Hot wire narrow gap tungsten inert gas arc welding method for dissimilar steel pipe joint

Abstract

The present application belongs to the technical field of dissimilar steel welding, and particularly relates to a hot-wire narrow-gap tungsten inert gas arc welding method for dissimilar steel pipe joints. The method comprises the following steps: step 1, groove processing: processing the welding groove at the joint of a CB2 steel casting and a F92 steel forging into a butt type U-shaped narrow-gap groove or a lap type U-shaped narrow-gap groove; step 2, welding preparation; step 3, welding: step 301, performing backing welding by using a hot-wire welding process to form a backing weld, and the welding mode is single-layer single-pass welding; step 302, performing filling welding on the basis of the backing weld by using the hot-wire welding process to form a filling layer, and the welding mode is multi-layer multi-pass welding; step 303, performing cap welding on the basis of the filling layer by using the hot-wire welding process to form a cap layer; and step 4, post-welding heat treatment. The method can improve the welding quality of the joint of the CB2 steel casting and the F92 steel forging at the dissimilar steel pipe joint.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of dissimilar steel welding, and particularly relates to a hot-wire narrow-gap tungsten argon arc welding method for pipe connection of dissimilar steels. BACKGROUND

[0002] High-temperature and high-pressure parts such as cylinders and valve shells have the characteristics of complex structure, large size and harsh service conditions, and are often cast with CB2 steel (13Cr9Mo2Co1NiVNbNB). CB2 steel is a high-strength martensitic heat-resistant steel with excellent high-temperature strength and creep resistance, and is one of the commonly used materials for ultra-supercritical units. However, in some special structural parts, in order to balance the strength and toughness of the material, weldability and service reliability, F92 steel (10Cr9MoW2VNbNB) forgings need to be used in combination. F92 steel has a dense structure, high strength and good toughness, and can significantly improve the service performance of the product when used in combination with CB2 steel. In the manufacturing process, the pipe openings of the F92 steel forgings and the CB2 steel castings are connected by welding to form an overall structure. However, due to the large differences in physical and chemical properties, organization and performance between CB2 steel and F92 steel, the welded joint area is prone to stress concentration, uneven organization and mismatched performance.

[0003] At present, traditional welding methods such as shielded metal arc welding (SMAW) are commonly used in the industry. In order to facilitate operation, a larger groove angle (about 60-80°) is usually designed, which can improve the accessibility of the welding gun, but will cause the problem of large metal filling, which in turn leads to welding defects, abnormal physical and chemical properties, unstable quality and other problems in the welded joint, making it difficult to ensure the consistency and reliability of the welded joint. At the same time, the above method also has the disadvantages of large welding material consumption, much smoke and poor working environment. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a hot-wire narrow-gap tungsten argon arc welding method for pipe connection of dissimilar steels, which can improve the welding quality of the welded joint at the pipe connection of CB2 steel castings and F92 steel forgings.

[0005] The technical solution adopted by the application to solve the technical problem is: a hot-wire narrow-gap tungsten argon arc welding method for pipe connection of dissimilar steels, comprising the following steps:

[0006] Step 1, groove processing:

[0007] The welding groove at the pipe connection of the CB2 steel casting and the F92 steel forging is processed into a butt-type U-shaped narrow-gap groove or a lap-type U-shaped narrow-gap groove;

[0008] Step 2, preparation before welding:

[0009] Positioning and assembling the CB2 steel castings and the F92 steel forged joints, so that the welding assembly end faces of the CB2 steel castings and the F92 steel forged joints are horizontal;

[0010] Step 3, welding:

[0011] Step 301, using a hot wire welding process to perform backing welding to form a backing layer, and the welding mode is single-layer single-pass welding;

[0012] Step 302, using a hot wire welding process to perform filling welding on the basis of the backing layer to form a filling layer, and the welding mode is multi-layer multi-pass welding;

[0013] Step 303, using a hot wire welding process to perform surface welding on the basis of the filling layer to form a surface layer;

[0014] Step 4, post-weld heat treatment:

[0015] The welding assembly of the CB2 steel castings and the F92 steel forged joints is put into the furnace as a whole for post-weld stress relief heat treatment.

[0016] Further, the step 302 includes the following steps:

[0017] Step 3021, using a hot wire welding process to perform initial filling welding on the basis of the backing layer to form an initial filling layer covering the backing layer;

[0018] Step 3022, using a hot wire welding process to perform middle filling welding on the basis of the initial filling layer to form a middle filling layer adjacent to the initial filling layer;

[0019] The middle filling layer includes a plurality of middle filling welding units arranged in sequence along the welding seam depth direction d, each middle filling welding unit includes a CB2 steel casting side welding bead, an F92 steel forging side welding bead, and an intermediate welding bead; one end of the CB2 steel casting side welding bead is connected with the CB2 steel casting, and the other end extends towards the F92 steel forging and gradually thins; one end of the F92 steel forging side welding bead is connected with the F92 steel forging, and the other end extends towards the CB2 steel casting and gradually thins; the end of the CB2 steel casting side welding bead away from the CB2 steel casting is arranged in overlapping with the end of the F92 steel forging side welding bead away from the F92 steel forging, and forms an arc structure recessed towards the backing layer, the intermediate welding bead is located at the recessed structure, and the CB2 steel casting side welding bead and the F92 steel forging side welding bead are connected with the intermediate welding bead; the intermediate welding bead has a structure of thick in the middle and thin at both ends, one end of the intermediate welding bead has a spacing with the CB2 steel casting, and the other end of the intermediate welding bead has a spacing with the F92 steel forging;

[0020] Step 303, using a hot wire welding process to perform surface welding on the basis of the middle filling layer to form a surface layer;

[0021] The cover layer includes convexly arranged cover welding beads, and a plurality of cover welding beads are arranged in sequence and overlap along the welding seam width direction b; one end of the cover layer is located on the CB2 steel casting, and the other end is located on the F92 steel forging, and the two ends of the cover layer are smoothly transitioned.

[0022] Further, in the butt U-shaped narrow gap groove in step 1, the land of the groove at the CB2 steel casting pipe is S1, the land of the groove at the F92 steel forging pipe is S2, the length of the butt boss at the CB2 steel casting pipe is S3, the length of the butt boss at the F92 steel forging pipe is S4, S1=S2=S3=S4, and the value range of S1, S2, S3 and S4 is 2-3 mm;

[0023] The radius of the arc transition section of the groove at the CB2 steel casting pipe is R1, the radius of the arc transition section of the groove at the F92 steel forging pipe is R2, R1=R2, and the value range of R1 and R2 is 3-6 mm;

[0024] The angle of the bevel of the groove at the CB2 steel casting pipe is θ1, the angle of the bevel of the groove at the F92 steel forging pipe is θ2, θ1=θ2, and the value range of θ1 and θ2 is 3-6°;

[0025] The CB2 steel casting and the F92 steel forging have an assembly gap along the welding seam width direction b at the pipe.

[0026] Further, S1=S2=S3=S4=2 mm; R1=R2=4 mm; θ1=θ2=3.5°; and the assembly gap is 2-4 mm.

[0027] Further, in the overlap U-shaped narrow gap groove in step 1, the length of the boss bottom at the CB2 steel casting pipe is L1, the length of the boss bottom at the F92 steel forging pipe is L2, L1=L2, and the value range of L1 and L2 is 6-12 mm;

[0028] The length of the overlap boss top at the CB2 steel casting pipe is L3, the length of the overlap boss top at the F92 steel forging pipe is L4, the height of the overlap boss at the CB2 steel casting pipe is S5, the height of the overlap boss at the F92 steel forging pipe is S6, L3=L4=S5=S6, and the value range of L3, L4, S5 and S6 is 2-3 mm;

[0029] The height of the overlap groove at the CB2 steel casting pipe is S7, the height of the overlap groove at the F92 steel forging pipe is S8, S7=S8, and the value range of S7 and S8 is 2.5-3.5 mm;

[0030] The height difference between the overlap boss height S5 at the CB2 steel casting pipe joint and the overlap groove height S8 at the F92 steel forging pipe joint is 0.5mm, and S5 < S8;

[0031] The height difference between the overlap groove height S7 at the CB2 steel casting pipe joint and the overlap boss height S6 at the F92 steel forging pipe joint is 0.5mm, and S6 < S7;

[0032] The circular arc transition section of the bevel at the CB2 steel casting pipe joint is R3, the circular arc transition section of the bevel at the F92 steel forging pipe joint is R4, R3 = R4, the value range of R3 and R4 is 4~6mm, R3 < L1, and R4 < L2;

[0033] The bevel angle of the bevel at the CB2 steel casting pipe joint is θ3, the bevel angle of the bevel at the F92 steel forging pipe joint is θ4, θ3 = θ4, and the value range of θ3 and θ4 is 3~6°.

[0034] Further, L1 = L2 = 8mm; L3 = L4 = S5 = S6 = 2mm; S7 = S8 = 2.5mm; R3 = R4 = 4mm; and θ3 = θ4 = 3°.

[0035] Further, in the step 2, before the positioning and assembling of the CB2 steel casting and the F92 steel forging pipe joint, the step of non-destructive testing of the welding bevel is further included, that is, the non-destructive testing operation is performed on the welding bevel at the CB2 steel casting and the F92 steel forging pipe joint.

[0036] Further, in the step 2, after the non-destructive testing operation of the welding bevel at the CB2 steel casting and the F92 steel forging pipe joint, before the positioning and assembling of the CB2 steel casting and the F92 steel forging pipe joint, the step of cleaning the surface penetrant of the welding bevel to expose the metal luster of the welding bevel is further included.

[0037] Further, in the step 2, after the positioning and assembling of the CB2 steel casting and the F92 steel forging pipe joint, the step of welding preheating is further included, that is, the local preheating is performed on the welding position of the positioned and assembled CB2 steel casting and F92 steel forging and the surrounding 200mm range of the welding zone, the preheating mode adopts natural gas flame heating or induction heating, and the preheating temperature is 150~220℃.

[0038] Further, in the step 2, after the positioning and assembling of the CB2 steel casting and the F92 steel forging pipe joint, and before the welding preheating, the step of point welding the inner side of the CB2 steel casting and the F92 steel forging pipe joint in the circumferential direction is further included.

[0039] Further, the step 2 before welding preparation further comprises the steps that: before welding, the equipment is debugged, the power polarity is selected as direct current positive connection, the shielding gas is argon, the gas mixing ratio is greater than or equal to 99.99%, the shielding gas flow is 16 L / min, the tail shielding gas is 22 L / min, and the back shielding gas is 35 L / min.

[0040] Further, in the step 301, the welding current value is 120-200 A, the voltage is 9-12 V, the welding speed is 8 cm / min, the wire feeding speed is 80 cm / min, and the maximum heat input is 18.0 kJ / cm.

[0041] Further, in the step 302, the welding current is 120-280 A, the voltage is 9-14 V, the welding speed is 8-10 cm / min, the average wire feeding speed is 80-140 cm / min, and the maximum heat input is 29.4 kJ / cm.

[0042] Further, in the step 303, the welding current is 120-200 A, the voltage is 9-12 V, the welding speed is 8 cm / min, the wire feeding speed is 80 cm / min, and the maximum heat input is 18.00 kJ / cm.

[0043] Further, the excess height of the cover layer is 2-3 mm.

[0044] Further, the step 4 of post-welding heat treatment specifically comprises the following steps:

[0045] The welding area temperature is reduced to 90-150 DEG C, and the temperature interval is kept for not less than 2 h, so that the martensite organization is completely converted; then the temperature is increased to 730 DEG C ± 10 DEG C at a temperature increasing rate of less than or equal to 80 DEG C / h, and the temperature interval is kept for 32 h; after the keeping temperature is finished, the temperature is reduced to less than or equal to 250 DEG C at a temperature reducing rate of less than or equal to 55 DEG C / h, and then the furnace is discharged, and the air cooling is performed to room temperature.

[0046] Compared with the prior art, the present application has the beneficial effects that: the present application provides a hot wire narrow gap tungsten argon arc welding method for dissimilar steel pipe connection, which can improve the welding quality of the welding joint at the dissimilar steel pipe connection between the CB2 steel casting and the F92 steel forging. Compared with traditional manual welding, the welding joint quality and the physical and chemical performance stability are significantly improved, the design of the narrow and deep groove greatly reduces the welding metal filling amount, reduces the manufacturing cost, and shortens the production cycle. It also has the advantages of less smoke, improved working environment, etc. The technical advantages are outstanding, the economic benefits are significant, and it has a very high engineering application prospect and promotion value. BRIEF DESCRIPTION OF DRAWINGS

[0047] Figure 1 is a flow chart of the present application;

[0048] Figure 2is a schematic diagram of CB2 steel castings and F92 steel forged pipe joints;

[0049] Figure 3 is a schematic diagram of butt U-shaped narrow gap groove;

[0050] Figure 4 is a schematic diagram of processing the groove into butt U-shaped narrow gap groove and using hot wire welding process for welding;

[0051] Figure 5 is a schematic diagram of lap U-shaped narrow gap groove;

[0052] Figure 6 is a schematic diagram of processing the groove into lap U-shaped narrow gap groove and using hot wire welding process for welding;

[0053] Figure 7 is a macroscopic morphology diagram of butt welding joint prepared by the present application;

[0054] Figure 8 is a macroscopic morphology diagram of lap welding joint prepared by the present application after removing the lap platform by mechanical processing;

[0055] Figure 9 is a microstructure diagram of butt welding joint prepared by the present application;

[0056] Figure 10 is a microstructure diagram of lap welding joint prepared by the present application;

[0057] Reference signs:

[0058] 1-CB2 steel castings; 2-F92 steel forgings; 3-priming layer; 4-starting filling layer; 5-CB2 steel castings side welding; 6-F92 steel forgings side welding; 7-intermediate welding; 8-capping welding. DETAILED DESCRIPTION

[0059] The present application will be further described below in conjunction with the accompanying drawings Figure 1 , 2 , 3, 4, 5, 6, 7, 8, 9 and 10, and examples.

[0060] The hot wire narrow gap tungsten argon arc welding method for dissimilar steel pipe joints comprises the following steps:

[0061] Step 1, groove processing:

[0062] The welding groove at the pipe joint of CB2 steel castings 1 and F92 steel forgings 2 is processed into butt U-shaped narrow gap groove or lap U-shaped narrow gap groove. Figure 3 , Figure 5 as shown.

[0063] The butt U-shaped narrow gap groove and the overlapping U-shaped narrow gap groove both have the characteristics of narrow and deep groove, can greatly reduce the filling amount of weld metal, reduce the manufacturing cost and shorten the production cycle.

[0064] Specifically, in the butt U-shaped narrow gap groove in the step 1, the land of the groove at the connecting pipe of the CB2 steel casting 1 is S1, the land of the groove at the connecting pipe of the F92 steel forging 2 is S2, the length of the butt boss of the groove at the connecting pipe of the CB2 steel casting 1 is S3, the length of the butt boss of the groove at the connecting pipe of the F92 steel forging 2 is S4, S1=S2=S3=S4, the value range of S1, S2, S3 and S4 is 2-3 mm;

[0065] The radius of the arc transition section of the groove at the connecting pipe of the CB2 steel casting 1 is R1, the radius of the arc transition section of the groove at the connecting pipe of the F92 steel forging 2 is R2, R1=R2, the value range of R1 and R2 is 3-6 mm;

[0066] The angle of the bevel of the groove at the connecting pipe of the CB2 steel casting 1 is θ1, the angle of the bevel of the groove at the connecting pipe of the F92 steel forging 2 is θ2, θ1=θ2, the value range of θ1 and θ2 is 3-6°.

[0067] When the butt U-shaped narrow gap groove is adopted, the connecting pipe of the CB2 steel casting 1 and the connecting pipe of the F92 steel forging 2 have an assembly gap along the weld width direction b.

[0068] Preferably, S1=S2=S3=S4=2 mm; R1=R2=4 mm; θ1=θ2=3.5°; and the assembly gap is 2-4 mm.

[0069] Specifically, the overlapping U-shaped narrow gap groove in the step 1 is that the connecting pipe of the CB2 steel casting 1 and the connecting pipe of the F92 steel forging 2 are provided with boss structures arranged in the radial direction.

[0070] The length of the bottom of the boss at the connecting pipe of the CB2 steel casting 1 is L1, the length of the bottom of the boss at the connecting pipe of the F92 steel forging 2 is L2, L1=L2, the value range of L1 and L2 is 6-12 mm;

[0071] The length of the top of the overlapping boss at the connecting pipe of the CB2 steel casting 1 is L3, the length of the top of the overlapping boss at the connecting pipe of the F92 steel forging 2 is L4, the height of the overlapping boss at the connecting pipe of the CB2 steel casting 1 is S5, the height of the overlapping boss at the connecting pipe of the F92 steel forging 2 is S6, L3=L4=S5=S6, the value range of L3, L4, S5 and S6 is 2-3 mm;

[0072] The height of the overlapping groove at the connecting pipe of the CB2 steel casting 1 is S7, the height of the overlapping groove at the connecting pipe of the F92 steel forging 2 is S8, S7=S8, the value range of S7 and S8 is 2.5-3.5 mm.

[0073] The height difference between the overlap boss height S5 at the pipe joint of the CB2 steel casting 1 and the overlap groove height S8 at the pipe joint of the F92 steel forging 2 is 0.5 mm, and S5 < S8;

[0074] The height difference between the overlap groove height S7 at the pipe joint of the CB2 steel casting 1 and the overlap boss height S6 at the pipe joint of the F92 steel forging 2 is 0.5 mm, and S6 < S7;

[0075] The circular arc transition section of the bevel at the pipe joint of the CB2 steel casting 1 is R3, the circular arc transition section of the bevel at the pipe joint of the F92 steel forging 2 is R4, R3 = R4, the value range of R3 and R4 is 4-6 mm, R3 < L1, and R4 < L2;

[0076] The bevel angle of the bevel at the pipe joint of the CB2 steel casting 1 is θ3, the bevel angle of the bevel at the pipe joint of the F92 steel forging 2 is θ4, θ3 = θ4, and the value range of θ3 and θ4 is 3-6°.

[0077] Preferably, L1 = L2 = 8 mm; L3 = L4 = S5 = S6 = 2 mm; S7 = S8 = 2.5 mm; R3 = R4 = 4 mm; and θ3 = θ4 = 3°.

[0078] Step 2, welding preparation:

[0079] The pipe joint of the CB2 steel casting 1 and the F92 steel forging 2 is positioned and assembled, so that the pipe welding assembly end faces of the CB2 steel casting 1 and the F92 steel forging 2 are horizontal.

[0080] Preferably, in the step 2 welding preparation, before the pipe joint of the CB2 steel casting 1 and the F92 steel forging 2 is positioned and assembled, the method further comprises the step of non-destructive testing of the welding bevel: performing non-destructive testing of the welding bevel at the pipe joint of the CB2 steel casting 1 and the F92 steel forging 2.

[0081] Preferably, in the step 2 welding preparation, after the non-destructive testing of the welding bevel at the pipe joint of the CB2 steel casting 1 and the F92 steel forging 2 is performed, before the pipe joint of the CB2 steel casting 1 and the F92 steel forging 2 is positioned and assembled, the method further comprises the step of cleaning the surface penetrant of the welding bevel to expose the metal luster of the welding bevel.

[0082] Preferably, after the positioning and assembling of the CB2 steel casting 1 and the F92 steel forging 2 at the joint, the step 2 of the welding preparation further comprises a step of preheating before welding: locally preheating the joint and the surrounding area within a range of 200 mm of the CB2 steel casting 1 and the F92 steel forging 2 after positioning and assembling, and the preheating mode adopts natural gas flame heating or induction heating, and the preheating temperature is 150-220℃. The preheating temperature is monitored in real time by using a contact type temperature measuring gun or an infrared temperature measuring instrument.

[0083] After the positioning and assembling of the CB2 steel casting 1 and the F92 steel forging 2 at the joint, and before the preheating before welding, the step 2 of the welding preparation further comprises a step of circumferentially spot welding the inside of the joint between the CB2 steel casting 1 and the F92 steel forging 2. Specifically, by means of a square special knife bar with a width of 40 mm and a length of 150 mm, the joint between the CB2 steel casting 1 and the F92 steel forging 2 is circumferentially spot welded at intervals of 120° to form three evenly distributed spot welding positions, so as to achieve the purpose of fixing the workpiece and the series circuit. Of course, the joint between the CB2 steel casting 1 and the F92 steel forging 2 can also be circumferentially spot welded at intervals of 90° to form four evenly distributed spot welding positions.

[0084] Preferably, the step 2 of the welding preparation further comprises a step of debugging the equipment before welding: the power polarity is selected as direct current positive connection, the shielding gas is argon, the gas mixing ratio is greater than or equal to 99.99%, the shielding gas flow is 16 L / min, the tail protection gas is 22 L / min, and the back protection gas is 35 L / min.

[0085] The welding filler material is selected from 1.0 mm Thermanit MTS 5Co1 welding wire. The welding wire is heated to 200-600℃ before being sent into the molten pool, i.e. red-hot state.

[0086] The welding equipment adopts hot wire narrow gap tungsten argon arc welding equipment.

[0087] Step 3, welding:

[0088] Step 301, primer welding is performed by using a hot wire welding process to form a primer layer 3, and the welding mode is single-layer single-pass welding. Specifically, the welding current is 120-200 A, the voltage is 9-12 V, the welding speed is 8 cm / min, the wire feeding speed is 80 cm / min, and the maximum heat input is 18.0 kJ / cm.

[0089] Step 302, filling welding is performed on the basis of the primer layer 3 by using a hot wire welding process to form a filling layer, and the welding mode is multi-layer multi-pass welding. Specifically, the welding current is 120-280 A, the voltage is 9-14 V, the welding speed is 8-10 cm / min, the average wire feeding speed is 80-140 cm / min, and the maximum heat input is 29.4 kJ / cm.

[0090] Specifically, as shown in Figure 4 、 Figure 6 the step 302 comprises the following steps:

[0091] Step 3021, using hot wire welding process to carry out initial filling welding on the basis of the primer layer 3, to form the initial filling layer 4 covering the primer layer 3.

[0092] Step 3022, using hot wire welding process to carry out middle filling welding on the basis of the initial filling layer 4, to form the middle filling layer adjacent to the initial filling layer 4.

[0093] The middle filling layer comprises a plurality of middle filling welding units arranged in sequence along the welding seam depth direction d, each middle filling welding unit comprising a CB2 steel casting side welding bead 5, a F92 steel forging side welding bead 6 and an intermediate welding bead 7; one end of the CB2 steel casting side welding bead 5 is connected with the CB2 steel casting 1, and the other end extends towards the F92 steel forging 2 and gradually thins; one end of the F92 steel forging side welding bead 6 is connected with the F92 steel forging 2, and the other end extends towards the CB2 steel casting 1 and gradually thins; the end of the CB2 steel casting side welding bead 5 away from the CB2 steel casting 1 is arranged in overlapping manner with the end of the F92 steel forging side welding bead 6 away from the F92 steel forging 2, and forms an arc-shaped structure which is recessed towards the primer layer 3, the intermediate welding bead 7 is located at the recessed structure, and the CB2 steel casting side welding bead 5 and the F92 steel forging side welding bead 6 are connected with the intermediate welding bead 7; the intermediate welding bead 7 has a structure of thick in the middle and thin at both ends, one end of the intermediate welding bead 7 has a spacing with the CB2 steel casting 1, and the other end of the intermediate welding bead 7 has a spacing with the F92 steel forging 2.

[0094] Step 303, using hot wire welding process to carry out surface welding on the basis of the filling layer, to form the surface layer.

[0095] The surface layer comprises a plurality of surface welding beads 8 arranged in sequence and overlapping along the welding seam width direction b; one end of the surface layer is located on the CB2 steel casting 1, and the other end is located on the F92 steel forging 2, and both ends of the surface layer are smoothly transitioned.

[0096] Specifically, the welding current is 120-200 A, the voltage is 9-12 V, the welding speed is 8 cm / min, the wire feeding speed is 80 cm / min, and the maximum heat input is 18.00 kJ / cm.

[0097] Preferably, the excess height of the surface layer is 2-3 mm.

[0098] It is worth noting that during the whole welding process, the slag and spatter on the surface of each weld should be cleaned, and the weld surface should be checked for cracks, pores and other welding defects. If there are welding defects, they should be cleaned in time by mechanical method. The temperature between the weld layers during the whole welding process is controlled at 150~300℃.

[0099] Table 1

[0100]

[0101] Step 4, post-weld heat treatment:

[0102] The welded assembly of the CB2 steel casting 1 and the F92 steel forging 2 is put into the furnace as a whole for post-weld stress relief heat treatment.

[0103] Specifically, the temperature of the welding area is reduced to 90~150℃, and the holding time in this temperature range is not less than 2h, so as to realize complete transformation of the martensitic structure; then the temperature is increased to 730±10℃ at a rate of ≤80℃ / h, and the holding time in this temperature range is 32h; after the holding is completed, the temperature is reduced to ≤250℃ at a rate of ≤55℃ / h, and then the furnace is discharged, and the air cooling is carried out to room temperature.

[0104] Preferably, step 4 is followed by step 5, which is to perform non-destructive testing on the welding groove again.

[0105] Preferably, step 5 is followed by step 6, which is to perform physical and chemical performance testing on the welding groove.

[0106] The welding groove at the joint of the CB2 steel casting 1 and the F92 steel forging 2 is processed into a lap type U-shaped narrow gap groove, so as to facilitate the rapid positioning and assembly of the CB2 steel casting 1 and the F92 steel forging 2. When the welding groove at the joint of the CB2 steel casting 1 and the F92 steel forging 2 is a lap type U-shaped narrow gap groove, step 4 is further preceded by the step of removing the lap by mechanical processing, that is, removing the boss structure by mechanical processing, and reducing the thickness e=S5+S7=S8+S6=4.5mm, as shown in Figure 6 .

[0107] In order to evaluate the physical and chemical properties of the welded joint prepared by the present application, after the welded joint prepared in the present embodiment passes the non-destructive testing, the physical and chemical performance test is carried out according to the ASME Ⅸ standard requirement, and the test items include room temperature tensile test, high temperature tensile test, high temperature short time endurance test, guide bending test, impact absorption test, hardness test, macro and micro metallographic test, and weld chemical composition test. The following experimental data are further explained.

[0108] The joint room temperature tensile property test results of the welded joints in the embodiment are shown in Table 2. It should be noted that the welded joint formed by the butt type U-shaped narrow gap groove is a butt welded joint, and the welded joint formed by the lap type U-shaped narrow gap groove is a lap welded joint.

[0109] Table 2

[0110]

[0111] The guide bending property test results of the welded joints in the embodiment are shown in Table 3.

[0112] Table 3

[0113]

[0114] The high temperature tensile property test results of the welded joints in the embodiment at 620℃ are shown in Table 4.

[0115] Table 4

[0116]

[0117] The impact toughness test results of the welded joints in the embodiment are shown in Table 5.

[0118] Table 5

[0119]

[0120] The hardness test results of the welded joints in the embodiment are shown in Table 6.

[0121] Table 6

[0122]

[0123] The macroscopic morphology of the butt welded joint in the embodiment is shown in Figure 7 , the macroscopic morphology of the lap welded joint after the lap platform is removed by machining is shown in Figure 8 , the microstructure of the butt welded joint is shown in Figure 9 , and the microstructure of the lap welded joint is shown in Figure 10 . The microstructures of the two welded joint forms are the same, and the test results are shown in Table 7.

[0124] Table 7

[0125]

[0126] The weld chemical compositions of the two welded joint forms in the embodiment are approximately the same, as shown in Table 8.

[0127] Table 8

[0128]

[0129] In summary, the welding joint obtained by using the application meets the material standard requirements in room temperature tensile, guide bending, high temperature tensile, impact toughness, hardness, macrostructure, microstructure and weld seam chemical composition, and can solve the problem of great welding difficulty of the CB2 steel casting 1 and the F92 steel forging 2 dissimilar steel connecting pipe.

[0130] The embodiments of the specific implementation are the preferred embodiments of the application, and are not intended to limit the protection scope of the application. Equivalent changes made according to the structure, shape and principle of the application should be covered within the protection scope of the application.

Claims

1. A hot-wire narrow-gap tungsten inert gas welding method for dissimilar steel pipe connections, characterized in that, Including the following steps: Step 1, Beveling: The welding bevel at the joint between the CB2 steel casting (1) and the F92 steel forging (2) is processed into a butt-joint U-shaped narrow gap bevel or an lap-joint U-shaped narrow gap bevel. Step 2, Pre-welding preparation: Position and assemble the CB2 steel casting (1) and F92 steel forging (2) at the nozzle, so that the welding assembly end faces of the CB2 steel casting (1) and F92 steel forging (2) are both horizontal; Step 3, Welding: Step 301: Hot wire welding process is used to perform root pass welding to form root pass (3), and the welding method is single layer single pass welding; Step 302: Hot wire welding process is used to fill the base layer (3) to form a fill layer. The welding method is multi-layer and multi-pass welding. Step 302 includes the following steps: Step 3021: Using hot wire welding process, initial filler welding is performed on the basis of the base layer (3) to form an initial filler layer (4) covering the base layer (3). Step 3022: Using hot wire welding process, a middle filler weld is performed on the basis of the initial filler layer (4) to form a middle filler layer adjacent to the initial filler layer (4); The intermediate filler layer includes multiple intermediate filler weld bead units arranged sequentially along the weld depth direction d. Each intermediate filler weld bead unit includes a CB2 steel casting side weld bead (5), an F92 steel forging side weld bead (6), and an intermediate weld bead (7). One end of the CB2 steel casting side weld bead (5) is connected to the CB2 steel casting (1), and the other end extends towards the F92 steel forging (2) and gradually thins. One end of the F92 steel forging side weld bead (6) is connected to the F92 steel forging (2), and the other end extends towards the CB2 steel casting (1) and gradually thins. The CB2 steel casting side weld bead (5) 5) The end away from the CB2 steel casting (1) overlaps with the end away from the F92 steel forging (2) of the side weld (6), forming an arc-shaped structure that is concave towards the bottom layer (3). The middle weld (7) is located in the concave structure. The CB2 steel casting side weld (5) and the F92 steel forging side weld (6) are both connected to the middle weld (7). The middle weld (7) has a structure that is thick in the middle and thin at both ends. There is a gap between one end of the middle weld (7) and the CB2 steel casting (1), and there is a gap between the other end of the middle weld (7) and the F92 steel forging (2). Step 303: A cover layer is formed by performing a hot wire welding process on the filler layer. A hot-wire welding process is used to perform a cover weld on the middle filler layer to form a cover layer; The cover layer includes a protruding cover weld (8), and multiple cover welds (8) are arranged in sequence along the weld width direction b; one end of the cover layer is located on the CB2 steel casting (1), and the other end is located on the F92 steel forging (2), and both ends of the cover layer are smoothly transitioned. Step 4, Post-weld heat treatment: The CB2 steel casting (1) and F92 steel forging (2) were assembled into a furnace and subjected to post-weld stress relief heat treatment. When the welding bevel in step 1 is a butt-joint U-shaped narrow gap bevel, the blunt edge of the bevel at the nozzle of the CB2 steel casting (1) is S1, the blunt edge of the bevel at the nozzle of the F92 steel forging (2) is S2, the length of the butt joint boss of the bevel at the nozzle of the CB2 steel casting (1) is S3, and the length of the butt joint boss of the bevel at the nozzle of the F92 steel forging (2) is S4, S1=S2=S3=S4, and the range of values ​​for S1, S2, S3 and S4 is 2~3mm; The radius of the arc transition section of the bevel at the nozzle of the CB2 steel casting (1) is R1, and the radius of the arc transition section of the bevel at the nozzle of the F92 steel forging (2) is R2. R1=R2, and the range of R1 and R2 is 3~6mm. The bevel angle of the CB2 steel casting (1) at the nozzle is θ1, and the bevel angle of the F92 steel forging (2) at the nozzle is θ2. θ1=θ2, and the range of θ1 and θ2 is 3~6°. The CB2 steel casting (1) and the F92 steel forging (2) have an assembly gap along the weld width direction b at the joint; The values ​​of S1=S2=S3=S4=2mm; R1=R2=4mm; θ1=θ2=3.5°; and the assembly clearance is 2~4mm. When the welding bevel in step 1 is an overlapping U-shaped narrow gap bevel, the bottom length of the boss at the pipe of the CB2 steel casting (1) is L1, and the bottom length of the boss at the pipe of the F92 steel forging (2) is L2, L1 = L2, and the range of L1 and L2 is 6~12mm. The top length of the overlapping boss at the pipe joint of the CB2 steel casting (1) is L3, the top length of the overlapping boss at the pipe joint of the F92 steel forging (2) is L4, the height of the overlapping boss at the pipe joint of the CB2 steel casting (1) is S5, and the height of the overlapping boss at the pipe joint of the F92 steel forging (2) is S6. L3=L4=S5=S6, and the range of values ​​for L3, L4, S5 and S6 is 2~3mm. The overlap groove height at the nozzle of the CB2 steel casting (1) is S7, and the overlap groove height at the nozzle of the F92 steel forging (2) is S8. S7 = S8, and the range of S7 and S8 is 2.5~3.5mm. The height difference between the overlapping boss height S5 at the nozzle of the CB2 steel casting (1) and the overlapping groove height S8 at the nozzle of the F92 steel forging (2) is 0.5mm, and S5 < S8. The height difference between the overlap groove height S7 at the nozzle of the CB2 steel casting (1) and the overlap boss height S6 at the nozzle of the F92 steel forging (2) is 0.5mm, and S6 < S7. For CB2 steel castings (1), the arc transition section of the bevel at the nozzle is R3; for F92 steel forgings (2), the arc transition section of the bevel at the nozzle is R4. R3 = R4, the range of R3 and R4 is 4~6mm, R3 < L1, R4 < L2. The bevel angle of the CB2 steel casting (1) at the nozzle is θ3, and the bevel angle of the F92 steel forging (2) at the nozzle is θ4. θ3 = θ4, and the range of θ3 and θ4 is 3~6°. The values ​​are: L1=L2=8mm; L3=L4=S5=S6=2mm; S7=S8=2.5mm; R3=R4=4mm; θ3=θ4=3°.

2. The hot-wire narrow-gap tungsten inert gas welding method for dissimilar steel connectors as described in claim 1, characterized in that, In step 2, before welding preparation, before positioning and assembling the joint of the CB2 steel casting (1) and the F92 steel forging (2), the following step is also included: non-destructive testing of the weld bevel: non-destructive testing is performed on the weld bevel of the joint of the CB2 steel casting (1) and the F92 steel forging (2).

3. The hot-wire narrow-gap tungsten inert gas welding method for dissimilar steel connectors as described in claim 2, characterized in that, In step 2, before welding preparation, after performing non-destructive testing on the weld bevel at the joint of the CB2 steel casting (1) and the F92 steel forging (2), before positioning and assembling the joint of the CB2 steel casting (1) and the F92 steel forging (2), the following steps are also included: cleaning the surface penetrant of the weld bevel so that the weld bevel reveals a metallic luster.

4. The hot-wire narrow-gap tungsten inert gas welding method for dissimilar steel connectors as described in claim 1, characterized in that, In step 2, the pre-welding preparation includes positioning and assembling the CB2 steel casting (1) and F92 steel forging (2) at the pipe joint, followed by the pre-welding preheating step: local preheating is performed on the welding positions and the area around the welding zone of the CB2 steel casting (1) and F92 steel forging (2) after positioning and assembly. The preheating method is natural gas flame heating or induction heating, and the preheating temperature is 150~220℃.

5. The hot-wire narrow-gap tungsten inert gas welding method for dissimilar steel connectors as described in claim 4, characterized in that, Step 2, the pre-welding preparation, after positioning and assembling the CB2 steel casting (1) and F92 steel forging (2) at the nozzle, and before preheating before welding, also includes the step of spot welding the inner side of the CB2 steel casting (1) and F92 steel forging (2) at the nozzle along the circumferential direction.

6. The hot-wire narrow-gap tungsten inert gas welding method for dissimilar steel connectors as described in claim 1, characterized in that, Step 2, pre-welding preparation, also includes the following steps: debugging the equipment before welding, selecting DC positive polarity for the power supply, using argon as the shielding gas, with a gas mixing ratio ≥99.99%, a shielding gas flow rate of 16L / min, a tail shielding gas flow rate of 22L / min, and a back shielding gas flow rate of 35L / min.

7. The hot-wire narrow-gap tungsten inert gas welding method for dissimilar steel connectors as described in claim 1, characterized in that, In step 301, the root pass welding has a welding current of 120~200A, a voltage of 9~12V, a welding speed of 8cm / min, a wire feed speed of 80cm / min, and a maximum heat input of 18.0kJ / cm.

8. The hot-wire narrow-gap tungsten inert gas welding method for dissimilar steel connectors as described in claim 1, characterized in that, In step 302, the filler welding has a welding current of 120~280A, a voltage of 9~14V, a welding speed of 8~10cm / min, an average wire feed speed of 80~140cm / min, and a maximum heat input of 29.4kJ / cm.

9. The hot-wire narrow-gap tungsten inert gas welding method for dissimilar steel connectors as described in claim 1, characterized in that, In step 303, the cover welding current is 120~200A, the voltage is 9~12V, the welding speed is 8cm / min, the wire feed speed is 80cm / min, and the maximum heat input is 18.00kJ / cm.

10. The hot-wire narrow-gap tungsten inert gas welding method for dissimilar steel connectors as described in claim 1, characterized in that, The excess height of the cover layer is 2~3mm.

11. The hot-wire narrow-gap tungsten inert gas welding method for dissimilar steel connectors as described in claim 1, characterized in that, Step 4, post-weld heat treatment, specifically includes the following steps: Reduce the temperature of the welding zone to 90~150℃ and hold it in this temperature range for no less than 2 hours to achieve complete transformation of martensite structure; then raise the temperature to 730±10℃ at a rate of ≤80℃ / h and hold it in this temperature range for 32 hours; after the holding period, reduce the temperature to ≤250℃ at a rate of ≤55℃ / h and remove it from the furnace, then air cool it to room temperature.

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