Preparation and welding method of solid gas shielded welding wire for weathering steel

Abstract

This invention discloses a method for preparing solid gas-shielded welding wire for weathering steel, comprising: S1, smelting raw materials into steel and casting them into square billets with a side length of 150mm; S2, heating the square billets in a heating furnace at 600℃ and holding them at that temperature for 4 hours, then feeding them into a wire rod rolling mill and rolling them into Φ5.5mm wire rods at a temperature of 1010℃~1030℃; S3, pickling the wire rods to remove surface oxide scale, drawing them to Φ2.4mm using a multi-pass reducing mill, and holding them in a hydrogen annealing furnace; S4, drawing them to Φ1.2mm again using a multi-pass reducing mill and copper plating the surface, finally producing solid gas-shielded welding wire. The advantage of this invention is that it achieves a good match between the weld metal and the weathering steel base material in terms of mechanical properties and atmospheric corrosion resistance, giving the weld metal good strength, low-temperature toughness, crack resistance, and atmospheric corrosion resistance, meeting the welding requirements of the weathering steel base material.

Description

Technical Field

[0001] This invention belongs to the field of welding materials technology, and particularly relates to the preparation of a solid gas shielded welding wire for weathering steel and its welding method. Background Technology

[0002] In infrastructure construction, transportation, and marine engineering, traditional steel structures rely heavily on coatings to protect against atmospheric corrosion. This not only results in high construction costs and short maintenance cycles but also makes them susceptible to localized corrosion due to coating damage, threatening structural safety. Weathering steel, by adding alloying elements such as Cu, Cr, Ni, and P, can form a stable, dense, and self-healing protective rust layer on its surface during long-term service. It achieves excellent atmospheric corrosion resistance without the need for coating, while also possessing high strength and good weldability.

[0003] However, there are many problems with the welding of existing weathering steels, mainly including: On the one hand, the weather resistance of the weld is not well matched with that of the base metal: existing welding of weathering steel mostly uses conventional low-alloy steel welding wire or ordinary gas-shielded welding wire. The original design of these welding wires was not optimized for the corrosion protection requirements of weathering steel, and the content of key weathering alloying elements such as Ni, Cr, and Cu in the weld metal is significantly different from that of the weathering steel base metal. This results in the weld area becoming a weak link in corrosion resistance after the welded joint is formed, preferentially corroding in the atmospheric environment, destroying the overall corrosion resistance of the structure, severely shortening the service life of the steel structure, and failing to meet the engineering requirements for long-term structural durability.

[0004] On the other hand, it is difficult to simultaneously achieve satisfactory comprehensive mechanical properties: while some existing welding wires can meet the strength requirements for welding weathering steel, they have significant shortcomings in low-temperature toughness and crack resistance. In low-temperature environments such as high altitudes and high latitudes, welded joints are prone to brittle fracture due to insufficient low-temperature toughness; in conditions such as thick plate welding and complex structure welding, welds are prone to cold or hot cracks, affecting the safety of the structure. At the same time, existing welding wires also have limitations in welding process adaptability, making it difficult to ensure welding efficiency while simultaneously ensuring weld formation quality and performance stability. Summary of the Invention

[0005] The purpose of this invention is to solve the problems of mismatched weather resistance and insufficient comprehensive mechanical properties of existing weathering steel welding materials. It provides a method for preparing solid gas-shielded welding wire for weathering steel. By rationally controlling the alloy element composition and content of the welding wire, the weld metal achieves a good match with the weathering steel base material in terms of mechanical properties and atmospheric corrosion resistance. The weld metal has good strength, low-temperature toughness and crack resistance, while adapting to efficient and stable gas-shielded welding processes to meet welding requirements under different working conditions.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing solid gas-shielded welding wire for weathering steel involves first smelting the raw material into molten steel and casting it into a square billet with a side length of 150 mm using a die casting method. The billet is then placed in a heating furnace and heated to 600 ℃, held for 4 hours, and then fed into a wire rod rolling mill. It is rolled into a Φ5.5 mm wire rod at a temperature of 1010℃~1030℃. Next, the wire rod is pickled to remove the surface oxide scale, drawn to Φ2.4 mm using a multi-pass reducing mill, held in a hydrogen annealing furnace, drawn to Φ1.2 mm using another multi-pass reducing mill, and then copper-plated on the surface to finally produce a solid gas-shielded welding wire.

[0007] Furthermore, the chemical composition and weight percentage of the solid gas shielded welding wire include: C: 0.006-0.040 wt%, Si: 0.40-0.80 wt%, Mn: 0.95-1.37 wt%, Cr: 1.10-1.95 wt%, Ni: 1.14-2.31 wt%, Cu: 0.40-0.67 wt%, Ti: 0.01-0.08 wt%, S≤0.008%, P≤0.020%, with the balance being Fe and unavoidable impurities.

[0008] The design principles of the above chemical components are as follows: C is used to provide the strength basis of weld metal, but too high a content will increase the tendency for cold cracking and weaken low-temperature toughness, so it should be kept in a low range. Si and Mn mainly play a role in deoxidation and strengthening, while improving weld formation. However, excessive content will lead to an increased tendency of weld hardening, which is not conducive to improving toughness. Ni is beneficial for improving the low-temperature toughness of weld metal and enhancing its weather resistance; Cr and Cu are important elements for forming weather resistance and can improve the atmospheric corrosion resistance of weld metal. However, excessive Cu content can easily cause hot brittleness. Ti plays a role in deoxidation and grain refinement, which is beneficial to improving the weld microstructure and enhancing the overall mechanical properties.

[0009] Furthermore, the diameter of the solid gas shielded welding wire is 1.0 mm to 1.2 mm; a copper plating layer is provided on the surface of the welding wire to improve conductivity, wire feeding stability and surface protection performance.

[0010] To further achieve the objectives of this invention, a welding method for a solid gas-shielded welding wire for weathering steel is also provided. This welding wire is used for gas-shielded welding of weathering steel plates or components, and is suitable for butt joints and fillet joints, as well as flat welding, horizontal welding, vertical welding, and overhead welding positions. Specifically: S1. Before welding, clean the bevel of the workpiece and its two sides to remove rust, oil, moisture and oxide scale. The preheating temperature before welding is 60℃~120℃. S2, assembly welding, assembly welding is performed according to the conventional spot welding method, with no gap left at the root; S3, during welding, a mixed shielding gas of Ar+CO2 is used for gas protection, with Ar accounting for 75% to 85% by volume and CO2 accounting for 15% to 25% by volume; the shielding gas flow rate is 15L / min to 25L / min. S4 employs multi-layer, multi-pass welding. The welding current for the first layer is 120A–160A, the welding voltage is 18V–22V, and the welding speed is 18cm / min–30cm / min. The welding current for the second layer and subsequent layers is 180A–280A, the welding voltage is 22V–30V, and the welding speed is 30cm / min–60cm / min. The interpass temperature is controlled between 80℃ and 150℃. S5. After welding, slow cooling is performed. If necessary, hydrogen removal treatment is performed. The hydrogen removal temperature is 180℃~250℃, and the holding time is 0.5h~2h.

[0011] Compared with the prior art, the advantages of the technical solution of the present invention are as follows: (1) This invention achieves good matching between the weld metal and the weathering steel base material in terms of atmospheric corrosion resistance by synergistically designing key weathering elements such as Ni, Cr, and Cu. (2) By controlling the content of C, Si, and Mn and adding trace amounts of Ti, this invention can improve low-temperature toughness and crack resistance while ensuring the strength of the weld metal; (3) The present invention uses solid welding wire, which has a mature manufacturing process, stable wire feeding, and is suitable for semi-automatic and automatic welding, and has good adaptability to welding processes; (4) The cladding metal prepared by the welding wire of the present invention was subjected to an impact test at -40℃, and the test values ​​were 64J, 80J, 72J and 70J, respectively, indicating that it has good low temperature impact toughness. (5) After a 72-hour corrosion test, no obvious morphological cracks were observed on the surface of the cladding metal prepared using the welding wire of the present invention. After cleaning the corrosion products, no obvious morphological defects were observed on the surface, and the average corrosion rate was 0.8005 g / m. 2 The value of ·h indicates that it has good resistance to atmospheric corrosion. Detailed Implementation Example 1

[0012] To make the present invention clearer, the preparation of a solid gas shielded welding wire for weathering steel 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.

[0013] In this embodiment, the welding of a 20mm thick Q450NQR1 weathering steel plate using the solid gas shielded welding wire of the present invention is taken as an example.

[0014] The chemical composition of the solid gas shielded welding wire used, by weight percentage, is as follows: C: 0.008wt%, Si: 0.43wt%, Mn: 0.97wt%, Ni: 1.12wt%, Cr: 1.95wt%, Cu: 0.48wt%, Ti: 0.03wt%, P: 0.015wt%, S: 0.004wt%, with the balance being Fe and unavoidable impurities.

[0015] The above chemical composition was used to smelt steel, and the 150mm square billet was produced by ingot casting.

[0016] The billet is placed in a heating furnace and kept at 600℃ for 4 hours before being fed into a wire rod rolling mill and rolled into Φ5.5mm wire rod at a temperature of 1010~1030℃. The wire rod is then pickled to remove the surface oxide scale, and then drawn to Φ2.4mm using a multi-stage reducing mill, and then placed in a hydrogen annealing furnace for heat preservation. Finally, the wire is drawn to Φ1.2mm using a multi-stage reduction mill and then plated with copper to produce a solid gas-shielded welding wire.

[0017] Before welding, the steel plate to be welded should be beveled in a V-shape with a bevel angle of 30°±2°, leaving a blunt edge of 1.5mm to 2.0mm. Before welding, clean the bevel and the area within 20mm on both sides, and preheat to 100℃.

[0018] Assembly welding is performed using conventional spot welding methods, with no gaps left at the root.

[0019] During welding, a shielding gas mixture of 80% Ar and 20% CO2 is used, with a gas flow rate of 20 L / min.

[0020] The welding current for the first layer is 130A to 145A, the voltage is 19V to 21V, and the welding speed is 20cm / min to 25cm / min; the welding current for the second layer and subsequent layers is 200A to 240A, the voltage is 24V to 27V, and the welding speed is 35cm / min to 45cm / min; the interpass temperature is controlled at 100℃ to 120℃.

[0021] After using the above welding wire and process, the weld formation is good, the fusion is stable, the spatter is small, and the flaw detection is qualified. The tensile strength of the joint is 639 and 628 MPa, there are no cracks in the bending, and the low-temperature impact resistance of the weld at -40℃ is 82, 77, and 89 J. The joint meets the welding requirements of Q450NQR1 weathering steel. Example 2

[0022] In this embodiment, the welding of a 20mm thick Q450EWR1 weathering steel plate using the solid gas shielded welding wire of the present invention is taken as an example.

[0023] The chemical composition of the solid gas shielded welding wire used, by weight percentage, is as follows: C: 0.028wt%, Si: 0.58wt%, Mn: 1.10wt%, Ni: 1.83wt%, Cr: 1.56wt%, Cu: 0.52wt%, Ti: 0.05wt%, P: 0.008wt%, S: 0.007wt%, with the balance being Fe and unavoidable impurities.

[0024] The above chemical composition was used to smelt steel, and the 150mm square billet was produced by ingot casting.

[0025] The billet is placed in a heating furnace and kept at 600℃ for 4 hours before being fed into a wire rod rolling mill and rolled into Φ5.5mm wire rod at a temperature of 1010~1030℃. The wire rod is then pickled to remove the surface oxide scale, and then drawn to Φ2.4mm using a multi-stage reducing mill, and then placed in a hydrogen annealing furnace for heat preservation. Finally, the wire is drawn to Φ1.2mm using a multi-stage reduction mill and then plated with copper to produce a solid gas-shielded welding wire.

[0026] Before welding, the steel plate to be welded should be beveled in a V-shape with a bevel angle of 30°±2°, leaving a blunt edge of 1.5mm to 2.0mm. Before welding, clean the bevel and the area within 20mm on both sides, and preheat to 120℃.

[0027] Assembly welding is performed using conventional spot welding methods, with no gaps left at the root.

[0028] During welding, a mixed shielding gas of 80% Ar + 20% CO2 is used, with a gas flow rate of 18 L / min ~ 20 L / min.

[0029] The welding current for the root pass is 135A~150A, the voltage is 19V~21V, and the welding speed is 20cm / min~25cm / min; the welding current for the fill and cover passes is 200A~240A, the voltage is 24V~27V, and the welding speed is 35cm / min~45cm / min; the interpass temperature is controlled at 120℃~150℃.

[0030] After welding, the weldment is slowly cooled and then kept at 200℃ for 1 hour for hydrogen removal treatment.

[0031] After using the above welding wire and process, the weld formation is good, the fusion is stable, the spatter is small, and the flaw detection is qualified. The tensile strength of the joint is 673 and 679 MPa, there are no cracks in the bending, and the low-temperature impact resistance of the weld at -40℃ is 81, 96, and 85 J. The joint meets the welding requirements of Q450NQR1 weathering steel. Example 3

[0032] In this embodiment, the welding of a 20mm thick Q500NQR1 weathering steel plate using the solid gas shielded welding wire of the present invention is taken as an example.

[0033] The chemical composition of the solid gas welding wire used, by weight percentage, is as follows: C: 0.037wt%, Si: 0.74wt%, Mn: 1.25wt%, Ni: 2.30wt%, Cr: 1.15wt%, Cu: 0.65wt%, Ti: 0.07wt%, P: 0.012wt%, S: 0.006wt%, with the balance being Fe and unavoidable impurities.

[0034] The above chemical composition was used to smelt steel, and the steel was then cast into 150 mm square billets using the die casting method.

[0035] The billet is placed in a heating furnace and kept at 600℃ for 4 hours before being fed into a wire rod rolling mill and rolled into Φ5.5mm wire rod at a temperature of 1010~1030℃. The wire rod is then pickled to remove the surface oxide scale, and then drawn to Φ2.4mm using a multi-stage reducing mill, and then placed in a hydrogen annealing furnace for heat preservation. Finally, the wire is drawn to Φ1.2mm using a multi-stage reduction mill and then plated with copper to produce a solid gas-shielded welding wire.

[0036] Before welding, the steel plate to be welded should be beveled in a V-shape with a bevel angle of 30°±2°, leaving a blunt edge of 1.5mm to 2.0mm. Before welding, clean the bevel and the area within 20mm on both sides, and preheat to 80℃.

[0037] Assembly welding is performed using conventional spot welding methods, with no gaps left at the root.

[0038] During welding, a shielding gas mixture of 80% Ar and 20% CO2 is used, with a gas flow rate of 20 L / min.

[0039] The welding current for the first layer is 130A to 145A, the voltage is 19V to 21V, and the welding speed is 20cm / min to 25cm / min; the welding current for the second layer and subsequent layers is 200A to 240A, the voltage is 24V to 27V, and the welding speed is 35cm / min to 45cm / min; the interpass temperature is controlled at 100℃ to 120℃.

[0040] After welding, the material is slowly cooled and then subjected to hydrogen removal treatment at 220℃ for 1 hour.

[0041] After using the above welding wire and process, the weld formation is good, the fusion is stable, the spatter is small, and the flaw detection is qualified. The tensile strength of the joint is 689 and 682 MPa, there are no cracks in the bending, and the low-temperature impact test of the weld at -40℃ is 79, 81, and 86 J. The joint meets the welding requirements of Q500NQR1 weathering steel.

[0042] 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 method for preparing a solid gas-shielded welding wire for weathering steel, characterized in that: S1, the raw materials are smelted into steel and cast into a square billet with a side length of 150mm by ingot casting. S2, the billet is placed in a heating furnace and heated to 600 ℃. After holding at the temperature for 4 hours, it is sent to the wire rod rolling mill and rolled into Φ5.5mm wire rod at a temperature of 1010℃~1030℃. S3, pickling the wire rod to remove the surface oxide scale, drawing it to Φ2.4mm using a multi-stage reducing mill, and then holding it in a hydrogen annealing furnace; S4 is then drawn to Φ1.2mm using a multi-stage reducing mill and copper plated on the surface to finally produce a solid gas-shielded welding wire.

2. The method for preparing solid gas-shielded welding wire for weathering steel according to claim 1, characterized in that: The chemical composition and weight percentage of the solid gas shielded welding wire include: C: 0.006-0.040 wt%, Si: 0.40-0.80 wt%, Mn: 0.95-1.37 wt%, Cr: 1.10-1.95 wt%, Ni: 1.14-2.31 wt%, Cu: 0.40-0.67 wt%, Ti: 0.01-0.08 wt%, S≤0.008%, P≤0.020%, with the balance being Fe and unavoidable impurities.

3. The method for preparing solid gas-shielded welding wire for weathering steel according to claim 2, characterized in that: The solid gas shielded welding wire has a diameter of 1.0 mm to 1.2 mm, and the surface of the welding wire is plated with a copper layer.

4. The method for preparing solid gas-shielded welding wire for weathering steel according to claim 2, characterized in that: The chemical composition of the solid gas shielded welding wire, by weight percentage, is as follows: C: 0.008wt%, Si: 0.43wt%, Mn: 0.97wt%, Ni: 1.12wt%, Cr: 1.95wt%, Cu: 0.48wt%, Ti: 0.03wt%, P: 0.015wt%, S: 0.004wt%, with the balance being Fe and unavoidable impurities.

5. The method for preparing solid gas-shielded welding wire for weathering steel according to claim 2, characterized in that: The chemical composition of the solid gas shielded welding wire, by weight percentage, is as follows: C: 0.028wt%, Si: 0.58wt%, Mn: 1.10wt%, Ni: 1.83wt%, Cr: 1.56wt%, Cu: 0.52wt%, Ti: 0.05wt%, P: 0.008wt%, S: 0.007wt%, with the balance being Fe and unavoidable impurities.

6. The method for preparing solid gas-shielded welding wire for weathering steel according to claim 2, characterized in that: The chemical composition of the solid gas welding wire, by weight percentage, is as follows: C: 0.037wt%, Si: 0.74wt%, Mn: 1.25wt%, Ni: 2.30wt%, Cr: 1.15wt%, Cu: 0.65wt%, Ti: 0.07wt%, P: 0.012wt%, S: 0.006wt%, with the balance being Fe and unavoidable impurities.

7. A welding method for solid gas-shielded welding wire for weathering steel as described in claim 3, characterized in that: S1. Before welding, clean the bevel of the workpiece and its two sides. The preheating temperature before welding is 60℃~120℃. S2, assembly welding, assembly welding is performed according to the conventional spot welding method, with no gap left at the root; S3, during welding, a mixed shielding gas of Ar+CO2 is used for gas protection, with Ar accounting for 75% to 85% by volume and CO2 accounting for 15% to 25% by volume; the shielding gas flow rate is 15L / min to 25L / min. S4 employs multi-layer, multi-pass welding. The welding current for the first layer is 120A–160A, the welding voltage is 18V–22V, and the welding speed is 18cm / min–30cm / min. The welding current for the second layer and subsequent layers is 180A–280A, the welding voltage is 22V–30V, and the welding speed is 30cm / min–60cm / min. The interpass temperature is controlled between 80℃ and 150℃. S5. After welding, slow cooling is performed. If necessary, hydrogen removal treatment is performed. The hydrogen removal temperature is 180℃~250℃, and the holding time is 0.5h~2h.

8. The welding method for solid gas-shielded welding wire for weathering steel according to claim 7, characterized in that: In step S1, before welding, the steel plate to be welded adopts a V-shaped bevel with a bevel angle of 30°±2° and a blunt edge of 1.5mm to 2.0mm. Before welding, the bevel and the area within 20mm on both sides are cleaned.

9. The welding method for solid gas-shielded welding wire for weathering steel according to claim 7, characterized in that: In step S3, a protective gas mixture of 80% Ar and 20% CO2 is used, with a gas flow rate of 18 L / min to 20 L / min.

10. The welding method for solid gas-shielded welding wire for weathering steel according to claim 7, characterized in that: In step S4, the welding current for the first layer is 130A to 145A, the voltage is 19V to 21V, and the welding speed is 20cm / min to 25cm / min; the welding current for the second layer and subsequent layers is 200A to 240A, the voltage is 24V to 27V, and the welding speed is 35cm / min to 45cm / min.