CN114247961A

CN114247961A - Method for welding and heat treating SA-335P11 and SA-240TYPE310S dissimilar steel

Info

Publication number: CN114247961A
Application number: CN202010996897.3A
Authority: CN
Inventors: 沈斌强; 王飞; 方战华; 陈杰恒; 何仲; 喜鑫; 陈益希
Original assignee: Jiangsu Libert Inc
Current assignee: Jiangsu Libert Inc
Priority date: 2020-09-21
Filing date: 2020-09-21
Publication date: 2022-03-29
Anticipated expiration: 2040-09-21
Also published as: CN114247961B

Abstract

The invention discloses a method for welding and thermally treating SA-335P11 and SA-240TYPE310S dissimilar steel, which comprises the following steps: A. preparing before welding; B. processing and cleaning a groove; C. overlaying a nickel alloy isolation layer, and performing stress relief heat treatment on the nickel alloy isolation layer and a workpiece heat affected zone; D. preparation before pairing: E. the first workpiece and the second workpiece are subjected to material pairing and tack welding; F. manual argon tungsten-arc welding is adopted to carry out backing welding on the root part of the groove; G. filling the cover surface by adopting manual arc welding; H. polishing and removing welding lines on the inner surface and the outer surface of the deposited metal, polishing and removing undercut at a welding toe part, and ensuring smooth transition between the deposited metal and the inner surface and the outer surface of a workpiece; I. checking a welding seam VT; J. detecting a welding seam PT; K. and (5) detecting a weld joint by RT. The welding and heat treatment method welds the isolating layer on the first workpiece, not only meets the technical requirements of the stress relief heat treatment of the SA-335P11 material, but also avoids the accelerated sensitization of the SA-240TYPE310S material.

Description

Method for welding and heat treating SA-335P11 and SA-240TYPE310S dissimilar steel

Technical Field

The invention relates to a method for welding and heat treating dissimilar steel, in particular to a method for welding and heat treating SA-335P11 and SA-240TYPE310S dissimilar steel.

Background

At present, in the petrochemical industry, some process pipelines or plates are made of steel materials of two different materials, and because the steel materials are different, such as SA-335P11 high-temperature alloy chrome molybdenum steel material and SA-240TYPE310S austenitic stainless steel material, when the two materials need to be welded together, the welding and heat treatment technical difficulty is very high, the quality requirement is high, particularly the welding technical difficulty of the petrochemical device process pipelines made of heterogeneous steel with large-diameter and thick-pipe walls is higher, the process is more complex, the preheating temperature, the inter-channel and interlayer temperature and the linear energy requirements are high, the welding seam deposited metal filling amount is large, the working period is long, the welding operator operation skill requirement is high, and due to the characteristics, the welding work cannot be completed by the conventional welding and heat treatment method.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: the welding and heat treatment method for the SA-335P11 and SA-240TYPE310S dissimilar steel materials is provided, and the isolating layer is welded on the first workpiece, so that the technical requirement of stress relief heat treatment of the SA-335P11 material is met, and the accelerated sensitization of the SA-240TYPE310S material is avoided.

In order to solve the technical problems, the technical scheme of the invention is as follows: a method for welding and thermally treating SA-335P11 and SA-240TYPE310S dissimilar steel comprises the following steps:

A. preparing before welding;

B. defining a workpiece with the material of SA-335P11 as a first workpiece, defining a workpiece with the material of SA-240TYPE310S as a second workpiece, processing grooves on the end faces of the notches of the first workpiece and the second workpiece, and cleaning the inner and outer surfaces of the grooves; the groove is a V-shaped groove, the included angle between the groove surface and the normal direction is 32 degrees +/-2.5 degrees, and the truncated edge is 0-2 mm;

C. carrying out nickel alloy isolation layer surfacing and heat treatment on the bevel face of the first workpiece, and comprising the following steps:

c1) inspecting the quality of the bevel face of the first workpiece:

c2) arranging a thermocouple and an electric heating tape on the surface of the first workpiece except the bevel face, wrapping heat preservation cotton outside the electric heating tape, fixing, and performing preheating preparation;

c3) the bevel face preheating temperature and nickel alloy isolating layer surfacing process control comprises the following steps:

c31) the welding wire for the bevel surfacing is ERNiGr-3, and the diameter is 2.4 mm; GTAW is adopted in the process for overlaying the bevel face;

c32) surfacing a first layer on the bevel face: preheating a first workpiece to 150-180 ℃, wherein a surfacing welding bead is a linear welding bead, and performing channel pressing welding, wherein the width of each channel is less than 13mm, the thickness of each channel is less than 2.0mm, the current is 115-145A, the voltage is 8-11V, and the temperature between channels is 150-180 ℃;

c33) surfacing a second layer on the bevel face: preheating a first workpiece to 120-150 ℃, wherein a surfacing welding bead is a linear welding bead, performing channel pressing welding, the width of each channel is less than 13mm, the thickness of each channel is less than 2.0mm, the current is 115-150A, the voltage is 8-11V, and the temperature between channels is 120-150 ℃;

c34) surfacing a third layer on the bevel face: the first workpiece is not preheated, the surfacing welding bead is a linear welding bead, and the bead pressing welding is carried out, wherein the width of each bead is less than 13mm, the thickness of each bead is less than 2.4mm, the current is 140-170A, the voltage is 9-13V, and the inter-bead temperature is less than 100 ℃;

c35) surfacing a fourth layer on the bevel face: the first workpiece is not preheated, the surfacing welding bead is a linear welding bead, and the bead pressing welding is carried out, wherein the width of each bead is less than 13mm, the thickness of each bead is less than 2.4mm, the current is 140-170A, the voltage is 9-13V, and the inter-bead temperature is less than 100 ℃;

c36) surfacing a fifth layer on the bevel face: the first workpiece is not preheated, the surfacing welding bead is a linear welding bead, and the bead pressing welding is carried out, wherein the width of each bead is less than 13mm, the thickness of each bead is less than 2.0mm, the current is 140-170A, the voltage is 9-13V, and the inter-bead temperature is less than 100 ℃;

the first cladding metal and the last cladding metal of each layer of bead welding of the bevel face exceed the outer surface and the inner surface of the first workpiece by 0-1.5 mm;

c37) polishing and removing the extra height of the isolation layer to be flush with the inner surface and the outer surface of the first workpiece;

c4) stress relief heat treatment is carried out on the bevel face surfacing welding isolation layer, the heat preservation temperature of the stress relief heat treatment of the bevel face argon arc surfacing welding isolation layer is 720 +/-15 ℃, and the heat preservation time is not less than 135 minutes; the heating rate is 56 ℃/h-220 ℃/h, and the cooling rate is 56 ℃/h-280 ℃/h; the charging temperature is room temperature, and the cooling mode is furnace cooling;

c5) detecting the surface quality appearance and PT of the isolation layer;

D. determining the preparation work and technical requirements before pairing the first workpiece and the second workpiece, comprising the following steps:

d1) confirming that the material of a hydraulic assembly device, a tooling fixture and a fixture at the contact part of a point fixing block and a first workpiece and a second workpiece for assembly is the same as or the same as the material of the workpieces;

d2) the first workpiece and the second workpiece are paired to form a gap within the range of 1-6 mm, and the allowable deviation of the inner wall and the outer wall of a welded junction formed by pairing is as follows:

tolerance of the inner wall of the tube: the thickness of the wall is 20+1mm, and the maximum thickness cannot exceed 3 mm;

tube outer wall tolerance: the thickness of the wall is 10+2mm, and the maximum thickness cannot exceed 8 mm;

E. the method comprises the following steps of performing parallel spot welding on a first workpiece and a second workpiece by material group, performing spot welding on the root of a welding line by manual tungsten electrode argon arc welding, wherein an ERNiCr-3 welding wire is adopted, the diameter is phi 2.4, and the method comprises the following sub-steps according to different types of the welding line:

e1) for a circumferential weld pair: uniformly dividing the circumference of the whole circumferential weld into 12 equal parts, temporarily not setting hydraulic group pairers at

positions

3, 6, 9 and 12 of a clock point position, arranging eight hydraulic group pairers at

positions

1, 2, 4, 5, 7, 8, 10 and 11, and additionally setting hydraulic group pairers if the misalignment exceeds the standard in the

position ranges

3, 6, 9 and 12 of the clock point position;

e2) for the longitudinal weld pairing: uniformly dividing the whole longitudinal weld into a plurality of equal parts, wherein the length of each equal part is 300-400 mm, arranging hydraulic assembly devices at the equal parts, and additionally arranging the hydraulic assembly devices if the position range of the equal parts has staggered edges exceeding the standard;

e3) for circumferential weld tack welding: starting tack welding at the root of a groove at a position 10mm away from the edge of the hydraulic assembly on one side of the hydraulic assembly; the length of the point-fixed welding seam is 40-50 mm, and the thickness is 3-5 mm; the WPS used for spot welding is the same as that used for formal welding;

e4) for longitudinal seam tack welding: extending the sectional spot welding from the middle point of the length of the longitudinal welding line to two sides; starting tack welding at the root of a groove at a position 10mm away from the edge of the hydraulic assembly on one side of the hydraulic assembly; the length of the point-fixed welding seam is 40-50 mm, and the thickness is 3-5 mm; the WPS used for spot welding is the same as that used for formal welding;

e5) checking the quality of spot welding;

e6) dismantling the hydraulic assembling devices one by one;

e7) polishing two ends of the point welding spots into a gentle slope shape;

F. manual argon tungsten-arc welding is adopted to carry out backing welding on the root of the groove, and metal is deposited by the backing welding to form a backing welding layer; backing welding two layers, wherein each layer has 1 path, an ERNiCr-3 welding wire is selected, the diameter is phi 1.6 or phi 2.4, a linear welding path is adopted, the swing width of a welding torch is not more than 3 times of the diameter of the welding wire, the current is 130-205A, the voltage is 10-16V, the temperature between the paths/layers is less than 100 ℃, the residual height of the back of a backing welding deposited metal relative to the inner wall of a workpiece after welding is less than 3mm, and the thickness of the deposited metal after welding 2 layers is 3-5 mm;

G. filling the capping surface by adopting manual arc welding, adopting linear welding bead and symmetrical welding, wherein the width of a welding line is not more than 3 times of the diameter of the steel core, and the temperature between the welding lines/layers is less than 100 ℃; the welding rod is made of ENiCrFe-2, when the diameter is phi 3.2mm, the current is 120-140A, the voltage is 23-30V, and the thickness of each layer is less than 3.2 mm; the method is characterized in that the electrode is ENiCrFe-2, when the diameter is phi 4.0mm, the current is 125-165A, the voltage is 23-30V, and the thickness of each layer is less than 4 mm; the rest height of the surface of the welding seam is less than 2.5 mm;

H. polishing and removing welding lines on the inner surface and the outer surface of the deposited metal, polishing and removing undercut at a welding toe part, and ensuring smooth transition between the deposited metal and the inner surface and the outer surface of a workpiece;

I. checking a welding seam VT;

J. detecting a welding seam PT;

K. and (5) detecting a weld joint by RT.

As a preferable scheme, the step c2) of fixing the thermocouple on the first workpiece by using the heat insulation cotton and the electric heating tape to prepare for preheating the bevel face comprises the following specific steps:

c21) drawing a reference line: drawing a groove edge line reference line at a position 30 +/-0.2 mm away from a bevel edge line on the outer wall of the first workpiece;

c22) determining the number of arranged thermocouples according to the shape and the size of the first workpiece;

when the first workpiece is a pipe, the outer diameter of the pipe is less than phi 114.3mm, and 1 thermocouple is arranged;

the outer diameter of the tube is more than or equal to phi 114.3mm and less than phi 508mm, and 2 thermocouples are arranged at equal intervals;

the outer diameter of the tube is more than or equal to phi 508mm and less than phi 914mm, and 3 thermocouples are arranged at equal intervals;

the outer diameter of the tube is more than or equal to phi 914mm, and 4 thermocouples are arranged at equal intervals;

when the first workpiece is a plate, respectively arranging thermocouples at positions 100mm away from two ends of the plate;

c23) the top end where the thermocouple thermistor is located at a position 10mm away from the edge line of the bevel;

c24) and the thermocouple, the electric heating belt and the heat insulation cotton are bound and fixed on the outer wall of the first workpiece.

By adopting the mode for preheating, the temperature difference of the workpiece can be controlled, and the preheating is more uniform, so that the overlaying of the isolation layer is better facilitated.

As a preferred scheme, the grinding step of the step c37) is moved to be before the step E, and grinding is carried out before the group fitting.

As a preferable scheme, the step c5) of detecting the surface quality appearance and PT of the isolation layer specifically comprises:

c51) checking the thickness of the isolation layer by taking the reference line as a basis to ensure that the thickness of the isolation layer is more than 6mm to check the surface quality of the cladding metal of the surfacing layer;

c52) detecting isolation layer surface PT, if detect when unqualified, fill repair welding according to the same build-up welding's of isolation layer mode after polishing the defective position, carry out thickness detection and PT detection once more after repair welding back thermal treatment, satisfy the technological requirement until the isolation layer.

As a preferable scheme, in the step F, the corresponding welding method for the circumferential weld and the linear longitudinal weld is as follows:

firstly, for circumferential weld welding, the following two welding methods are adopted:

f1) the workpiece rotates around the center line of the workpiece, arcs between the clock point positions 1 → 12, and is welded in the anticlockwise direction; manual argon tungsten-arc welding is performed for backing welding of 2 layers, each layer is subjected to 1 pass, a welding wire is phi 1.6 or phi 2.4, linear welding passes are adopted, and joints between layers are staggered by more than 10 mm;

f2) horizontally fixing a workpiece, backing welding by manual argon tungsten-arc welding, and performing linear welding bead by sectional symmetrical welding; equally dividing the annular welding seam into 12 sections, and dividing the 12 sections of welding seams into two groups;

f21) determining the sequence, welding direction, arc striking position and welding of the first group of piecewise symmetry welding: wherein the first set of welding sequences; according to hour positions 6 → 5, 11 → 12; 3 → 2, 8 → 9; 6 → 7, 1 → 12; 4 → 3, 9 → 10; welding in sequence; wherein 6 → 5, 11 → 12 is a pair of symmetrical solder segments, 3 → 2, 8 → 9 is a pair of symmetrical solder segments, 6 → 7, 1 → 12 is a pair of symmetrical solder segments, 4 → 3, 9 → 10 is a pair of symmetrical solder segments;

first set of welding directions: taking the welding direction as the advancing direction;

the first group of welding arc starting positions and welding: when welding is carried out for 6 → 5, 6 → 7, 3 → 2, 9 → 10, respectively, the arc starts from 10mm before the

points

6, 3, 9, then the arc respectively turns back to the root part of the groove 10mm after the

points

6, 3, 9, the arc penetrates the blunt edge to form a fusion hole, and then the arc moves forward to form a welding line; when in welding 11 → 12, 4 → 3, 1 → 12, 8 → 9, respectively, the arc is started from 10mm before the tack welding end of the 11, 4, 1, 8 point position, and then the arc is folded back to the gentle slope of the tack welding end of the 11, 4, 1, 8 point position to melt the joint; arcing until the arc passes through the positions of 12, 3, 12 and 9;

f22) determining the welding sequence, the welding direction, the arc striking position and the welding of the second group of sectional symmetry: wherein the second set of welding sequences; according to 7 → 8, 2 → 1; 5 → 4, 10 → 11; wherein 5 → 4, 10 → 11 is a symmetric solder segment, and 7 → 8, 2 → 1 is a symmetric solder segment;

the second group of welding directions take the welding direction as the advancing direction;

and (3) welding the second group of welding arc starting positions: when each welding section is welded, firstly, the tack welding point ends at the two ends of the welding section are polished into gentle slopes, then, arcs are started from the positions, 10mm away from the tack welding point ends of the welding section, then, the tack welding point ends are folded backwards to the gentle slopes of the tack welding point ends, after the gentle slopes of the ends are melted, the arcs walk forwards again, and then, the arcs are closed after the arc is connected with the welding point ends of the front welding section;

for backing welding of the longitudinal welding seam, uniformly dividing the whole longitudinal welding seam into a plurality of equal parts, wherein the equal parts are 300-400 mm in length; then, the step of skip welding is carried out from the middle part of the length of the welding seam to two sides in a segmented mode; joints between the inter-layer channels need to be staggered; the joint position of the second layer of welding bead and the joint position of the first layer of welding bead are staggered by a distance larger than 10mm, and the joints of each layer of welding bead are mutually staggered by a distance larger than 10 mm.

According to the scheme, for the first welding mode of the circumferential weld, manual argon tungsten-arc welding backing welding is adopted, anticlockwise, linear welding beads and channel pressing welding are adopted, transverse shrinkage stress of the weld is relatively reduced, the thickness of each layer of cladding metal is controlled, and the overheating condition of the cladding metal is avoided; for the second welding mode of the circumferential weld, segmented symmetrical welding is adopted, manual argon tungsten-arc welding backing welding is adopted, the welding is finished according to the segmented symmetrical welding, the circumferential length of the weld of the pipe is divided into 12 equal segments, symmetrical welding is carried out, the welding stress is ensured to be flat and horizontal, and the areas of welding heat input and a heat affected zone are relatively reduced; the thickness of each layer of cladding metal is controlled, so that the overheating condition of the cladding metal is avoided;

while the longitudinal welding seam adopts the step-by-step symmetric skip welding from the middle point to the two sides, linear welding and pressure welding, so that the welding heat input and the heat affected zone area are relatively reduced, and the welding stress is relatively reduced; the thickness of each layer of cladding metal is controlled, and the overheating condition of the cladding metal is avoided.

After the technical scheme is adopted, the invention has the effects that:

1. in the welding and heat treatment method, pre-welding preheating and post-welding heat treatment processes are carried out, after an isolating layer is overlaid on the bevel face of the SA-335P11 high-alloy chromium-molybdenum steel material, stress relief heat treatment is carried out independently, the welding residual stress between the SA-335P11 high-alloy chromium-molybdenum steel and the cladding metal is relieved, the diffusion hydrogen in the cladding metal and the first workpiece in the heat affected zone is relieved, cold cracks of the cladding metal and the first workpiece in the near seam zone are avoided, the welding seam is not welded at the moment, the austenitic stainless steel SA-240TYPE310S does not participate in the stress relief heat treatment together, the damage of sensitized treatment of the austenitic stainless steel SA-240TYPE310S is avoided, and the intergranular corrosion resistance of the austenitic stainless steel SA-240TYPE310S is protected;

2. an isolation layer is welded on the end face of the groove of the first workpiece, and the first layer and the second layer of the isolation layer are preheated before surfacing, so that the base metal near the end face of the groove is heated and expanded, the difference of thermal expansion of two different metals is reduced, the cooling speed of the cladding metal is reduced, the diffusion hydrogen in the cladding metal is favorably discharged, and the welding stress of the two different metals during welding is reduced; the method protects the intergranular corrosion resistance of the austenitic stainless steel, reduces the welding stress and deformation of the weld deposit metal and a heat affected zone, reduces the internal pores, slag inclusion and crack tendency of the weld deposit metal, reduces the heat input of the weld, and ensures that the weld deposit metal is not overheated.

Drawings

The invention is further illustrated with reference to the following figures and examples.

FIG. 1 is a partial axial structural cross-sectional view of a first workpiece at a bevel in accordance with an embodiment of the invention;

FIG. 2 is a cross-sectional view of a bevel face preheating and thermocouple arrangement of a first workpiece according to an embodiment of the invention;

FIG. 3 is a schematic illustration of a bevel-faced weld deposit isolation layer of a first workpiece according to an embodiment of the invention;

FIG. 4 is a schematic illustration of the polishing of the inner and outer surfaces of a spacer layer according to an embodiment of the invention;

FIG. 5 is a schematic diagram of post stress relief heat treatment of an isolation layer according to an embodiment of the invention;

FIG. 6 is a schematic view of a circumferential weld and a longitudinal weld of an embodiment of the invention distributed symmetrically in segments;

FIG. 7 is a schematic diagram of groove pairing using a hydraulic group pairing device according to an embodiment of the invention;

FIG. 8 is a schematic illustration of a groove root tack weld of an embodiment of the invention;

FIG. 9 is a schematic view of groove root backing welding of an embodiment of the invention;

FIG. 10 is a schematic view of a groove fill weld overlay of an embodiment of the invention;

in the drawings: 1. a first workpiece; 101. a bevel face; 102. a blunt edge; 2. an electrical heating belt; 3. heat preservation cotton; 4. a thermocouple; 5. an isolation layer; 6. a longitudinal weld; 7. a circumferential weld; 8. a second workpiece; 9. a hydraulic group assembling device; 901. an outer positioning plate; 902. a pull rod; 903. an inner positioning plate; 904. a hydraulic cylinder; 10. fixing welding spots; 11. backing welding to deposit metal; 12. the cap weld is filled.

Detailed Description

The present invention is described in further detail below with reference to specific examples.

As shown in fig. 1 to 10, a method for welding and heat treating different TYPEs of steel materials SA-335P11 and SA-240TYPE310S comprises the following steps:

A. preparing before welding;

a1) determining the execution standard of welding and heat treatment:

the execution criteria in this embodiment are:

ASME IX-2017 evaluation Standard of welding and brazing Process, welder, brazing welder, welding and brazing operator;

ASME VIII-1-2017 pressure vessel construction rules

a2) Checking whether the specification, the grade, the specification and the grade of the welding material and the gas of the pipe meet the standard or not; in this embodiment, a tube 1 of SA-335P11 and SA-240TYPE310S φ 970 × 28mm is taken as an example, and Table 1 records technical parameters of the tube 1 and a welding material in the specification;

serial number	Name of Material	Material brand/standard number	Specification of materials	Manufacturing standard
					1	Carbon steel pipe	SA-335 P11	φ970×28	ASME B36.10M
2	Stainless steel pipe	SA-240 TYPE310S	φ970×28	ASME B36.10M
					3	Nickel alloy welding wire	ERNiCr-3	φ2.0/φ2.4	AWS A5.14
4	Nickel alloy welding rod	ENiCrFe-2	φ3.2/φ4.0	AWS A5.11
					5	Argon gas	Ar	99.997％	GB/T4842-2017

TABLE 1

a3) Selecting a tool:

the welding equipment needed is: an inversion direct current argon arc/manual arc welding machine WS-400E or the same type of arc welding power supply, an argon pressure reducing meter, a welding rod drying box, a welding rod heat-preserving barrel, heat treatment equipment ZW-II-240 or the same type of equipment, a thermocouple 4, a point thermometer, groove processing equipment, nondestructive and physicochemical inspection equipment and the like.

The ammeter, voltmeter and argon gas decompression meter of the inverter direct current argon arc/manual arc welding machine WS-400E and the corresponding measuring instruments of the equipment are required to be calibrated and within the validity period of calibration.

The tools needed are mainly: angle grinder, steel wire brush, semicircle file, flashlight, welding seam inspection chi, acetone, cotton yarn and labour protection article, heating band, heat preservation cotton 3 etc..

a4) Checking the welding materials; checking whether the purity of argon is 99.997%, checking whether the surface of a welding wire for the argon arc welding torch is clean, and checking whether the physicochemical parameters of the welding wire for the pipe and the argon arc welding torch are qualified;

a5) processing a bevel face 101 on the end faces of the cut of the first workpiece 1 and the second workpiece 8 to be welded, wherein the bevel is a V-shaped bevel as shown in figure 1, the included angle between the bevel face 101 and the normal direction is 32 degrees +/-2.5 degrees, and the blunt edge 102 at the root part of the bevel is 0-2 mm;

a6) removing impurities such as oil, rust, oxide skin and the like within the range of 20mm from the inner surface and the outer surface of the bevel face 101 to expose the metallic luster, and scrubbing with acetone if necessary to expose the metallic luster;

B. defining a workpiece with the material SA-335P11 as a first workpiece 1, defining a workpiece with the material SA-240TYPE310S as a second workpiece 8, machining grooves on the end faces of the notches of the first workpiece 1 and the second workpiece 8 and cleaning the inner and outer surfaces of the grooves; the groove is a V-shaped groove, the included angle between the groove surface 101 and the normal direction is 32 degrees +/-2.5 degrees, and the truncated edge 102 is 0-2 mm;

C. the nickel alloy isolation layer 5 overlaying welding is carried out on the bevel face 101 of the first workpiece 1, and the method comprises the following steps:

c1) quality inspection of the bevel face 101 of the first workpiece 1: the method specifically comprises the following steps: the bevel face 101 is not subjected to visual inspection to have defects such as cracks, interlayers, burrs and the like; carrying out 100% PT inspection on the bevel face 101; checking and checking the size of the groove;

c2) arranging a thermocouple 4 and an electric heating belt 2 on the surface of the first workpiece except the bevel face 101, wrapping heat preservation cotton 3 outside the electric heating belt 2, fixing, and performing preheating preparation;

the specific mode of the step c2) is as follows:

the step c2) of fixing the thermocouple on the first workpiece 1 by using the heat insulation cotton and the electric heating tape 2 to prepare for preheating the bevel face 101 specifically comprises the following steps:

c21) drawing a reference line: drawing a groove edge line reference line at a position 30 +/-0.2 mm away from a bevel edge line on the outer wall of the first workpiece 1, and measuring the thickness of the overlaying welding isolation layer 5 by using the reference line;

c22) determining the number of the arranged thermocouples 4 according to the shape and the size of the first workpiece 1;

when the first workpiece 1 is a pipe, the outer diameter of the pipe is less than phi 114.3mm, 1 thermocouple 4 is arranged, and the position of the thermocouple 4 is arranged at the 3-point position;

the outer diameter of the tube is more than or equal to phi 114.3mm and less than phi 508mm, and 2 thermocouples 4 are arranged at equal intervals; arranged at the 3 o 'clock and 9 o' clock positions;

the outside diameter of the tube is more than or equal to phi 508mm and less than phi 914mm, and 3 thermocouples 4 are arranged at equal intervals; arranged at three positions of 3 points, 7 points and 11 points;

the outer diameter of the tube is more than or equal to phi 914mm, and 4 thermocouples 4 are arranged at equal intervals; arranged at four positions of 3, 6, 9 and 12;

when the first workpiece 1 is a plate, respectively arranging thermocouples 4 at positions 100mm away from two ends of the plate;

c23) the top end of the thermocouple 4, where the thermistor is located, is located at a position 10mm away from the edge line of the bevel;

c24) and the thermocouple 4, the electric heating belt 2 and the heat insulation cotton 3 are fixed on the outer wall of the first workpiece 1 in a bundling manner.

Adopt above-mentioned mode to preheat, can control the difference in temperature of work piece, preheat more evenly to better make things convenient for the build-up welding of isolation layer 5. The electric heating belt 2 heats the workpiece, the thermocouples 4 are used for detecting the temperature of the workpiece, and the plate is simpler to heat relative to the pipe, so that the temperature can be accurately detected only by arranging the two thermocouples 4.

c3) The preheating temperature of the bevel face 101 and the surfacing process control of the nickel alloy isolating layer 5 comprise the following steps:

c31) the welding wire for overlaying welding of the bevel face 101 is ERNiGr-3, and the diameter is phi which is 2.4 mm; GTAW is adopted in the process for overlaying the bevel face 101;

c32) bead face 101 overlay first layer: preheating a first workpiece 1 to 150-180 ℃, wherein a surfacing welding bead is a linear welding bead, and a channel pressing welding is carried out, wherein the width of each channel is less than 13mm, the thickness of each channel is less than 2.0mm, the current is 115-145A, the voltage is 8-11V, and the temperature between channels is 150-180 ℃;

c33) bead face 101 overlay second layer: preheating a first workpiece 1 to 120-150 ℃, wherein a surfacing welding bead is a linear welding bead, and a channel pressing welding is carried out, wherein the width of each channel is less than 13mm, the thickness of each channel is less than 2.0mm, the current is 115-150A, the voltage is 8-11V, and the temperature between channels is 120-150 ℃;

c34) surfacing a third layer on the bevel face 101: the method comprises the following steps that a first workpiece 1 is not preheated, a surfacing welding bead is a linear welding bead, and channel pressing welding is carried out, wherein the width of each channel is less than 13mm, the thickness of each channel is less than 2.4mm, the current is 140-170A, the voltage is 9-13V, and the inter-channel temperature is less than 100 ℃;

c35) surfacing of a fourth layer on the bevel face 101: the method comprises the following steps that a first workpiece 1 is not preheated, a surfacing welding bead is a linear welding bead, and channel pressing welding is carried out, wherein the width of each channel is less than 13mm, the thickness of each channel is less than 2.4mm, the current is 140-170A, the voltage is 9-13V, and the inter-channel temperature is less than 100 ℃;

c36) surfacing a fifth layer on the bevel face 101: the method comprises the following steps that a first workpiece 1 is not preheated, a surfacing welding bead is a linear welding bead, and channel pressing welding is carried out, wherein the width of each channel is less than 13mm, the thickness of each channel is less than 2.0mm, the current is 140-170A, the voltage is 9-13V, and the inter-channel temperature is less than 100 ℃;

the first cladding metal and the last cladding metal of each layer of bead welding of the bevel face 101 exceed the outer surface and the inner surface of the first workpiece 1 by 0-1.5 mm;

c37) polishing and removing the residual height of the isolation layer 5 to be flush with the inner surface and the outer surface of the first workpiece 1; before the polishing step of the step c37) is moved to the step E, the polishing is completed before the assembly, and the isolation layer 5 after polishing can facilitate the accurate assembly of the first workpiece 1 and the second workpiece 8 without influencing the assembly precision.

c4) Stress relief heat treatment is carried out on the bevel face 101 surfacing isolation layer 5, the temperature of the stress relief heat treatment of the bevel face 101 argon arc surfacing isolation layer 5 is 720 +/-15 ℃, and the temperature preservation time is not less than 135 minutes; the heating rate is 56 ℃/h-220 ℃/h, and the cooling rate is 56 ℃/h-280 ℃/h; the charging temperature is room temperature, and the cooling mode is furnace cooling;

the method for eliminating stress heat treatment can be put into a heating furnace for heat treatment, and can also be used for heat treatment by wrapping the electric heating belt 2, and in the industry, when the mode of wrapping the electric heating belt 2 for heat treatment is adopted, the same expression method as that in the heating furnace is also generally adopted, such as: the furnace cooling is as follows: and after the power failure, the electric heating belt 2 and the heat insulation cotton 3 are not detached to carry out natural cooling.

The specific mode is that the electric heating belt 2 completely wraps the cladding metal of the surfacing isolation layer 5 and the heat affected zone of the first workpiece 1, as shown in fig. 5, the outside is wrapped and bundled by heat preservation cotton 3, and the total heating width is more than 50 mm; after the heat-insulating cotton 3 is bound and fixed, the surrounding environment of the heat-treated piece is provided with a certain heat dissipation space so as to be beneficial to uniform heat dissipation during the stress-relieving heat treatment cooling period, and thus the shape of the cooling curve can be better controlled.

And stopping power supply after the temperature is reduced to the specified temperature, and removing the heat preservation cotton 3, the electric heating belt 2 and the thermocouple 47. The cladding metal of the surfacing isolating layer 5 after heat treatment cannot be placed in the place where air convects, so that adverse temperature gradient is avoided.

During the stress relief heat treatment, the heating rate, temperature, holding time, and cooling rate are strictly controlled. The heat treatment equipment uses standard coordinate paper or an electronic automatic recorder to continuously and automatically record the temperature-time curve. The heat treatment profile must be continuous, uniform and must not show a drop line. After the heat treatment is finished, the heat treatment operator marks information such as heating and cooling speed, heat preservation temperature, heat preservation time, heat treatment report number, curve color, corresponding thermocouple number and paper feeding speed on the graph, and simultaneously issues a heat treatment report.

After the heat treatment, the surface of the first workpiece 1 is cleaned of scale and floating ash.

c5) Detecting the quality appearance and PT of the isolation layer 5;

the specific mode of detecting the quality appearance and PT of the isolation layer 5 in the step c5) is as follows:

c51) checking the thickness of the isolation layer 5 by taking the reference line as a basis, ensuring that the thickness of the isolation layer 5 is more than 6mm, checking the appearance forming quality of the cladding metal of the overlaying layer, if the thickness of the cladding metal is not satisfied, overlaying again according to the same overlaying process until the thickness is more than 6 mm;

c52) detect 5 surperficial PT of isolation layer, if detect when unqualified, fill repair welding according to isolation layer 5's the same build-up welding mode after polishing defective position, carry out thickness detection and PT detection once more after repair welding back heat treatment, satisfy the technological requirement until isolation layer 5.

So far, table 2 is a table of parameters of the welding and heat treatment process of the bevel surfacing welding isolation layer:

TABLE 2

D. The method for determining the preparation work and the technical requirements before pairing the first workpiece 1 and the second workpiece 8 comprises the following steps:

d1) confirming that the material of the clamp at the contact part of the hydraulic group assembler 9, the tooling clamp and the point fixing block for group combination with the first workpiece 1 and the second workpiece 8 is the same as or the same as the workpiece material; as shown in fig. 7, the hydraulic assembly device 9 includes a hydraulic cylinder 904, the hydraulic cylinder 904 is fixed on the outer positioning plate 901, the piston rod is connected to a pull rod 902, the pull rod 902 is provided with an insertion hole, the inner positioning plate 903 is inserted into the insertion hole, the pull rod 902 is positioned between the gap between the first workpiece 1 and the second workpiece 8, and then the inner positioning plate 903 is inserted from the inner side, so that the piston rod of the hydraulic cylinder acts to drive the inner positioning plate 903 and the outer positioning plate 901 to displace towards each other, thereby assembling the inner and outer walls of the workpieces and ensuring coaxiality or the same plane.

d2) The clearance between the first workpiece 1 and the second workpiece 8 in the pairing process is within the range of 1-6 mm, and the allowable deviation of the inner wall and the outer wall of the welded junction after the pairing process is as follows:

E. the method comprises the following steps of performing parallel spot welding on a first workpiece 1 and a second workpiece 8 by material group, performing spot welding on the root of a welding seam by manual argon tungsten-arc welding, wherein an ERNiCr-3 welding wire is adopted, the diameter is phi 2.4, and the method comprises the following steps according to different types of welding seams:

e1) for a circumferential weld pair: uniformly dividing the circumference of the whole circumferential weld 7 into 12 equal parts, temporarily not arranging hydraulic group pairers 9 at

positions

3, 6, 9 and 12 of a clock point position, arranging eight hydraulic group pairers 9 at

positions

1, 2, 4, 5, 7, 8, 10 and 11, and additionally arranging hydraulic group pairers 9 if the misalignment exceeds the standard in the position ranges 3, 6, 9 and 12 of the clock point position;

e2) for 6 pairs of longitudinal welds: uniformly dividing the whole longitudinal welding line 6 into a plurality of equal parts, wherein the equal parts are 300-400 mm in length, arranging hydraulic assembly devices 9 at the equal division positions, and additionally arranging the hydraulic assembly devices 9 if the staggered edges in the position range of the equal division points exceed the standard;

e3) for circumferential weld tack welding: starting tack welding at the root of a groove at a position 10mm away from the edge of the hydraulic assembly pairing device 9 on one side of the hydraulic assembly pairing device 9; the length of the point-fixed welding seam is 40-50 mm, and the thickness is 3-5 mm; the WPS used for spot welding is the same as that used for formal welding;

e4) 6-spot welding of longitudinal welding seam: the middle point of the length of the longitudinal welding line 6 is started, and segmented spot welding is extended towards two sides; starting tack welding at the root of a groove at a position 10mm away from the edge of the hydraulic assembly pairing device 9 on one side of the hydraulic assembly pairing device 9; the length of the point-fixed welding seam is 40-50 mm, and the thickness is 3-5 mm; the WPS used for spot welding is the same as that used for formal welding;

e5) checking the quality of spot welding;

e6) the hydraulic group assembling devices 9 are disassembled one by one;

e7) polishing two ends of the point welding spots 10 into a gentle slope shape;

F. manual argon tungsten-arc welding is adopted to perform backing welding on the root of the groove, and metal is deposited by the backing welding to form a backing welding layer 11; backing welding 11 comprises two layers, each layer comprises 1 track, the welding wire is ERNiCr-3 with the diameter of phi 1.6 or phi 2.4, a linear welding channel is adopted, the swing width of a welding torch is not more than 3 times of the diameter of the welding wire, the current is 130-205A, the voltage is 10-16V, the temperature between tracks and layers is less than 100 ℃, the residual height of the back of a backing welding deposited metal 11 relative to the inner wall of a workpiece after welding is less than 3mm, and the thickness of the deposited metal after welding 2 layers is 3-5 mm;

in the step F, the corresponding welding mode aiming at the circumferential weld 7 and the linear longitudinal weld 6 is as follows:

firstly, for welding the circumferential weld seam 7, the following two welding methods are adopted:

first set of welding directions:

the first group of welding arc starting positions and welding: taking the welding direction as the advancing direction; when welding is carried out for 6 → 5, 6 → 7, 3 → 2, 9 → 10, respectively, the arc starts from 10mm before the

points

6, 3, 9, then the arc turns back to the root of the groove 10mm after the

points

6, 3, 9, respectively, the arc penetrates the blunt edge 102 to form a molten hole, and then the arc moves forward to form a welding seam; when in welding 11 → 12, 4 → 3, 1 → 12, 8 → 9, respectively, the arc is started from 10mm before the tack welding end of the 11, 4, 1, 8 point position, and then the arc is folded back to the gentle slope of the tack welding end of the 11, 4, 1, 8 point position to melt the joint; arcing until the arc passes through the positions of 12, 3, 12 and 9;

and (3) welding the second group of welding arc starting positions: when each welding section is welded, firstly, the ends of point welding spots 10 at two ends of the welding section are polished into gentle slopes, then arcs are started from the positions, 10mm away from the ends of the point welding spots 10 of the welding section, then the arcs are folded backwards to the gentle slopes at the ends of the point welding spots 10, after the gentle slopes at the ends are melted, the arcs walk forwards again, and then the arcs are closed after the joints with the ends of the welding spots of the front welding section are connected;

secondly, for backing welding of the longitudinal welding seam 6, uniformly dividing the whole longitudinal welding seam 6 into a plurality of equal parts, wherein the equal parts are 300-400 mm in length; then, the step of skip welding is carried out from the middle part of the length of the welding seam to two sides in a segmented mode; joints between the inter-layer channels need to be staggered; the joint position of the second layer of welding bead and the joint position of the first layer of welding bead are staggered by a distance larger than 10mm, and the joints of each layer of welding bead are mutually staggered by a distance larger than 10 mm.

G. Filling the cap surface by adopting arc welding to form a filling cap surface welding line 12, adopting linear welding bead and symmetrical welding, wherein the width of the welding line is not more than 3 times of the diameter of the steel core, and the inter-channel/interlayer temperature is less than 100 ℃; the welding rod is made of ENiCrFe-2, when the diameter is phi 3.2mm, the current is 120-140A, the voltage is 23-30V, and the thickness of each layer is less than 3.2 mm; the method is characterized in that the electrode is ENiCrFe-2, when the diameter is phi 4.0mm, the current is 125-165A, the voltage is 23-30V, and the thickness of each layer is less than 4 mm; the rest height of the surface of the welding seam is less than 2.5 mm; arc-closing and filling arc pits; the stagger of the joints between the roads and the layers is more than 10 mm;

and F, the welding sequence and the welding direction of the filling cover surface welding are the same as those of the backing welding in the step F.

So far, Table 3 is a parameter table of the welding process of the isolating layer 5ERNiCr-3 and the SA-240TYPE310S groove weld:

TABLE 3

I. checking a welding seam VT;

J. detecting a welding seam PT;

K. and (5) detecting a weld joint by RT.

The above-mentioned embodiments are merely descriptions of the preferred embodiments of the present invention, and are not intended to limit the scope of the present invention, and various modifications and alterations made to the technical solution of the present invention without departing from the spirit of the present invention are intended to fall within the scope of the present invention defined by the claims.

Claims

The method for welding and thermally treating the SA-335P11 and SA-240TYPE310S dissimilar steel materials is characterized by comprising the following steps: the method comprises the following steps:

A. preparing before welding;

B. defining a workpiece with the material of SA-335P11 as a first workpiece, defining a workpiece with the material of SA-240TYPE310S as a second workpiece, processing grooves on the end faces of the notches of the first workpiece and the second workpiece, and cleaning the inner and outer surfaces of the grooves; the groove is a V-shaped groove, the included angle between the groove surface and the normal direction is 32 degrees +/-2.5 degrees, and the truncated edge is 0-2 mm;

C. carrying out nickel alloy isolation layer surfacing and heat treatment on the bevel face of the first workpiece, and comprising the following steps:

c1) inspecting the quality of the bevel face of the first workpiece:

c2) arranging a thermocouple and an electric heating tape on the surface of the first workpiece except the bevel face, wrapping heat preservation cotton outside the electric heating tape, fixing, and performing preheating preparation;

c3) the bevel face preheating temperature and nickel alloy isolating layer surfacing process control comprises the following steps:

c31) the welding wire for the bevel surfacing is ERNiGr-3, and the diameter is 2.4 mm; GTAW is adopted in the process for overlaying the bevel face;

c32) surfacing a first layer on the bevel face: preheating a first workpiece to 150-180 ℃, wherein a surfacing welding bead is a linear welding bead, and performing channel pressing welding, wherein the width of each channel is less than 13mm, the thickness of each channel is less than 2.0mm, the current is 115-145A, the voltage is 8-11V, and the temperature between channels is 150-180 ℃;

c33) surfacing a second layer on the bevel face: preheating a first workpiece to 120-150 ℃, wherein a surfacing welding bead is a linear welding bead, performing channel pressing welding, the width of each channel is less than 13mm, the thickness of each channel is less than 2.0mm, the current is 115-150A, the voltage is 8-11V, and the temperature between channels is 120-150 ℃;

c34) surfacing a third layer on the bevel face: the first workpiece is not preheated, the surfacing welding bead is a linear welding bead, and the bead pressing welding is carried out, wherein the width of each bead is less than 13mm, the thickness of each bead is less than 2.4mm, the current is 140-170A, the voltage is 9-13V, and the inter-bead temperature is less than 100 ℃;

c35) surfacing a fourth layer on the bevel face: the first workpiece is not preheated, the surfacing welding bead is a linear welding bead, and the bead pressing welding is carried out, wherein the width of each bead is less than 13mm, the thickness of each bead is less than 2.4mm, the current is 140-170A, the voltage is 9-13V, and the inter-bead temperature is less than 100 ℃;

c36) surfacing a fifth layer on the bevel face: the first workpiece is not preheated, the surfacing welding bead is a linear welding bead, and the bead pressing welding is carried out, wherein the width of each bead is less than 13mm, the thickness of each bead is less than 2.0mm, the current is 140-170A, the voltage is 9-13V, and the inter-bead temperature is less than 100 ℃;

the first cladding metal and the last cladding metal of each layer of bead welding of the bevel face exceed the outer surface and the inner surface of the first workpiece by 0-1.5 mm;

c37) polishing and removing the extra height of the isolation layer to be flush with the inner surface and the outer surface of the first workpiece;

c4) stress relief heat treatment is carried out on the bevel face surfacing welding isolation layer, the heat preservation temperature of the stress relief heat treatment of the bevel face argon arc surfacing welding isolation layer is 720 +/-15 ℃, and the heat preservation time is not less than 135 minutes; the heating rate is 56 ℃/h-220 ℃/h, and the cooling rate is 56 ℃/h-280 ℃/h; the charging temperature is room temperature, and the cooling mode is furnace cooling;

c5) detecting the surface quality appearance and PT of the isolation layer;

D. determining the preparation work and technical requirements before pairing the first workpiece and the second workpiece, comprising the following steps:

d1) confirming that the material of a hydraulic assembly device, a tooling fixture and a fixture at the contact part of a point fixing block and a first workpiece and a second workpiece for assembly is the same as or the same as the material of the workpieces;

d2) the first workpiece and the second workpiece are paired to form a gap within the range of 1-6 mm, and the allowable deviation of the inner wall and the outer wall of a welded junction formed by pairing is as follows:

tolerance of the inner wall of the tube: the thickness of the wall is 20+1mm, and the maximum thickness cannot exceed 3 mm;

tube outer wall tolerance: the thickness of the wall is 10+2mm, and the maximum thickness cannot exceed 8 mm;

E. the method comprises the following steps of performing parallel spot welding on a first workpiece and a second workpiece by material group, performing spot welding on the root of a welding line by manual tungsten electrode argon arc welding, wherein an ERNiCr-3 welding wire is adopted, the diameter is phi 2.4, and the method comprises the following sub-steps according to different types of the welding line:

e1) for a circumferential weld pair: uniformly dividing the circumference of the whole circumferential weld into 12 equal parts, temporarily not setting hydraulic group pairers at positions 3, 6, 9 and 12 of a clock point position, arranging eight hydraulic group pairers at positions 1, 2, 4, 5, 7, 8, 10 and 11, and additionally setting hydraulic group pairers if the misalignment exceeds the standard in the position ranges 3, 6, 9 and 12 of the clock point position;

e2) for the longitudinal weld pairing: uniformly dividing the whole longitudinal weld into a plurality of equal parts, wherein the length of each equal part is 300-400 mm, arranging hydraulic assembly devices at the equal parts, and additionally arranging the hydraulic assembly devices if the position range of the equal parts has staggered edges exceeding the standard;

e3) for circumferential weld tack welding: starting tack welding at the root of a groove at a position 10mm away from the edge of the hydraulic assembly on one side of the hydraulic assembly; the length of the point-fixed welding seam is 40-50 mm, and the thickness is 3-5 mm; the WPS used for spot welding is the same as that used for formal welding;

e4) for longitudinal seam tack welding: extending the sectional spot welding from the middle point of the length of the longitudinal welding line to two sides; starting tack welding at the root of a groove at a position 10mm away from the edge of the hydraulic assembly on one side of the hydraulic assembly; the length of the point-fixed welding seam is 40-50 mm, and the thickness is 3-5 mm; the WPS used for spot welding is the same as that used for formal welding;

e5) checking the quality of spot welding;

e6) dismantling the hydraulic assembling devices one by one;

e7) polishing two ends of the point welding spots into a gentle slope shape;

F. manual argon tungsten-arc welding is adopted to carry out backing welding on the root of the groove, and metal is deposited by the backing welding to form a backing welding layer; backing welding two layers, wherein each layer has 1 path, an ERNiCr-3 welding wire is selected, the diameter is phi 1.6 or phi 2.4, a linear welding path is adopted, the swing width of a welding torch is not more than 3 times of the diameter of the welding wire, the current is 130-205A, the voltage is 10-16V, the temperature between the paths/layers is less than 100 ℃, the residual height of the back of a backing welding deposited metal relative to the inner wall of a workpiece after welding is less than 3mm, and the thickness of the deposited metal after welding 2 layers is 3-5 mm;

G. filling the capping surface by adopting manual arc welding, adopting linear welding bead and symmetrical welding, wherein the width of a welding line is not more than 3 times of the diameter of the steel core, and the temperature between the welding lines/layers is less than 100 ℃; the welding rod is made of ENiCrFe-2, when the diameter is phi 3.2mm, the current is 120-140A, the voltage is 23-30V, and the thickness of each layer is less than 3.2 mm; the method is characterized in that the electrode is ENiCrFe-2, when the diameter is phi 4.0mm, the current is 125-165A, the voltage is 23-30V, and the thickness of each layer is less than 4 mm; the rest height of the surface of the welding seam is less than 2.5 mm;

H. polishing and removing welding lines on the inner surface and the outer surface of the deposited metal, polishing and removing undercut at a welding toe part, and ensuring smooth transition between the deposited metal and the inner surface and the outer surface of a workpiece;

I. checking a welding seam VT;

J. detecting a welding seam PT;

K. and (5) detecting a weld joint by RT.
2. The method for welding and heat treating SA-335P11 and SA-240TYPE310S dissimilar steel materials according to claim 1, wherein: the specific mode of the step c2) is as follows:

c21) drawing a reference line: drawing a groove edge line reference line at a position 30 +/-0.2 mm away from a bevel edge line on the outer wall of the first workpiece;

c22) determining the number of arranged thermocouples according to the shape and the size of the first workpiece;

when the first workpiece is a pipe, the outer diameter of the pipe is less than phi 114.3mm, and 1 thermocouple is arranged;

the outer diameter of the tube is more than or equal to phi 114.3mm and less than phi 508mm, and 2 thermocouples are arranged at equal intervals;

the outer diameter of the tube is more than or equal to phi 508mm and less than phi 914mm, and 3 thermocouples are arranged at equal intervals;

the outer diameter of the tube is more than or equal to phi 914mm, and 4 thermocouples are arranged at equal intervals;

when the first workpiece is a plate, respectively arranging thermocouples at positions 100mm away from two ends of the plate;

c23) the top end where the thermocouple thermistor is located at a position 10mm away from the edge line of the bevel;

c24) and the thermocouple, the electric heating belt and the heat insulation cotton are bound and fixed on the outer wall of the first workpiece.
3. The method for welding and heat treating SA-335P11 and SA-240TYPE310S dissimilar steel materials according to claim 1, wherein: the grinding step of the step c37) is moved to the step E, and grinding is carried out before pairing.
4. The method for welding and heat treating SA-335P11 and SA-240TYPE310S dissimilar steel materials according to claim 3, wherein: the step c5) of detecting the surface quality appearance and PT of the isolation layer is as follows:

c51) checking the thickness of the isolation layer by taking the reference line as a basis to ensure that the thickness of the isolation layer is more than 6mm to check the surface quality of the cladding metal of the surfacing layer;

c52) detecting isolation layer surface PT, if detect when unqualified, fill repair welding according to the same build-up welding's of isolation layer mode after polishing the defective position, carry out thickness detection and PT detection once more after repair welding back thermal treatment, satisfy the technological requirement until the isolation layer.
5. The method for welding and heat treating SA-335P11 and SA-240TYPE310S dissimilar steel materials according to claim 4, wherein: in the step F, the corresponding welding mode aiming at the circumferential weld and the linear longitudinal weld is as follows:

firstly, for circumferential weld welding, the following two welding methods are adopted:

f1) the workpiece rotates around the center line of the workpiece, arcs between the clock point positions 1 → 12, and is welded in the anticlockwise direction; manual argon tungsten-arc welding is performed for backing welding of 2 layers, each layer is subjected to 1 pass, a welding wire is phi 1.6 or phi 2.4, linear welding passes are adopted, and joints between layers are staggered by more than 10 mm;

f2) horizontally fixing a workpiece, backing welding by manual argon tungsten-arc welding, and performing linear welding bead by sectional symmetrical welding; equally dividing the annular welding seam into 12 sections, and dividing the 12 sections of welding seams into two groups;

f21) determining the sequence, welding direction, arc striking position and welding of the first group of piecewise symmetry welding: wherein the first set of welding sequences; according to hour positions 6 → 5, 11 → 12; 3 → 2, 8 → 9; 6 → 7, 1 → 12; 4 → 3, 9 → 10; welding in sequence; wherein 6 → 5, 11 → 12 is a pair of symmetrical solder segments, 3 → 2, 8 → 9 is a pair of symmetrical solder segments, 6 → 7, 1 → 12 is a pair of symmetrical solder segments, 4 → 3, 9 → 10 is a pair of symmetrical solder segments;

first set of welding directions: taking the welding direction as the advancing direction;

the first group of welding arc starting positions and welding: when welding is carried out for 6 → 5, 6 → 7, 3 → 2, 9 → 10, respectively, the arc starts from 10mm before the points 6, 3, 9, then the arc respectively turns back to the root part of the groove 10mm after the points 6, 3, 9, the arc penetrates the blunt edge to form a fusion hole, and then the arc moves forward to form a welding line; when in welding 11 → 12, 4 → 3, 1 → 12, 8 → 9, respectively, the arc is started from 10mm before the tack welding end of the 11, 4, 1, 8 point position, and then the arc is folded back to the gentle slope of the tack welding end of the 11, 4, 1, 8 point position to melt the joint; arcing until the arc passes through the positions of 12, 3, 12 and 9;

f22) determining the welding sequence, the welding direction, the arc striking position and the welding of the second group of sectional symmetry: wherein the second set of welding sequences; according to 7 → 8, 2 → 1; 5 → 4, 10 → 11; wherein 5 → 4, 10 → 11 is a symmetric solder segment, and 7 → 8, 2 → 1 is a symmetric solder segment;

the second group of welding directions take the welding direction as the advancing direction;

and (3) welding the second group of welding arc starting positions: when each welding section is welded, firstly, the tack welding point ends at the two ends of the welding section are polished into gentle slopes, then, arcs are started from the positions, 10mm away from the tack welding point ends of the welding section, then, the tack welding point ends are folded backwards to the gentle slopes of the tack welding point ends, after the gentle slopes of the ends are melted, the arcs walk forwards again, and then, the arcs are closed after the arc is connected with the welding point ends of the front welding section;

for backing welding of the longitudinal welding seam, uniformly dividing the whole longitudinal welding seam into a plurality of equal parts, wherein the equal parts are 300-400 mm in length; then, the step of skip welding is carried out from the middle part of the length of the welding seam to two sides in a segmented mode; joints between the inter-layer channels need to be staggered; the joint position of the second layer of welding bead and the joint position of the first layer of welding bead are staggered by a distance larger than 10mm, and the joints of each layer of welding bead are mutually staggered by a distance larger than 10 mm.