High-strength low-alloy steel welding method suitable for high heat input welding

Abstract

The invention discloses a high-strength low-alloy steel welding method suitable for high heat input welding, and belongs to the technical field of welding, the high-strength low-alloy steel welding method comprises the following steps: S1, steel pretreatment, S2, welding material selection and treatment, S3, welding parameter setting and welding, and S4, post-welding treatment, in the step S1, a to-be-welded part is cleaned, a laser cleaning technology and ultrasonic waves are adopted for cleaning and blow-drying, and after-welding treatment is carried out on the to-be-welded part; and finally, carrying out surface micro-nano structuring treatment. According to the method, through a series of innovative measures such as selection of a welding material containing special composite alloy elements, pre-magnetization treatment, a pulse-continuous current composite welding mode, dynamic arc swinging, variable-interval multi-layer and multi-pass welding, micro-vibration treatment and gradient temperature field rapid cooling treatment, grains of a welding seam and a heat affected zone can be effectively refined; and meanwhile, segregation of harmful elements can be effectively restrained, and welding residual stress is efficiently eliminated.

Description

Technical Field

[0001] The present invention relates to the field of welding technology, and particularly to a welding method for high-strength low-alloy steel suitable for large heat input welding. Background Art

[0002] High-strength low-alloy steel is widely used in many fields such as shipbuilding, bridge construction, and pressure vessels due to its high strength, good toughness, and excellent welding performance. In actual engineering, in order to improve welding efficiency, large heat input welding technology is widely adopted. However, traditional welding methods for high-strength low-alloy steel expose a series of serious problems when dealing with large heat input welding.

[0003] During the large heat input welding process, a large amount of heat input significantly slows down the cooling rate of the weld and the heat-affected zone, which directly leads to extremely coarse grains. The coarse grains will greatly reduce the toughness and strength of the weld and the heat-affected zone, seriously affecting the comprehensive mechanical properties of the welded joint, and further threatening the safe use of the entire structure. At the same time, existing welding methods are difficult to effectively suppress the segregation of harmful elements in the weld during large heat input welding. The segregation of harmful elements such as sulfur and phosphorus will form a large number of weak areas in the weld, becoming a high-incidence area for defects such as cracks, further reducing the quality and reliability of the welded joint. Moreover, traditional welding processes have poor effects on eliminating the residual stress generated during large heat input welding. The existence of residual stress will not only reduce the fatigue life of the structure but also may cause the structure to fail prematurely during use. Summary of the Invention

[0004] In order to solve the technical problems of easy occurrence of coarse grains, segregation of harmful elements, and large residual stress in the welding method of high-strength low-alloy steel during large heat input welding, the present invention proposes a welding method for high-strength low-alloy steel suitable for large heat input welding.

[0005] In order to solve the above problems, the technical solution proposed by the present invention is: a welding method for high-strength low-alloy steel suitable for large heat input welding, including the following steps: S1, pre-treatment of steel; S2, selection and treatment of welding materials; S3, setting of welding parameters and welding; S4, post-weld treatment. In step S1, the surface of the high-strength low-alloy steel to be welded is deeply cleaned. First, laser cleaning technology is used to remove impurities such as oil stains, rust, and scale; after cleaning, ultrasonic cleaning is carried out in deionized water, and then dried with dry nitrogen. Finally, surface micro-nano structuring treatment is performed on the cleaned part to be welded.

[0006] As an improvement, the surface micro-nano structuring treatment in step S1 includes using chemical etching or laser micro-machining methods to form uniformly distributed micro-nano structures on the welding surface.

[0007] As an improvement, in step S2, a Ti-B-RE composite alloy is selected as the welding material, and the specific alloy element contents are as follows: the Ti content is 0.03% - 0.06%, the B content is 0.002% - 0.006%, and the rare earth element content is 0.01% - 0.03%.

[0008] As an improvement, in step S2, the welding material is pre-magnetized; the welding material is placed in a specific magnetic field environment to generate a certain magnetic domain structure inside it.

[0009] As an improvement, in step S3, during high heat input welding, the welding heat input is controlled within the range of 50 - 100 kJ / cm; meanwhile, the welding speed is controlled between 15 - 30 cm / min; a pulsed - continuous current hybrid welding mode is adopted; during the welding process, pulsed current and continuous current are applied periodically; the peak current of the pulsed current is 400 - 600 A, the pulse frequency is 50 - 100 Hz, and the continuous current is 200 - 300 A; during the welding process, the arc is made to swing regularly through an arc control system; the arc swing amplitude is 3 - 6 mm, and the swing frequency is 6 - 12 Hz.

[0010] As an improvement, in step S3, a variable-spacing multi-layer multi-pass welding method is adopted; the spacing between each layer of welds is dynamically adjusted according to the number of welding layers and the weld position; for the bottom layer of welds close to the base material, a smaller spacing is adopted; as the number of welding layers increases, the weld spacing is gradually increased; the bottom layer weld spacing is 2 - 3 mm, and the upper layer weld spacing is 4 - 6 mm; after each layer of weld is completed, a small vibration is applied to the weld through a vibration device installed on the welding equipment; the vibration frequency is 100 - 300 Hz, and the vibration amplitude is 0.1 - 0.5 mm.

[0011] As an improvement, in step S4, after welding, gradient temperature field rapid cooling is immediately adopted to form a gradient temperature field in the weld and the heat affected zone during the cooling process; the cooling rate in the area close to the weld center is faster, being 20 - 30 °C / s; the cooling rate in the area far from the weld center is slower, being 10 - 15 °C / s.

[0012] As an improvement, in step S4, the welded joint is placed in an environment where an ultrasonic generator and a magnetic field generator act together to perform ultrasonic - magnetic coupling treatment on the welded joint, the ultrasonic frequency is 20 - 40 kHz, the magnetic field strength is 0.5 - 1.5 T, and the treatment time is 30 - 40 min.

[0013] Advantages of the present invention: 1. Through a series of innovative measures such as selecting welding materials containing special composite alloy elements, pre-magnetization treatment, pulse-continuous current composite welding mode, dynamic arc oscillation, variable-spacing multi-layer multi-pass welding, micro-vibration treatment, and gradient temperature field rapid cooling treatment, the present invention can effectively refine the grains of the weld seam and the heat-affected zone.

[0014] 2. By means of dynamic arc oscillation, variable-spacing multi-layer multi-pass welding, and micro-vibration treatment, the present invention can promote the stirring and mixing in the molten pool, make harmful elements evenly distributed in the weld metal, and effectively inhibit the segregation of harmful elements.

[0015] 3. The ultrasonic-magnetic coupling residual stress elimination treatment method of the present invention can give full play to the synergistic effect of ultrasonic waves and magnetic fields and efficiently eliminate welding residual stress. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a flowchart of the high-strength low-alloy steel welding method applicable to high heat input welding in the specific embodiment of the present invention. SPECIFIC EMBODIMENT

[0017] The present invention will be further described below with reference to the drawings.

[0018] According to Figure 1 As shown: The present invention provides a high-strength low-alloy steel welding method applicable to high heat input welding, including the following steps: S1. Steel pretreatment, S2. Selection and treatment of welding materials, S3. Setting of welding parameters and welding, S4. Post-weld treatment.

[0019] In step S1, the surface of the high-strength low-alloy steel to be welded is deeply cleaned. First, the laser cleaning technology is used to remove impurities such as oil stains, rust, and oxide scales. Laser cleaning has the advantages of non-contact, high precision, and pollution-free, and can thoroughly remove surface micro-impurities, making the welding surface reach an extremely high cleanliness. After cleaning, ultrasonic cleaning is carried out in deionized water to further remove the remaining micro-particles on the surface. Finally, it is dried with dry nitrogen.

[0020] In step S1, the surface of the cleaned part to be welded is subjected to surface micro-nano structuring treatment. Through chemical etching or laser micro-machining methods, uniformly distributed micro-nano structures are formed on the welding surface. These micro-nano structures can increase the contact area between the welding material and the base material, improve the bonding strength of the welding, and at the same time play a certain role in hindering the growth of grains.

[0021] In step S2, a Ti-B-RE composite alloy is selected as the welding material. The specific alloy element contents are as follows: the Ti content is 0.03% - 0.06%, the B content is 0.002% - 0.006%, and the rare earth element content is 0.01% - 0.03%. Ti can form fine TiN particles, which play a role in pinning grain boundaries and refining grains; B can reduce the grain boundary energy and inhibit grain growth; rare earth elements can purify the weld metal, reduce the content of harmful elements, and improve the toughness and crack resistance of the weld.

[0022] In step S2, the welding material is pre-magnetized; the welding material is placed in a specific magnetic field environment to generate a certain magnetic domain structure inside it. Pre-magnetization can change the electromagnetic characteristics of the molten pool during welding, promote stirring and convection in the molten pool, facilitate the escape of gas and impurities, and also help refine grains.

[0023] In step S3, during high heat input welding, the welding heat input is controlled within the range of 50 - 100 kJ / cm; at the same time, the welding speed is controlled between 15 - 30 cm / min; a pulsed - continuous current hybrid welding mode is adopted; during welding, pulsed current and continuous current are applied periodically; the peak current of the pulsed current is 400 - 600 A, the pulse frequency is 50 - 100 Hz, and the continuous current is 200 - 300 A; the pulsed current can provide high energy in a short time, promote stirring and mixing in the molten pool, and is beneficial to refining grains and reducing segregation of harmful elements; the continuous current ensures the stability of the welding process and the forming quality of the weld. During welding, the arc is made to swing regularly through an arc control system; the arc swing amplitude is 3 - 6 mm, and the swing frequency is 6 - 12 Hz.

[0024] In step S3, a variable-spacing multi-layer multi-pass welding method is adopted; the spacing between each layer of welds is dynamically adjusted according to the number of welding layers and the weld position; for the bottom layer of welds close to the base metal, a smaller spacing is used; as the number of welding layers increases, the weld spacing is gradually increased; the bottom layer weld spacing is 2 - 3 mm, and the upper layer weld spacing is 4 - 6 mm; after each layer of weld is completed, a small vibration is applied to the weld through a vibration device installed on the welding equipment; the vibration frequency is 100 - 300 Hz, and the vibration amplitude is 0.1 - 0.5 mm. Dynamic arc swing can expand the stirring range of the molten pool, make the weld metal more uniform, reduce the aggregation of harmful elements, and also help improve the appearance quality of the weld.

[0025] In step S4, after welding, a gradient temperature field is immediately used for rapid cooling, so that a gradient temperature field is formed in the weld and the heat-affected zone during the cooling process; the cooling rate in the area close to the weld center is relatively fast, being 20 - 30 °C / s; the cooling rate in the area far from the weld center is relatively slow, being 10 - 15 °C / s. This gradient temperature field can effectively inhibit the growth of grains and at the same time reduce the thermal stress generated during the cooling process.

[0026] In step S4, the welded joint is placed in an environment where an ultrasonic generator and a magnetic field generator act together to perform ultrasonic-magnetic coupling treatment on the welded joint. The ultrasonic frequency is 20 - 40 kHz, the magnetic field strength is 0.5 - 1.5 T, and the treatment time is 30 - 40 min. Ultrasonic waves can cause microscopic vibrations in the metal lattice, promote the movement and annihilation of dislocations, thereby releasing residual stress; the magnetic field can change the magnetic domain structure inside the metal and act synergistically with ultrasonic waves to further enhance the effect of eliminating residual stress. Example 1

[0027] The area to be welded is subjected to laser cleaning, then cleaned with ultrasonic waves in deionized water for 10 min, and finally dried with dry nitrogen.

[0028] The welding surface is subjected to micro-nano structuring treatment by chemical etching to form uniform micro-nano structures.

[0029] A welding material with a Ti content of 0.03%, a B content of 0.002%, and a rare earth element content of 0.01% is selected and subjected to pre-magnetization treatment.

[0030] A pulsed-continuous current composite welding mode is set. The peak value of the pulsed current is 400 A, the pulsed frequency is 50 Hz, and the continuous current is 200 A. The arc is made to swing regularly through an arc control system; the arc swing amplitude is 3 mm, and the swing frequency is 6 Hz.

[0031] The variable-spacing multi-layer multi-pass welding method is adopted. The weld spacing of the bottom layer is 2 mm, and the weld spacing of the upper layer is 4 mm. After each layer of weld is completed, micro-vibration treatment is immediately carried out. The vibration frequency is 100 Hz, and the vibration amplitude is 0.1 mm.

[0032] Gradient temperature field rapid cooling is adopted. The cooling rate at the weld center is 20 °C / s, and the cooling rate in the area far from the weld center is 10 °C / s. Ultrasonic-magnetic coupling treatment is carried out on the welded joint. The ultrasonic frequency is 20 kHz, the magnetic field strength is 0.5 T, and the treatment time is 30 min. Example 2

[0033] The area to be welded is subjected to laser cleaning, then cleaned with ultrasonic waves in deionized water for 10 min, and finally dried with dry nitrogen.

[0034] The welding surface is subjected to micro-nano structuring treatment by chemical etching to form uniform micro-nano structures.

[0035] Select a welding material with a Ti content of 0.06%, a B content of 0.006%, and a rare earth element content of 0.03%, and perform pre-magnetization treatment.

[0036] Set the pulse - continuous current composite welding mode, with a pulse current peak value of 600 A, a pulse frequency of 100 Hz, and a continuous current of 300 A. Make the arc swing regularly through the arc control system; the arc swing amplitude is 6 mm and the swing frequency is 12 Hz.

[0037] Adopt the variable-spacing multi-layer multi-pass welding method, with the bottom layer weld spacing of 3 mm and the upper layer weld spacing of 6 mm. After each layer of weld is completed, immediately perform micro-vibration treatment, with a vibration frequency of 300 Hz and a vibration amplitude of 0.5 mm.

[0038] Adopt gradient temperature field rapid cooling, with the cooling rate at the weld center being 30 °C / s and the cooling rate in the area far from the weld center being 15 °C / s. Perform ultrasonic - magnetic coupling treatment on the welded joint, with an ultrasonic frequency of 40 kHz, a magnetic field strength of 1.5 T, and a treatment time of 40 min.

[0039] The above describes the present invention and its implementation manners. This description is not restrictive. What is shown in the drawings is only one of the implementation manners of the present invention, and the actual structure is not limited thereto. Generally speaking, if those of ordinary skill in the art are inspired by it and, without departing from the gist of the present invention, design similar structural manners and embodiments to this technical solution without creative efforts, they shall fall within the protection scope of the present invention.

Claims

1. A high-strength low-alloy steel welding method suitable for high-line energy welding, characterized in that: The following steps are involved: S1, steel pretreatment, S2, welding material selection and processing, S3, welding parameter setting and welding, S4, post-weld treatment; In step S1, the high-strength low-alloy steel to-be-welded area is deeply cleaned, and impurities are first removed by laser cleaning technology; after cleaning, it is cleaned in deionized water with ultrasound, blown dry with dry nitrogen, and finally the cleaned area to be welded is subjected to surface micro-nanostructuring treatment.

2. The high-strength low-alloy steel welding method according to claim 1, characterized in that: Surface micro-nanostructuring treatment includes using chemical etching or laser micromachining methods to form uniformly distributed micro-nano structures on the welding surface.

3. The high-strength low-alloy steel welding method according to claim 1, characterized in that: In step S2, a Ti-B-RE composite alloy is selected as the welding material, and the specific alloy element content is: Ti content 0.03% - 0.06%, B content 0.002% - 0.006%, and rare earth element content 0.01% - 0.03%.

4. The high-strength low-alloy steel welding method according to claim 3, characterized in that: Step S2 also includes pre-magnetizing the welding material, placing the welding material in a magnetic field environment to generate a magnetic domain structure inside the welding material.

5. The high-strength low-alloy steel welding method according to claim 1, characterized in that: In step S3, during high energy line welding, the welding energy line is controlled within the range of 50-100 kJ / cm; at the same time, the welding speed is controlled between 15-30 cm / min; and a pulse-continuous current composite welding mode is adopted; During the welding process, pulse current and continuous current are applied; the peak current of the pulse current is 400-600A, the pulse frequency is 50-100Hz, and the continuous current is 200-300A; during the welding process, the arc is swung by the arc control system; the arc swing amplitude is 3-6mm, and the swing frequency is 6-12Hz.

6. The high-strength low-alloy steel welding method according to claim 1, characterized in that: In step S3, a variable-spacing multi-layer multi-pass welding method is adopted; the spacing between each layer of welds is dynamically adjusted according to the number of welding layers and the weld position; a smaller spacing is adopted for the bottom weld close to the parent material; as the number of welding layers increases, the weld spacing is gradually increased; the bottom weld spacing is 2-3mm, and the upper weld spacing is 4-6mm; after each layer of weld is completed, vibration is applied to the weld by a vibration device installed on the welding equipment; the vibration frequency is 100-300Hz, and the vibration amplitude is 0.1-0.5mm.

7. The high-strength low-alloy steel welding method according to claim 1, characterized in that: In step S4, after welding, a gradient temperature field is immediately used for rapid cooling, so that a gradient temperature field is formed in the weld and the heat affected zone during the cooling process; the cooling rate of the area close to the center of the weld is faster, at 20-30°C / s; the cooling rate of the area far from the center of the weld is slower, at 10-15°C / s.

8. The high-strength low-alloy steel welding method according to claim 7, characterized in that: In step S4, the weld joint is placed in an environment where an ultrasonic generator and a magnetic field generator work together to perform ultrasonic-magnetic coupling treatment on the weld joint, with an ultrasonic frequency of 20-40 kHz, a magnetic field strength of 0.5-1.5 T, and a treatment time of 30-40 min.

Images