Method for improving weld quality and welding efficiency of high carbon steel plate strip

Abstract

The application discloses a method for improving the welding quality and efficiency of high-carbon steel plate strips, which comprises the following steps: after the butt joint of two high-carbon steel plate strips, laser-arc hybrid welding and online heat treatment are simultaneously performed; along the welding direction, the arc welding is performed in front of the laser welding to perform single-sided welding on the butt joint, the laser-arc hybrid welding promotes the gas escape in the welding process, thereby reducing the hole defects in the weld, and the high welding speed is realized under the low laser power, thereby improving the welding efficiency; meanwhile, the back of the butt joint is in the rear of the welding position, the online tempering heat treatment is performed on the formed weld through induction heating at the same speed as the welding speed, so that the formation of the hardened structure is reduced, the welding stress is reduced, and the weld toughness and the cold crack resistance are improved; and the welding parameters and the heat treatment power are determined according to the average thickness of the two high-carbon steel plate strips, so that the process is adjusted and optimized, and the influence of the thickness change on the welding quality is avoided. The method can effectively improve the welding quality and efficiency.

Description

Technical Field

[0001] This invention belongs to the field of strip steel welding, and specifically relates to a method for improving the quality and welding efficiency of high carbon steel plate strip welds. Background Technology

[0002] When a carbon steel pickling and pickling-rolling combined unit is operating, the beginning and end of the strip are usually welded together to ensure continuous production. High-carbon steel itself has a high carbon content, which increases the likelihood of cold cracking and deteriorates weldability. Furthermore, the combined effect of Mn and Si in high-carbon steel strips further increases the carbon equivalent, making them highly susceptible to hardening and prone to cold cracking during welding, resulting in extremely poor weldability. Currently, even when welding high-carbon steel strips, if a full weld surface is obtained, the weld is still highly prone to cracking after welding, affecting subsequent production efficiency. Summary of the Invention

[0003] The purpose of this invention is to provide a method for improving the quality and welding efficiency of high-carbon steel plate and strip welds, which can effectively improve the quality and welding efficiency of high-carbon steel plate and strip welds, and the resulting welded joints have good toughness and are not prone to breakage.

[0004] The technical solution adopted in this invention is:

[0005] A method for improving the weld quality and welding efficiency of high-carbon steel strips involves simultaneously performing laser-arc hybrid welding and online heat treatment on the weld joint after the weld ends of two high-carbon steel strips with a thickness difference within a certain range are butted together. Along the welding direction, arc welding precedes laser welding on one side of the weld joint. This laser-arc hybrid welding promotes gas escape during the welding process, reducing porosity defects in the weld, and achieves high welding speed at low laser power, thus improving welding efficiency. Simultaneously, behind the weld position on the back side of the weld, in sync with the welding speed, induction heating is used to perform online tempering heat treatment on the formed weld to reduce the formation of hardened structures and welding stress, thereby improving weld toughness and cold crack resistance. Furthermore, welding parameters and heat treatment power are determined based on the average thickness of the two high-carbon steel strips to adjust and optimize the process, avoiding the impact of thickness variations on weld quality.

[0006] Preferably, the carbon content of the high-carbon steel strip is 0.6%-0.8% by mass. The thicknesses of the two high-carbon steel strips are h1 and h2, respectively, and the thickness difference between them must satisfy |h1-h2|≤0.5mm. The thickness range of the two strips is 1.5-5mm. The average thickness of the two high-carbon steel strips is divided into 14 small increments or 7 large increments, with 0.25mm as a small increment and 0.5mm as a large increment. Each increase in the average thickness of the two high-carbon steel strips from 1.5mm to 5mm increases the laser power and heat treatment power of laser welding. Each increase in the large increment increases the welding voltage and welding current of arc welding.

[0007] Preferably, the arc welding machine for performing arc welding adopts the push-pull wire system CMT process, the laser welding machine for performing laser welding adopts a solid-state laser, and the induction heater for performing induction heating is moved by a traveling trolley and ensures coordinated movement with the arc welding machine and the laser welding machine.

[0008] Preferably, the welding speed of laser-arc hybrid welding and the travel speed of induction heating are both 2.5 m / min.

[0009] Preferably, in laser-arc hybrid welding: the welding torch angle α is 40°-50°; the welding wire is carbon steel welding wire with a diameter of 1.0 mm and an extension length l of 10-15 mm; the laser defocusing amount d is 5±0.5 mm, with the defocusing amount d taking the upper surface of the strip as a reference, positive when the laser focus is above the upper surface and negative when it is below the strip; the laser wire spacing D is 3-5 mm.

[0010] Preferably, during laser-arc hybrid welding, protective gas is blown onto both the front and back sides of the welding area, with the protective gas on the front side of the weld being blown out by the welding torch.

[0011] Preferably, the shielding gas on the front side of the weld is a mixture of argon and carbon dioxide, with a flow rate of 25-30 L / min and a pressure of 0.4-0.6 MPa; the shielding gas on the back side of the weld is argon, with a flow rate of 8-12 L / min, a blowing angle θ of 30°-40°, and a pressure of 0.4-0.6 MPa.

[0012] Preferably, during induction heating: the distance h between the induction heating station and the lower surface of the workpiece is 4±0.5mm; the length L of induction heating is determined by the travel speed of induction heating to ensure sufficient heating time is applied to the formed weld.

[0013] Preferably, the welding ends of the two high-carbon steel strips are cut before welding to ensure that the welding surfaces fit tightly together.

[0014] The beneficial effects of this invention are:

[0015] This method applies laser-arc hybrid welding to butt welding of high-carbon steel strips. Laser-arc hybrid welding can achieve greater penetration and a wider upper surface weld width at lower laser power. This facilitates gas escape during welding, reducing porosity and improving weld quality. Furthermore, it enables high welding speeds at low laser power, increasing welding efficiency and reducing costs. Simultaneously, the method uses induction heating for online tempering of the formed weld, allowing for timely tempering and improving weld toughness and resistance to cold cracking. The method determines welding parameters and heat treatment power based on the average thickness of the two high-carbon steel strips, ensuring good treatment results for strips of varying thicknesses and avoiding the impact of thickness variations on weld quality. The resulting welded joints exhibit good toughness and are less prone to breakage. Attached Figure Description

[0016] Figure 1 This is a schematic diagram illustrating the simultaneous laser-arc composite welding and online heat treatment at the seam in an embodiment of the present invention.

[0017] In the diagram: 1-Induction heater; 2-Workpiece; 3-Laser; 4-Welding torch. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0019] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0020] The features and performance of this application will be further described in detail below with reference to the embodiments.

[0021] This embodiment discloses a method for improving the weld quality and welding efficiency of high-carbon steel strip. For two high-carbon steel strips with a thickness difference within a certain range, after the weld ends of the two strips are butt-jointed, laser-arc hybrid welding and online heat treatment are simultaneously performed at the joint. Figure 1 As shown:

[0022] Along the welding direction, arc welding is performed first and laser welding is performed later for single-sided welding of the joint. The laser-arc hybrid welding promotes the escape of gas during the welding process, thereby reducing porosity defects in the weld, and achieves high welding speed at low laser power, thereby improving welding efficiency.

[0023] Meanwhile, behind the welding position, on the back of the joint, in sync with the welding speed, the formed weld is subjected to online tempering heat treatment by induction heating to reduce the formation of hardened structures and reduce welding stress, thereby improving the weld toughness and cold crack resistance.

[0024] Furthermore, welding parameters and heat treatment power were determined based on the average thickness of the two high-carbon steel strips to adjust and optimize the process and avoid the impact of thickness variations on welding quality.

[0025] In this embodiment, preferably, the welding ends of the two high-carbon steel strips can be cut before welding to ensure that the welding surfaces fit tightly together.

[0026] In this embodiment, the carbon content of the high-carbon steel strip is 0.6%-0.8% by mass. The thicknesses of the two high-carbon steel strips are h1 and h2, respectively, and the thickness difference between them must satisfy |h1-h2|≤0.5mm. The thickness range of the two strips is 1.5-5mm. The average thickness of the two high-carbon steel strips is divided into 14 small increments or 7 large increments, with 0.25mm as a small increment and 0.5mm as a large increment. Each time a small increment is added, the laser power and heat treatment power of laser welding increase accordingly. Each time a large increment is added, the welding voltage and welding current of arc welding increase accordingly. By dividing the average thickness into several levels and determining the welding parameters and heat treatment power according to the level, scientific quantitative control can be achieved. After establishing a database based on the relationship between the levels and each parameter, parameter guidance can be provided by directly inputting the level. In particular, the adjustment of the laser power and heat treatment power levels is more sensitive than the adjustment of the electric welding voltage and electric welding current levels, so that laser welding and heat treatment play the main regulatory role and ensure the treatment effect.

[0027] In this embodiment, preferably, the arc welding machine performing arc welding adopts a push-pull wire system CMT process, the laser welding machine performing laser welding adopts a solid-state laser (fiber laser or disk laser), and the induction heater 1 performing induction heating is moved by a traveling carriage and ensures coordinated movement with the arc welding machine and the laser welding machine. The use of the push-pull wire system CMT process ensures precise and stable wire feeding. Compared with gas lasers, solid-state lasers have advantages such as low price, simple structure, convenient maintenance, and low operating costs. The coordinated movement of the three ensures optimal processing results.

[0028] In this embodiment, preferably, the welding speed of laser-arc hybrid welding and the travel speed of induction heating are both 2.5 m / min.

[0029] In this embodiment, during laser-arc hybrid welding: the angle α of the welding torch 4 is 40°-50°; the welding wire is a carbon steel welding wire with a diameter of 1.0 mm and an extension l of 10-15 mm; the defocusing amount d of the laser 3 is 5±0.5 mm, with the defocusing amount d taking the upper surface of the strip as a reference, positive when the laser 3 focal point is above the upper surface, and negative when it is below the strip surface; the wire spacing D is 3-5 mm.

[0030] In this embodiment, shielding gas is blown onto both the front and back sides of the welding area during laser-arc hybrid welding. The shielding gas on the front side of the weld is blown out by the welding torch 4 to ensure welding quality. The shielding gas on the front side of the weld is a mixture of argon and carbon dioxide (argon + 18% carbon dioxide), with a flow rate of 25-30 L / min and a pressure of 0.4-0.6 MPa. The shielding gas on the back side of the weld is argon (99.99% purity), with a flow rate of 8-12 L / min, a blowing angle θ of 30°-40°, and a pressure of 0.4-0.6 MPa.

[0031] In this embodiment, during induction heating: the distance h between the induction heating station and the lower surface of the workpiece is 4±0.5mm; the length L of induction heating is determined by the travel speed of induction heating to ensure sufficient heating time is applied to the formed weld.

[0032] In this embodiment, the specific welding parameters and heat treatment power are shown in Table 1 below.

[0033] Table 1. Correspondence between welding parameters and heat treatment power and the average thickness of the two high-carbon steel strips.

[0034]

[0035]

[0036] This correspondence table applies not only to welding between high carbon steel plates and strips, but also to welding between high carbon steel plates and strips and different base materials such as medium carbon steel and plain carbon steel.

[0037] This method applies laser-arc hybrid welding to butt welding of high-carbon steel strips. Laser-arc hybrid welding can achieve greater penetration and a wider upper surface weld width at lower laser power. This facilitates gas escape during welding, reducing porosity and improving weld quality. Furthermore, it enables high welding speeds at low laser power, increasing welding efficiency and reducing costs. Simultaneously, the method uses induction heating for online tempering of the formed weld, allowing for timely tempering and improving weld toughness and resistance to cold cracking. The method determines welding parameters and heat treatment power based on the average thickness of the two high-carbon steel strips, ensuring good treatment results for strips of varying thicknesses and avoiding the impact of thickness variations on weld quality. The resulting welded joints exhibit good toughness and are less prone to breakage.

[0038] Application examples

[0039] Two high-carbon steel strips, made of 65Mn and 75Cr1 respectively, with carbon contents of 0.65% and 0.75%, and thicknesses of 4.2mm and 4.5mm respectively, have an average thickness of 4.35mm. The two strips were first clamped together, and the weld ends were sheared. The weld ends were then butt-jointed, and the joint was simultaneously subjected to laser-arc hybrid welding and online heat treatment. The laser-arc hybrid welding speed and induction heating travel speed were both 2.5m / min, the laser power was 6.2kW, the welding voltage was 15.9V, the welding current was 138A, the heat treatment power was 24kW, and the defocusing amount was 5mm. After treatment, the weld was free of cracks, and the cupping test showed no longitudinal tearing along the weld, indicating a satisfactory result. No weld breakage occurred during subsequent processing steps (pickling and rolling).

[0040] The embodiments described above are some, but not all, of the embodiments of this application. The detailed description of the embodiments of this application is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

Claims

1. A method for improving the weld quality and welding efficiency of high-carbon steel plate strips, characterized in that, For two high-carbon steel strips with a thickness difference within a certain range, after the welded ends are butted, laser-arc hybrid welding and online heat treatment are simultaneously performed at the joint: along the welding direction, arc welding is performed first and laser welding is performed later for single-sided welding of the joint. The laser-arc hybrid welding promotes gas escape during the welding process, thereby reducing porosity defects in the weld, and achieves high welding speed at low laser power, thereby improving welding efficiency. At the same time, behind the welding position, on the back side of the joint, in sync with the welding speed, induction heating is used to perform online tempering heat treatment on the formed weld to reduce the formation of hardened structures and reduce welding stress, thereby improving weld toughness and cold crack resistance. Furthermore, welding parameters and heat treatment power were determined based on the average thickness of the two high-carbon steel strips to adjust and optimize the process and avoid the impact of thickness variations on welding quality. The carbon content of the high-carbon steel strip is 0.6%-0.8% by mass. The thicknesses of the two high-carbon steel strips are h1 and h2, respectively. The thickness difference between the two must satisfy |h1-h2|≤0.5mm, and the thickness range of the two strips is 1.5-5mm. The average thickness of the two high-carbon steel strips is divided into 14 small grades or 7 large grades, with 0.25mm as a small grade and 0.5mm as a large grade. Each increase in the average thickness of the two high-carbon steel strips is equivalent to an increase in the laser power and heat treatment power of laser welding, and an increase in the welding voltage and welding current of arc welding.

2. The method for improving the weld quality and welding efficiency of high-carbon steel plate strip as described in claim 1, characterized in that: The arc welding machine for arc welding adopts the push-pull wire system CMT process, the laser welding machine for laser welding adopts a solid-state laser, and the induction heater for induction heating is moved by a traveling trolley and ensures coordinated movement with the arc welding machine and the laser welding machine.

3. The method for improving the weld quality and welding efficiency of high-carbon steel plate strip as described in claim 1, characterized in that: The welding speed of laser-arc hybrid welding and the travel speed of induction heating are both 2.5 m / min.

4. The method for improving the weld quality and welding efficiency of high-carbon steel plate strip as described in claim 1, characterized in that, In laser-arc hybrid welding: the welding torch angle α is 40°-50°; the welding wire is carbon steel welding wire with a diameter of 1.0 mm and an extension length l of 10-15 mm; the laser defocusing amount d is 5±0.5 mm, with the defocusing amount d taking the upper surface of the strip as a reference. The laser focus is positive when it is above the upper surface and negative when it is below the strip; the laser wire spacing D is 3-5 mm.

5. The method for improving the weld quality and welding efficiency of high-carbon steel plate strip as described in claim 1, characterized in that: During laser-arc hybrid welding, shielding gas is blown onto both the front and back sides of the welding area, with the shielding gas on the front side of the weld being blown out by the welding torch.

6. The method for improving the weld quality and welding efficiency of high-carbon steel plate strip as described in claim 5, characterized in that: The shielding gas on the front side of the weld is a mixture of argon and carbon dioxide, with a flow rate of 25-30 L / min and a pressure of 0.4-0.6 MPa; the shielding gas on the back side of the weld is argon, with a flow rate of 8-12 L / min, a blowing angle of 30°-40°, and a pressure of 0.4-0.6 MPa.

7. The method for improving the weld quality and welding efficiency of high-carbon steel plate strip as described in claim 1, characterized in that, During induction heating: the distance h between the induction heating station and the lower surface of the workpiece is 4±0.5mm; the length L of induction heating is determined by the travel speed of induction heating to ensure sufficient heating time is applied to the formed weld.

8. The method for improving the weld quality and welding efficiency of high-carbon steel plate strip as described in claim 1, characterized in that: Before the welding ends of the two high-carbon steel strips are joined, the welding ends are cut to ensure that the welding surfaces fit tightly together.

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