Welding method of ultrahigh-strength steel with yield strength of 1,500 MPa for engineering machinery

Abstract

The invention belongs to the technical field of ultrahigh-strength steel for engineering machinery, and discloses a welding method of ultrahigh-strength steel with yield strength of 1500MPa for engineering machinery. C: 0.20% to 0.30%; 0.20% to 0.40% of Si; 0.90% to 1.20% of Mn; 0.50% to 1.20% of Ni; 0.50% to 0.80% of Mo; 0.02% to 0.05% of Nb; 0.03% to 0.08% of V; 0.001% to 0.02% of Ti; s < = 0.002%; p < = 0.008%; 0.40% to 1.00% of Cr; and the balance of Fe and inevitable impurity elements. Welding materials and optimal welding parameters are selected, preheating before welding and heat treatment after welding are controlled, welding of the ultrahigh-strength steel for engineering machinery with the yield of 1500 MPa is achieved, welding forming is good, and the use requirements of users are met.

Description

Technical Field

[0001] The present invention relates to the technical field of ultra-high-strength steel for engineering machinery, and in particular to a welding method for ultra-high-strength steel for engineering machinery with a yield strength of 1500 MPa. Background Art

[0002] As the construction machinery industry grows larger, the number of components manufactured through integrated forming is decreasing. Most construction equipment now requires welded components. Statistics show that welded components account for 50% to 70% of the equipment's total weight. This is especially true for the main body of hydraulic supports, which are almost entirely welded. Therefore, the performance of welded joints in high-strength steel used in construction machinery directly impacts the quality of the equipment.

[0003] As higher-strength high-strength steels are applied in engineering machinery, their welding properties are being extensively studied and applied. For example, 1100 MPa-grade high-strength structural steel plates have complex alloy compositions, high hardenability, and high sensitivity to weld cracks, resulting in poor weldability. A company produced S890QL crane booms. After welding, multiple parallel transverse cracks appeared on the weld surface. Observation and research revealed that some even penetrated the root and tore through the parent material. Most of these cracks appeared 24 hours after welding and are typical delayed cracks, posing a significant safety hazard to welded engineering components and equipment.

[0004] 1500 MPa-grade ultra-high-strength structural steel plate currently boasts the highest yield strength for use in engineering machinery. Due to the high carbon equivalent content of alloying elements, this plate exhibits high welding stresses and a greater tendency to cold cracking during welding. The manufacture of engineering components such as large crane booms and urban dump truck frames often requires welding. To maximize the application of 1500 MPa-grade ultra-high-strength structural steel plate, welding becomes a critical step in its use, and weld joint performance is a key indicator of the safety performance of ultra-high-strength structural steel plate.

[0005] Therefore, it is necessary to develop targeted welding methods for ultra-high-strength steel for engineering machinery with the highest yield strength, select welding materials, use optimal welding parameters, accurately control pre-weld treatment and post-weld treatment, and optimize the quality of welded joints by adjusting parameters such as welding heat input, preheating temperature, and post-weld heat treatment methods to ensure the joint quality and performance of 1500 MPa-grade ultra-high-strength structural steel plates. Summary of the Invention

[0006] The purpose of the present invention is to provide a welding method for ultra-high-strength steel for engineering machinery with a yield strength of 1500 MPa. By optimizing the steps of weld groove selection and processing, welding material selection, gas shielded welding shielding gas ratio, pretreatment of steel plates before welding, spot welding and fixation of steel plates, preheating before welding, ceramic padding on the back of the weld root gap, formal welding, and post-weld heat treatment, the quality and performance of 1500 MPa grade ultra-high-strength steel welded joints for engineering machinery are optimized.

[0007] To achieve the above object, the technical solution of the present invention is as follows: a method for welding ultra-high-strength steel for engineering machinery with a yield strength of 1500 MPa, wherein the chemical composition of the ultra-high-strength steel is as follows by weight percentage: C: 0.20%-0.30%; Si: 0.20%-0.40%; Mn: 0.90%-1.20%; Ni: 0.50%-1.20%; Mo: 0.50%-0.80%; Nb: 0.02%-0.05%; V: 0.03%-0.08%; Ti: 0.001%-0.02%; S≤0.002%; P≤0.008%; Cr: 0.40%-1.00%; the balance being Fe and unavoidable impurity elements; the welding steps specifically comprising:

[0008] (1) Welding groove selection and processing: For steel plates with a thickness of 7mm-10mm, a Y-shaped groove is opened with a groove angle α of 60°±2°, a blunt edge height p of 2mm, and a root gap b of 1.5mm~2mm;

[0009] (2) Selection of welding materials;

[0010] (3) Gas shielded welding gas ratio;

[0011] (4) Pretreatment of steel plates before welding;

[0012] (5) The steel plates are fixed by spot welding;

[0013] (6) Preheating before welding;

[0014] (7) A ceramic liner is attached to the back of the weld root gap;

[0015] (8) Formal welding;

[0016] (9) Post-weld heat treatment.

[0017] To ensure the pass rate of cold-bending welds in ultra-high-strength steel plates and improve weld toughness, the welding wire must exhibit a higher elongation (≥15%), a lower carbon equivalent (Ceq) of ≈0.42, and finer austenite grains. Furthermore, it must exhibit low heat input sensitivity and a narrow HAZ softening zone, minimizing the risk of crack growth during cold bending. The final welding wire chemical composition, by weight, is as follows: C: 0.08%-0.10%; Si: 0.70%-0.90%; Mn: 1.60%-1.80%; Ni: 2.10%-2.30%; Mo: 0.50%-0.70%; P ≤ 0.009%; Cr: 0.30%-0.50%. The wire diameter is 1.0-1.2 mm.

[0018] In the gas shielded welding shielding gas ratio, CO2 gas shielded welding uses a mixed gas of 70~80% Ar and 20~30% CO2 as the shielding gas, wherein the purity of Ar is 99.99% and the purity of CO2 is 99.99%; during welding, the shielding gas flow rate is 22 L / min~24 L / min.

[0019] The steel plate pretreatment before welding is specifically as follows: the magnetic properties of the test steel plate are measured before welding, if there is magnetism, it is demagnetized using a demagnetizer, and the area within 20 mm near the welding groove is polished clean to remove impurities.

[0020] When the steel plate group is fixed by spot welding, the grooves of the two steel plates are placed relative to each other before welding and fixed by spot welding; steel plates of the same material are used to strike an arc at the position where welding begins, and are fixed by spot welding, with the welding point interval being no greater than 60 mm.

[0021] During the preheating before welding, the preheating temperature of welding is T=1440Pcm-392, where Pcm is the cold crack sensitivity coefficient of the steel plate to be welded.

[0022] When the ceramic liner is affixed to the back of the weld root gap, the ceramic liner is affixed to the back of the root gap after preheating the steel plate, and welding is performed from the front side, forming both sides at one time, and the weld on the back side is full.

[0023] During the formal welding, metal-arc gas shielded welding is adopted, the welding current is 220A to 240A, the voltage is 23V to 24V, and the welding speed is 300mm / min to 400mm / min.

[0024] During the post-weld heat treatment, the welded steel plate is heated to 150° C. to 160° C., wrapped with asbestos for 60 to 80 minutes, and then cooled to room temperature in air to eliminate the diffusible hydrogen content in the weld joint.

[0025] Beneficial effects of the present invention: The welding method of ultra-high-strength steel for engineering machinery with a yield strength of 1500MPa described in the present invention, by combining weld design and welding parameter ratio and selecting specific welding wire, successfully achieves the -40°C impact energy ≥45J of the ultra-high-strength steel plate weld with a yield strength of 1500MPa and the room temperature tensile strength of the weld ≥1000MPa, thereby achieving a good match between the strength and toughness of the 1500MPa ultra-high-strength steel plate weld. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the steel plate welding groove structure of the present invention. DETAILED DESCRIPTION

[0027] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the present invention are further described below in conjunction with the accompanying drawings and specific implementation methods.

[0028] Example 1

[0029] A 7mm thick ultra-high strength steel for engineering machinery with a yield strength of 1500MPa is selected for welding. The chemical composition of the ultra-high strength steel is as follows in percentage by weight: C: 0.20%-0.30%; Si: 0.20%-0.40%; Mn: 0.90%-1.20%; Ni: 0.50%-1.20%; Mo: 0.50%-0.80%; Nb: 0.02%-0.05%; V: 0.03%-0.08%; Ti: 0.001%-0.02%; S≤0.002%; P≤0.008%; Cr: 0.40%-1.00%; the remainder is Fe and unavoidable impurity elements.

[0030] Selection and processing of steel plate weld groove: a single Y-shaped groove is made for 7mm thick steel plate, the groove angle (α) is 60°±2°, the blunt edge height p is 2mm, and the root gap b is 2mm.

[0031] For the selection of welding materials, a solid welding wire with a diameter of 1.2 mm with limited composition is selected. The chemical composition of the welding wire is as follows by weight percentage: C: 0.08%-0.10%; Si: 0.70%-0.90%; Mn: 1.60%-1.80%; Ni: 2.10%-2.30%; Mo: 0.50%-0.70%; P≤0.009%; Cr: 0.30%-0.50%.

[0032] Shielding gas ratio: CO2 gas shielded welding uses a mixed gas of 80% Ar and 20% CO2. The shielding gas flow rate during welding is 22 L / min, of which the purity of Ar is 99.99% and the purity of CO2 is 99.99%.

[0033] During the pretreatment of steel plates before welding, the magnetic properties of the test steel plates must be measured before welding. If there is magnetism, a demagnetizer must be used to demagnetize the plates. The area within 20 mm near the welding groove must be polished clean to remove impurities such as oxide scale.

[0034] The steel plates are fixed by spot welding. Before welding, the grooves of the two steel plates are placed opposite each other, leaving a 2mm gap at the root. Spot welding is used to facilitate subsequent welding. To ensure the quality of the steel plate welds, steel plates of the same material are used to strike the arc at the starting point of welding, and are fixed by spot welding. The welding point interval is 50mm.

[0035] During preheating before welding, the preheating temperature of welding is T=1440Pcm-392, where Pcm is the cold crack sensitivity coefficient of the steel plate to be welded, and the preheating temperature is 130 ℃.

[0036] A ceramic liner is attached to the back of the weld root gap after preheating to prevent the occurrence of molten pool holes during welding. Weld from the front.

[0037] The formal welding was carried out using metal-arc gas shielded welding with a welding current of 220A, a voltage of 23V, a welding speed of 300mm / min, and a welding heat input of 10.12kJ / cm.

[0038] Post-weld heat treatment: After welding is completed, the steel plate is heated to 160°C, wrapped with asbestos for 60 minutes, and then cooled to room temperature in air to allow the hydrogen in the weld to diffuse and eliminate the diffusible hydrogen content in the weld joint.

[0039] After welding using the above method, the weld seam of the 1500MPa yield strength ultra-high-strength steel for engineering machinery was well-formed. Mechanical property testing revealed that the weld joint had a tensile strength of 1032MPa, no cracks were observed during bending, and the weld had low-temperature impact strengths of 46.6J, 45.1J, and 47.3J at -40°C, meeting operational requirements.

[0040] Example 2

[0041] A 7mm thick ultra-high strength steel for engineering machinery with a yield strength of 1500MPa is selected for welding. The chemical composition of the ultra-high strength steel is as follows in percentage by weight: C: 0.20%-0.30%; Si: 0.20%-0.40%; Mn: 0.90%-1.20%; Ni: 0.50%-1.20%; Mo: 0.50%-0.80%; Nb: 0.02%-0.05%; V: 0.03%-0.08%; Ti: 0.001%-0.02%; S≤0.002%; P≤0.008%; Cr: 0.40%-1.00%; the remainder is Fe and unavoidable impurity elements.

[0042] Selection and processing of steel plate weld groove: a single Y-shaped groove is made for 7mm thick steel plate, the groove angle (α) is 60°±2°, the blunt edge height p is 2mm, and the root gap b is 2mm.

[0043] For the selection of welding materials, solid welding wire with a diameter of 1.2 mm is selected. The chemical composition of the welding wire is as follows by weight percentage: C: 0.08%-0.10%; Si: 0.70%-0.90%; Mn: 1.60%-1.80%; Ni: 2.10%-2.30%; Mo: 0.50%-0.70%; P≤0.009%; Cr: 0.30%-0.50%.

[0044] Shielding gas ratio: CO2 gas shielded welding uses a mixed gas of 80% Ar and 20% CO2. The shielding gas flow rate during welding is 22 L / min, of which the purity of Ar is 99.99% and the purity of CO2 is 99.99%.

[0045] When pre-treating the steel plate before welding, it is required to measure the magnetism of the test steel plate before welding. If it is magnetic, it needs to be demagnetized using a demagnetizer. The area within 20 mm near the welding groove should be polished clean to remove impurities such as oxide scale.

[0046] The steel plates are fixed by spot welding. Before welding, the grooves of the two steel plates are placed opposite each other, leaving a 2mm gap at the root. Spot welding is used to facilitate subsequent welding. To ensure the quality of the steel plate welds, steel plates of the same material are used to strike the arc at the starting point of welding, and are fixed by spot welding. The welding point interval is 50mm.

[0047] During preheating before welding, the preheating temperature of welding is T=1440Pcm-392, where Pcm is the cold crack sensitivity coefficient of the steel plate to be welded, and the preheating temperature is 130 ℃.

[0048] A ceramic liner is attached to the back of the weld root gap after preheating to prevent the occurrence of molten pool holes during welding. Weld from the front.

[0049] The formal welding was carried out using gas metal shielded welding with a welding current of 240A, a voltage of 24V, a welding speed of 400mm / min and a welding heat input of 8.65kJ / cm.

[0050] Post-weld heat treatment: After welding is completed, the steel plate is heated to 160°C, wrapped with asbestos for 60 minutes, and then cooled to room temperature in air to allow the hydrogen in the weld to diffuse and eliminate the diffusible hydrogen content in the weld joint.

[0051] After welding using the above method, the weld seam of the 1500MPa yield strength ultra-high-strength steel for engineering machinery was well-formed. Mechanical property testing revealed that the weld joint had a tensile strength of 1069MPa, no cracks were observed during bending, and the weld had low-temperature impact strengths of 49.6J, 47.3J, and 48.5J at -40°C, meeting operational requirements.

[0052] Example 3

[0053] A 10 mm thick ultra-high strength steel with a yield strength of 1500 MPa for engineering machinery is selected for welding. The chemical composition of the ultra-high strength steel is as follows in percentage by weight: C: 0.20%-0.30%; Si: 0.20%-0.40%; Mn: 0.90%-1.20%; Ni: 0.50%-1.20%; Mo: 0.50%-0.80%; Nb: 0.02%-0.05%; V: 0.03%-0.08%; Ti: 0.001%-0.02%; S≤0.002%; P≤0.008%; Cr: 0.40%-1.00%; the remainder is Fe and unavoidable impurity elements.

[0054] Selection and processing of steel plate weld groove: a single Y-shaped groove is made for a 10mm thick steel plate, the groove angle (α) is 60°±2°, the blunt edge height p is 2mm, and the root gap b is 2mm.

[0055] For the selection of welding materials, a solid welding wire with a diameter of 1.2 mm with limited composition is selected. The chemical composition of the welding wire is as follows by weight percentage: C: 0.08%-0.10%; Si: 0.70%-0.90%; Mn: 1.60%-1.80%; Ni: 2.10%-2.30%; Mo: 0.50%-0.70%; P≤0.009%; Cr: 0.30%-0.50%.

[0056] Shielding gas ratio: CO2 gas shielded welding uses a mixed gas of 80% Ar and 20% CO2. The shielding gas flow rate during welding is 22 L / min, of which the purity of Ar is 99.99% and the purity of CO2 is 99.99%.

[0057] During the pretreatment of steel plates before welding, the magnetic properties of the test steel plates must be measured before welding. If there is magnetism, a demagnetizer must be used to demagnetize the plates. The area within 20 mm near the welding groove must be polished clean to remove impurities such as oxide scale.

[0058] The steel plates are fixed by spot welding. Before welding, the grooves of the two steel plates are placed opposite each other, leaving a 2mm gap at the root. Spot welding is used to facilitate subsequent welding. To ensure the quality of the steel plate welds, steel plates of the same material are used to strike the arc at the starting point of welding, and are fixed by spot welding. The welding point interval is 50mm.

[0059] During preheating before welding, the preheating temperature of welding is T=1440Pcm-392, where Pcm is the cold crack sensitivity coefficient of the steel plate to be welded, and the preheating temperature is 130 ℃.

[0060] A ceramic liner is attached to the back of the weld root gap after preheating to prevent the occurrence of molten pool holes during welding. Weld from the front.

[0061] The formal welding was carried out using metal-arc gas shielded welding with a welding current of 220A, a voltage of 23V, a welding speed of 300mm / min, and a welding heat input of 10.12kJ / cm.

[0062] Post-weld heat treatment: After welding is completed, the steel plate is heated to 160°C, wrapped with asbestos for 60 minutes, and then cooled to room temperature in air to allow the hydrogen in the weld to diffuse and eliminate the diffusible hydrogen content in the weld joint.

[0063] After welding using the above method, the weld seam of the 1500MPa yield strength ultra-high-strength steel for engineering machinery was well-formed. Mechanical property testing revealed that the weld joint had a tensile strength of 1019MPa, no cracks were observed during bending, and the weld had low-temperature impact strengths of 43.1J, 42.3J, and 44.6J at -40°C, meeting operational requirements.

[0064] Example 4

[0065] A 10 mm thick ultra-high strength steel with a yield strength of 1500 MPa for engineering machinery is selected for welding. The chemical composition of the ultra-high strength steel is as follows in percentage by weight: C: 0.20%-0.30%; Si: 0.20%-0.40%; Mn: 0.90%-1.20%; Ni: 0.50%-1.20%; Mo: 0.50%-0.80%; Nb: 0.02%-0.05%; V: 0.03%-0.08%; Ti: 0.001%-0.02%; S≤0.002%; P≤0.008%; Cr: 0.40%-1.00%; the remainder is Fe and unavoidable impurity elements.

[0066] Selection and processing of steel plate weld groove: a single Y-shaped groove is made for 7mm thick steel plate, the groove angle (α) is 60°±2°, the blunt edge height p is 2mm, and the root gap b is 2mm.

[0067] For the selection of welding materials, solid welding wire with a diameter of 1.2 mm is selected. The chemical composition of the welding wire is as follows by weight percentage: C: 0.08%-0.10%; Si: 0.70%-0.90%; Mn: 1.60%-1.80%; Ni: 2.10%-2.30%; Mo: 0.50%-0.70%; P≤0.009%; Cr: 0.30%-0.50%.

[0068] Shielding gas ratio: CO2 gas shielded welding uses a mixed gas of 80% Ar and 20% CO2. The shielding gas flow rate during welding is 22 L / min, of which the purity of Ar is 99.99% and the purity of CO2 is 99.99%.

[0069] When pre-treating the steel plate before welding, it is required to measure the magnetism of the test steel plate before welding. If it is magnetic, it needs to be demagnetized using a demagnetizer. The area within 20 mm near the welding groove should be polished clean to remove impurities such as oxide scale.

[0070] The steel plates are fixed by spot welding. Before welding, the grooves of the two steel plates are placed opposite each other, leaving a 2mm gap at the root. Spot welding is used to facilitate subsequent welding. To ensure the quality of the steel plate welds, steel plates of the same material are used to strike the arc at the starting point of welding, and are fixed by spot welding. The welding point interval is 50mm.

[0071] During preheating before welding, the preheating temperature of welding is T=1440Pcm-392, where Pcm is the cold crack sensitivity coefficient of the steel plate to be welded, and the preheating temperature is 130 ℃.

[0072] A ceramic liner is attached to the back of the weld root gap after preheating to prevent the occurrence of molten pool holes during welding. Weld from the front.

[0073] The formal welding was carried out using gas metal shielded welding with a welding current of 240A, a voltage of 24V, a welding speed of 400mm / min and a welding heat input of 8.65kJ / cm.

[0074] Post-weld heat treatment: After welding is completed, the steel plate is heated to 160°C, wrapped with asbestos for 60 minutes, and then cooled to room temperature in air to allow the hydrogen in the weld to diffuse and eliminate the diffusible hydrogen content in the weld joint.

[0075] After welding using the above method, the weld seam of the 1500MPa yield strength ultra-high-strength steel for engineering machinery was well-formed. Mechanical property testing revealed that the weld joint had a tensile strength of 1036MPa, no cracks were observed during bending, and the weld had low-temperature impact strengths of 47.3J, 44.9J, and 46.2J at -40°C, meeting operational requirements.

[0076] Comparative Example 1

[0077] A 7 mm thick ultra-high strength steel with a yield strength of 1500 MPa for engineering machinery is selected for welding. The chemical composition of the ultra-high strength steel is as follows in percentage by weight: C: 0.20%-0.30%; Si: 0.20%-0.40%; Mn: 0.90%-1.20%; Ni: 0.50%-1.20%; Mo: 0.50%-0.80%; Nb: 0.02%-0.05%; V: 0.03%-0.08%; Ti: 0.001%-0.02%; S≤0.002%; P≤0.008%; Cr: 0.40%-1.00%; the remainder is Fe and unavoidable impurity elements.

[0078] Selection and processing of steel plate weld groove: a single Y-shaped groove is made for 7mm thick steel plate, the groove angle α is 60°±2°, the blunt edge height p is 2mm, and the root gap b is 2mm.

[0079] For the selection of welding materials, solid welding wire with a diameter of 1.2 mm is selected. The chemical composition of the welding wire is as follows by weight percentage: C: 0.08%-0.10%; Si: 0.70%-0.90%; Mn: 1.60%-1.80%; Ni: 2.10%-2.30%; Mo: 0.50%-0.70%; P≤0.009%; Cr: 0.30%-0.50%.

[0080] Shielding gas ratio: CO2 gas shielded welding uses a mixed gas of 80% Ar and 20% CO2. The shielding gas flow rate during welding is 22 L / min, of which the purity of Ar is 99.99% and the purity of CO2 is 99.99%.

[0081] When pre-treating the steel plate before welding, it is required to measure the magnetism of the test steel plate before welding. If it is magnetic, it needs to be demagnetized using a demagnetizer. The area within 20 mm near the welding groove should be polished clean to remove impurities such as oxide scale.

[0082] The steel plates are fixed by spot welding. Before welding, the grooves of the two steel plates are placed opposite each other, leaving a 2mm gap at the root. Spot welding is used to facilitate subsequent welding. To ensure the quality of the steel plate welds, steel plates of the same material are used to strike the arc at the starting point of welding, and are fixed by spot welding. The welding point interval is 50mm.

[0083] During preheating before welding, the preheating temperature of welding is T=1440Pcm-392, where Pcm is the cold crack sensitivity coefficient of the steel plate to be welded, and the preheating temperature is 130 ℃.

[0084] A ceramic liner is attached to the back of the weld root gap after preheating to prevent the occurrence of molten pool holes during welding. Weld from the front.

[0085] The formal welding was carried out using gas metal shielded welding with a welding current of 230A, a voltage of 23V, a welding speed of 200mm / min and a welding heat input of 15.87kJ / cm.

[0086] Post-weld heat treatment: After welding is completed, the steel plate is heated to 160°C, wrapped with asbestos for 60 minutes, and then cooled to room temperature in air to allow the hydrogen in the weld to diffuse and eliminate the diffusible hydrogen content in the weld joint.

[0087] After welding using the above method, the weld seam of the 1500MPa yield strength ultra-high-strength steel for engineering machinery was well-formed. Mechanical property testing revealed a tensile strength of 946MPa for the welded joint, no cracking during bending, and low-temperature impact strengths of the weld at -40°C of 26.4J, 27.5J, and 24.5J. Compared with Example 2, the higher heat input resulted in a greater amount of coarse Widmanstätten ferrite growing from the austenite grain boundaries into the grains at the center of the weld, while the heat-affected zone consisted primarily of lath bainite. This structural characteristic resulted in a simultaneous decrease in both weld strength and impact energy.

[0088] Table 1 Mechanical properties of welded joints of Examples and Comparative Examples (tensile properties are tested at room temperature)

[0089]

[0090] The above examples and comparative examples show that the welding method of ultra-high-strength steel for engineering machinery with a yield strength of 1500 MPa described in the present invention, through Example 1, Example 2, Example 3 and Example 4, obtains weld joints with excellent comprehensive mechanical properties, and the weld has an impact energy KV2 ≥ 45J at -40°C and a tensile strength Rm ≥ 1030 MPa.

[0091] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A welding method for ultra-high strength steel for engineering machinery with a yield strength of 1500 MPa, characterized in that: The chemical composition of the ultra-high strength steel is as follows by weight percentage: C: 0.20%-0.30%; Si: 0.20%-0.40%; Mn: 0.90%-1.20%; Ni: 0.50%-1.20%; Mo: 0.50%-0.80%; Nb: 0.02%-0.05%; V: 0.03%-0.08%; Ti: 0.001%-0.02%; S≤0.002%; P≤0.008%; Cr: 0.40%-1.00%; the balance is Fe and unavoidable impurity elements. The welding steps specifically include: (1) Welding groove selection and processing: For steel plates with a thickness of 7mm-10mm, a Y-shaped groove is opened with a groove angle α of 60°±2°, a blunt edge height p of 2mm, and a root gap b of 1.5mm~2mm; (2) Selection of welding materials; (3) Gas shielded welding gas ratio; (4) Pretreatment of steel plates before welding; (5) The steel plates are fixed by spot welding; (6) Preheating before welding; (7) A ceramic liner is attached to the back of the weld root gap; (8) Formal welding; (9) Post-weld heat treatment.

2. The welding method of ultra-high strength steel for engineering machinery with a yield strength of 1500 MPa according to claim 1, characterized in that: In the selection of the welding materials, the chemical composition of the welding wire is as follows by weight percentage: C: 0.08%-0.10%; Si: 0.70%-0.90%; Mn: 1.60%-1.80%; Ni: 2.10%-2.30%; Mo: 0.50%-0.70%; P≤0.009%; Cr: 0.30%-0.50%, and the welding wire diameter is 1.0~1.2 mm.

3. The welding method of ultra-high strength steel for engineering machinery with a yield strength of 1500 MPa according to claim 1, characterized in that: In the gas shielded welding shielding gas ratio, CO2 gas shielded welding uses a mixed gas of 70~80% Ar and 20~30% CO2 as the shielding gas, wherein the purity of Ar is 99.99% and the purity of CO2 is 99.99%; during welding, the shielding gas flow rate is 22L / min~24L / min.

4. The welding method of ultra-high strength steel for engineering machinery with a yield strength of 1500 MPa according to claim 1, characterized in that: The steel plate pretreatment before welding is specifically as follows: the magnetic properties of the test steel plate are measured before welding, if there is magnetism, it is demagnetized using a demagnetizer, and the area within 20 mm near the welding groove is polished clean to remove impurities.

5. The welding method of ultra-high strength steel for engineering machinery with a yield strength of 1500 MPa according to claim 1, characterized in that: When the steel plate group is fixed by spot welding, the grooves of the two steel plates are placed relative to each other before welding and fixed by spot welding; steel plates of the same material are used to strike an arc at the position where welding begins, and are fixed by spot welding, with the welding point interval being no greater than 60 mm.

6. The welding method of ultra-high strength steel for engineering machinery with a yield strength of 1500 MPa according to claim 1, characterized in that: During the preheating before welding, the preheating temperature of welding is T=1440Pcm-392, where Pcm is the cold crack sensitivity coefficient of the steel plate to be welded.

7. The welding method of ultra-high strength steel for engineering machinery with a yield strength of 1500 MPa according to claim 1, characterized in that: When the ceramic liner is affixed to the back of the weld root gap, the ceramic liner is affixed to the back of the root gap after preheating the steel plate, and welding is performed from the front side, forming both sides at one time, and the weld on the back side is full.

8. The welding method of ultra-high strength steel for engineering machinery with a yield strength of 1500 MPa according to claim 1, characterized in that: During the formal welding, metal-arc gas shielded welding is adopted, the welding current is 220A to 240A, the voltage is 23V to 24V, and the welding speed is 300mm / min to 400mm / min.

9. The welding method of ultra-high strength steel for engineering machinery with a yield strength of 1500 MPa according to claim 1, characterized in that: During the post-weld heat treatment, the welded steel plate is heated to 150° C. to 160° C., wrapped with asbestos for 60 to 80 minutes, and then cooled to room temperature in air to eliminate the diffusible hydrogen content in the weld joint.

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