Low temperature gas shielded welding wire and method of welding same

Abstract

The application discloses a low-temperature gas shielded welding wire, and chemical components and mass percentages of welding materials of the low-temperature gas shielded welding wire are as follows: C is less than or equal to 0.07%, Si is less than or equal to 0.6%, Mn is less than or equal to 1.6%, P is less than or equal to 0.010%, S is less than or equal to 0.008%, Cr is less than or equal to 1.0%, Ni is less than or equal to 4.0%, Cu is less than or equal to 0.10%, Mo is less than or equal to 0.5%, Ti is less than or equal to 0.10%, Al is less than or equal to 0.08%, V is less than or equal to 0.05%, O is less than or equal to 0.006%, As is less than or equal to 0.010%, Sn is less than or equal to 0.010%, Sb is less than or equal to 0.005%, Ca is less than or equal to 0.01%, and the total amount of other elements except Fe should be less than or equal to 0.5%. The low-temperature gas shielded welding wire has the advantages that the welding wire has excellent impact toughness in a low-temperature environment of-40 DEG C / -60 DEG C under a large-current high-heat-input welding process.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical technology, and particularly relates to a low-temperature gas shielded welding wire and its welding method. Background Technology

[0002] In the field of engineering machinery manufacturing, gas shielded welding has become the mainstream welding process due to its advantages such as high welding efficiency, good weld formation, and high degree of automation. However, welding operations in low-temperature environments face a dual challenge: on the one hand, to improve construction efficiency, users urgently need welding materials that can adapt to high-current, high-heat-input welding processes to reduce the number of welding layers and shorten the construction cycle; on the other hand, low-temperature environments place extremely high demands on the low-temperature toughness of welded joints. Welded joints must maintain sufficient impact resistance at extreme low temperatures of -40℃ or even -60℃ to avoid equipment failure and safety accidents caused by low-temperature brittle fracture. Therefore, developing a gas shielded welding wire that combines high heat input adaptability with excellent low-temperature toughness has become a key technical problem that the engineering machinery industry urgently needs to solve.

[0003] However, conventional gas-shielded welding wires currently on the market face many insurmountable technical bottlenecks when dealing with high heat input welding requirements in low-temperature environments: Firstly, high heat input and low-temperature toughness cannot be simultaneously achieved: the composition design of existing gas-shielded welding materials is mostly based on conventional welding conditions, making it difficult to meet the requirements of both high heat input welding processes and low-temperature toughness. When high current and high heat input welding are used, the grain size of the weld metal will significantly coarsen, leading to a sharp decrease in low-temperature toughness. If heat input is restricted to ensure low-temperature toughness, welding efficiency will be reduced, failing to meet the high-efficiency construction needs of the engineering machinery industry. This performance contradiction severely restricts the manufacturing efficiency and service safety of mining equipment in low-temperature environments.

[0004] Secondly, the range of welding process parameters is limited: Taking the widely used 1.2mm diameter gas-shielded welding wire as an example, its conventional welding current upper limit is about 350A, which is close to the parameter limit in engineering applications. If the welding current is further increased, problems such as wire burn-through, increased spatter, and poor weld formation are likely to occur, making it impossible to achieve stable and efficient welding operations. In scenarios such as welding thick plates and large structural components in low-temperature environments, the demand for welding efficiency is even more urgent, and the existing process parameter range of welding wires can hardly meet the actual production needs.

[0005] Third, insufficient low-temperature toughness: Although some existing gas-shielded welding wires claim to have certain low-temperature performance, their impact toughness often fails to meet engineering application requirements in extreme low-temperature environments of -40℃ / -60℃. In low-temperature environments, brittle phases in the weld metal are prone to crack propagation, leading to premature failure of the welded joint and seriously affecting the service life and reliability of engineering machinery. Summary of the Invention

[0006] The purpose of this invention is to solve the problems of insufficient adaptability to high heat input and low temperature toughness of existing gas-shielded welding materials. It provides a low-temperature gas-shielded welding wire that improves low-temperature toughness by precisely controlling the Ni content, reducing the C content to reduce the precipitation of brittle phases, and appropriately adding other trace elements to optimize welding process performance. This allows the welding wire to maintain excellent impact toughness in low-temperature environments of -40℃ / -60℃ even under high current and high heat input welding processes.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A low-temperature gas-shielded welding wire is produced by drawing high-heat-input low-temperature gas-shielded welding wire rods. The composition of the welding material includes Ti, Si, Mn, Cr, Ni, Cu, Mo, and microalloying elements in specific proportions, while strictly controlling harmful elements such as As, Sn, and Sb. Through precise control of the composition range, the mechanism of action of impurity elements, the microstructure and properties of the deposited metal, and the strengthening mechanism of the deposited metal, the performance of the weld metal is optimally optimized. It also meets the requirements of high-current, high-heat-input welding processes and exhibits excellent impact resistance at -40℃ / -60℃. The chemical composition of the welding material, by weight percentage, includes: C≤0.07%, Si≤0.6%, Mn≤1.6%, P≤0.010%, S≤0.008%, Cr≤1.0%, Ni≤4.0%, Cu≤0.10%, Mo≤0.5%, Ti≤0.10%, Al≤0.08%, V≤0.05%, O≤0.006%, As≤0.010%, Sn≤0.010%, Sb≤0.005%, Ca≤0.01%, and the total amount of other elements except Fe should not exceed 0.5%.

[0008] The functions and mechanisms of the above components are as follows: Ti is a key element in high-current, high-heat-input welding processes, playing a role in carbon fixation and nitrogen fixation. TiN pins austenite grain boundaries, preventing drastic grain growth under high-current, high-heat-input conditions, thereby improving low-temperature impact toughness after welding.

[0009] C is one of the most powerful alloying elements, which can improve the tensile strength and hardness of welds. However, under high current and high heat input welding processes, excessive C content will significantly increase the sensitivity to cold cracking and promote the formation of brittle structures. Therefore, this invention implements ultra-low carbon control and uses other alloying elements to compensate for the strength loss caused by C reduction, and comprehensively controls C to ≤0.07%.

[0010] Mn is a solid solution strengthening and austenite stabilizing element that promotes the formation of acicular ferrite. However, excessive Mn content can also increase cold cracking sensitivity. Considering the overall weld strength, Mn should be controlled to ≤1.6%.

[0011] During welding, silicon (Si) forms low-density silicate slag that floats to the weld surface, reducing oxide inclusions and resulting in purer weld metal. Si compounds also stabilize the arc, improving welding processability. Furthermore, Si atoms can form interstitial solid solutions, significantly increasing weld strength and hardness. However, excessive Si can severely hinder dislocation movement due to solid solution strengthening, leading to weld embrittlement and promoting the formation of brittle phases such as proeutectoid ferrite and lamellar ferrite. Considering all factors, Si content should be controlled to ≤0.6%. Exceeding 0.6% significantly increases the weld's embrittlement tendency and noticeably reduces low-temperature impact performance at -60℃.

[0012] The addition of chromium (Cr) can significantly improve weld strength, but excessive Cr content will drastically reduce the low-temperature toughness and molten pool fluidity of the weld after welding, hindering the removal of gases and inclusions and affecting the weld metallurgical quality. Therefore, considering all factors, Cr should be controlled to ≤1.0%.

[0013] Ni can refine grain size and improve the low-temperature impact toughness of welds. Due to the requirements of high-current, high-heat-input welding processes, and considering the loss of Ni during welding and ensuring low-temperature toughness at -60℃, this patent requires a certain increase in Ni content. Taking into account the cost of welding wire, the final Ni content is controlled to be ≤4.0%.

[0014] Mo can expand the bainite region, increase the content of acicular ferrite in the weld, and improve the strength and toughness of the weld. However, Mo is expensive, so Mo is controlled to be ≤0.5%.

[0015] Al, as a strong deoxidizing element, can refine grains to a certain extent. However, excessive addition can easily produce inclusions such as aluminum oxide, which can embrittle the weld and severely reduce its ductility and toughness. It can also increase the instability of the arc and increase spatter. Therefore, Al should be controlled to be ≤0.08%.

[0016] Cu (Cu) has a solid solution strengthening effect, which can improve the strength and hardness of weld metal, but it will reduce the ductility and toughness of the weld metal. When Cu atoms dissolve into the ferrite lattice, they cause lattice distortion, thereby increasing the strength and hardness of the steel. Therefore, Cu content should be controlled to be ≤0.10%.

[0017] V is a strong carbide-forming element. During high-temperature austenitization, it can effectively pin the austenite grain boundaries, preventing austenite grain growth and improving weld strength and hardness. However, it also increases hardenability and reduces weld toughness to some extent. Therefore, V should be controlled to be ≤0.05%.

[0018] S and P: S forms a low-melting-point eutectic with Fe, leading to hot brittleness, reducing the plasticity and impact toughness of the weld, and worsening atmospheric corrosion resistance. P has a strong segregation effect; excessive P content easily causes hot cracking. Phosphates themselves are hard and brittle, easily causing cold brittleness in steel, reducing its plasticity and toughness. Therefore, P ≤ 0.010% and S ≤ 0.008% should be controlled.

[0019] Other harmful elements such as As, Sn, and Sb differ significantly from Fe in atomic size. During welding thermal cycling, they tend to segregate towards grain boundaries, weakening the intergranular bonding force and making cracks more likely to propagate at these grain boundaries. This significantly reduces the low-temperature impact toughness of the weld metal. These hazards are further aggravated under high-current, high-heat-input welding processes. Therefore, it is necessary to strictly control the above-mentioned harmful elements: As ≤ 0.010, Sn ≤ 0.010, and Sb ≤ 0.005.

[0020] Furthermore, the gas-shielded welding wire is obtained from wire rod through pickling, rough drawing, annealing, and fine drawing. Pickling removes oxide scale and surface impurities, rough drawing yields φ3.2mm wire rod, and after full annealing at 1050℃±20℃, it is finely drawn to φ1.2mm welding wire.

[0021] To further achieve the objectives of this invention, a welding method for low-temperature gas-shielded welding wire is also provided, specifically including: welding current of 350~450A, welding voltage of 30~35V, welding speed of 25~35cm / min, heat input of 20~40kJ / cm, and interpass temperature of 200~250℃.

[0022] Compared with the prior art, the advantages of the technical solution of the present invention are as follows: (1) This invention increases the amount of cladding in a single weld, reduces the number of welding passes, improves welding efficiency, and shortens the construction period by ensuring that the welding current, voltage and other parameters are within the set process range and the welding speed is as close as possible to the lower limit. (2) The present invention ensures that the interpass temperature of the welding is within the set process range, avoids the formation of a large amount of hardened structure in the weld due to the interpass temperature being too low or after complete cooling, and improves the low-temperature impact toughness at -40℃ / -60℃ while meeting the construction requirements of high current and high heat input. Detailed Implementation Example 1

[0023] To make the present invention clearer, a low-temperature gas-shielded welding wire and its welding method are further described below. The specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention.

[0024] The composition of the low-temperature gas-shielded welding wire in this embodiment is configured by mass percentage as follows: C: 0.05%, Si: 0.3%, Mn: 1.2%, P: 0.008%, S: 0.006%, Cr: 0.5%, Ni: 2.0%, Cu: 0.05%, Mo: 0.2%, Ti: 0.05%, Al: 0.04%, V: 0.02%, O: 0.003%, As: 0.005%, Sn: 0.005%, Sb: 0.002%, Ca: 0.005%, with the remainder being Fe and unavoidable impurities. The total amount of all elements except Fe is 0.3%, which meets the composition requirements.

[0025] The above-mentioned gas-shielded welding wire is prepared as follows: (1) Raw material pretreatment: Select the welding wire rod with the above composition, first pickle it, use hydrochloric acid solution to remove the oxide scale and impurities on the surface of the rod, the pickling time is 30 min, then rinse it with clean water, and dry it at 80℃ for 2 h to ensure that there is no residual moisture and acid on the surface of the rod.

[0026] (2) Rough drawing: The dried wire rod is fed into the drawing production line and gradually rough drawn to φ3.2mm through multiple dies. During the drawing process, the surface reduction rate of each pass is controlled between 15% and 20% to ensure uniform deformation of the wire rod.

[0027] (3) Annealing treatment: The coarsely drawn wire rod is placed in an annealing furnace and annealed at 1050℃±20℃ for 1 hour. Then it is cooled to room temperature with the furnace to eliminate the internal stress generated during the drawing process and improve the metallographic structure of the wire rod.

[0028] (4) Fine drawing: The annealed wire rod is fed back into the drawing production line for fine drawing to produce wire, and finally a finished welding wire with a diameter of 1.2mm is obtained. During the drawing process, the precision of the mold is strictly controlled to ensure that the diameter error of the welding wire is within ±0.02mm.

[0029] For welding, 500MPa grade engineering machinery steel with a plate thickness of 20mm is selected. The welding process parameters are set as follows: welding current 350A, welding voltage 30V, welding speed 35cm / min, calculated linear energy of 20.57kJ / cm, and interpass temperature controlled at 200℃.

[0030] After welding, the welded joint was subjected to performance testing. The tensile test results showed that the tensile strength of the deposited metal rod was 590 MPa; in the low-temperature impact test, it achieved 138 J at -40℃ and 93 J at -60℃, demonstrating good low-temperature toughness; metallographic observation revealed that the weld and heat-affected zone had uniform microstructure, without defects such as cracks and porosity, indicating excellent welding quality. Example 2

[0031] The composition of the low-temperature gas-shielded welding wire in this embodiment is configured by mass percentage as follows: C: 0.07%, Si: 0.6%, Mn: 1.6%, P: 0.010%, S: 0.008%, Cr: 1.0%, Ni: 4.0%, Cu: 0.10%, Mo: 0.5%, Ti: 0.10%, Al: 0.08%, V: 0.05%, O: 0.006%, As: 0.010%, Sn: 0.010%, Sb: 0.005%, Ca: 0.01%, with the remainder being Fe and unavoidable impurities. The total amount of other elements except Fe is 0.45%, which meets the composition requirements.

[0032] The above-mentioned gas-shielded welding wire is prepared as follows: (1) Raw material pretreatment: The welding wire rod with the above composition is pickled, soaked in sulfuric acid solution for 40 minutes to remove oxide scale and surface impurities, then rinsed with high pressure water, and dried in a 90℃ drying oven for 1.5 hours to ensure that the surface of the wire rod is clean and dry.

[0033] (2) Rough drawing: The dried wire rod is fed into the drawing production line and rough drawn to φ3.2mm through multiple dies. The surface reduction rate of each pass is controlled at about 18% to ensure that the wire rod does not crack during the drawing process.

[0034] (3) Annealing treatment: The coarsely drawn wire rod is placed in an annealing furnace and annealed at 1030℃ for 1 hour. Then it is slowly cooled to room temperature to effectively refine the wire rod grains and improve its plasticity and toughness.

[0035] (4) Precision drawing: The annealed wire rod is precision drawn and drawn into a finished welding wire with a diameter of 1.2mm through a high-precision die. The diameter of the welding wire is monitored throughout the process to ensure that the dimensional accuracy meets the standard.

[0036] For welding, 550MPa grade engineering machinery steel with a plate thickness of 20mm is selected. The welding process parameters are: welding current 450A, welding voltage 35V, welding speed 25cm / min, calculated line energy of 37.8kJ / cm, and interpass temperature controlled at 250℃.

[0037] After welding, various performance tests were conducted on the welded joint. Tensile test results showed that the tensile strength of the deposited metal rod was 603 MPa; in the low-temperature impact test, the impact strength was 149 J at -40℃ and 110 J at -60℃, indicating good low-temperature toughness; non-destructive testing showed that the welded joint had no internal defects, the weld formation was aesthetically pleasing, and it fully met the welding quality requirements for steel used in engineering machinery. Example 3

[0038] The composition of the low-temperature gas-shielded welding wire in this embodiment is configured by mass percentage as follows: C: 0.06%, Si: 0.4%, Mn: 1.4%, P: 0.009%, S: 0.007%, Cr: 0.8%, Ni: 3.0%, Cu: 0.08%, Mo: 0.3%, Ti: 0.07%, Al: 0.06%, V: 0.03%, O: 0.004%, As: 0.008%, Sn: 0.007%, Sb: 0.003%, Ca: 0.007%, with the remainder being Fe and unavoidable impurities. The total amount of other elements except Fe is 0.38%, which meets the composition requirements.

[0039] The above-mentioned gas-shielded welding wire is prepared as follows: (1) Raw material pretreatment: The welding wire rod of this composition is pickled and soaked in a mixture of hydrochloric acid and sulfuric acid for 35 minutes to remove the surface oxide scale and impurities. After rinsing, it is dried at 85°C for 1.8 hours to ensure that there are no residual contaminants on the surface of the wire rod.

[0040] (2) Rough drawing: The dried wire rod is fed into the drawing production line and rough drawn to φ3.2mm. The surface reduction rate of each pass is controlled between 16% and 19% to ensure the stability of the wire rod drawing process.

[0041] (3) Annealing treatment: The rough drawn wire rod is placed in an annealing furnace and annealed at 1070℃ for 1 hour. Then it is cooled with the furnace to optimize the metallographic structure of the wire rod and fully release the internal stress.

[0042] (4) Fine drawing: The annealed wire rod is finely drawn to produce a finished welding wire with a diameter of 1.2mm. The drawing speed and die wear are strictly controlled to ensure the stable quality of the welding wire.

[0043] For welding, 520MPa grade engineering machinery steel with a plate thickness of 20mm is selected. The welding process parameters are set as follows: welding current 400A, welding voltage 32V, welding speed 30cm / min, heat input 25.6kJ / cm, and interpass temperature controlled at 220℃.

[0044] After welding, the welded joint was subjected to performance tests. Tensile tests showed that the tensile strength of the deposited metal rod was 600 MPa; in the low-temperature impact test, it achieved 145 J of impact at -40℃ and 100 J of impact at -60℃, demonstrating excellent low-temperature toughness; metallographic analysis showed that the weld structure was dense, the softening degree of the heat-affected zone was low, and the welded joint had excellent comprehensive performance, which could meet the requirements of engineering machinery in low-temperature environments.

[0045] In summary, after adopting the gas-shielded welding wire and welding process of the present invention, the tensile strength of the deposited metal rod is 590~603MPa, and the impact strength at -40℃ is 149J, 145J, and 138J, with an average value of not less than 100J; at the same time, the impact strength at -60℃ is 110J, 100J, and 93J, with an average value of not less than 80J, which meets the application requirements.

[0046] In addition to the embodiments described above, the present invention may have other implementations. All technical solutions formed by equivalent substitution or equivalent transformation fall within the protection scope claimed by the present invention.

Claims

1. A low-temperature gas-shielded welding wire, characterized in that: The chemical composition and mass percentage of the welding material include: C≤0.07%, Si≤0.6%, Mn≤1.6%, P≤0.010%, S≤0.008%, Cr≤1.0%, Ni≤4.0%, Cu≤0.10%, Mo≤0.5%, Ti≤0.10%, Al≤0.08%, V≤0.05%, O≤0.006%, As≤0.010%, Sn≤0.010%, Sb≤0.005%, Ca≤0.01%, and the total amount of other elements except Fe should not exceed 0.5%.

2. The low-temperature gas-shielded welding wire according to claim 1, characterized in that: The gas-shielded welding wire is obtained from wire rod through pickling, rough drawing, annealing, and fine drawing. Pickling removes oxide scale and surface impurities, rough drawing yields φ3.2mm wire rod, and after full annealing at 1050℃±20℃, it is finely drawn to φ1.2mm welding wire.

3. A welding method for the low-temperature gas-shielded welding wire as described in claim 2, characterized in that: Welding current 350~450A, welding voltage 30~35V, welding speed 25~35cm / min, linear energy 20~40kJ / cm, interpass temperature 200~250℃.

4. The welding method of the low-temperature gas-shielded welding wire according to claim 3, characterized in that: The welding process parameters were set as follows: welding current 350A, welding voltage 30V, welding speed 35cm / min, calculated linear energy of 20.57kJ / cm, and interpass temperature controlled at 200℃. The low-temperature impact performance after welding with the above welding parameters was 138J at -40℃ and 93J at -60℃.

5. The welding method of the low-temperature gas-shielded welding wire according to claim 3, characterized in that: The welding process parameters were set as follows: welding current 450A, welding voltage 35V, welding speed 25cm / min, calculated line energy 37.8kJ / cm, and interpass temperature controlled at 250℃. The low-temperature impact performance after welding with the above welding parameters was 149J at -40℃ and 110J at -60℃.

6. The welding method of the low-temperature gas-shielded welding wire according to claim 3, characterized in that: The welding process parameters were set as follows: welding current 400A, welding voltage 32V, welding speed 30cm / min, linear energy 25.6kJ / cm, and interpass temperature controlled at 220℃. The low-temperature impact performance after welding with the above welding parameters was 145J at -40℃ and 100J at -60℃.