Welding process of low-alloy ultrahigh-strength steel with yield strength of 1300MPa

Abstract

The invention relates to the technical field of steel welding, and discloses a welding process of low-alloy ultrahigh-strength steel with the yield strength of 1300MPa, the welding mode is gas shielded welding, and the welding process comprises the specific steps of groove machining, pretreatment before welding, backing welding, filling welding and cosmetic welding. Wherein the backing welding, the filling welding and the cosmetic welding all adopt Aussteel Benberle GM120 high-strength steel welding wires, the welding wires do not need to be switched back and forth, the operation is simple, the implementation is easy in production, the welding method can be popularized to automatic robot welding, efficient production is realized, good obdurability matching of welding seams can be ensured by strictly controlling heat input and interlayer temperature, and the welding quality is improved. And fine grains are obtained in a coarse grain area of a heat affected zone, the softening and embrittlement phenomena are reduced, and an obtained welding joint has excellent tensile strength and impact resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of steel welding, and specifically to a welding process for a low-alloy ultra-high-strength steel with a yield strength of 1300 MPa class. Background Art

[0002] Due to its advantages such as high strength, high toughness, good formability and workability, low-alloy ultra-high-strength steel has been widely used in the fields of construction machinery, port machinery, coal mining machinery, etc., and can be used to manufacture boom of large-tonnage cranes, boom of concrete pump trucks, boom of fire truck pump trucks, high-performance hydraulic supports, ultra-large-tonnage port cranes, etc. With the increasing requirements for lightweight, low-alloy high-strength steel has great advantages in reducing self-weight, improving load-bearing capacity, and reducing transportation and installation costs.

[0003] At present, the demand for low-alloy ultra-high-strength steel with a yield strength greater than 1000 MPa is continuously expanding. In the actual production process, the quality of welded joints is the key factor affecting the application and popularization of low-alloy high-strength steel. Chinese Patent Application CN105598596A discloses a non-preheating combined welding method for 1200 MPa high-strength steel, Chinese Patent Application CN106270957A discloses a gas shielded welding method for 1000 MPa class construction machinery high-strength steel thick plates, and Chinese Patent Application CN105014208A discloses a welding method for 900 MPa class high-strength steel. The above high-strength steel welding processes are complex, with problems such as low-strength wire backing welding, high-strength steel wire filling welding, gouging for root cleaning, low-strength wire sealing and surfacing, and post-weld heat preservation, which are not easy to execute and seriously affect production efficiency.

[0004] Therefore, in order to solve the above problems, the present invention provides a welding method for a low-alloy ultra-high-strength steel with a yield strength of 1300 MPa class, which is simple to operate, easy to execute in production, and easy to be promoted to automated robot welding to achieve high-efficiency production. Summary of the Invention

[0005] (1) Technical Problems to be Solved

[0006] In order to solve the above technical problems, the present invention provides a welding process for a low-alloy ultra-high-strength steel with a yield strength of 1300 MPa class, which has the advantages of simple operation, easy execution in production, and can achieve high-efficiency production. At the same time, it can ensure the strength and toughness of the welded joint.

[0007] (2) Technical Solutions

[0008] In order to achieve the above object, the present invention discloses a welding process for a low-alloy ultra-high-strength steel with a yield strength of 1300 MPa class, including the following steps:

[0009] S1. Groove machining: A V-shaped groove is opened at the joint of the steel plate to be welded.

[0010] S2. Pre-welding pretreatment: The steel plate with a V-shaped groove is subjected to pre-welding pretreatment.

[0011] S3. Root pass welding: Using argon-rich gas as the shielding gas, the steel plate after pre-welding pretreatment is subjected to root pass welding.

[0012] S4. Fill pass welding: The steel plate after root pass welding is subjected to fill pass welding.

[0013] S5. Cap pass welding: The steel plate after fill pass welding is subjected to cap pass welding. After welding is completed, a welded joint is obtained.

[0014] As a further solution of the present invention, the steel plate in S1 is pretreated before welding. The steel plate is cleaned with 1 mol / L hydrochloric acid solution, 1 mol / L sodium hydroxide solution and acetone for 10 minutes respectively, then washed with anhydrous ethanol and deionized water for 5 minutes, and dried by blowing with nitrogen. After pretreatment, the thickness of the steel plate is 12 mm.

[0015] As a further solution of the present invention, the processing method of the V-shaped groove in S1 includes one of thermal cutting method and mechanical method.

[0016] As a further solution of the present invention, the groove angle of the V-shaped groove in S1 is 60°, there is no root face, and the butt joint gap of the steel plate is 0 - 1 mm.

[0017] As a further solution of the present invention, during the root pass welding in S3, fill pass welding in S4, and cap pass welding in S5, the Voestalpine Bohler GM120 high-strength steel wire is used.

[0018] As a further solution of the present invention, the specific steps of the pre-welding pretreatment of the steel plate with a V-shaped groove in S2 are as follows: including grinding the area to be welded to expose the metallic luster, preheating to 120 - 150 °C, and selecting a suitable root butt joint gap according to the plate thickness.

[0019] As a further solution of the present invention, during the root pass welding in S3 the wire diameter is, the welding voltage is 22 V, the welding current is 160 A, the gas flow rate is 20 L / min, the interlayer welding temperature is 120 - 150 °C, and the welding speed is 150 mm / min.

[0020] As a further solution of the present invention, the root pass welding in S3, fill pass welding in S4, and cap pass welding in S5 are all carried out in an argon-rich gas environment, where the argon-rich gas is 85% Ar + 15% CO 2 .

[0021] As a further solution of the present invention, in S4, the welding voltage for filling welding is 28V, the welding current is 260A, the gas flow rate is 20L / min, the welding speed is 300mm / min, and the interlayer temperature is controlled at 120 - 200°C.

[0022] As a further solution of the present invention, in S5, the welding voltage for capping welding is 28V, the welding current is 260A, the gas flow rate is 20L / min, the welding speed is 300mm / min, and the interlayer temperature is controlled at 120 - 200°C.

[0023] (III) Beneficial technical effects

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] (1) During the welding process of the 1300MPa grade low alloy ultra-high strength steel in the present invention, the welding method is gas shielded welding. The specific steps are groove machining, pre-welding pretreatment, backing welding, filling welding, and capping welding. Among them, backing welding, filling welding, and capping welding all use voestalpine bohler GM120 high strength steel welding wire, without the need to switch welding wires back and forth. The operation is simple, easy to implement in production, and can be extended to automated robot welding to achieve high-efficiency production. By strictly controlling the heat input within 1.5kJ / mm and controlling the interlayer temperature, good strength and toughness matching of the weld seam is ensured, the coarse grain zone of the heat affected zone obtains relatively fine grains, softening and embrittlement phenomena are reduced, the grains in the welding heat affected zone are relatively fine, the strength loss is small, and the impact toughness is good.

[0026] (2) In the present invention, through pre-welding pretreatment first, defects such as porosity and cracks after welding are avoided, the cooling rate of the welded joint is reduced, the time for austenite cooling transformation is extended, the tendency to produce hardened structure is avoided or reduced, and the diffusion and escape of hydrogen in the weld seam are promoted, thereby preventing the generation of cold cracks. Secondly, preheating can also reduce the temperature difference between the welding zone and the surrounding base metal, make the temperature gradient relatively evenly distributed within a wider range, thereby reducing the peak value of welding stress. At the same time, a suitable root joint gap can ensure root penetration. Backing welding can ensure the initial shape and quality of the weld seam, enhance the welding strength and tightness, reduce defects such as cracks and slag inclusions in the weld seam, and provide a good foundation for subsequent welding. Then filling welding is carried out to fill the gap of the weld seam and meet the required strength requirements. Under the condition of not affecting the mechanical properties of the weld, the welding material and the base material jointly form a new composite material with uniform chemical composition and stable mechanical properties. Finally, capping welding is carried out to form a beautiful and uniform weld surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0028] Figure 1 Schematic diagram of the V-groove form in the present invention;

[0029] Figure 2 Schematic diagram of the welded joint in the present invention;

[0030] In the figure: a, plate thickness; d, assembly gap; α, groove angle; 1, root pass; 2, filling layer; 3, cover layer. Specific embodiments

[0031] The following will combine the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the protection scope of the present invention.

[0032] The present invention provides a welding process for a low-alloy ultra-high-strength steel with a yield strength of 1300 MPa, including the following steps:

[0033] S1. Groove machining: The steel plate is pre-treated. The steel plate is cleaned with 1 mol / L hydrochloric acid solution, 1 mol / L sodium hydroxide solution and acetone for 10 minutes respectively, then washed with anhydrous ethanol and deionized water for 5 minutes, and dried by blowing with nitrogen. After pre-treatment, the thickness of the steel plate is 12 mm. A V-groove is opened at the welded joint of the steel plate. The processing method of the V-groove includes one of thermal cutting method and mechanical method. The groove angle of the V-groove is 60°, without blunt edge, and the assembly gap of the steel plate is 0-1 mm;

[0034] S2. Pre-welding pre-treatment: The steel plate with the V-groove is pre-treated before welding. The area to be welded is polished to expose the metallic luster, preheated to 120-150 °C, and a suitable root assembly gap is selected according to the plate thickness;

[0035] S3. Root pass welding: Use argon-rich gas as the shielding gas. The argon-rich gas is 85% Ar + 15% CO 2 , and the steel plate after pre-welding pre-treatment is subjected to root pass welding. Use the Bohler GM120 high-strength steel wire of voestalpine. During the root pass welding process, the wire diameter is The welding voltage is 22V, the welding current is 160A, the gas flow rate is 20L / min, the interlayer welding temperature is 120 - 150°C, and the welding speed is 150mm / min;

[0036] S4. Filler welding: Filler welding is carried out on the steel plate after root welding. Argon-rich gas is used as the shielding gas, and the argon-rich gas is 85% Ar + 15% CO 2 , and Bohler GM120 high-strength steel welding wire of voestalpine is adopted. The welding voltage for filler welding is 28V, the welding current is 260A, the gas flow rate is 20L / min, the welding speed is 300mm / min, and the interlayer temperature is controlled at 120 - 200°C;

[0037] S5. Surfacing welding: Surfacing welding is carried out on the steel plate after filler welding. Argon-rich gas is used as the shielding gas, and the argon-rich gas is 85% Ar + 15% CO 2 , and Bohler GM120 high-strength steel welding wire of voestalpine is adopted. The welding voltage for surfacing welding is 28V, the welding current is 260A, the gas flow rate is 20L / min, the welding speed is 300mm / min, the interlayer temperature is controlled at 120 - 200°C. After welding is completed, a welded joint is obtained.

[0038] The present invention provides a welded joint prepared by the above method. The specific welding process is as follows:

[0039] A steel plate with a yield strength of 1300MPa and a thickness of 12mm is used, a 60° V-groove is opened, preheated to 120°C before welding, and Bohler GM120 welding wire is used to complete root, filler, and surfacing welding. During the welding process, argon-rich gas is used as the shielding gas, and the argon-rich gas is 85% Ar + 15% CO 2 , the interlayer temperature is controlled at 150°C, and the welding parameters are as follows: During root welding, the welding current is 160A, the welding voltage is 22V, and the welding speed is 150mm / min; During filler and surfacing welding, the welding current is 260A, the welding voltage is 28V, and the welding speed is 300mm / min, and a welded joint is obtained.

[0040] By using the above welding process, a smooth welded joint can be obtained, without defects such as cracks and pores, with good mechanical properties. The room-temperature tensile strength of the weld metal is greater than 1217MPa. At a test temperature of -40°C, the impact energy of the V-notch impact test of the weld metal is greater than 47J, and the 6a cold bending test is qualified.

[0041] Although embodiments of the present invention have been shown and described, those of ordinary skill in the art will understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. All equivalent changes and improvements made in accordance with the scope of the present invention application shall still fall within the scope covered by the present invention.

Claims

1. A welding process for low alloy ultra-high strength steel with a yield strength of 1300 MPa, characterized in that: The steps include: S1. Groove processing: Make a V-shaped groove at the joint to be welded on the steel plate; S2. Pre-welding pretreatment: Pre-welding pretreatment is performed on the steel plate after the V-shaped groove is opened; S3, base welding: use argon-rich gas as the shielding gas to perform base welding on the steel plate after pretreatment before welding; S4, filling welding: filling welding is performed on the steel plate after base welding; S5. Cover welding: Cover welding is performed on the steel plate below the filling welding. After welding is completed, a welded joint is obtained.

2. The welding process of a low alloy ultra-high strength steel with a yield strength of 1300 MPa according to claim 1, characterized in that: The steel plate in S1 is pretreated before welding. The steel plate is cleaned for 10 minutes using 1 mol / L hydrochloric acid solution, 1 mol / L sodium hydroxide solution and acetone respectively, then washed for 5 minutes using anhydrous ethanol and deionized water, and dried using nitrogen gas. After pretreatment, the steel plate has a thickness of 12 mm.

3. The welding process of a low alloy ultra-high strength steel with a yield strength of 1300 MPa according to claim 1, characterized in that: The processing method of the V-shaped groove in S1 includes a thermal cutting method and a mechanical method.

4. The welding process of a low alloy ultra-high strength steel with a yield strength of 1300 MPa according to claim 1, characterized in that: The groove angle of the V-shaped groove in S1 is 60°, there is no blunt edge, and the gap between the steel plates is 0-1 mm.

5. The welding process of a low alloy ultra-high strength steel with a yield strength of 1300 MPa according to claim 1, characterized in that: In the processes of base welding in S3, filling welding in S4 and cover welding in S5, Voestalpine Böhler GM120 high-strength steel welding wire is used.

6. The welding process of a low alloy ultra-high strength steel with a yield strength of 1300 MPa according to claim 1, characterized in that: The specific steps of pre-welding the steel plate after the V-groove is opened in S2 are as follows: grinding the area to be welded to reveal the metallic luster, preheating to 120-150° C., and selecting a suitable root assembly gap according to the plate thickness.

7. The welding process of a low alloy ultra-high strength steel with a yield strength of 1300 MPa according to claim 1, characterized in that: During the base welding process in S3, the diameter of the welding wire is φ1.2 mm, the welding voltage is 22 V, the welding current is 160 A, the gas flow rate is 20 L / min, the interlayer welding temperature is 120-150° C., and the welding speed is 150 mm / min.

8. The welding process of a low alloy ultra-high strength steel with a yield strength of 1300 MPa according to claim 1, characterized in that: The base welding in S3, the filling welding in S4 and the cover welding in S5 are all carried out in an argon-rich gas environment, wherein the argon-rich gas is 85% Ar+15% CO2.

9. The welding process of a low alloy ultra-high strength steel with a yield strength of 1300 MPa according to claim 1, characterized in that: The welding voltage of the filling welding in S4 is 28V, the welding current is 260A, the gas flow rate is 20L / min, the welding speed is 300mm / min, and the interlayer temperature is controlled at 120-200°C.

10. The welding process of a low alloy ultra-high strength steel with a yield strength of 1300 MPa according to claim 1, characterized in that: The welding voltage of the cover welding in S5 is 28V, the welding current is 260A, the gas flow rate is 20L / min, the welding speed is 300mm / min, and the interlayer temperature is controlled at 120-200°C.

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