. By adding rare earth Ce and controlling its content within the above range, this invention effectively refines the size of inclusions. During the oxide metallurgical process in the molten pool reaction, Ce-rich oxides combine with larger inclusions to form large inclusions. These large inclusions float to the surface and are discharged from the molten pool, thereby refining the inclusion size, reducing the possibility of larger diameter inclusions becoming crack initiations, and improving the low-temperature toughness of the weld metal.

[0040] By mass percentage, the welding material for 650MPa submerged arc welding suitable for welding with a heat input of 125kJ / cm provided by this invention includes P: ≤0.015%, preferably ≤0.010%. P in the welding material of this invention is a harmful element, and its content should be strictly controlled to a low level.

[0041] By mass percentage, the welding material for 650MPa submerged arc welding suitable for welding with a heat input of 125kJ / cm provided by this invention includes S: ≤0.005%, preferably ≤0.004%. S in the welding material of this invention is a harmful element, and its content should be strictly controlled to a low level.

[0042] By mass percentage, the welding material for 650MPa submerged arc welding suitable for 125kJ / cm heat input welding provided by this invention comprises Pb+Sn+As+Sb+Bi≤0.008%, preferably≤0.007%. Pb+Sn+As+Sb+Bi in the welding material of this invention are all harmful elements, and their content should be strictly controlled to a low level.

[0043] By weight percentage, the 650MPa grade submerged arc welding material provided by this invention, suitable for welding with a heat input of 125kJ / cm, includes the balance Fe.

[0044] In this invention, the mass percentage of elements in the 650MPa grade submerged arc welding material preferably has the following relationship: 0.50≤δ≤0.63, 575≤η≤635.

[0045] In this invention, δ is defined as: δ = (1.2Cr + Ni + Mo) / (1.5Si + Mn + 60Ce). By controlling the content relationship of the above elements to satisfy 0.50 ≤ δ ≤ 0.63, this invention enables Si and Mn to transition to the weld pool reaction during welding, participating in the deoxidation and impurity removal process of the weld, reducing the burn-off of Cr, Ni, and Mo, and generating silicate inclusions with low density and easy floating. At the same time, Si can improve the increased viscosity of the weld pool caused by the addition of alloying elements, improve fluidity, and make inclusions in the weld easier to float and reduce.

[0046] In this invention, η is:

[0047] η = 885 - 316C - 62.3Mn + 40.5Si - 49.4Ni - 17.8Cr - 63.4Mo - 78.5B. This invention achieves this by controlling the content relationship of the above elements to satisfy 575 ≤ η ≤ 635. The addition of alloying elements in the weld significantly affects the solid-state phase transformation, controlling the phase transformation temperature to approximately between 580 and 625°C. This suppresses the formation of proeutectoid ferrite and side-plate ferrite, promotes heterogeneous nucleation of acicular ferrite on inclusions, improves the weld microstructure, and ultimately improves the weld's mechanical properties.

[0048] In this invention, the surface of the welding material is preferably further coated with a copper plating layer. By coating the surface of the welding material with a copper plating layer, this invention can extend the shelf life of the welding material, enhance its electrical conductivity, and make its welding performance more stable under high heat input conditions.

[0049] In this invention, the thickness of the copper plating layer is preferably 0.18–0.23 μm. By controlling the thickness of the copper plating layer within the above range, this invention enables the copper plating layer to have good protective and conductive properties.

[0050] The welding material provided by this invention is suitable for welding with a high heat input of 125 kJ / cm, and the weld metal produced has a tensile strength of 650 MPa, high elongation, and excellent impact toughness of KV2 at -40℃, meeting the requirements of relevant domestic standards / specifications, and has sufficient impact absorption energy margin; at the same time, the weld metal microstructure has a high content of acicular ferrite and effective inclusions.

[0051] The method for preparing 650MPa-grade submerged arc welding materials suitable for 125kJ / cm heat input welding, as described in this invention, preferably includes the following steps:

[0052] (1) The raw materials are melted and cast in sequence to obtain ingots;

[0053] (2) The ingot obtained in step (1) is forged, rolled, drawn and post-treated in sequence to obtain a 650MPa grade submerged arc welding material suitable for welding with a heat input of 125kJ / cm.

[0054] The present invention preferably involves melting and casting the raw materials sequentially to obtain ingots.

[0055] In this invention, the raw materials preferably include one or more of the following: industrial pure iron, carbon raiser, ferromanganese, ferrochrome, electrolytic nickel, ferromolybdenum, ferrotitanium, ferrovanadium, and ferroboron, as well as ferrosilicon, metallic aluminum, and metallic cerium. This invention does not have special requirements regarding the source of the raw materials; any commercially available materials in the art that can be used and whose dosage can be calculated according to elemental ratios are acceptable.

[0056] In this invention, the preferred melting temperature is 1550–1600°C. This invention does not have specific requirements for the melting time, as long as the raw materials are sufficiently melted and uniformly melted at the specified melting temperature.

[0057] In this invention, the casting temperature is preferably 1400–1550°C. By controlling the casting temperature within this range, this invention can reduce casting defects in the ingot and ensure a uniform ingot structure.

[0058] After obtaining the ingot, the present invention preferably performs forging, rolling, drawing and post-treatment on the ingot in sequence to obtain a 650MPa grade submerged arc welding material suitable for welding with a heat input of 125kJ / cm.

[0059] In this invention, the initial forging temperature is preferably ≥1100℃; the final forging temperature is preferably ≥950℃. By controlling the forging temperature within the above range, this invention can ensure that the ingot has low deformation resistance, achieve sufficient deformation, effectively close casting defects, and achieve preliminary grain refinement.

[0060] In this invention, the rolling temperature is preferably 1100–1200°C. By controlling the rolling temperature within this range, this invention enables the welding material to have a denser microstructure and further achieves grain refinement.

[0061] In this invention, the drawing process preferably includes sequentially performing a first pickling, borax treatment, rough drawing, a first fine drawing, a second pickling, and a second fine drawing. This invention does not impose special requirements on the specific parameters of the various operations in the drawing process; conventional drawing operations in the art are sufficient to ensure that the dimensions of the welding material meet the usage requirements.

[0062] In this invention, the post-processing preferably includes sequential electroless copper plating, layer winding, and packaging. This invention does not have special requirements for the specific operations of the electroless copper plating and layer winding, as long as the copper plating layer thickness and the required solder material morphology are achieved.

[0063] The preparation method provided by this invention produces a 650MPa grade submerged arc welding material suitable for 125kJ / cm heat input welding with uniform and dense microstructure, and its welding performance is more stable when used for 125kJ / cm heat input submerged arc welding.

[0064] The present invention also provides a welding method for the welding materials described in the above technical solution, comprising: submerged arc welding of the base metal with welding materials and sintering flux under a heat input of 50-125 kJ / cm to obtain a welded part.

[0065] In this invention, the alkalinity of the sintering flux is preferably B. ⅡW ≥1.9, more preferably 1.9 to 3.0. In this invention, the sintering flux preferably includes an alkaline sintering flux based on Fe powder-MgO-SiO2-CaF2-Al2O3. By using the above-mentioned type of sintering flux, this invention can more effectively achieve smokeless, odorless, arc-free, and spatter-free welding, ensuring that the weld metal has good mechanical properties and surface quality.

[0066] In this invention, the submerged arc welding parameters preferably include: a welding voltage of 30–40V, a welding current of 620–910A, and a welding speed of 30–40cm / min; more preferably, they include: a welding voltage of 32–40V, a welding current of 630–910A, and a welding speed of 32–40cm / min. By controlling the submerged arc welding parameters within the above ranges, this invention can ensure that the required heat input is obtained during the submerged arc welding process and ensure the stability of the welding process.

[0067] In this invention, the base metal is preferably made of Q500qE. By selecting the above-mentioned type of base metal, this invention ensures that the mechanical properties of the weld metal obtained after welding with the welding material match the mechanical properties of the base metal.

[0068] In this invention, the preferred bevel type for submerged arc welding is a 45° V-groove. By employing this type of bevel, the present invention is more conducive to obtaining weld metal with stable connections and excellent mechanical properties.

[0069] In this invention, the welding position for submerged arc welding is preferably horizontal. By employing this welding position, the present invention facilitates more uniform heating of the molten metal pool, thereby obtaining weld metal with excellent mechanical properties.

[0070] In this invention, the submerged arc welding layer temperature is preferably ≤160℃, more preferably 80~160℃. By controlling the submerged arc welding layer temperature within the above range, this invention can ensure more stable welding under conditions of high heat input, and the heat of the weld can be dissipated as quickly as possible, avoiding grain coarsening caused by residual welding heat.

[0071] The welding method provided by this invention is more conducive to obtaining weld metal with stable welding performance and excellent mechanical properties.

[0072] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0073] Examples 1-3 and Comparative Examples 1-3

[0074] The elements and their mass percentages in the welding materials for 650MPa-grade submerged arc welding suitable for 125kJ / cm heat input welding provided in Examples 1-3 and the welding materials in Comparative Examples 1-3 are shown in Table 1.

[0075] Table 1 shows the elements and their mass percentages (%, balance Fe) of the welding materials for 650MPa-grade submerged arc welding suitable for 125kJ / cm heat input welding provided in Examples 1-3 and the welding materials of Comparative Examples 1-3.

[0076]

[0077] The specific preparation methods for 650MPa-grade submerged arc welding materials suitable for welding with a heat input of 125kJ / cm provided in Examples 1-3 are as follows:

[0078] (1) The raw materials are smelted and cast in sequence to obtain ingots; specifically: industrial pure iron, carbon raiser, ferrosilicon, metallic manganese, metallic chromium, electrolytic nickel, ferromolybdenum, ferrotitanium, ferrovanadium, ferroboron, metallic aluminum and metallic cerium are smelted at 1600℃ to obtain alloy liquid, and then the alloy liquid is cast at 1560℃ to obtain ingots.

[0079] (2) The ingot obtained in step (1) is sequentially forged, rolled, drawn, and post-treated to obtain a 650MPa grade submerged arc welding material suitable for welding with a heat input of 125kJ / cm; specifically: the ingot obtained in step (1) is forged at an initial forging temperature of 1200℃ and a final forging temperature of 1050℃ to obtain a 50×50mm square billet; then the billet is held at 1150℃ for 1 hour to reach the rolling temperature and rolled in 15 passes to obtain The wire rods are then subjected to pickling, borax treatment (neutralization and lubrication), and rough drawing in sequence. Precision drawing Pickling and fine drawing Surface chemical copper plating, layering, and packaging.

[0080] The preparation methods of Comparative Examples 1 to 3 are the same as those of Examples 1 to 3, omitting the raw materials such as ferrovanadium, ferroboron and metallic aluminum in step (1). Other raw materials are added in proportion according to the element content in Table 1. The remaining technical features are the same as those of Examples 1 to 3.

[0081] Application Examples 1-3 and Comparative Application Examples 1-3

[0082] Welding methods were employed using the 650MPa-grade submerged arc welding materials provided in Examples 1-3, suitable for welding with a heat input of 125kJ / cm, and the welding materials of Comparative Examples 1-3. The welding method involved submerging arc welding the base metal with the 650MPa-grade submerged arc welding materials provided in Examples 1-3 and the welding materials of Comparative Examples 1-3, respectively, using sintered flux under a heat input of 50kJ / cm. Six groups of deposited metal specimens were obtained. The specimens from Examples 1-3 and Comparative Examples 1-3 were numbered D1-D6 sequentially. (Five samples were taken from each group for performance testing). The welding method was performed according to the welding parameters in Table 2; these parameters are shown in Table 2.

[0083] Table 2 shows the welding parameters for application examples 1-3 and comparative application examples 1-2.

[0084]

[0085]

[0086] Examples 4-6 and Comparative Examples 4-6

[0087] The elements and their mass percentages in the welding materials for 650MPa-grade submerged arc welding suitable for 125kJ / cm heat input welding provided in Examples 4-6 and the welding materials of Comparative Examples 4-6 are shown in Table 3.

[0088] Table 3 shows the elements and their mass percentages (%, balance Fe) of the welding materials for 650MPa submerged arc welding suitable for 125kJ / cm heat input welding provided in Examples 4-6 and the welding materials of Comparative Examples 4-6.

[0089]

[0090]

[0091] The preparation methods of the welding materials in Examples 4-6 are the same as those in Examples 1-3.

[0092] In the preparation methods of welding materials in Comparative Examples 4 and 6, the raw materials such as ferrovanadium, ferroboron and metallic aluminum in step (1) of the preparation methods in Examples 1 to 3 are omitted. In the preparation method of welding materials in Comparative Example 5, the raw materials such as ferrovanadium, ferroboron, metallic aluminum and metallic cerium in step (1) of the preparation methods in Examples 1 to 3 are omitted. Other raw materials are added in proportion according to the element content in Table 3. The remaining technical features are the same as those in the preparation methods of Examples 1 to 3.

[0093] Application Examples 4-6 and Comparative Application Examples 4-6

[0094] Welding methods were employed using the 650MPa-grade submerged arc welding materials provided in Examples 4-6, suitable for welding with a heat input of 125kJ / cm, and the welding materials in Comparative Examples 4-6. The welding method involved submerging arc welding the base metal with the 650MPa-grade submerged arc welding materials provided in Examples 4-6 and the welding materials in Comparative Examples 4-6, respectively, using sintered flux under a heat input of 100kJ / cm. Six groups of deposited metal specimens were obtained. The specimens from Examples 4-6 and Comparative Examples 4-6 were numbered D7-D12, respectively. (Five samples were taken from each group for performance testing). The welding method was performed according to the welding parameters in Table 4; these parameters are shown in Table 4.

[0095] Table 4 shows the welding parameters for application examples 4-6 and comparative application examples 4-6.

[0096]

[0097]

[0098] Examples 7-10 and Comparative Examples 7-10

[0099] Table 5 shows the elements and their mass percentages in the welding materials for 650MPa submerged arc welding suitable for 125kJ / cm heat input welding provided in Examples 7-10 and the welding materials in Comparative Examples 7-10.

[0100] Table 5 shows the elements and their mass percentages (%) of the welding materials for 650MPa-grade submerged arc welding suitable for 125kJ / cm heat input welding provided in Examples 7-10 and the welding materials of Comparative Examples 7-10.

[0101]

[0102]

[0103] The preparation methods of the welding materials in Examples 7-10 are the same as those in Examples 1-3.

[0104] The preparation methods of welding materials in Comparative Examples 7-10 omit the raw materials such as ferrovanadium, ferroborone, metallic aluminum and metallic cerium in step (1) of the preparation methods in Examples 1-3. Other raw materials are added in proportion according to the element content in Table 5. The remaining technical features are the same as those in the preparation methods of Examples 1-3.

[0105] Application Examples 7-10 and Comparative Application Examples 7-10

[0106] Welding methods were employed using the 650MPa-grade submerged arc welding materials provided in Examples 7-10, suitable for welding with a heat input of 125kJ / cm, and the welding materials of Comparative Examples 7-10. The welding method involved submerging arc welding the base metal with the 650MPa-grade submerged arc welding materials provided in Examples 7-10 and the welding materials of Comparative Examples 7-10, respectively, using sintered flux. Eight groups of deposited metal specimens were obtained. The specimens from Examples 7-10 and Comparative Examples 7-10 were numbered D13-D20, respectively. (Five samples were taken from each group for performance testing). The welding method was performed according to the welding parameters in Table 6; these parameters are shown in Table 6.

[0107] Table 6 shows the welding parameters for application examples 7-10 and comparative application examples 7-10.

[0108]

[0109]

[0110] Twenty groups of weld metal specimens (five samples from each group for performance testing and average value) from Application Examples 1-10 and Comparative Application Examples 1-10 were subjected to non-destructive testing to inspect for welding defects. Ultrasonic testing was used for non-destructive testing of the weld metal, and all specimens passed the tests. Samples were taken from the welded weld metal, and the specimen dimensions and test methods were performed according to GB / T 228. Impact specimens were cut from the center of the weld metal, with the longitudinal axis of the impact specimen perpendicular to the length of the weld metal, the notch face perpendicular to the surface of the weld metal, and the notch axis located at the center of the weld metal. The specimen dimensions were 10×10×55mm, and the impact test method was performed according to GB / T 229. The tensile and impact test results of the 20 groups of weld metal specimens from Application Examples 1-10 and Comparative Application Examples 1-10 are shown in Table 7, with the values ​​in parentheses representing the average values.

[0111] Table 7 shows the tensile and impact properties of the deposited metals (groups D1-D20) in Application Examples 1-10 and Comparative Application Examples 1-10.

[0112]

[0113]

[0114] As shown in Table 7, the tensile strength of the weld metal in Application Examples 1-10 is between 671 and 703 MPa, and the yield strength is between 549 and 592 MPa, which meets the strength requirements of the invention. The impact absorption energy (KV2) of the weld metal at -40℃ is between 120 and 125 J, and the elongation is between 22% and 24.5%. In contrast, the chemical composition of Application Examples 1-10 does not meet the requirements of the invention, and the strength of the weld metal is either too high or too low and does not meet the standard, nor can the low-temperature impact toughness of the weld metal be guaranteed.

[0115] For the impact specimens of the weld metal corresponding to Examples 1-2 and Comparative Application Examples 1-2, metallographic specimens were taken for microstructure observation. The observation results of Application Example 1 are as follows: Figure 1 As shown, the observation results of Example 2 are as follows: Figure 2 As shown, the observation results are compared with those in Application Example 1. Figure 3 As shown, compare the observation results of application example 2. Figure 4 As shown.

[0116] Depend on Figures 1-2 It can be seen that the microstructure of the deposited metal in Application Examples 1-2 is mainly composed of acicular ferrite, with a small amount of grain boundary ferrite and granular bainite, while the microstructure of the deposited metal in Comparative Application Examples 1-10 is mainly composed of blocky ferrite, a small amount of acicular ferrite and granular bainite.

[0117] The content of acicular ferrite in the weld metal microstructure corresponding to cases 1-10 and comparative application cases 1-10 was statistically analyzed, and the statistical results are shown in Table 8.

[0118] Table 8. Statistical results of acicular ferrite content in the microstructure of welded metal in Application Examples 1-10 and Comparative Application Examples 1-10

[0119] Experiment number Needle-like ferrite content (%) Experiment number Needle-like ferrite content (%) Application Example 1 83 Comparative Application Example 1 33 Application Example 2 85 Comparative Application Example 2 34 Application Example 3 79 Comparative Application Example 3 39 Application Example 4 76 Comparative Application Example 4 27 Application Example 5 86 Comparative Application Example 5 28 Application Example 6 73 Comparative Application Example 6 31 Application Example 7 83 Comparative Application Example 7 41 Application Example 8 71 Comparative Application Example 8 44 Application Example 9 69 Comparative Application Example 9 40 Application Example 10 72 Comparative Application Example 10 27

[0120] As shown in Table 8, the content of acicular ferrite in the microstructure of the weld metal in Application Examples 1-10 is not less than 69%, while the highest content of acicular ferrite in the microstructure of the weld metal in Application Examples 1-10 is only 44%. Acicular ferrite has fine grains and large-angle grain boundaries, which can hinder crack propagation. Therefore, the weld metals of Application Examples 1-10 of the present invention can exhibit better impact toughness.

[0121] To analyze the reasons for the increased proportion of acicular ferrite in the weld metals of Application Examples 1-10, the metallographic samples corresponding to Example 1 were subjected to SEM electron microscopy and EDS testing, respectively. The results are as follows: Figure 5 , Figure 6 As shown.

[0122] Depend on Figures 5-6 It can be seen that the metal inclusions in Application Example 1 are mainly complex inclusions enriched with Ce, Ti, Mn and O elements, which become nucleation points of acicular ferrite. It was also found that the probability of inclusions with a size of 0.6 to 1.8 μm becoming nucleation points increases.

[0123] The proportion of effective inclusions in the deposited metal microstructure corresponding to use cases 1-10 and comparative application examples 1-10 was statistically analyzed, and the statistical results are shown in Table 9.

[0124] Table 9. Statistical results of the proportion of effective inclusions in the weld metal microstructure of Application Examples 1-10 and Comparative Application Examples 1-10.

[0125]

[0126] As shown in Table 9, the effective inclusion volume content in the weld metal microstructure of Application Examples 1-10 is 71-86%, while the effective inclusion volume content in Comparative Application Examples 1-10 is only 24-40%. This indicates that the welding material provided by the present invention can effectively utilize effective inclusions as nucleation sites for acicular ferrite during welding, thereby increasing the acicular ferrite content and thus effectively improving the mechanical properties of the weld metal.

[0127] The effective inclusions in the deposited metal microstructure were observed using scanning electron microscopy, corresponding to Example 1 and Comparative Application Example 1, respectively. The observation results are as follows: Figure 7 , Figure 8 As shown.

[0128] Depend on Figures 7-8 It can be seen that the number of effective inclusions in the weld metal structure of Application Example 1 is significantly greater than that in Comparative Application Example 1. This indicates that the weld metal prepared by the welding material provided in Application Example 1 can effectively utilize effective inclusions as nucleation sites for acicular ferrite, thereby increasing the acicular ferrite content and thus effectively improving the mechanical properties of the weld metal.

[0129] In summary, the welding material provided by this invention is suitable for welding with a high heat input of 125 kJ / cm, and the weld metal produced has a tensile strength of 650 MPa, high elongation, and excellent impact toughness at -40℃, meeting the requirements of relevant domestic standards / specifications, and has sufficient impact absorption energy margin; at the same time, the weld metal microstructure has a high content of acicular ferrite and effective inclusions.

[0130] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A welding material for 650MPa submerged arc welding suitable for welding with a heat input of 125kJ / cm, characterized in that, The composition includes the following elements by mass percentage: C: 0.06~0.09%, Si: ≤0.09%, Mn: 2.30~2.55%, Cr: 0.30~0.45%, Ni: 1.05~1.65%, Mo: 0.40~0.58%, V: 0.04~0.05%, Ti: 0.14~0.24%, B: 0.0005~0.006%, Als: ≤0.015%, Ce: ≤0.030%, P: ≤0.015%, S: ≤0.005%, Pb+Sn+As+Sb+Bi≤0.008%, and balance Fe; The mass percentage of elements in the 650MPa grade submerged arc welding material has the following relationship: 0.50≤δ≤0.63, 575≤η≤635; where δ=(1.2Cr+Ni+Mo) / (1.5Si+Mn+60Ce); η=885-316C-62.3Mn+40.5Si-49.4Ni-17.8Cr-63.4Mo-78.5B.

2. The welding material as described in claim 1, characterized in that, The surface of the welding material is also coated with a copper plating layer.

3. The welding material as described in claim 2, characterized in that, The thickness of the copper plating layer is 0.18~0.23μm.

4. The welding method of the welding material as described in any one of claims 1 to 3, characterized in that, include: Submerged arc welding is performed on the base metal using welding materials and sintered flux under a heat input of 50~125kJ / cm to obtain the welded part.

5. The welding method as described in claim 4, characterized in that, The basicity of the sintering flux is B. IIW ≥1.

9.

6. The welding method as described in claim 4, characterized in that, The parameters for submerged arc welding include: welding voltage of 30~40V, welding current of 620~910A, and welding speed of 30~40cm / min.

7. The welding method as described in claim 4, characterized in that, The base metal is made of Q500qE.

8. The welding method as described in claim 4, characterized in that, The submerged arc welding groove is a 45° V-groove.

9. The welding method as described in claim 4, characterized in that, The welding position for the submerged arc welding is horizontal.

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