Submerged arc horizontal position welding method for 9Ni steel medium plate
By using an asymmetric Y-groove submerged arc horizontal welding method, the problems of hot cracking, cold cracking, and poor low-temperature toughness in the welding of 9Ni steel medium and thick plates were solved, achieving efficient and high-quality welding results.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-16
- Publication Date
- 2026-03-27
AI Technical Summary
Existing welding methods for 9Ni steel medium and thick plates are complex and prone to problems such as hot cracking, cold cracking, arc blow, and poor low-temperature toughness, especially at the welded joint where the strength is poor.
The submerged arc horizontal welding method using an asymmetric Y-groove includes pretreatment, root pass welding, fill pass welding, and cover pass welding steps. It combines nickel-chromium-molybdenum welding wire and a specific flux to perform double-sided welding and cleaning to ensure welding quality.
It improves the low-temperature impact toughness and strength of welded joints, reduces hot cracking, enhances welding efficiency and quality, and simplifies the operation process.
Smart Images
Figure CN121732946A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the technical field of 9Ni steel welding, specifically a submerged arc horizontal welding method for 9Ni steel medium-thick plates. Background Technology
[0002] In existing technology, 9Ni steel is an ultra-low temperature steel with a nickel content of approximately 9%. 9Ni steel medium-thick plates refer to 9Ni steel plates with a thickness between 5-100 mm. 9Ni steel medium-thick plates are low-temperature toughness steels used in shipbuilding and marine engineering, characterized by high strength, excellent low-temperature toughness, and good weldability. They exhibit excellent low-temperature toughness at -196℃, and are therefore widely used in low-temperature environments for liquefied gas carriers, land vessels, and cryogenic marine engineering.
[0003] However, current welding methods generally use flat welding, which is more complicated to operate. At the same time, the welded joint may have quality problems such as poor strength. The main problems that are prone to occur during the welding of 9Ni steel include hot cracking, cold cracking, arc magnetic blow, and low temperature toughness, among which hot cracking is more prominent.
[0004] Therefore, there is an urgent need to develop a new welding method for 9Ni steel medium and thick plates. Summary of the Invention
[0005] The purpose of this invention is to provide an improved submerged arc horizontal welding method for 9Ni steel medium-thick plates. Through the improvement of the method, the welded joint has excellent low-temperature impact toughness, improves welding quality, simplifies operation, and improves welding efficiency.
[0006] To achieve the above objectives, the technical solution of the present invention is: a submerged arc horizontal welding method for 9Ni steel medium-thick plates, characterized by the following steps: S1, pretreatment: a bevel is processed on the edge of the steel plate to be welded, an asymmetrical Y-shaped bevel is formed between the two steel plates to be welded, and the flux is preheated and kept at a certain temperature; S2, during welding: first, root pass welding is performed at the bottom of the asymmetrical Y-shaped bevel, then filler weld is performed inside the bevel, and finally cover pass welding is performed on the surface; S3, after welding, cleaning is performed: after the welded steel plate has cooled naturally to room temperature, the weld surface is cleaned with a wire brush to complete the welding work.
[0007] Preferably, in step S1, the asymmetrical Y-shaped bevel has an upper bevel angle that is 2-3.5 times the lower bevel angle. The upper bevel angle is 40° on one side, the lower bevel angle is 15° on one side, the blunt edge is 4mm, and the gap is 0-1mm.
[0008] Furthermore, in step S1, a 9Ni steel plate with a thickness of 18-24mm is used, the welding wire is ERNICrMo-3 nickel-chromium-molybdenum welding wire with a nickel content of more than 60% and a diameter of 2.4mm, the flux is N100-50BS, and the flux is heated to 315°C and held for 1 hour before welding.
[0009] Furthermore, in step S2, double-sided welding is performed. That is, after asymmetrical Y-shaped bevel welding is performed on the front side, the back side is cleaned and a bevel is made before welding on the back side.
[0010] Furthermore, in step S2, the welding current for the root pass is 220~290A, the welding voltage is 29~31V, and the welding speed is 24~28cm / min; the welding current for the fill pass is 190~280A, the welding voltage is 28~31V, and the welding speed is 23~28cm / min; and the welding current for the cover pass is 240~270A, the welding voltage is 29~30V, and the welding speed is 23~28cm / min. The welding heat input is 10~35KJ / cm, and during fill pass welding, the interpass temperature for multi-layer welding is less than or equal to 150℃.
[0011] Furthermore, during bevel welding, after the first root pass, the filler and cover pass are directly performed. The first filler and cover pass weld should have straight edges and protrude longitudinally from the bevel edge by 1-2mm. Subsequent welds are based on the previous welds and are filled layer by layer. Before each weld, the welding wire is aligned with the upper edge of the previously formed weld, and the welding wire is tilted downward at an appropriate angle. The welding wire forms an angle of 25-30 degrees with the upper edge of each formed weld.
[0012] Furthermore, the direction of root cleaning of the back weld should be consistent with that of the front weld to avoid deviation. During the grinding process, defects such as pores, incomplete penetration, and incomplete fusion in the weld should be removed, and a bevel with a depth of 8mm and a width of 14mm should be made.
[0013] Compared with the prior art, the technical solution of the present invention not only improves the overall technical solution, but also includes many improvements in details. Specifically, it has the following beneficial effects: 1. The improved solution of the present invention first pre-treats the steel plates to be welded by processing bevels on the edges, forming an asymmetrical Y-shaped bevel between the two steel plates to be welded, and preheating and holding the flux; during welding, first perform root pass welding at the bottom of the asymmetrical Y-shaped bevel, then perform filler weld within the bevel, and finally perform cover pass welding on the surface, so that the welded joint has excellent strength, cold bending and low-temperature impact toughness, improves welding quality and increases welding efficiency; 2. In the technical solution of the present invention, double-sided welding is performed, that is, after the asymmetrical Y-shaped bevel welding is performed on the front side, the back side is cleaned and a bevel is made before welding on the back side. This can effectively improve the bending performance of the back side, so that the welded joint can bend the core side by 180° without cracks, effectively improving the welding quality and reducing hot cracks. 3. The process steps of this invention are simple and reasonable, easy to implement, reduce the difficulty of manual operation, improve welding quality and welding efficiency, and are easy to promote and utilize. Attached Figure Description
[0014] Figure 1 This is a schematic diagram of the asymmetric Y-shaped groove for submerged arc horizontal welding according to the present invention.
[0015] Figure 2 This is a schematic diagram showing the angle between the submerged arc welding wire and the weld seam according to the present invention.
[0016] Figure label: 1. Steel plate to be welded, 2. Asymmetrical Y-shaped bevel, 3. Welding torch nozzle, 4. Welding wire. Detailed Implementation
[0017] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0018] This invention provides a submerged arc horizontal welding method for 9Ni steel medium-thick plates, see details below. Figure 1 The difference between this method and existing technology is as follows: S1. Pretreatment: Process a bevel on the edge of the steel plate to be welded, forming an asymmetrical Y-shaped bevel between the two steel plates to be welded. Preheat the flux and keep it warm. S2. During welding: First, perform root pass welding at the bottom of the asymmetrical Y-shaped bevel, then perform fill pass welding inside the bevel, and finally perform cover pass welding on the surface. S3. Cleaning after welding: After the welded steel plates have cooled naturally to room temperature, use a wire brush to grind the weld surface clean to complete the welding work.
[0019] Now, beveling is done on the steel plates to be welded, creating an asymmetrical Y-shaped bevel between the two plates. During welding, the root pass is performed first, followed by the fill pass, and finally the cap pass. This results in a welded joint with excellent strength, cold bending, and low-temperature impact toughness, improving weld quality and efficiency. Double-sided welding is also possible: after asymmetrical Y-shaped bevel welding on the front side, the back side is cleaned, a bevel is created, and then welding is performed. This effectively improves the back bending performance, allowing the welded joint to bend 180° without cracking, significantly improving weld quality and reducing hot cracking.
[0020] Example 1 This embodiment describes a submerged arc horizontal welding method for 9Ni steel medium-thick plates. See details below. Figure 1 The difference between this method and existing technology is as follows: S1. Pretreatment: Process a bevel on the edge of the steel plate to be welded, forming an asymmetrical Y-shaped bevel between the two steel plates to be welded. Preheat the flux and keep it warm. S2. During welding: First, perform root pass welding at the bottom of the asymmetrical Y-shaped bevel, then perform fill pass welding inside the bevel, and finally perform cover pass welding on the surface. S3. Cleaning after welding: After the welded steel plates have cooled naturally to room temperature, use a wire brush to grind the weld surface clean to complete the welding work.
[0021] Specifically, in step S1, the asymmetrical Y-shaped bevel has an upper bevel angle that is 2-3.5 times the lower bevel angle. The upper bevel angle is 40° on one side, the lower bevel angle is 15° on one side, the blunt edge is 4mm, and the gap is 0.3mm. In step S1, a 18-24mm thick 9Ni steel plate is used, the welding wire is ERNICrMo-3 nickel-chromium-molybdenum welding wire with a nickel content of over 60%, the wire diameter is 2.4mm, and the flux is N100-50BS. The flux is heated to 315°C and held for 1 hour before welding.
[0022] Furthermore, in step S2, double-sided welding is performed. That is, after asymmetrical Y-groove welding on the front side, the back side is cleaned and a groove is created before welding on the back side. The groove here can be a U-groove, a V-groove symmetrical groove, or a V-groove asymmetrical groove.
[0023] In step S2, the welding current for the root pass is 220-290A, the welding voltage is 29-31V, and the welding speed is 24-28cm / min; the welding current for the fill pass is 190-280A, the welding voltage is 28-31V, and the welding speed is 23-28cm / min; the welding current for the cover pass is 240-270A, the welding voltage is 29-30V, and the welding speed is 23-28cm / min. The welding heat input is 10-35KJ / cm, and the interpass temperature for multi-layer welding during fill pass welding is less than or equal to 150℃.
[0024] Furthermore, during bevel welding, after the first root pass, the filler and cover pass are directly performed. The first filler and cover pass weld must have straight edges and protrude longitudinally 1-2mm from the bevel edge. Subsequent welds are based on the previous weld, filling layer by layer. Before each weld, the welding wire is aligned with the upper edge of the previously formed weld, and the welding wire 4 is tilted downwards at an appropriate angle. In this embodiment, the welding wire 4 forms a 28-degree angle with the upper edge of each formed weld. See [reference needed]. Figure 2This avoids excessive arc penetration into the base material on the upper side of the bevel, which could cause significant sagging of the deposited metal, resulting in undercut on the upper side and curling on the lower side. The direction of root cleaning on the back side of the weld should be consistent with that of the front side weld to avoid deviation. During grinding, defects such as porosity, incomplete penetration, and lack of fusion within the weld must be removed, creating a bevel 8mm deep and 14mm wide. Double-sided welding effectively improves the bending performance on the back side, allowing the welded joint to bend 180° without cracking, thus significantly improving weld quality.
[0025] Example 2 This embodiment describes the following submerged arc horizontal welding method for 9Ni steel medium-thick plates, with the following steps: S1, pretreatment: a bevel is processed on the edge of the steel plate to be welded, forming an asymmetrical Y-shaped bevel between the two steel plates to be welded, and the flux is preheated and kept at a certain temperature; S2, welding: first, root pass welding is performed at the bottom of the asymmetrical Y-shaped bevel, then filler weld welding is performed inside the bevel, and finally cover weld welding is performed on the surface; S3, cleaning after welding: after the welded steel plates have cooled naturally to room temperature, the weld surface is cleaned with a wire brush to complete the welding work.
[0026] Specifically, the implementation steps are as follows: (1) Welding materials Base material: 9Ni steel with a thickness of 18mm; Welding material: ERNICrMo-3, welding wire diameter: 2.4mm; flux: N100-50BS, preheat to 315°C and hold for 1 hour.
[0027] (2) Welding method The welding method is submerged arc automatic horizontal welding, using a SAWH-1 type submerged arc automatic horizontal welding machine. The bevel adopts an asymmetrical Y-type bevel, with an upper bevel angle of 40° on one side and a lower bevel angle of 15° on one side. The blunt edge is 4mm, and the gap is 0-1mm.
[0028] (3) Welding test The welding process uses the following welding parameters.
[0029] Table 1 Welding process parameters for the embodiment (4) Test results Welded joints were inspected according to GB / T2650-2008, GB / T2651-2008, and GB / T2653-2008, including tensile, bending (180° side bending of the joint), impact, and hardness tests. The test results are shown in Tables 2 and 3, and meet the standard requirements.
[0030] Table 2 Tensile and bending properties of the embodiments Table 3 Impact performance of the embodiments As can be seen from the test data in Table 2-3 and the test parameters in Table 1, the welding of 9Ni steel medium-thick plates using the method of the present invention results in welds that meet quality requirements in terms of appearance and have no significant surface defects; the tensile strength of the welded joint is not less than 690MPa; there are no cracks at 180° when the bending mandrel diameter D=6a (plate thickness); and the welded joint has excellent low-temperature impact toughness.
[0031] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.
Claims
1. A submerged arc horizontal welding method for 9Ni steel medium-thick plates, characterized in that: The steps are as follows: S1. Pretreatment: Process a bevel on the edge of the steel plate to be welded, forming an asymmetrical Y-shaped bevel between the two steel plates to be welded. Preheat the flux and keep it at a certain temperature. S2. Welding: First, perform root pass welding at the bottom of the asymmetrical Y-shaped bevel, then perform fill pass welding inside the bevel, and finally perform cover pass welding on the surface. S3. Cleaning after welding: After the welded steel plates have cooled naturally to room temperature, use a wire brush to grind the weld surface clean to complete the welding work.
2. The submerged arc horizontal welding method for 9Ni steel medium-thick plates according to claim 1, characterized in that: In step S1, for the asymmetrical Y-shaped bevel, the upper bevel angle is 2-3.5 times the lower bevel angle.
3. The submerged arc horizontal welding method for 9Ni steel medium-thick plates according to claim 2, characterized in that: The upper bevel angle is 40° on one side, the lower bevel angle is 15° on one side, the blunt edge is 4mm, and the gap is 0-1mm.
4. The submerged arc horizontal welding method for 9Ni steel medium-thick plates according to claim 1, characterized in that: In step S1, a 9Ni steel plate with a thickness of 18-24mm is used, the welding wire is a nickel-chromium-molybdenum welding wire with a nickel content of more than 60% and a diameter of 2.4mm, the flux is N100-50BS, and the flux is heated to 315°C and held for 1 hour before welding.
5. The submerged arc horizontal welding method for 9Ni steel medium-thick plates according to claim 1, characterized in that: In step S2, double-sided welding is performed. That is, after asymmetrical Y-shaped bevel welding is performed on the front side, the back side is cleaned and a bevel is made before welding on the back side.
6. The submerged arc horizontal welding method for 9Ni steel medium-thick plates according to claim 1, characterized in that: In step S2, the welding current for the root pass is 220~290A, the welding voltage is 29~31V, and the welding speed is 24~28cm / min; the welding current for the fill pass is 190~280A, the welding voltage is 28~31V, and the welding speed is 23~28cm / min; and the welding current for the cover pass is 240~270A, the welding voltage is 29~30V, and the welding speed is 23~28cm / min.
7. The submerged arc horizontal welding method for 9Ni steel medium-thick plates according to claim 5, characterized in that: The welding heat input is 10~35KJ / cm. When performing filler welding, the interpass temperature of multi-layer welding is less than or equal to 150℃.
8. A submerged arc horizontal welding method for 9Ni steel medium-thick plates according to claim 5, characterized in that: When welding the bevel, after the first root pass, the filler and cover pass should be performed directly. The first filler and cover pass should have straight edges and protrude 1-2mm beyond the bevel edge longitudinally. Each subsequent pass should be based on the previous pass and filled layer by layer. Before each pass, the welding wire should be aligned with the upper edge of the previously formed weld, with the welding wire angle pointing downwards at an appropriate angle. The welding wire should form an angle of 25-30 degrees with the upper edge of each formed weld.
9. A submerged arc horizontal welding method for 9Ni steel medium-thick plates according to claim 5, characterized in that: The direction of root cleaning of the back weld should be consistent with that of the front weld to avoid deviation. During the grinding process, defects such as pores, incomplete penetration and lack of fusion in the weld should be removed, and a bevel with a depth of 8mm and a width of 14mm should be made.