A small-angle full-penetration welding method for extra-thick plates

Abstract

The present invention discloses a method for full penetration welding of extra-thick plates at small angles. The thickness of the extra-thick plates to be welded is greater than or equal to 50 cm; a gap is left between the welding plates, and the two sides are welded with double-sided welds with large and small angles; the large angle side is processed into a J-shaped groove by carbon arc gouging, and then a ceramic liner is attached. The small angle side is welded first, and then the large angle side is welded. The weld is welded using flat multi-pass full welding. The method for full penetration welding of extra-thick plates at small angles of the present invention adopts a double-sided welding structure with a gap left between the welding plates; a ceramic liner is attached to the large angle side, and the small angle side is welded first, and then the large angle side; the weld is welded using flat welding. After the ceramic liner is attached to the large angle side, the small angle side is welded; after the small angle side is welded, the large angle side is welded. The present invention realizes full penetration fillet welds of small angle welds of extra-thick plates, reduces the welding difficulty and the probability of welding leakage; the weld is well-formed and well-fused, solving the shortcomings of conventional fillet welds in small angle welding.

Description

Technical Field

[0001] The invention belongs to the field of welding technology, in particular to the field of bridge steel structure welding technology, and relates to a small-angle full-penetration welding method for extra-thick plates. Background Art

[0002] With the rapid advancement of bridge construction technology, urban steel bridges are evolving from meeting functional requirements to addressing both functional and landscape needs. Modern bridge designs often present the structure itself as a landscape sculpture, with graceful lines that blend seamlessly with nature. The pursuit of novel systems and unique, elegant curved surfaces often comes at the expense of structural stability, presenting significant technical challenges in bridge construction.

[0003] In existing bridge construction, the cross-section of the steel arch wall panels of the bridge is often curved in both directions, the angle between the wall panels changes gradually, the minimum angle of the main weld at the acute angle is only 22°, the main weld is fully penetrated, the weld quality grade is high, the internal space of the arch rib is small, and welding is difficult.

[0004] Thick plate full-penetration fillet welds are typically welded using methods such as carbon arc gouging, gap-reserving backing, and ceramic or steel backing. When welding on one side of a full-penetration weld is inconvenient, a steel or ceramic backing is attached to the back of the weld. Alternatively, a single-sided welding and double-sided forming process without a backing is used. For curved welds in bridge arch rib panels, applying a steel backing to the back cannot ensure close contact with the base material because the angle is too small, the backing space is limited, and there is no suitable ceramic available. For steel plates up to 80mm thick, the single-sided welding and double-sided forming process without a backing is extremely difficult and cannot guarantee weld quality. Summary of the Invention

[0005] The present invention discloses a method for full penetration welding of extra-thick plates at small angles. The present invention aims to provide a method for full penetration welding of extra-thick plates at small angles, thereby overcoming the shortcomings of conventional full penetration fillet weld welding methods in small-angle welding.

[0006] The present invention is achieved through the following technical solutions:

[0007] The method is characterized by a small-angle full penetration welding of extra-thick plates, with the thickness of the two welded extra-thick plates being greater than or equal to 50cm. The method is characterized by leaving a gap between the two welded plates, and welding the two sides with a large and small angle double-sided weld seam. The large-angle side is processed into a J-shaped groove by carbon arc gouging and then a ceramic liner is attached. The small-angle side is welded first, followed by the large-angle side. The weld seam is welded using flat multi-pass full-pass welding.

[0008] The welding method includes the following steps:

[0009] Welding preparation: The ends of the inclined steel plates in the two welding plates are cut to form an inclined surface with an acute angle of less than 90 degrees. A gap weld is formed between the ends of the inclined steel plates and the welding surface of the flat steel plates, with a small angle of less than or equal to 22 degrees on one side and a large angle of greater than 22 degrees and less than 90 degrees on the other side. A gradually changing J-shaped groove is formed on the large-angle side and the end surface of the inclined steel plate by carbon arc gouging, and a ceramic liner is attached to the top of the J-shaped groove.

[0010] Welding steps and conditions: Multi-pass welding is used. The first pass is welded on the small angle side, and the order is 2 to 4 passes outward from the small angle side. After the small angle welding is completed, the ceramic liner is removed and the other side is welded. The fifth pass is welded on the large angle side, and the order is 6 passes outward until the full weld is completed. The welding method adopts CO2 gas shielded welding with a purity of >99.5%. The welding wire is HTW-58 with a diameter of 1.2mm.

[0011] The gap between the two welding plates is 3 to 8 mm; the ceramic liner is a round rod ceramic liner with a diameter of φ6 to φ10 mm.

[0012] The welding preheating temperature is 120-150℃, and the interpass temperature is 120-200℃; welding preheating adopts flame preheating or electric heating, the preheating range is more than 100mm on each side of the weld, and the temperature is measured within 30-50mm from the weld.

[0013] The first welding parameter of the present invention is a current of 220-240A, an arc voltage of 28-30V, a welding speed of 15.6m / h, and an interpass temperature of 120°C; the second to fourth welding parameters are a current of 260-280A, an arc voltage of 30-32V, a welding speed of 16.2-30.7m / h, and an interpass temperature of 120-145°C; the fifth welding parameter is a current of 220-240A, an arc voltage of 28-30V, a welding speed of 15.6m / h, and an interpass temperature of 120-145°C. The welding parameters for the 6th to 197th passes are as follows: welding current 260-280A, arc voltage 30-32V, welding speed 20.5-30.1m / h, and interpass temperature 120-165°C; the welding parameters for the 198th to full pass are as follows: welding current 260-280A, arc voltage 30-32V, welding speed 25.6-33.4m / h, and interpass temperature 125-155°C.

[0014] This method for full penetration welding of extra-thick plates at small angles utilizes a double-sided welding structure with a gap between the plates. A ceramic backing is placed on the high-angle side, and welding is performed on the low-angle side first, followed by the high-angle side. The weld seam is welded flat. After the ceramic backing is placed on the high-angle side, welding is performed on the low-angle side. After welding the low-angle side, welding is then performed on the high-angle side. If the weld seam on the back of the low-angle side is poorly formed, carbon arc gouging can be performed on the high-angle side.

[0015] The method for full penetration welding of extra-thick plates with small angles according to the present invention has the following beneficial effects:

[0016] 1. By using the method of attaching ceramic liner on the large angle side, the small angle side is welded first, and then the large angle side is welded, thus achieving full penetration fillet weld of small angle weld of extra thick plate.

[0017] 2. Using round rod ceramic liners of different specifications according to different gaps can reduce the difficulty of welding on the small angle side and also reduce the probability of welding leakage.

[0018] 3. The welding process of the present invention ensures that the weld is well formed and fused, which can provide a reference for welding of similar structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of J-shaped groove processing; in the figure, a J-shaped groove with a gradual angle from the outside to the flat steel plate side is formed at the end of the end face of the inclined steel plate by carbon arc air gouging, and the gradual angle gradually increases as it approaches the welded flat steel plate.

[0020] Figure 2 It is a schematic diagram of the test groove form.

[0021] Figure 3 It is a schematic diagram of welding deposition; in the figure, the numbers represent each weld bead, the first weld is on the small angle side, and the order outward from the small angle side is 2 to 4 weld bead, the fifth weld is on the large angle side, and the order outward is 6 weld bead to full weld.

[0022] In the figure, A is the ceramic liner, T is the thickness of the welded steel plate, b is the gap between the plates, and α is the maximum angle of the weld. DETAILED DESCRIPTION

[0023] The present invention is further described below in conjunction with specific embodiments. The specific embodiments are further explanations of the principles of the present invention and do not limit the present invention in any way. Technologies that are the same or similar to the present invention do not exceed the scope of protection of the present invention.

[0024] Combined with the attached drawings.

[0025] The small-angle full-penetration welding method for extra-thick plates in this embodiment is completed by the following welding method:

[0026] 1. The welding material is 80mm thick Q420qD steel plate, and the small angle of the fillet weld is 22°; the welding method is CO2 gas shielded welding with a purity of >99.5%; the welding wire is HTW-58 with a diameter of 1.2mm.

[0027] 2. Welding steel plates need to be processed into J-shaped grooves. First, flame cutting is used to form V-shaped grooves, and then carbon arc gouging is used to form J-shaped grooves. Figure 2 shown.

[0028] 3. The gap between the plates should be controlled at 3~8mm. After attaching φ8mm round rod ceramic liner on the large angle side, weld the small angle side. Figure 3 As shown in the figure, after the small angle side is welded, the large angle side can be welded. If the back weld of the small angle side is poor, carbon arc gouging can be performed on the large angle side.

[0029] 4. Welding adopts multi-layer and multi-pass welding, such as Figure 3 As shown; the first welding specification parameters are current 220 ~ 240A, arc voltage 28 ~ 30V, welding speed 15.6m / h, and interpass temperature 120℃; the second to fourth welding specification parameters are current 260 ~ 280A, arc voltage 30 ~ 32V, welding speed 16.2 ~ 30.7m / h, and interpass temperature 120 ~ 145℃; the fifth welding specification parameters are current 220 ~ 240A, arc voltage 28 ~ 30V, The welding speed is 16.7m / h, and the interpass temperature is 120℃; the standard welding parameters for the 6th to 197th passes are current 260~280A, arc voltage 30~32V, welding speed 20.5~30.1m / h, and interpass temperature 120~165℃; the standard welding parameters for the 198th to 212th passes are current 260~280A, arc voltage 30~32V, welding speed 25.6~33.4m / h, and interpass temperature 125~155℃.

[0030] 5. After welding, the weld should be inspected for appearance, and after passing the appearance inspection, non-destructive testing should be carried out. The non-destructive testing should be carried out 48 hours after welding.

[0031] The mechanical properties of the joints in this embodiment are shown in Tables 1 and 2. The measured lower yield strength (ReL) was 520 MPa, exceeding the standard value of 420 MPa; the measured tensile strength (Rm) was 560 MPa, exceeding the standard value of 540 MPa; and the measured elongation (A) was 30%, exceeding the standard value of 19%. The minimum low-temperature impact energy measured at the weld was 218 J, and the minimum measured heat-affected zone was 182 J, exceeding the standard value of 47 J. The maximum hardness in all zones of the joint was 180 HV10, less than the standard value of 380 HV10.

[0032] The test results show that the weld strength, elongation and low-temperature impact energy are all higher than the standard values, and the mechanical properties of the joint meet the standard requirements.

[0033] Table 1 Weld tensile and impact test results

[0034]

[0035] Table 2 Joint hardness test results (HV10)

[0036] weld metal heat-affected zone parent material Maximum hardness Standard value 157～180 154～174 160～171 180 No more than 380HV10

Claims

1. A method for full penetration welding of extra-thick plates at a small angle, wherein the thickness of the two welded extra-thick plates is greater than or equal to 50 cm; characterized in that: A gap is left between the two welding plates, and the two sides are welded with double-sided welds with large and small angles. The large-angle side is processed into a J-shaped groove by carbon arc gouging and then a ceramic liner is attached. The small-angle side is welded first, and then the large-angle side. The weld is welded with flat multi-pass full welding. The welding method includes the following steps: Welding preparation: The ends of the inclined steel plates in the two welding plates are cut to form an inclined surface with an acute angle of less than 90 degrees. A gap weld is formed between the ends of the inclined steel plates and the welding surface of the flat steel plates, with a small angle of less than or equal to 22 degrees on one side and a large angle of greater than 22 degrees and less than 90 degrees on the other side. A gradually changing J-shaped groove is formed on the large-angle side and the end surface of the inclined steel plate by carbon arc gouging, and a ceramic liner is attached to the top of the J-shaped groove. Welding steps and conditions: Multi-pass welding is used. The first pass is welded on the small angle side, and the order is 2 to 4 passes outward from the small angle side. After the small angle welding is completed, the ceramic liner is removed and the other side is welded. The fifth pass is welded on the large angle side, and the order is 6 passes outward until the full weld is completed. The welding method adopts CO2 gas shielded welding with a purity of >99.5%. The welding wire is HTW-58 with a diameter of 1.2mm.

2. The method for full penetration welding of extra thick plates with small angles according to claim 1, characterized in that: The gap between the two welding plates is 3 to 8 mm; the ceramic liner is a round rod ceramic liner with a diameter of φ6 to φ10 mm.

3. The method for full penetration welding of extra thick plates with small angles according to claim 2, characterized in that: The welding preheating temperature is 120-150℃, and the interpass temperature is 120-200℃; welding preheating adopts flame preheating or electric heating, the preheating range is more than 100mm on each side of the weld, and the temperature is measured within 30-50mm from the weld.

4. The method for full penetration welding of extra thick plates with small angles according to claim 3, characterized in that: The welding parameters for the first pass are current 220-240A, arc voltage 28-30V, welding speed 15.6m / h, and interpass temperature 120°C; the welding parameters for the second to fourth passes are current 260-280A, arc voltage 30-32V, welding speed 16.2-30.7m / h, and interpass temperature 120-145°C; the welding parameters for the fifth pass are current 220-240A, arc voltage 28-30V, welding speed 16.7m / h, interpass temperature 120℃; the welding parameters for the 6th to 197th passes are current 260~280A, arc voltage 30~32V, welding speed 20.5~30.1m / h, interpass temperature 120~165℃; the welding parameters for the 198th to full pass are current 260~280A, arc voltage 30~32V, welding speed 25.6~33.4m / h, interpass temperature 125~155℃.

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