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

Abstract

The invention discloses a method for improving welding seam quality and welding efficiency of high-carbon steel plate strips, which is characterized in that after two high-carbon steel plate strips are in butt joint, laser-arc hybrid welding and online heat treatment are simultaneously carried out: in the welding direction, electric arc welding is carried out before laser welding is carried out, and then single-side welding is carried out on an abutted seam, so that gas escape in the welding process is promoted through the laser-arc hybrid welding; therefore, hole defects in the welding seam are reduced, high welding speed is realized under low laser power, and the welding efficiency is improved; meanwhile, on-line tempering heat treatment is conducted on a formed welding seam through induction heating behind the welding position and on the back face of an abutted seam at the speed synchronous with the welding speed, so that formation of a hardening structure is reduced, the welding stress is reduced, and therefore the toughness and the cold crack resistance of the welding seam are improved; and moreover, welding parameters and 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 thickness change on welding quality is avoided. The method can effectively improve the welding seam quality and the welding efficiency.

Description

Technical Field

[0001] The present invention belongs to the field of strip steel welding, and in particular relates to a method for improving the weld quality and welding efficiency of high-carbon steel strips. Background Art

[0002] When carbon steel pickling and pickling mills are in operation, the strip's head and tail are typically welded together to ensure continuous production. High-carbon steel's inherent high carbon content increases the likelihood of cold cracking, resulting in poor weldability. Furthermore, the combined effects of manganese and silicon in high-carbon steel strips further increase the carbon equivalent, making them highly susceptible to hardening. This makes them susceptible to cold cracking during welding and results in extremely poor weldability. Currently, even when welding high-carbon steel strips with a smooth surface, the weld is still prone to cracking, impacting subsequent production efficiency. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for improving the weld quality and welding efficiency of high carbon steel plates and strips, which can effectively improve the weld quality and welding efficiency of high carbon steel plates and strips, and the obtained product weld joints have good toughness and are not easy to break.

[0004] The technical solution adopted in the present invention is:

[0005] A method for improving the weld quality and welding efficiency of high-carbon steel strips. For two high-carbon steel strips with a thickness difference within a certain range, after the welding ends of the two high-carbon steel strips are butt-jointed, laser arc hybrid welding and online heat treatment are simultaneously performed on the joint: along the welding direction, arc welding is performed in front and laser welding is performed in the back to weld the joint on one side. The laser arc hybrid welding not only promotes gas escape during the welding process, thereby reducing hole defects in the weld, but also achieves a 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 synchronization with the welding speed, the formed weld is subjected to online tempering heat treatment by induction heating to reduce the formation of hardened structure and welding stress, thereby improving the toughness and cold crack resistance of the weld. In addition, the welding parameters and heat treatment power are determined according to the average thickness of the two high-carbon steel strips, so as to adjust and optimize the process and avoid the influence of thickness changes on welding quality.

[0006] Preferably, the mass ratio of the carbon content of the high carbon steel strip is 0.6%-0.8%. Assuming that 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 is 1.5-5mm; with 0.25mm as a small gear and 0.5mm as a large gear, the average thickness of the two high carbon steel strips is divided into 14 small gears or 7 large gears from 1.5mm to 5mm. With each additional small gear, the laser power and heat treatment power of laser welding will increase accordingly, and with each additional large gear, the welding voltage and welding current of arc welding will increase accordingly.

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

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

[0009] Preferably, during laser arc hybrid welding: the welding gun angle α is 40°-50°; the welding wire is a carbon steel welding wire with a diameter of 1.0 mm and a dry extension l of 10-15 mm; the laser defocus d is 5±0.5 mm, and the defocus d is based on the upper surface of the plate strip. The laser focus is positive when it is located above the upper surface and negative when it is located below the plate surface; the filament spacing D is 3-5 mm.

[0010] Preferably, shielding gas is blown toward both the front and back sides of the welding portion during laser arc hybrid welding, and the shielding gas toward the front side of the weld is blown out by the welding gun.

[0011] Preferably, the shielding gas on the front 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 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±0.5 mm; the induction heating length L is determined by the induction heating travel speed to ensure that sufficient heating time is applied to the formed weld.

[0013] Preferably, before the welded ends of the two high carbon steel strips are butt-jointed, the welded ends are sheared to ensure that the butt joint surfaces are tightly fitted.

[0014] The beneficial effects of the present invention are:

[0015] This method applies laser arc hybrid welding to the butt welding of high-carbon steel plates and strips. Laser arc hybrid welding can achieve greater penetration depth and larger upper surface weld width at lower laser power. Therefore, on the one hand, it is beneficial to the escape of gas during the welding process, thereby reducing hole defects in the weld and improving weld quality. On the other hand, it can achieve high welding speed at low laser power, thereby improving welding efficiency and reducing costs and increasing efficiency. At the same time, this method uses induction heating to perform online tempering heat treatment on the formed weld, which can temper the weld in time, thereby improving the weld toughness and cold crack resistance. This method determines the welding parameters and heat treatment power based on the average thickness of the two high-carbon steel plates and strips, so that high-carbon steel plates and strips of different thicknesses can achieve good treatment effects, avoiding the influence of thickness changes on welding quality. The product obtained by this method has good toughness and is not easy to break. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of simultaneous laser arc hybrid welding and online heat treatment at a seam in an embodiment of the present invention.

[0017] In the figure: 1-induction heater; 2-workpiece; 3-laser; 4-welding gun. DETAILED DESCRIPTION

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Generally, the components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0019] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments in the present application without creative work are within the scope of protection of the present application.

[0020] The features and performance of the present application are 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 strips. For two high carbon steel strips with a thickness difference within a certain range, after the weld ends of the two strips are butted together, laser arc hybrid welding and online heat treatment are simultaneously performed on the joint. Figure 1 As shown:

[0022] Along the welding direction, arc welding is performed in front and laser welding is performed in the back for single-sided welding of the butt joint. Laser arc hybrid welding not only promotes gas escape during welding, thereby reducing hole defects in the weld, but also achieves high welding speed at low laser power, thereby improving welding efficiency.

[0023] At the same time, behind the welding position, on the back of the seam, synchronized with the welding speed, the formed weld is subjected to online tempering heat treatment by induction heating to reduce the formation of hardened structure and welding stress, thereby improving the toughness and cold crack resistance of the weld.

[0024] In addition, the welding parameters and heat treatment power are determined according to the average thickness of the two high-carbon steel strips to adjust and optimize the process and avoid the influence of thickness changes on welding quality.

[0025] In this embodiment, preferably, before the welded ends of the two high-carbon steel strips are butt-jointed, the welded ends may be sheared to ensure that the butt-jointed surfaces are tightly fitted.

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

[0027] In this embodiment, preferably, the arc welder for arc welding adopts a push-pull system CMT process, the laser welder for laser welding adopts a solid-state laser (fiber laser or disk laser), and the induction heater 1 for induction heating is driven by a traveling carriage and ensures coordinated movement with the arc welder and the laser welder. The use of the push-pull system CMT process can ensure accurate and stable wire feeding. Compared with gas lasers, solid-state lasers have the advantages of low price, simple structure, easy maintenance, and low cost of use. The coordinated movement of the three can ensure the processing effect.

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

[0029] In this embodiment, during laser arc hybrid welding: the angle α of the welding gun 4 is 40°-50°; the welding wire is a carbon steel welding wire with a diameter of 1.0 mm and a dry extension l of 10-15 mm; the defocus amount d of the laser 3 is 5±0.5 mm, and the defocus amount d is based on the upper surface of the plate strip. The focus of the laser 3 is positive when it is located above the upper surface and negative when it is located below the plate surface; the filament spacing D is 3-5 mm.

[0030] In this embodiment, shielding gas is blown toward both the front and back sides of the weld during laser arc hybrid welding, and shielding gas for the front side of the weld is blown out by the welding gun 4 to ensure welding quality; wherein, the shielding gas for 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 for the back side of the weld is argon (purity 99.99%), 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±0.5 mm; the length L of the induction heating is determined by the traveling speed of the induction heating, ensuring that sufficient heating time is applied to the formed weld.

[0032] In this embodiment, the 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 high carbon steel strips at two locations

[0034]

[0035]

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

[0037] This method applies laser arc hybrid welding to the butt welding of high-carbon steel plates and strips. Laser arc hybrid welding can achieve greater penetration depth and larger upper surface weld width at lower laser power. Therefore, on the one hand, it is beneficial to the escape of gas during the welding process, thereby reducing hole defects in the weld and improving weld quality. On the other hand, it can achieve high welding speed at low laser power, thereby improving welding efficiency and reducing costs and increasing efficiency. At the same time, this method uses induction heating to perform online tempering heat treatment on the formed weld, which can temper the weld in time, thereby improving the weld toughness and cold crack resistance. This method determines the welding parameters and heat treatment power based on the average thickness of the two high-carbon steel plates and strips, so that high-carbon steel plates and strips of different thicknesses can achieve good treatment effects, avoiding the influence of thickness changes on welding quality. The product obtained by this method has good toughness and is not easy to break.

[0038] Application Examples

[0039] There are two high-carbon steel strips to be welded, made of 65Mn and 75Cr1, with carbon contents of 0.65% and 0.75%, respectively, and thicknesses of 4.2mm and 4.5mm, respectively, with an average thickness of 4.35mm. The two high-carbon steel strips are first clamped with a clamping device, and the weld ends are sheared. The weld ends are then butted together, and the joint is then simultaneously subjected to laser arc hybrid welding and online heat treatment. The welding speed of the laser arc hybrid welding and the travel speed of the induction heating are both 2.5m / min, the laser power is 6.2kW, the welding voltage is 15.9V, the welding current is 138A, the heat treatment power is 24kW, and the defocus distance is 5mm. After treatment, the weld is crack-free, the cupping test crack does not tear along the longitudinal direction of the weld, and the cupping test results are qualified. The weld does not break during the subsequent process (pickling + rolling).

[0040] The embodiments described above are part of the embodiments of the present application, rather than all of the embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative efforts 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 strips, characterized in that: For two high-carbon steel strips with a thickness difference within a certain range, after the welding ends of the two are butt-jointed, laser arc hybrid welding and online heat treatment are performed simultaneously on the joint: along the welding direction, arc welding is performed in front and laser welding is performed in the back to weld the joint on one side. Laser arc hybrid welding not only promotes gas escape during welding, thereby reducing porosity defects in the weld, but also 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, induction heating is used to perform online tempering heat treatment on the formed weld in synchronization with the welding speed to reduce the formation of hardened structure and welding stress, thereby improving weld toughness and cold crack resistance. In addition, the welding parameters and heat treatment power are determined according to the average thickness of the two high-carbon steel strips to adjust and optimize the process and avoid the influence of thickness changes on welding quality.

2. The method for improving the weld quality and welding efficiency of a high carbon steel strip according to claim 1, wherein: The mass ratio of the carbon content of the high carbon steel strip is 0.6%-0.8%. Assuming that 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 is 1.5-5mm; with 0.25mm as a small gear and 0.5mm as a large gear, the average thickness of the two high carbon steel strips is divided into 14 small gears or 7 large gears from 1.5mm to 5mm. With each additional small gear, the laser power and heat treatment power of laser welding will increase accordingly, and with each additional large gear, the welding voltage and welding current of arc welding will increase accordingly.

3. The method for improving the weld quality and welding efficiency of a high carbon steel strip according to claim 1, wherein: The arc welding machine for arc welding adopts the CMT process of the push-pull wire system, the laser welding machine for laser welding adopts a solid laser, and the induction heater for induction heating is driven by a traveling trolley and ensures coordinated movement with the arc welding machine and the laser welding machine.

4. The method for improving the weld quality and welding efficiency of a high carbon steel strip according to claim 1, wherein: The welding speed of laser arc hybrid welding and the traveling speed of induction heating are both 2.5m / min.

5. The method for improving the weld quality and welding efficiency of high carbon steel strip according to claim 1, wherein: During laser arc hybrid welding: the welding gun angle α is 40°-50°; the welding wire is carbon steel wire with a diameter of 1.0 mm and a dry extension l of 10-15 mm; the laser defocus d is 5±0.5 mm, and the defocus d is based on the upper surface of the plate and strip. The laser focus is positive when it is above the upper surface and negative when it is below the plate surface; the filament spacing D is 3-5 mm.

6. The method for improving the weld quality and welding efficiency of a high carbon steel strip according to claim 1, wherein: During laser arc hybrid welding, shielding gas is blown toward the front and back of the welding part, and the shielding gas on the front of the weld is blown out by the welding gun.

7. The method for improving the weld quality and welding efficiency of a high carbon steel strip according to claim 6, wherein: The shielding gas on the front of the weld is a mixture of argon and carbon dioxide, with a flow rate of 25-30L / min and a pressure of 0.4-0.6Mpa; the shielding gas on the back of the weld is argon, with a flow rate of 8-12L / min, a blowing angle θ of 30°-40°, and a pressure of 0.4-0.6MPa.

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

9. The method for improving the weld quality and welding efficiency of a high carbon steel strip according to claim 1, wherein: Before butting the welded ends of two high carbon steel strips, the welded ends are sheared to ensure that the butt joint surfaces fit tightly.

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