1650 mpa grade and above ultra-high strength steel welding solid core welding wire and method

Abstract

This invention provides a solid welding wire and method for welding ultra-high strength steel of grade 1650MPa and above, to solve the technical problem that the tensile strength of the weld metal is insufficient to reach 1650MPa or above when welding 30CrMnSiA ultra-high strength steel with existing welding wires, while ensuring that the weld has sufficient impact toughness, that is, the weld impact toughness KU2 is maintained above 45J. The invention is characterized by the following chemical composition and its wt% content: C=0.38~0.45, Si=0.20~1.20, Mn=0.20~0.70, Cr=0.25~1.25, Ni=0.20~1.20, Mo=0.10~1.00, V=0.05~0.07, Al=0.02~0.05, Cu≤0.1, S≤0.005, P≤0.012, Fe=balance.

Description

Technical Field

[0001] This invention relates to the field of ultra-high strength steel welding technology, and in particular to a solid welding wire and method for welding ultra-high strength steel of grade 1650MPa and above. Background Technology

[0002] 30CrMnSiA is a high-strength, high-toughness structural steel widely used in aviation, aerospace and other fields, with a tensile strength greater than 1650MPa. The chemical composition of 30CrMnSiA is as follows (wt%): C=0.28~0.34, Cr=0.80~1.10, Mn=0.80~1.10, Si=0.90~1.20, P≤0.025, S≤0.025. 30CrMnSiA steel has the following welding difficulties: (1) High carbon equivalent, about 0.7~0.9%, with a large tendency to harden; (2) High sensitivity to cold cracking: it is very easy to generate hydrogen-induced delayed cracks; (3) High requirements for the performance matching of welded joints. The typical indicators at room temperature at the weld are: yield strength (Rp0.2) ≥1280MPa, tensile strength (Rm) ≥1650MPa, and impact toughness (KU2) ≥45J.

[0003] Table 1 summarizes the mechanical properties of welded joints using commercial welding wires or welding wire of CN201510806207.2. Currently, commonly available solid welding wires (such as the H08Mn2SiA series and general-purpose high-strength alloy welding wires) generally exhibit a "strength-toughness mismatch" when welding 30CrMnSiA steel: they have sufficient impact toughness but severely insufficient tensile strength (usually below 1400MPa, far below the requirement of 1650MPa). The highest strength grade in the national standard GB / T8110-2008 "Carbon Steel and Low Alloy Steel Welding Wires for Gas Shielded Arc Welding" is only 830MPa, which also fails to meet the welding strength requirements. Patent document CN201510806207.2 reports a 1500MPa grade ultra-high-strength steel welding wire with a maximum strength of 1550MPa, but this still cannot meet higher strength requirements. The strength of the weld metal becomes the weakest link in the entire joint, restricting the safe use of the structure. Patent document CN 117564546A discloses a welding wire using 35CrMnSiA as the base material, with a tensile strength at the weld exceeding 1458MPa after welding. According to its embodiment, the highest weld strength is 1630MPa, which cannot meet higher strength requirements. The core reason for the above problem is that the alloy system design of existing commercial or special welding wires (especially the content of strengthening elements such as C, Ni, Cr, and Mo) has not been optimized for the post-weld heat treatment state of 30CrMnSiA, and therefore cannot form a microstructure that matches the strength of the base material after heat treatment.

[0004] Table 1. Mechanical properties of the weld joint after welding commercial welding wire or CN201510806207.2 welding wire to the base metal.

[0005] Summary of the Invention

[0006] The purpose of this invention is to provide a solid welding wire and method for welding ultra-high strength steel of grade 1650MPa and above, so as to solve the technical problem that the tensile strength of the weld metal is insufficient when welding 30CrMnSiA ultra-high strength steel with existing welding wires and cannot reach 1650MPa and above, while ensuring that the weld has sufficient impact toughness, that is, the weld impact toughness KU2 is maintained above 45J.

[0007] The technical solution of the present invention is as follows:

[0008] Solid welding wire for welding ultra-high strength steel of grade 1650MPa and above, characterized in that it includes the following chemical composition and its wt% content: C=0.38~0.45, Si=0.20~1.20, Mn=0.20~0.70, Cr=0.25~1.25, Ni=0.20~1.20, Mo=0.10~1.00, V=0.05~0.07, Al=0.02~0.05, Cu≤0.1, S≤0.005, P≤0.012, Fe=balance.

[0009] Solid welding wire is in the shape of a round bar with a diameter of φ1.0mm~φ1.6mm, and is produced by rolling and drawing steel ingots.

[0010] Solid welding wire is in the form of strips, which are made by cutting steel plates.

[0011] After welding 30CrMnSiA steel with solid welding wire, the weld and the 30CrMnSiA steel to be welded are subjected to overall heat treatment according to the heat treatment regime of 30CrMnSiA steel, which is quenched at 890℃ and tempered at 230℃. The tensile strength of the weld is greater than 1650MPa and the impact toughness KU2 is greater than 45J.

[0012] A method for manufacturing solid welding wire for welding ultra-high strength steel of grade 1650MPa and above, characterized by comprising the following steps:

[0013] Step 1: Determine the steelmaking raw materials based on the chemical composition and wt% content of the solid welding wire for welding ultra-high strength steel of grade 1650MPa and above.

[0014] Step 2: The steelmaking raw materials are smelted into steel ingots using a vacuum induction furnace;

[0015] Step 3: The steel ingot is hot-rolled, pickled, and drawn to the required diameter to make a disc or straight bar finished welding wire, or the steel ingot is rolled into a steel plate, and then the steel plate is cut into strips and used as a welding rod after surface cleaning.

[0016] The method of using solid welding wire for welding ultra-high strength steel of grade 1650MPa and above is characterized by including the following steps:

[0017] Step 1: Use the solid welding wire for welding ultra-high strength steel of grade 1650MPa and above to weld 30CrMnSiA steel workpieces. The 30CrMnSiA steel is in a quenched and tempered state. The welding method is tungsten inert gas welding. The welding parameters are as follows: welding current is 80 A to 180 A, welding speed is 1.2 mm / s to 2.5 mm / s, arc voltage is 10 V to 14 V, preheating temperature is 150℃ to 250℃, and interpass temperature is 200℃ to 250℃.

[0018] Step 2: Immediately heat the welded 30CrMnSiA steel workpiece to 250℃~350℃ to remove hydrogen;

[0019] Step 3: Perform overall heat treatment on the welded parts of the 30CrMnSiA steel workpiece after hydrogen removal according to the heat treatment regime of 30CrMnSiA steel. The heat treatment regime includes holding at 890℃ for 1.5h + water cooling, holding at 230℃ for 2h after water cooling + air cooling. The metallographic structure at the weld is martensitic laths with fine carbides. The tensile strength at the weld is greater than 1650MPa and the impact toughness KU2 is greater than 45J.

[0020] The technical effects of the present invention are as follows: The solid welding wire and method for welding ultra-high strength steel of grade 1650MPa and above, through the combination of the above-mentioned composition design and welding-heat treatment process, can achieve the following outstanding effects: (1) Ultra-high strength matching: the tensile strength at the weld (R m The yield strength (R) is consistently above 1650 MPa, and can reach up to 1760 MPa or more. p0.2 (1) Stable strength of over 1370MPa, fully meeting the ultra-high strength requirements of the 30CrMnSiA shell for the welded joint. (2) Good toughness: While achieving ultra-high strength, the weld impact toughness (KU2) remains above 45J, achieving a good balance between high strength and high toughness. (3) Reasonable hardness matching: The weld hardness is about 48 HRC, forming a smooth transition with the base material (about 48.5 HRC) and the heat-affected zone, reducing stress concentration. (4) Strong process applicability: It is particularly suitable for manual TIG welding, solving the welding problems of complex structures or small-batch production that may be inaccessible by automatic welding. Attached Figure Description

[0021] Figure 1 This is a schematic diagram comparing the strength and toughness of the weld seam after welding 30CrMnSiA steel plates with the solid welding wire for welding ultra-high strength steel of grade 1650MPa and above, and the comparative welding wire. Figure 1 The horizontal axis represents tensile strength (MPa, scaled from 600, 800 to 1800). Figure 1 The middle vertical axis represents impact toughness (charpy impactenergy / KU2 / J, scaled from 40, 60 to 180). Figure 1 The results show that the tensile strength of the welding wire of the present invention is greater than 1650MPa and the impact toughness KU2 is greater than 50J. Figure 1 Although the impact toughness of proportions 1, 2 and 3 is relatively high, their tensile strength is far lower than 1650MPa.

[0022] Figure 2 The image shows the microstructure of the weld seam after heat treatment following welding of a 30CrMnSiA steel plate with the solid welding wire of the present invention (grade 1650MPa and above) for ultra-high strength steel. Figure 2 The microstructure shows fine carbides on the martensitic laths, which makes the tensile strength at the weld greater than 1650 MPa. Detailed Implementation

[0023] The following is in conjunction with the attached diagram ( Figures 1-2 The present invention will be described in conjunction with the examples.

[0024] Figure 1 This is a schematic diagram comparing the strength and toughness of the weld seam after welding 30CrMnSiA steel plates with the solid welding wire for welding ultra-high strength steel of grade 1650MPa and above, and the comparative welding wire. Figure 2 This is a metallographic image of the weld seam after heat treatment following welding of 30CrMnSiA steel plates using the solid welding wire for ultra-high strength steel of grade 1650MPa and above according to this invention. (Reference) Figures 1 to 2 As shown, the solid welding wire for welding ultra-high strength steel of grade 1650MPa and above includes the following chemical composition and its wt% content: C=0.38~0.45, Si=0.20~1.20, Mn=0.20~0.70, Cr=0.25~1.25, Ni=0.20~1.20, Mo=0.10~1.00, V=0.05~0.07, Al=0.02~0.05, Cu≤0.1, S≤0.005, P≤0.012, Fe=balance.

[0025] Solid welding wire is in the shape of a round bar with a diameter of φ1.0mm~φ1.6mm, and is produced by rolling and drawing steel ingots.

[0026] Solid welding wire is in the form of strips, which are made by cutting steel plates.

[0027] After welding 30CrMnSiA steel with solid welding wire, the weld and the 30CrMnSiA steel to be welded are subjected to overall heat treatment according to the heat treatment regime of 30CrMnSiA steel, which is quenched at 890℃ and tempered at 230℃. The tensile strength of the weld is greater than 1650MPa and the impact toughness KU2 is greater than 45J.

[0028] A method for manufacturing solid welding wire for welding ultra-high strength steel of grade 1650MPa and above includes the following steps: Step 1, determining the steelmaking raw materials based on the chemical composition and wt% content of the above-mentioned solid welding wire for welding ultra-high strength steel of grade 1650MPa and above; Step 2, smelting the steelmaking raw materials into steel ingots using a vacuum induction furnace; Step 3, hot rolling, pickling, and drawing the steel ingots to the required diameter to produce disc-shaped or straight strip-shaped finished welding wires, or rolling the steel ingots into steel plates, then cutting the steel plates into strips, and using them as welding rods after surface cleaning.

[0029] The method of using solid welding wire for welding ultra-high strength steel of grade 1650MPa and above includes the following steps: Step 1, using the above-mentioned solid welding wire for welding ultra-high strength steel of grade 1650MPa and above to weld 30CrMnSiA steel workpieces, wherein the 30CrMnSiA steel is in a quenched and tempered state, the welding method is tungsten inert gas welding, and the welding parameters are as follows: welding current is 80 A~180A, welding speed is 1.2 mm / s~2.5 mm / s, and arc voltage is 10 V~14V, preheating temperature is 150℃~250℃, interpass temperature is 200℃~250℃; Step 2, immediately heat the welded 30CrMnSiA steel workpiece to 250℃~350℃ for dehydrogenation; Step 3, perform overall heat treatment on the dehydrogenated 30CrMnSiA steel workpiece welded parts according to the heat treatment regime of 30CrMnSiA steel. The heat treatment regime includes holding at 890℃ for 1.5h + water cooling, holding at 230℃ for 2h after water cooling + air cooling. The metallographic structure at the weld is martensitic laths with fine carbides. The tensile strength at the weld is greater than 1650MPa, and the impact toughness KU2 is greater than 45J.

[0030] A solid welding wire for welding ultra-high strength steel with a tensile strength of 1650MPa or higher and its welding process: The mass percentage of each component of the welding wire is as follows: C=0.38~0.45, Si=0.20~1.20, Mn=0.20~0.70, Cr=0.25~1.25, Ni=0.20~1.20, Mo=0.10~1.00, V=0.05~0.07, Al=0.02~0.05, Cu≤0.1, S≤0.005, P≤0.012, Fe=balance.

[0031] The specific preparation process is as follows:

[0032] (1) Rolling and drawing method: the above components are smelted into steel ingots in a vacuum induction furnace and then hot rolled, pickled and drawn to the required diameter (Φ1.0mm~Φ1.6mm) to make disc-shaped or straight-shaped finished welding wire.

[0033] (2) Plate modification method: Steel plates with the above-mentioned composition are made into strips by laser cutting or machining, and after surface cleaning (grinding off the oxide scale), they are used as welding rods. Suitable for the experimental stage or small-batch customization.

[0034] The welding parameters for this welding wire are:

[0035] Manual tungsten inert gas welding (TIG welding) can be used, or automatic TIG welding can also be used. The welding current is 80~180A; the arc voltage is 10~14V; the welding speed is 1.2~2.5mm / s; the preheating temperature is 150~250℃; the interpass temperature is 200~250℃; immediately after welding, the workpiece is heated to 250~350℃ for hydrogen removal.

[0036] The present invention discloses a solid welding wire for welding ultra-high strength steel of grade 1650MPa and above, with the following chemical composition by mass percentage: C=0.38~0.45, Si=0.20~1.20, Mn=0.20~0.70, Cr=0.25~1.25, Ni=0.20~1.20, Mo=0.10~1.00, V=0.05~0.07, Al=0.02~0.05, Cu≤0.1, S≤0.005, P≤0.012, Fe=balance.

[0037] C: Provides solid solution strengthening and ensures sufficient lath martensite formation. Too low a C content results in insufficient strength, while too high a content impairs toughness and weldability. Taking all factors into consideration, the C content in this invention is between 0.38% and 0.45%.

[0038] Si serves two purposes: firstly, it acts as a deoxidizer in steel, and secondly, it prevents the formation of cementite, thus improving tempering resistance. Taking all factors into consideration, the Si content in this invention is controlled between 0.20% and 1.20%.

[0039] Mn: As an element that removes oxygen and sulfur, it provides solid solution strengthening, improving strength and toughness. However, excessively high Mn content can reduce strength. Considering all factors, the Mn content in this invention is controlled between 0.20% and 0.70%.

[0040] Cr and Mo work synergistically to improve hardenability and produce a secondary hardening effect. In particular, they can precipitate fine alloy carbides during post-weld tempering, which is key to achieving high strength. Taking all factors into consideration, the Cr content in this invention is controlled between 0.25% and 1.25%, and the Mo content is controlled between 0.10% and 1.00%.

[0041] Ni significantly improves toughness and hardenability, while solid solution strengthening ensures good crack resistance and impact toughness even at ultra-high strength. However, excessively high Ni content leads to excessively high costs. Considering all factors, the Ni content in this invention is controlled between 0.20% and 1.20%.

[0042] V: As a microalloying element, adding a small amount of V can form MC-type carbides, refine the grains, and improve both strength and toughness. However, excessive addition will reduce toughness. Taking all factors into consideration, the V content in this invention is controlled between 0.05% and 0.07%.

[0043] Al: Added in trace amounts, besides deoxidation, Al combines with N to form AlN, which can reduce free nitrogen, pin austenite grain boundaries, refine austenite grains, and improve the strength of steel without reducing its ductility and toughness. Taking all factors into consideration, the Al content in this invention is controlled between 0.02% and 0.05%.

[0044] The requirements for controlling the content of harmful impurities in the welding wire of this invention are: Cu≤0.1%, S≤0.005%, P≤0.012%. This reduces segregation and prevents hot cracking or embrittlement of the weld.

[0045] The present invention discloses a preparation process for solid welding wire for welding ultra-high strength steel of grade 1650MPa and above using the above-mentioned formula. The specific processing steps are as follows:

[0046] (1) Rolling and drawing method: The above components are smelted into steel ingots in a vacuum induction furnace, and then hot rolled, pickled and drawn to the required diameter (usually φ1.0mm~φ1.6mm) to make disc-shaped or straight-shaped finished welding wire.

[0047] (2) Plate modification method: Steel plates with the above-mentioned composition are made into strips by laser cutting or machining, and after surface cleaning (grinding off the oxide scale), they are used as welding rods. Suitable for the experimental stage or small-batch customization.

[0048] Welding method: The welding wire is used to weld 30CrMnSiA steel. Manual tungsten inert gas welding (manual TIG welding) is preferred, but automatic TIG welding can also be used.

[0049] Key points of the welding process include: welding current 80-180A; arc voltage 10-14V; welding speed 1.2-2.5mm / s; preheating temperature 150-250℃; interpass temperature 200-250℃; and immediate post-weld heating of the workpiece to 250-350℃ for hydrogen removal.

[0050] Subsequent steps: After welding, the weld metal must undergo overall heat treatment according to the heat treatment regime of the 30CrMnSiA base metal (quenching at 890℃ + tempering at 230℃). This heat treatment is a necessary condition for the weld metal to obtain an ultra-high strength structure that matches the base metal.

[0051] Example: Preparation of welding wire of the present invention: Steel ingots were smelted according to the following proportions: C: 0.38%, Si: 1.00%, Mn: 0.70%, Cr: 1.05%, Ni: 0.90%, Mo: 0.20%, V: 0.50%, Al: 0.025%, S: 0.004%, P: 0.005%, with the balance being Fe.

[0052] Comparative Example 1 Welding wire (30CrMnSi2NiA welding wire) composition: steel ingots were smelted according to the following proportions: C: 0.30%, Si: 1.00%, Mn: 1.00%, Cr: 1.00%, Ni: 2.21%, S: 0.005%, P: 0.005%, with the balance being Fe.

[0053] Comparative Example 2: Welding wire (YD115 welding wire) composition: steel ingots were smelted according to the following proportions: C: 0.11%, Si: 0.11%, Mn: 6.45%, Cr: 18.25%, Ni: 9.61%, Mo: 0.45%, S: 0.005%, P: 0.006%, with the balance being Fe.

[0054] Comparative Example 3: Welding wire (H08Mn2SiA welding wire) composition: steel ingots were smelted according to the following proportions: C: 0.08%, Si: 0.78%, Mn: 1.95%, Cr: 0.04%, Ni: 0.01%, Cu: 0.16%, S: 0.003%, P: 0.005%, with the balance being Fe.

[0055] Welding wire preparation: hot-rolled, pickled, and drawn into finished welding wires with a diameter of φ1.6mm.

[0056] Welding test: Using 30CrMnSiA steel plate (quenched and tempered) as the base material, manual TIG butt welding was performed using the welding wire of this invention and the comparative welding wire composition. Welding current 140A; arc voltage 12V; welding speed 2mm / s; preheating temperature 230℃; interpass temperature 220℃; immediately after welding, the weldment was heated to 300℃ for hydrogen removal.

[0057] Post-weld heat treatment: The weldment is placed in a heat treatment furnace and held at 890℃ for 1.5 hours according to the standard process for 30CrMnSiA, followed by water cooling, and then held at 230℃ for 2 hours before air cooling.

[0058] Performance testing: Post-weld mechanical property tests were conducted. Tensile testing was performed according to GB / T2651 and GB / T228.1-2021B20, and impact testing was performed according to GB / T2650 and GB / T229-2020. The test results show that the tensile strength (R) of the weld seam of the welding wire of this invention is [missing information]. m The yield strength (R) consistently reaches over 1650 MPa. p0.2 The weld strength is stable at over 1370 MPa, the weld impact toughness (KU2) is maintained above 45 J, and the weld hardness is approximately 48 HRC.

[0059] Table 2 shows the mechanical properties of the weld seam after welding the welding wire of the present invention and the comparative welding wire to the base material (30CrMnSiA steel).

[0060]

[0061] Contents not described in detail in this specification are existing technologies known to those skilled in the art. It is hereby indicated that the above description is intended to help those skilled in the art understand the present invention, but does not limit the scope of protection of the present invention. Any equivalent substitutions, modifications, improvements, and / or simplifications of the above descriptions that do not depart from the essence of the present invention fall within the scope of protection of the present invention.

Claims

1. A solid welding wire for welding ultra-high strength steel of grade 1650MPa and above, characterized in that, The chemical composition and its wt% content are as follows: C=0.38~0.45, Si=0.20~1.20, Mn=0.20~0.70, Cr=0.25~1.25, Ni=0.20~1.20, Mo=0.10~1.00, V=0.05~0.07, Al=0.02~0.05, Cu≤0.1, S≤0.005, P≤0.012, Fe=balance.

2. The solid welding wire for welding ultra-high strength steel of grade 1650MPa and above as described in claim 1, characterized in that, Solid welding wire is in the shape of a round bar with a diameter of φ1.0mm~φ1.6mm, and is produced by rolling and drawing steel ingots.

3. The solid welding wire for welding ultra-high strength steel of grade 1650MPa and above as described in claim 1, characterized in that, Solid welding wire is in the form of strips, which are made by cutting steel plates.

4. The solid welding wire for welding ultra-high strength steel of grade 1650MPa and above as described in claim 1, characterized in that, After welding 30CrMnSiA steel with solid welding wire, the weld and the 30CrMnSiA steel to be welded are subjected to overall heat treatment according to the heat treatment regime of 30CrMnSiA steel, which is quenched at 890℃ and tempered at 230℃. The tensile strength of the weld is greater than 1650MPa and the impact toughness KU2 is greater than 45J. A method for manufacturing solid welding wire for welding ultra-high strength steel of grade 5.1650MPa and above, characterized in that, Includes the following steps: Step 1: Determine the steelmaking raw materials based on the chemical composition and wt% content of the solid welding wire for welding ultra-high strength steel of grade 1650MPa and above as described in claim 1. Step 2: The steelmaking raw materials are smelted into steel ingots using a vacuum induction furnace; Step 3: The steel ingot is hot-rolled, pickled, and drawn to the required diameter to make a disc or straight bar finished welding wire, or the steel ingot is rolled into a steel plate, and then the steel plate is cut into strips and used as a welding rod after surface cleaning. The method of using solid welding wire for welding ultra-high strength steel of grade 6.1650MPa and above is characterized by including the following steps: Step 1: Use the solid welding wire for welding ultra-high strength steel of grade 1650MPa or above as described in claim 1 to weld 30CrMnSiA steel workpieces. The 30CrMnSiA steel is in a quenched and tempered state. The welding method is tungsten inert gas welding. The welding parameters are as follows: welding current is 80 A to 180 A, welding speed is 1.2 mm / s to 2.5 mm / s, arc voltage is 10 V to 14 V, preheating temperature is 150℃ to 250℃, and interpass temperature is 200℃ to 250℃. Step 2: Immediately heat the welded 30CrMnSiA steel workpiece to 250℃~350℃ to remove hydrogen; Step 3: Perform overall heat treatment on the welded parts of the 30CrMnSiA steel workpiece after hydrogen removal according to the heat treatment regime of 30CrMnSiA steel. The heat treatment regime includes holding at 890℃ for 1.5h + water cooling, holding at 230℃ for 2h after water cooling + air cooling. The metallographic structure at the weld is martensitic laths with fine carbides. The tensile strength at the weld is greater than 1650MPa and the impact toughness KU2 is greater than 45J.

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