Method for improving welding efficiency of 9% nickel steel butt joint welding seam

Abstract

The application discloses a method for improving welding efficiency of 9% nickel steel vertical butt joint plate welds, comprising the following steps: (1) X-type grooves are formed on the 9% nickel steel plate, and the plate is matched according to the X-type groove matching size requirements; (2) the bevel of the groove surface of the 9% nickel steel plate is polished, and the impurities on the two sides of the groove front and back welds are removed; (3) a Kama plate is used to strengthen and fix the back weld of the 9% nickel steel plate, and an arc extinguishing plate is additionally arranged at the arc extinguishing end of the 9% nickel steel plate weld; (4) when the front of the X-type groove of the 9% nickel steel plate is welded, bottoming welding is first performed, then filling welding is performed, and then surface welding is performed; (5) when the back of the X-type groove of the 9% nickel steel plate is welded, bottoming welding is first performed, then filling welding is performed, and then surface welding is performed; (6) the appearance of the front and back welds and the internal quality of the welds are inspected. The application has good weld root fusion, reduces the welding workload and lowers the construction cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nickel steel welding, in particular to a method for improving the welding efficiency of 9% nickel steel vertical butt joint panel welds. BACKGROUND

[0002] With the development of LNG natural gas transportation and storage, LNG storage tanks are being used more and more widely, and the main material of LNG storage tanks is 9% nickel steel. Therefore, it is very important to do a good job in welding 9% nickel steel LNG storage tanks and improve the welding quality and efficiency of 9% nickel steel LNG storage tanks. As far as the current domestic use is concerned, the panel butt joint of 9% nickel steel LNG storage tank mainly adopts the method of front welding and back welding after carbon stripping.

[0003] However, the method for improving the welding efficiency of 9% nickel steel vertical butt joint panel welds is difficult to operate and has high requirements for panel assembly. At present, the vertical butt joint panel welds of 9% nickel steel LNG storage tanks are welded by the method of front welding and back welding after carbon stripping. Since the back weld is carbon stripped by a carbon rod, the back weld needs to be polished after carbon stripping. Therefore, the carbon stripping and polishing work is heavy, and the welding efficiency is low. Therefore, the current welding method has high cost in terms of labor hours, energy use and material consumption, which is not conducive to the improvement of welding quality and efficiency of 9% nickel steel LNG storage tank construction. Therefore, the above problems need to be solved. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a method for improving the welding efficiency of 9% nickel steel vertical butt joint panel welds. Compared with the traditional welding method, the root fusion of the weld is good, the welding workload is reduced, the welding efficiency is improved by more than 1 times, the material cost is reduced by 30%, the labor cost is reduced by 50%, and the construction cost is reduced, thereby improving the welding quality and efficiency of 9% nickel steel vertical butt joint panel welds.

[0005] To solve the above technical problems, the present application adopts the following technical scheme: the method for improving the welding efficiency of 9% nickel steel vertical butt joint panel welds comprises the following steps:

[0006] (1) X-type grooves are formed in the 9% nickel steel panel, and the vertical butt joint panel is assembled according to the size requirements of the X-type grooves;

[0007] (2) The bevel of the 9% nickel steel panel is polished, and the impurities on both sides of the front and back welds of the panel are removed;

[0008] (3) using the Kama plate to strengthen the 9% nickel steel plate weld back and ensure the assembly gap; then install the same plate thickness and same bevel angle arc extinguishing plate at the arc extinguishing end of the 9% nickel steel plate weld;

[0009] (4) using the welding method of welding from bottom to top, and when welding the X-type bevel front of the 9% nickel steel plate, first welding the front of the backing weld; then clean the weld slag on the surface of the backing weld, then welding the front of the filling weld; then clean the weld slag on the surface of the filling weld, then using the multi-layer and multi-pass annealing welding method to weld the front of the surface weld;

[0010] In the above steps, the front welding layer number is 4 layers and 7 passes, and the front of the backing weld selects the welding rod with the ENiGrMo-6 brand and the φ3.2 specification, the welding current is 100~110A, the welding voltage is 21~22V, and the welding speed is 80~100mm / min; the up and down angle of the welding rod is 85~95°, the left and right angle of the welding rod is 85~95°, and the arc length of the welding rod is controlled within 2mm; the first layer of the backing weld uses the continuous arc breaking operation method and combines the left and right sawtooth welding swing gesture to weld, the continuous arc breaking of the welding rod should be at the position of the weld gap hole, and then a hole is formed at the front end of the weld pool during welding; the back weld height is controlled within 1~2mm, and the weld width is controlled within 4~6mm; the shrinkage hole generated at the crater position is ground to a transition slope at the backing weld joint, and the welding rod is quickly pulled to the joint position after the arc is started from the upper end of the weld joint;

[0011] In the above steps, the front of the filling weld selects the welding rod with the ENiGrMo-6 brand and the φ3.2 specification, the welding current is 120~130A, the welding voltage is 22~24V, and the welding speed is 100~150mm / min; the up and down angle of the welding rod is 85~95°, and the left and right angle of the welding rod is 85~95°; the left and right sawtooth continuous arc welding swing gesture is used during the filling weld, and the two sides are slightly paused during the left and right swing to ensure the penetration of the backing weld on both sides; the single pass weld width is not greater than 3.5 times the diameter of the welding rod, and the thickness of the single pass weld is controlled within 4mm; the third layer of the front of the filling weld starts to take the separate welding arrangement, and the annealing welding pass arrangement is used when the fourth layer of the surface is welded, and the weld slag on the surface of each weld is removed before the next welding;

[0012] (5) when welding the X-type bevel back of the 9% nickel steel plate, first welding the back of the backing weld; then clean the weld slag on the surface of the backing weld, then welding the back of the filling weld; then clean the weld slag on the surface of the filling weld, then using the multi-layer and multi-pass annealing welding method to weld the back of the surface weld;

[0013] In the above step, the back side of the filling cover surface welding is welded by 4 layers and 7 passes, and the back side of the filling cover surface welding is welded by 4 layers and 7 passes. The welding electrode is ENiGrMo-6, the specification is φ3.2, the welding current is 90-110A, the welding voltage is 21-23V, and the welding speed is 100-150mm / min. The up and down angle of the welding electrode is 85-95°, the left and right angle of the welding electrode is 85-95°, and the arc length of the welding electrode is controlled within 2mm. The back side of the filling cover surface welding adopts continuous arc left and right zigzag welding swing gesture, the welding electrode is in the front end of the molten pool, the molten pool is slightly stopped on both sides during the welding left and right swing, and the molten pool is quickly swung in the middle, so as to ensure the penetration of the back side of the filling cover surface welding and the flatness of the welding seam. The single pass welding seam width is not greater than 3.5 times the diameter of the welding electrode, and the thickness of the single pass welding seam is controlled within 4mm.

[0014] In the above step, the back side of the filling cover surface welding is welded by 4 layers and 7 passes, and the back side of the filling cover surface welding is welded by 4 layers and 7 passes. The welding electrode is ENiGrMo-6, the specification is φ3.2, the welding current is 120-130A, the welding voltage is 22-24V, and the welding speed is 100-150mm / min. The up and down angle of the welding electrode is 85-95°, the left and right angle of the welding electrode is 85-95°, and the arc length of the welding electrode is controlled within 2mm. The back side of the filling cover surface welding adopts continuous arc left and right zigzag welding swing gesture, the welding electrode is in the front end of the molten pool, the molten pool is slightly stopped on both sides during the welding left and right swing, and the molten pool is quickly swung in the middle, so as to ensure the penetration of the back side of the filling cover surface welding and the flatness of the welding seam. The single pass welding seam width is not greater than 3.5 times the diameter of the welding electrode, and the thickness of the single pass welding seam is controlled within 4mm.

[0015] (6) The appearance of the welding seam and the internal quality of the welding seam are inspected.

[0016] Preferably, in the above step (1), the 9% nickel steel plate is 9% nickel steel with a thickness of 30mm; the joint form of the 9% nickel steel plate is X-shaped, and the two side bevel angles are 50-60°, the bevel face is 1-2mm, and the root gap is 3-5mm.

[0017] Preferably, in the above step (2), the impurity removal range is within 30mm of the bevel of the 9% nickel steel plate.

[0018] Preferably, in the step (4), the front face cover welding selects the welding rod with the ENiGrMo-6 mark and the φ3.2 specification, the welding current is 120-130 A, the welding voltage is 22-24 V, and the welding speed is 100-150 mm / min; the up-down angle of the welding rod is 85-95°, the left-right angle of the welding rod is 85-95°, and the arc length of the welding rod is controlled within 2 mm; the left-right sawtooth continuous arc welding swing gesture is adopted during the cover welding, the two sides are slightly paused during the left-right swing, so as to ensure the fusion of the filling weld on both sides of the corner; the edge of the molten pool is controlled to cover the position of the groove edge line and the previous weld during the welding, so as to ensure the superposition forming of the cover weld, and the interlayer temperature of the weld is controlled to be 60-120 ℃ during the front face welding.

[0019] Preferably, in the step (5), the back face cover welding selects the welding rod with the ENiGrMo-6 mark and the φ3.2 specification, the welding current is 120-130 A, the welding voltage is 22-24 V, and the welding speed is 100-150 mm / min; the up-down angle of the welding rod is 85-95°, the left-right angle of the welding rod is 85-95°, and the arc length of the welding rod is controlled within 2 mm; the left-right sawtooth swing welding swing gesture is adopted during the cover welding, and the edge of the molten pool needs to be controlled to cover the position of the groove edge line and the previous weld during the welding of each weld of the cover welding, so as to ensure the superposition forming of the cover weld, and the interlayer temperature of the weld is controlled to be 60-120 ℃ during the back face welding.

[0020] The beneficial effects of the present application are as follows:

[0021] (1) Compared with the traditional welding method, the present application has good weld root fusion, reduces the welding workload, improves the welding efficiency by more than 1 times, reduces the material cost by 30%, reduces the labor cost by 50%, further reduces the construction cost, and improves the welding quality and welding efficiency of the 9% nickel steel vertical butt joint panel weld by 9%;

[0022] (2) The present application does not need to perform carbon planing, grinding and polishing on the back face, so that the welding efficiency of the 9% nickel steel vertical butt joint panel weld is greatly improved;

[0023] (3) The present application effectively controls the welding heat input in the welding process, ensures the fusion ratio of the weld, strictly controls the interlayer temperature of the weld, and has good forming of the front and back faces of the weld, and good mechanical properties such as tensile and bending, and meets the low-temperature impact requirement of-196 ℃;

[0024] (4) The welding method without carbon planing of the present application can effectively prevent the problem of carbon penetration in the weld caused by carbon planing, so that the internal quality of the 9% nickel steel vertical butt joint panel weld is improved. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to make the technical solutions in the embodiments of the present application clearer, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings described in the following are only some embodiments described in the present application, and other drawings can also be obtained according to these drawings without any creative effort for those skilled in the art.

[0026] Figure 1 The schematic diagram of assembling the butt joint plate of the present application.

[0027] Figure 2 The schematic diagram of assembling the Kama plate of the present application.

[0028] Figure 3 The schematic diagram of assembling the arc extinguishing plate of the present application.

[0029] Figure 4 The schematic diagram of the welding bead of the present application.

[0030] In the figure, 1-9% nickel steel plate; 2-Kama plate; 3-arc extinguishing plate. DETAILED DESCRIPTION

[0031] The technical solutions of the present application will be described clearly and completely in the following through specific embodiments.

[0032] A method for improving the welding efficiency of the welding seam of the 9% nickel steel vertical butt joint plate of the present application, as shown in the figure, comprises the following steps: Figures 1-4

[0033] (1) X-type grooves are formed on the 9% nickel steel plate 1, and the vertical butt joint plate is assembled according to the size requirements of the X-type grooves;

[0034] In the above step, the 9% nickel steel plate 1 is made of 9% nickel steel with the EN10028-4 mark and the thickness of 30 mm. The material has very good mechanical properties, especially the mechanical properties at extremely low temperatures, such as the impact performance of more than 41 J at-196 ℃, but the material has higher requirements for the control of the welding line energy during the welding process, and the welding process is relatively complex, and the interpass temperature should be strictly controlled during the welding process.

[0035] In the present application, the joint form of the 9% nickel steel plate 1 is X-shaped, and the groove angle of the two surfaces is 50-60°, the groove face bevel is 1-2 mm, and the root gap is 3-5 mm.

[0036] (2) The groove face bevel of the 9% nickel steel plate 1 is polished, and the bottom paint and rust impurities on the two sides of the groove front and back welds are removed;

[0037] In the above step, the impurity removal range is within 30 mm on the two sides of the groove front and back welds of the 9% nickel steel plate 1. ​

[0038] (3) Adopting the Kama plate 2 to strengthen and fix the back of the 9% nickel steel plate 1 weld, and to ensure the assembly gap; then installing the same plate thickness and same bevel angle of the arc extinguishing plate 3 at the arc extinguishing end of the 9% nickel steel plate 1 weld, and further ensuring the welding quality of the 9% nickel steel plate 1 weld starting and ending arc weld.

[0039] (4) Adopting the welding method of welding from bottom to top, and when welding the X-type bevel front of the 9% nickel steel plate 1, first performing the front of the backing welding; then cleaning the welding slag on the surface of the backing weld, then performing the front of the filling welding; then cleaning the welding slag on the surface of the filling weld, then performing the front of the cap welding by using the multi-layer and multi-pass annealing welding method;

[0040] In the above steps, the front welding layer number is 4 layers and 7 passes, and the front of the backing welding selects the welding rod with the ENiGrMo-6 brand and the φ3.2 specification, the welding current is 100~110A, the welding voltage is 21~22V, and the welding speed is 80~100mm / min; the up and down angle of the welding rod is 85~95°, the left and right angle of the welding rod is 85~95°, and the arc length of the welding rod is controlled within 2mm; the first layer of the backing welding adopts the continuous arc breaking operation method and combines the left and right sawtooth welding swing gesture to perform the welding, the continuous arc breaking of the welding rod should be at the position of the welding gap hole, and then a hole is formed at the front end of the welding pool during the welding, so that the back of the welding can achieve the effect of single-sided welding and double-sided forming; the back of the welding height is controlled within 1~2mm, and the welding width is controlled within 4~6mm; the shrinkage hole generated at the crater position is ground to a transition slope at the joint of the backing weld, and the welding rod is quickly pulled to the joint position after the arc is started from the upper end of the welding joint, and then the welding forming and joint quality of the backing weld are ensured.

[0041] In the above steps, the front of the filling welding selects the welding rod with the ENiGrMo-6 brand and the φ3.2 specification, the welding current is 120~130A, the welding voltage is 22~24V, and the welding speed is 100~150mm / min; the up and down angle of the welding rod is 85~95°, and the left and right angle of the welding rod is 85~95°; the left and right sawtooth continuous arc welding swing gesture is adopted during the filling welding, and the two sides are slightly paused during the left and right swing to ensure the penetration of the backing weld on both sides; at the same time, the welding speed should be controlled, the single pass welding width is not greater than 3.5 times of the diameter of the welding rod, and the thickness of the single pass welding is controlled within 4mm; the third layer of the front of the filling welding starts to adopt the separate welding arrangement, and the annealing welding pass arrangement is adopted when the fourth layer of the cap is welded, and the welding slag on the surface of each welding is removed before the next welding.

[0042] In the above steps, the front face cover surface welding selects the welding rod with the brand ENiGrMo-6 and the specification of φ3.2, the welding current is 120-130A, the welding voltage is 22-24V, and the welding speed is 100-150mm / min; the up-down angle of the welding rod is 85-95°, the left-right angle of the welding rod is 85-95°, and the arc length of the welding rod is controlled within 2mm; the left-right sawtooth continuous arc welding swing gesture is adopted during the cover surface welding, the two sides are slightly paused during the left-right swing, so as to ensure the penetration of the filling weld on both sides of the corner; the edge of the molten pool is controlled to cover the position of the groove edge and the previous weld during the welding, so as to ensure the superposition and formation of the cover surface weld, and the interlayer temperature of the weld is controlled to be 60-120℃ during the front face welding.

[0043] The welding rod used in the present application has a linear expansion coefficient close to 9% nickel steel, does not need preheating before welding, has high low-temperature toughness and good crack resistance; in addition, the welding material needs to be placed in a constant-temperature room, and the welding material is prevented from being damp to avoid welding defects during welding.

[0044] (5) when welding the X-shaped groove reverse surface of the 9% nickel steel plate 1, the reverse surface is first subjected to bottom welding; then the welding slag on the surface of the bottom welding weld is cleaned, and then the reverse surface is subjected to filling welding; then the welding slag on the surface of the filling welding weld is cleaned, and then the reverse surface is subjected to cover surface welding in a multi-layer and multi-pass annealing welding manner;

[0045] In the above steps, after the front face welding is completed, the reverse surface does not need to be cleaned by carbon planing, and is directly subjected to bottom welding; the reverse surface is subjected to bottom filling cover surface welding in 4 layers and 7 passes, and the bottom welding of the reverse surface selects the welding rod with the brand ENiGrMo-6 and the specification of φ3.2, the welding current is 90-110A, the welding voltage is 21-23V, and the welding speed is 100-150mm / min; the up-down angle of the welding rod is 85-95°, the left-right angle of the welding rod is 85-95°, and the arc length of the welding rod is controlled within 2mm; the continuous arc left-right sawtooth welding swing gesture is adopted for the bottom welding of the reverse surface, the welding rod is walked at the front end of the molten pool, the molten pool is slightly paused on both sides during the left-right swing, and then is quickly swung in the middle, so as to ensure the penetration of the bottom welding weld on both sides of the reverse surface and the flatness of the weld; the single-pass weld width is not greater than 3.5 times the diameter of the welding rod, and the thickness of the single-pass weld is controlled to be within 4mm.

[0046] In the above steps, the back side filling welding selects the welding rod with the brand ENiGrMo-6 and the specification of φ3.2, the welding current is 120~130A, the welding voltage is 22~24V, and the welding speed is 100~150mm / min; the up-down angle of the welding rod is 85~95°, the left-right angle of the welding rod is 85~95°, and the arc length of the welding rod is controlled within 2mm; the back side filling welding adopts the welding swing gesture of left and right zigzag swing, and the molten pool edge line of the back side filling welding needs to be controlled to cover the position of the groove edge line and the previous welding seam to ensure the superposition forming of the back side filling welding seam, and the interlayer temperature of the welding seam is controlled to be 60~120℃ during the back side welding.

[0047] In the above steps, the back side filling welding selects the welding rod with the brand ENiGrMo-6 and the specification of φ3.2, the welding current is 120~130A, the welding voltage is 22~24V, and the welding speed is 100~150mm / min; the up-down angle of the welding rod is 85~95°, the left-right angle of the welding rod is 85~95°, and the arc length of the welding rod is controlled within 2mm; the back side filling welding adopts the welding swing gesture of left and right zigzag swing, and the molten pool edge line of the back side filling welding needs to be controlled to cover the position of the groove edge line and the previous welding seam to ensure the superposition forming of the back side filling welding seam, and the interlayer temperature of the welding seam is controlled to be 60~120℃ during the back side welding.

[0048] (6) The appearance of the welding seam and the internal quality of the welding seam are inspected.

[0049] Through the welding of the present application, the visual appearance of the welding seam is good, and there are no defects such as undercut, porosity, incomplete fusion and crack, and the internal quality of the welding seam is also good and has no any defects through the non-destructive testing RT; in addition, according to the ASME specification volume V standard, the 9% nickel steel vertical butt joint plate welding seam is sampled to carry out tensile, impact, bending, macroscopic, microscopic and fatigue tests, and the test results show that all meet the welding process requirements of the 9% nickel steel.

[0050] The present application has the following advantages:

[0051] (1) Compared with the traditional welding method, the welding seam root of the present application is well fused, the welding workload is reduced, the welding efficiency is improved by more than 1 times, the material cost is reduced by 30%, the labor cost is reduced by 50%, and the construction cost is further reduced, and the welding quality and welding efficiency of the 9% nickel steel vertical butt joint plate welding seam are improved;

[0052] (2) The present application does not need to carbon mill and polish the back side, so that the welding efficiency of the 9% nickel steel vertical butt joint plate welding seam is greatly improved;

[0053] (3) The present application effectively controls the welding heat input of the welding process, guarantees the fusion ratio of the weld, strictly controls the interlayer temperature of the weld, forms a good front and back weld, and has good mechanical properties such as tensile and bending, and meets the low-temperature impact requirement of-196℃;

[0054] (4) The welding method without carbon planing back gouging adopted by the present application can effectively prevent the problem of carbon planing back gouging producing carburization in the weld, thereby improving the internal quality of the 9% nickel steel vertical butt joint panel weld.

[0055] The above-described embodiments are merely preferred embodiments of the present application and are not intended to limit the concept and scope of the present application. Various modifications and improvements to the technical solutions of the present application made by those of ordinary skill in the art without departing from the design concept of the present application shall fall within the protection scope of the present application. The technical content claimed by the present application has been fully recorded in the technical requirements.

Claims

1. A method for improving the welding efficiency of a 9% nickel steel butt joint panel weld, characterized by The method comprises the following steps: (1) X-shaped bevels are opened on 9% nickel steel plates, and the vertical butt joint assembly is completed according to the size requirements of the X-shaped bevels; (2) the chamfer of the 9% nickel steel plate is polished, and the impurities on both sides of the chamfer are removed; (3) the Kama plate is used to fix the weld back of the 9% nickel steel plate, and the assembly gap is ensured; the same plate thickness and the same bevel angle are used to install the arc extinguishing plate at the arc extinguishing end of the 9% nickel steel plate weld; (4) the welding method from bottom to top is used, and when the X-shaped bevel of the 9% nickel steel plate is welded, the front surface is first welded; then the weld slag on the surface of the backing weld is removed, and then the front surface is filled; then the weld slag on the surface of the filling weld is removed, and then the front surface is covered by using the multi-layer and multi-pass annealing welding method; In the above steps, the number of front welding passes is 4 layers and 7 passes, the backing weld on the front surface is selected from the ENiGrMo-6 welding rod with a specification of φ3.2, the welding current is 100-110 A, the welding voltage is 21-22 V, and the welding speed is 80-100 mm / min; the upper and lower angles of the welding rod during the backing welding are 85-95°, the left and right angles of the welding rod are 85-95°, and the arc length of the welding rod is controlled to be less than 2 mm; the first layer of the backing layer is welded by using the continuous arc breaking operation method combined with the left and right sawtooth welding swing gesture, the continuous arc breaking of the welding rod is located at the gap hole position of the weld, and then a hole is formed at the front end of the weld pool during welding; the back weld height is controlled to be 1-2 mm, and the weld width is controlled to be 4-6 mm; the shrinkage hole generated at the crater position is ground to form a transition slope at the backing weld joint, and the welding rod is quickly pulled to the joint position after the arc is started from the upper end of the weld joint; In the above steps, the filling weld on the front surface is selected from the ENiGrMo-6 welding rod with a specification of φ3.2, the welding current is 120-130 A, the welding voltage is 22-24 V, and the welding speed is 100-150 mm / min; the upper and lower angles of the welding rod during the filling welding are 85-95°, and the left and right angles of the welding rod are 85-95°; the left and right sawtooth continuous arc welding swing gesture is used during the filling welding, and the welds are slightly paused during the left and right swinging to ensure the penetration of the backing weld on both sides; the single-pass weld width is not greater than 3.5 times the diameter of the welding rod, and the thickness of the single-pass weld is controlled to be less than 4 mm; the third layer of the front filling weld starts to adopt the separate welding arrangement, and the annealing welding pass arrangement is used when the fourth layer of the front surface is welded, and the weld slag on the surface of each weld is removed before the next welding; (5) when the X-shaped bevel of the 9% nickel steel plate is welded, the back surface is first welded; then the weld slag on the surface of the backing weld is removed, and then the back surface is filled; then the weld slag on the surface of the filling weld is removed, and then the back surface is covered by using the multi-layer and multi-pass annealing welding method; In the above step, the back side of the bottom filler cap surface welding is welded by 4 layers and 7 passes, and the back side of the bottom welding uses the welding rod with the ENiGrMo-6 brand and the φ3.2 specification, the welding current is 90-110 A, the welding voltage is 21-23 V, and the welding speed is 100-150 mm / min; the up and down angle of the welding rod is 85-95°, the left and right angle of the welding rod is 85-95°, and the arc length of the welding rod is controlled within 2 mm; the back side of the bottom welding adopts the continuous arc left and right zigzag welding swing gesture, the welding rod walks in the front end of the molten pool, the molten pool is slightly stopped on both sides in the left and right swing, and then the penetration of the back side of the bottom welding seam and the flatness of the welding seam are ensured; the single pass welding seam width is not greater than 3.5 times of the welding rod diameter, and the thickness of the single pass welding seam is controlled within 4 mm; In the above step, the back side of the bottom filler cap surface welding is welded by 4 layers and 7 passes, and the back side of the bottom welding uses the welding rod with the ENiGrMo-6 brand and the φ3.2 specification, the welding current is 90-110 A, the welding voltage is 21-23 V, and the welding speed is 100-150 mm / min; the up and down angle of the welding rod is 85-95°, the left and right angle of the welding rod is 85-95°, and the arc length of the welding rod is controlled within 2 mm; the back side of the bottom welding adopts the continuous arc left and right zigzag welding swing gesture, the welding rod walks in the front end of the molten pool, the molten pool is slightly stopped on both sides in the left and right swing, and then the penetration of the back side of the bottom welding seam and the flatness of the welding seam are ensured; the single pass welding seam width is not greater than 3.5 times of the welding rod diameter, and the thickness of the single pass welding seam is controlled within 4 mm; (6) The appearance of the welding seam and the internal quality of the welding seam are inspected.

2. The method for improving the welding efficiency of the butt joint welding seam of the 9% nickel steel according to claim 1, characterized in that: In the above step (1), the 9% nickel steel plate uses the 9% nickel steel with the EN10028-4 brand and the 30 mm thickness; the joint form of the 9% nickel steel plate is X-shaped, and the two side bevel angles are 50-60°, the bevel face is 1-2 mm, and the root gap is 3-5 mm.

3. The method for improving the welding efficiency of the butt joint welding seam of the 9% nickel steel according to claim 1, characterized in that: In the above step (2), the impurity removal range is within 30 mm of the bevel welding seam on both sides of the 9% nickel steel plate.

4. The method for improving the welding efficiency of the butt joint welding seam of the 9% nickel steel according to claim 1, characterized in that: In the above step (4), the front side of the cap surface welding uses the welding rod with the ENiGrMo-6 brand and the φ3.2 specification, the welding current is 120-130 A, the welding voltage is 22-24 V, and the welding speed is 100-150 mm / min; the up and down angle of the welding rod is 85-95°, the left and right angle of the welding rod is 85-95°, and the arc length of the welding rod is controlled within 2 mm; the cap surface welding adopts the left and right zigzag continuous arc welding swing gesture, the molten pool is slightly stopped on both sides in the left and right swing, so as to ensure the penetration of the filler welding seam on both sides; the edge of the molten pool is controlled to be covered on the bevel line and the position of the previous welding seam during welding, so as to ensure the superposition of the cap surface welding seam, and the interlayer temperature of the welding seam is controlled to be 60-120℃ during the front side welding.

5. The method for improving the welding efficiency of the butt joint welding seam of the 9% nickel steel according to claim 1, characterized in that: In the step (5), the back cover welding selects the welding rod with the brand of ENiGrMo-6 and the specification of φ3.2, the welding current is 120-130 A, the welding voltage is 22-24 V, the welding speed is 100-150 mm / min; the up and down angle of the welding rod is 85-95°, the left and right angle of the welding rod is 85-95°, and the arc length of the welding rod is controlled within 2 mm; the left and right zigzag swing welding swing gesture is adopted during the cover welding, and the molten pool edge line needs to be controlled to cover the position of the groove edge line and the previous weld during the welding of each weld of the cover welding, so as to ensure the superposition forming of the cover weld, and the interlayer temperature of the weld is controlled at 60-120 ℃ during the back welding.

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