CN112518086B - Low-temperature steel pipeline welding process adopting pre-welding preheating - Google Patents
Low-temperature steel pipeline welding process adopting pre-welding preheating Download PDFInfo
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- CN112518086B CN112518086B CN202011417992.XA CN202011417992A CN112518086B CN 112518086 B CN112518086 B CN 112518086B CN 202011417992 A CN202011417992 A CN 202011417992A CN 112518086 B CN112518086 B CN 112518086B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K9/00—Arc welding or cutting
- B23K9/235—Preliminary treatment
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
- B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
- B23K35/24—Selection of soldering or welding materials proper
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K9/00—Arc welding or cutting
- B23K9/0026—Arc welding or cutting specially adapted for particular articles or work
- B23K9/0052—Welding of pipe panels
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K9/00—Arc welding or cutting
- B23K9/16—Arc welding or cutting making use of shielding gas
- B23K9/167—Arc welding or cutting making use of shielding gas and of a non-consumable electrode
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K9/00—Arc welding or cutting
- B23K9/23—Arc welding or cutting taking account of the properties of the materials to be welded
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K9/00—Arc welding or cutting
- B23K9/32—Accessories
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Abstract
The invention discloses a low-temperature steel pipeline welding process adopting pre-welding preheating, which comprises the following steps of: step one, preparing before welding; secondly, preheating the low-temperature steel pipe pile to be welded, wherein each side of the low-temperature steel pipe pile to be welded is not less than 3 times of the thickness of a weldment and not less than 100mm by taking the center of a welding seam as a reference during preheating; selecting materials with the strength and the toughness similar to those of the base metal as welding materials, wherein the welding materials comprise welding rods and welding wires prepared from the welding materials; step four, welding; the invention carries out pre-heating treatment before welding on the low-temperature steel pipe, can effectively avoid the weld joint and the affected area from generating a hardened structure, reduces the welding stress, prevents cracks from generating and improves the welding quality.
Description
Technical Field
The invention relates to the field of low-temperature steel pipeline welding processes. More specifically, the present invention relates to a process for welding low temperature steel pipes using pre-weld preheating.
Background
The container made of carbon steel and alloy steel below-20 ℃ is called as a low-temperature container and is mainly used for production of mediums such as liquefied petroleum gas, liquid ammonia, liquid oxygen, liquid nitrogen and the like, storage containers, conveying pipelines and equipment in service in cold regions. For the performance requirements of low-temperature steel, firstly, enough impact toughness is ensured at the use temperature, when the temperature of common carbon steel and alloy steel is reduced to below-20 ℃, the phenomenon of low-temperature embrittlement can occur, and Ni element is added into the steel to promote the formation of transformation austenite, so that the low-temperature toughness of a matrix is improved, therefore, in order to prevent accidents, special material manufacturing equipment and pipelines must be selected under the low-temperature environment or production condition, for example, low-temperature steel plates such as 16MnDR, 15MnNiDR, 15MnNiNbDR, 09MnNiDR, 08Ni3DR, 06Ni9DR and the like, pipes such as 16MnDG, 06Ni3MoDG, 09Mn2VDG and the like, and the common pipe in the international market also has American standard A333 series.
With the continuous development of science and technology, the demand of low-temperature steel is continuously increased, the construction market is also wide, the development of low-temperature steel manufacturing technology and equipment use also promotes the development of low-temperature pressure vessel and pressure pipeline welding technology, and the continuous improvement of low-temperature steel welding construction technology is the demand and power for the development of the field.
Disclosure of Invention
To achieve these objects and other advantages in accordance with the purpose of the invention, there is provided a low temperature steel pipe welding process using pre-weld preheating, comprising the steps of:
step one, preparation before welding
The method comprises the following steps that two low-temperature steel pipes to be welded are erected on a first supporting frame and a second supporting frame respectively, and the relative positions of the two low-temperature steel pipes to be welded are adjusted by adjusting the height and the inclination angle of the first supporting frame and the second supporting frame, so that the ends to be welded of the two low-temperature steel pipes are opposite;
step two, preheating before welding
Preheating the low-temperature steel pipe pile to be welded, wherein when preheating is carried out, the center of a welding seam is taken as a reference, and each side of the low-temperature steel pipe pile is not less than 3 times of the thickness of a weldment and not less than 100 mm;
step three, selecting welding materials
Selecting materials with the strength and the toughness similar to those of the base metal as welding materials, wherein the welding materials comprise welding rods and welding wires prepared from the welding materials, and the welding rods are baked at 350-400 ℃ before being used;
step four, welding
Step S41, grooving, wherein the groove angle needs to be controlled between 55-65 degrees, and the groove of the low-temperature steel pipeline and the two sides of the groove are polished and cleaned within the range of 20-30mm before welding;
s42, controlling the welding current to be 200-450A, the welding speed to be 350-650mm/min, controlling the number of welding layers to be 3-4, and adopting argon tungsten-arc welding when the first welding layer is welded, adopting argon tungsten-arc welding or shielded metal arc welding for the rest welding layers, wherein the thickness of each welding layer is less than 2-3 mm;
and during welding, if the welding current is increased/decreased, the welding speed is increased/decreased.
According to a preferred embodiment of the present invention, in the low temperature steel pipe welding process using pre-weld preheating, the welding tool includes the first support frame and the second support frame, both of which include:
the base is provided with three longitudinal sliding grooves and a plurality of transverse sliding grooves, the longitudinal sliding grooves are arranged along the length direction of the base, the transverse sliding grooves are arranged along the width direction of the base, and the transverse sliding grooves are communicated with the longitudinal sliding grooves in a crossed manner;
two groups of support rods are arranged at intervals along the length direction of the base, each group of support rods comprises three support rods which are respectively arranged on the three longitudinal sliding grooves, each support rod moves along the longitudinal sliding grooves and the transverse sliding grooves, and the height of each support rod is adjustable;
the top end of each supporting rod is provided with a containing mechanism, each containing mechanism comprises a bottom plate arranged at the top end of each supporting rod and a plurality of adjusting rods arranged on the bottom plate, one end, far away from the bottom plate, of each adjusting rod is provided with an arc-shaped base plate, and the base plates are spliced into an arc shape, wherein the height of each adjusting rod is adjustable;
and for any one of the two groups of support rods, the arcs formed by the base plates on the three support rods are matched with each other to form a bowl-shaped structure with two high ends and a low middle part.
According to a preferred embodiment of the invention, in the low-temperature steel pipeline welding process adopting pre-welding preheating, each support rod is provided with a lower support plate which is positioned below the bottom plate, the top of each support rod is sunken inwards to form an accommodating groove, a universal wheel is arranged in each support rod, the universal wheel protrudes out of the upper end surface of the accommodating groove, and the universal wheel can rotate in any direction in the accommodating groove;
the bottom plate is arranged on the universal wheel;
the bottom of the bottom plate is downwards connected with one ends of a plurality of springs, the other ends of the springs are connected with the lower supporting plate, and the springs are distributed annularly.
According to a preferred embodiment of the invention, in the low-temperature steel pipeline welding process adopting pre-welding preheating, the bottom of the support rod is provided with a travelling wheel.
According to a preferred embodiment of the present invention, in the low temperature steel pipe welding process using pre-weld preheating, the heating process requires multi-point temperature monitoring
According to a preferred embodiment of the present invention, in the low temperature steel pipe welding process using pre-weld preheating, the preheating temperature is controlled between 95 ℃ and 200 ℃.
According to a preferred embodiment of the present invention, in the low temperature steel pipe welding process using pre-weld preheating, the chemical composition of the welding material is similar to that of the base material.
The invention at least comprises the following beneficial effects:
firstly, when the low-temperature steel pipeline is welded, pre-welding preheating is firstly carried out. Firstly, the cooling speed of a welding joint can be reduced by preheating before welding, so that the diffusion hydrogen in weld metal can escape, and hydrogen-induced cracks can be effectively avoided; secondly, preheating before welding can prolong the time for cooling the heat affected zone, improve the crack resistance of the welded joint and avoid welding cracks; thirdly, the welding stress can be reduced by preheating before welding, the temperature difference between a welding area and the whole weldment can be reduced in the welding process, the welding strain rate is reduced, and welding cracks are effectively avoided. In a word, the preheating before welding mainly has the functions of avoiding the generation of a hardening structure on a welding seam and an affected area, reducing welding stress and preventing cracks from being generated, and the welding quality is improved.
Secondly, the invention selects proper welding materials according to the chemical and physical properties of the actually used cryogenic steel pipeline.
In the invention, welding is carried out by using a proper welding tool, so that the welding failure rate is reduced.
The two low-temperature steel pipes to be welded are erected on a first supporting frame and a second supporting frame respectively, the relative positions of the two low-temperature steel pipes to be welded are adjusted by adjusting the height and the inclination angle of the first supporting frame and the second supporting frame, so that the ends to be welded of the two low-temperature steel pipes are opposite, the positions of the two low-temperature steel pipes can be conveniently adjusted according to the shapes of the two pipes to be welded, and the pipes to be welded are not regular in shape in actual construction, and can not be welded well normally by adopting conventional horizontal placement.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention.
Drawings
Fig. 1 is a top view of the base of the first support and the second support of the present invention.
Fig. 2 is a schematic structural view of the first support frame and the second support frame of the present invention.
Detailed Description
The present invention is further described in detail below with reference to the attached drawings so that those skilled in the art can implement the invention by referring to the description text.
The following description is presented to disclose the invention so as to enable any person skilled in the art to practice the invention. The preferred embodiments in the following description are given by way of example only, and other obvious variations will occur to those skilled in the art. The basic principles of the invention, as defined in the following description, may be applied to other embodiments, variations, modifications, equivalents, and other technical solutions without departing from the spirit and scope of the invention.
It will be understood by those skilled in the art that in the present disclosure, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like are used in an orientation or positional relationship indicated in the drawings for ease of description and simplicity of description, and do not indicate or imply that the referenced devices or components must be constructed and operated in a particular orientation and thus are not to be considered limiting.
It is understood that the terms "a" and "an" should be interpreted as meaning that a number of one element or element is one in one embodiment, while a number of other elements is one in another embodiment, and the terms "a" and "an" should not be interpreted as limiting the number.
As shown in FIG. 1, the low-temperature steel pipeline welding process adopting pre-weld preheating of the invention comprises the following steps:
step one, preparation before welding
The method comprises the following steps that two low-temperature steel pipes to be welded are erected on a first supporting frame and a second supporting frame respectively, and the relative positions of the two low-temperature steel pipes to be welded are adjusted by adjusting the height and the inclination angle of the first supporting frame and the second supporting frame, so that the ends to be welded of the two low-temperature steel pipes are opposite;
step two, preheating before welding
Preheating the low-temperature steel pipe pile to be welded, wherein when preheating is carried out, the center of a welding seam is taken as a reference, and each side of the low-temperature steel pipe pile is not less than 3 times of the thickness of a weldment and not less than 100 mm;
the method for preheating before welding is various, such as flame heating, electric heating, power frequency induction heating, far infrared heating, furnace heating and the like, wherein the heating range is based on the center of a welding seam, and each side of the welding seam is not less than 3 times of the thickness of a welded part and is not less than 100 mm. Even during construction, flame heating and electric heating are generally used in many cases. During flame heating, the preheating area of the weldment is difficult to be uniformly heated, and the heating process needs to be carried out at multiple points for temperature monitoring so as to ensure uniform heating.
Firstly, the cooling speed of a welding joint can be reduced by preheating before welding, so that the diffusion hydrogen in weld metal can escape, and hydrogen-induced cracks can be effectively avoided; secondly, preheating before welding can prolong the time for cooling the heat affected zone, improve the crack resistance of the welded joint and avoid welding cracks; thirdly, the welding stress can be reduced by preheating before welding, the temperature difference between a welding area and the whole weldment can be reduced in the welding process, the welding strain rate is reduced, and welding cracks are effectively avoided. In a word, the preheating before welding mainly has the functions of avoiding the generation of a hardening structure on a welding seam and an affected area, reducing welding stress and preventing cracks from being generated, and the welding quality is improved.
It is noted that pre-weld heating is not as high as possible. If the preheating temperature is too high, the plasticity and toughness of the steel material are reduced sharply due to coarse weld grains, thereby damaging the excellent performance of the steel material. Therefore, the temperature is preferably controlled between 95 ℃ and 200 ℃ when the low-temperature steel is preheated, and the highest temperature is not more than 250 ℃.
Step three, selecting welding materials
Selecting materials with the strength and the toughness similar to those of the base metal as welding materials, wherein the welding materials comprise welding rods and welding wires prepared from the welding materials, and the welding rods are baked at 350-400 ℃ before being used;
the selection of the welding materials follows the following principle: firstly, the strength and the toughness of a welding material and a base material are quite similar, so that the welding seam and the base material have the same mechanical property and the stress working condition is met; secondly, the chemical components of the welding material are similar to those of the base material, so that the low-temperature performance of the welding line and the low-temperature performance of the base material are ensured to be similar, and the expansion coefficients of the welding line and the base material are also ensured to be similar; and thirdly, by the low-temperature impact test of the weldment in the welding process evaluation, the welding material and the base material are ensured to be in the same low-temperature condition, and the requirement of low-temperature impact energy absorption is met.
Also commonly used in the international market is the American standard A333 series. First, the chemical composition characteristics of A333 Gr3 need to be understood. A333 Gr3 belongs to Ni-containing low-temperature steel, wherein Ni is an important element for developing low-temperature steel, and the content of carbon is reduced and the content of S, P and N, H, O are strictly limited while increasing Ni, so that the aging brittleness and the temper brittleness are prevented.
Secondly, the mechanical properties of A333 Gr 3. For the performance requirements of the low-temperature steel pipeline, firstly, the mechanical properties at low temperature, especially the notch toughness at low temperature, should be satisfied, so the most important performance that the low-temperature steel must have is the low-temperature embrittlement resistance, which is essential for the low-temperature impact test in the evaluation of welding process. The design temperature of the propylene pipeline is-47.7 ℃, so that the test temperature is required to be lower than-47.7 ℃ to meet the requirement of the design working condition.
Meanwhile, the low-temperature steel material is also required to have the crack arrest performance of resisting the propagation of brittle cracks, namely, once the brittle fracture occurs, the fracture can be stopped to continue, the yield ratio of the general low-temperature steel is not too high, the large yield ratio shows that the reserve of plastic deformation capacity is small, and the stress redistribution capacity at the stress concentration part is low, so that the brittle fracture is easy to promote.
Step four, welding
Step S41, grooving, wherein the groove angle needs to be controlled between 55-65 degrees, and the groove of the low-temperature steel pipeline and the two sides of the groove are polished and cleaned within the range of 20-30mm before welding;
s42, controlling the welding current to be 200-450A, the welding speed to be 350-650mm/min, controlling the number of welding layers to be 3-4, and adopting argon tungsten-arc welding when the first welding layer is welded, adopting argon tungsten-arc welding or shielded metal arc welding for the rest welding layers, wherein the thickness of each welding layer is less than 2-3 mm;
and during welding, if the welding current is increased/decreased, the welding speed is increased/decreased.
Current and voltage: the welding current is mainly considered from the angle of welding heat input, when the welding current is increased, the welding heat input is increased, and when the heat is too large, the chemical components of deposited metal are changed, so that the mechanical property of weld metal is reduced, therefore, generally, when the current is increased, the welding speed is increased to adjust the heat output or reduce the current; under the condition that the welding speed and the welding current are not changed, the welding heat input is increased by increasing the arc voltage, the welding heat affected zone is increased, the welding seam crystal grains are easy to be thick, and the mechanical property of the welding seam is reduced.
Welding speed: when the welding current and voltage are not changed, the heat input is less when the welding speed is high, but the welding seam of each layer becomes thinner, and the number of welding tracks is increased; and if the speed is too low, the heat input is large, the heat influence is increased, and the quality of the welding seam is not facilitated.
The welding layer number: when the low-temperature steel is subjected to multilayer welding, the former welding bead has a preheating effect on the latter welding bead, and the heat input of the latter welding bead has a heat treatment effect of refining grains on the former welding bead, but the thickness of each welding bead is not too large and is smaller than 2-3mm, otherwise, metal structure grains are easily thickened, and the mechanical property of the welding bead is reduced.
According to a preferred embodiment of the present invention, in the low temperature steel pipe welding process using pre-weld preheating, the welding tool includes the first support frame and the second support frame, both of which include:
the base comprises a base 1, three longitudinal sliding grooves 2 and a plurality of transverse sliding grooves 3 are formed in the base 1, the longitudinal sliding grooves 2 are arranged along the length direction of the base 1, the transverse sliding grooves 3 are arranged along the width direction of the base 1, and the transverse sliding grooves 3 are communicated with the longitudinal sliding grooves 2 in a crossed mode;
two groups of support rods 4 are arranged at intervals along the length direction of the base, each group of support rods 4 comprises three support rods 4 which are respectively arranged on the three longitudinal sliding grooves 2, each support rod 4 moves along the longitudinal sliding groove 2 and the transverse sliding groove 3, and the height of each support rod 4 is adjustable;
each support rod 4 is provided with a lower support plate 6 which is positioned below the bottom plate 51, the top of each support rod 4 is sunken inwards to form an accommodating groove, a universal wheel 7 is arranged in each accommodating groove, the universal wheel 7 protrudes out of the upper end surface of each accommodating groove, and the universal wheels 7 can rotate in any direction in the accommodating grooves;
the top end of each supporting rod 4 is provided with a containing mechanism, the containing mechanism comprises a bottom plate 51 arranged at the top end of each supporting rod 4 and a plurality of adjusting rods 52 arranged on the bottom plate 51, one end, far away from the bottom plate 51, of each adjusting rod 52 is provided with an arc-shaped base plate 53, the base plates 53 are spliced into an arc shape, the bottom of the bottom plate 51 is downwards connected with one end of a plurality of springs 54, the other end of each spring 54 is connected with the lower supporting plate 6, the springs 54 are distributed annularly, and the height of each adjusting rod 4 is adjustable; the bottom plate 51 is disposed on the universal wheel 7.
And, for any one of the two sets of support rods, the arcs formed by the plurality of backing plates 53 on the three support rods 4 are matched with each other to form a bowl-shaped structure with high two ends and low middle.
In the embodiment, two low-temperature steel pipelines to be welded are erected on the first support frame and the second support frame respectively, the relative positions of the two low-temperature steel pipelines to be welded are adjusted by adjusting the height and the inclination angle of the first support frame and the second support frame, so that the two ends to be welded are opposite, the positions of the two pipelines to be welded can be conveniently adjusted according to the shapes of the two pipelines to be welded, and the pipelines to be welded are irregular in shape and can be placed horizontally in a conventional mode, so that good welding cannot be achieved generally.
Specifically, two steel pipes to be welded are erected on the first support frame and the second support frame respectively, and the heights and the inclination angles of the steel pipes to be welded are adjusted by adjusting the heights of the two groups of support rods 4 in the first support frame and the second support frame respectively. However, when the height of two sets of support bars 4 is adjusted, the steel pipe to be welded is placed on the holding mechanism, if the holding mechanism does not change the angle therewith, the steel pipe can be placed unstably, so the holding mechanism is not directly placed at the top end of the support bars 4 but placed on the universal wheels 7, and the universal wheels 7 can rotate in any direction in the holding grooves at the tops of the support bars 4 to adapt to the angle change caused during height adjustment, so that the holding mechanism is driven to change the angle, such as incline. And a circle of spring 54 is annularly arranged below the bottom plate 51 of the containing mechanism, along with the change of the angle of the containing mechanism along with the universal wheel 7, the spring 54 deforms, some springs 54 are compressed, some springs 54 are stretched, so that the containing mechanism is well supported, and after the steel pipe to be welded is taken away, the spring 54 recovers to deform, and the containing mechanism also recovers to deform so as to adapt to the adjustment of the height and the angle when the steel pipe is placed next time.
The top ends of the support rods 4 are provided with holding mechanisms, the steel pipelines to be welded are supported by using an arc shape formed by base plates 53 at the top ends of a plurality of adjusting rods 52, the distance between two adjacent support rods 4 is adjusted by moving the support rods 4 along the transverse sliding grooves 3, the height of the adjusting rods 4 on each holding mechanism is adjusted (namely, the height of the base plates is adjusted), and therefore the first support frame and the second support frame can be suitable for the steel pipelines with different sizes.
According to a preferred embodiment of the invention, in the low-temperature steel pipeline welding process adopting pre-welding preheating, the bottom of the support rod is provided with a travelling wheel.
According to a preferred embodiment of the present invention, in the low temperature steel pipe welding process using pre-weld preheating, the heating process requires multiple points for temperature monitoring.
While embodiments of the invention have been described above, it is not limited to the applications set forth in the description and the embodiments, which are fully applicable in various fields of endeavor to which the invention pertains, and further modifications may readily be made by those skilled in the art, it being understood that the invention is not limited to the details shown and described herein without departing from the general concept defined by the appended claims and their equivalents.
Claims (6)
1. A low-temperature steel pipeline welding process adopting pre-welding preheating is characterized by comprising the following steps:
step one, preparation before welding
The method comprises the following steps that two low-temperature steel pipes to be welded are erected on a first supporting frame and a second supporting frame respectively, and the relative positions of the two low-temperature steel pipes to be welded are adjusted by adjusting the height and the inclination angle of the first supporting frame and the second supporting frame, so that the ends to be welded of the two low-temperature steel pipes are opposite;
step two, preheating before welding
Preheating the low-temperature steel pipe to be welded, wherein in the preheating treatment, the center of a welding seam is taken as a reference, and each side of the low-temperature steel pipe is not less than 3 times of the thickness of a weldment and not less than 100 mm;
step three, selecting welding materials
Selecting materials with the strength and the toughness similar to those of the base metal as welding materials, wherein the welding materials comprise welding rods and welding wires prepared from the welding materials, and the welding rods are baked at 350-400 ℃ before being used;
step four, welding
Step S41, grooving, wherein the groove angle needs to be controlled between 55-65 degrees, and the groove of the low-temperature steel pipeline and the two sides of the groove are polished and cleaned within the range of 20-30mm before welding;
s42, controlling the welding current to be 200-450A, the welding speed to be 350-650mm/min, controlling the number of welding layers to be 3-4, and adopting argon tungsten-arc welding when the first welding layer is welded, adopting argon tungsten-arc welding or shielded metal arc welding for the rest welding layers, wherein the thickness of each welding layer is less than 2 mm;
in the welding process, if the welding current is increased, the welding speed is accelerated, and if the welding current is reduced, the welding speed is slowed down;
a welding tool comprising the first support frame and the second support frame, both comprising:
the base is provided with three longitudinal sliding grooves and a plurality of transverse sliding grooves, the longitudinal sliding grooves are arranged along the length direction of the base, the transverse sliding grooves are arranged along the width direction of the base, and the transverse sliding grooves are communicated with the longitudinal sliding grooves in a crossed manner;
two groups of support rods are arranged at intervals along the length direction of the base, each group of support rods comprises three support rods which are respectively arranged on the three longitudinal sliding grooves, each support rod moves along the longitudinal sliding grooves and the transverse sliding grooves, and the height of each support rod is adjustable;
the top end of each supporting rod is provided with a containing mechanism, each containing mechanism comprises a bottom plate arranged at the top end of each supporting rod and a plurality of adjusting rods arranged on the bottom plate, one end, far away from the bottom plate, of each adjusting rod is provided with an arc-shaped base plate, and the base plates are spliced into an arc shape, wherein the height of each adjusting rod is adjustable;
and for any one of the two groups of support rods, the arcs formed by the base plates on the three support rods are matched with each other to form a bowl-shaped structure with two high ends and a low middle part.
2. The process for welding the low-temperature steel pipelines by adopting the pre-welding preheating method according to claim 1, wherein each support rod is provided with a lower support plate which is positioned below the bottom plate, the top of each support rod is sunken inwards to form an accommodating groove, a universal wheel is arranged in each support rod, the universal wheel protrudes out of the upper end surface of the accommodating groove, and the universal wheel can rotate in any direction in the accommodating groove;
the bottom plate is arranged on the universal wheel;
the bottom of the bottom plate is downwards connected with one ends of a plurality of springs, the other ends of the springs are connected with the lower supporting plate, and the springs are distributed annularly.
3. The process for welding the cryogenic steel pipes with pre-weld preheating according to claim 1, wherein walking wheels are arranged at the bottom of the support rod.
4. The process of claim 1, wherein the heating process requires multiple points for temperature monitoring.
5. The process for welding of cold steel pipes according to claim 1, wherein the preheating temperature is controlled between 95 ℃ and 200 ℃.
6. The process of claim 1, wherein the chemical composition of the welding material is similar to that of the base material.
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|---|---|---|---|---|
| CN113070643B (en) * | 2021-04-09 | 2022-12-06 | 无锡市富惠钢管有限公司 | Low-temperature continuous welding process for thin-wall steel pipe |
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