CN114871532B - Manual deep hole welding method for heat exchange tube and tube plate - Google Patents
Manual deep hole welding method for heat exchange tube and tube plate Download PDFInfo
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- CN114871532B CN114871532B CN202210807035.0A CN202210807035A CN114871532B CN 114871532 B CN114871532 B CN 114871532B CN 202210807035 A CN202210807035 A CN 202210807035A CN 114871532 B CN114871532 B CN 114871532B
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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
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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
- B23K2101/00—Articles made by soldering, welding or cutting
- B23K2101/04—Tubular or hollow articles
- B23K2101/14—Heat exchangers
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Abstract
The invention belongs to the technical field of welding, discloses a manual deep hole welding method for a heat exchange tube and a tube plate, and aims to solve the problems that in the prior art, deep hole welding equipment is large in investment, and manual welding cannot meet quality requirements. The method is used for entering from a pipe box wire plugging hole at the end part of a box type air cooler and welding a heat exchange pipe and a pipe plate, the heat exchange pipe is inserted in a pipe hole of the pipe plate, and the end part of the heat exchange pipe is flush with one side of the pipe plate, and comprises the following steps: step 1, grooving: beveling the pipe hole of the pipe plate and the outer wall of the end part of the heat exchange pipe, and aligning the root parts of the bevels on the pipe plate and the heat exchange pipe to form a deep hole welding bevel; step 2, carrying out shielded metal arc welding: the welding rod extends into the deep hole welding groove from the wire plugging hole, and the electric arc extends into the deep hole welding groove from the wire plugging hole to weld the welding rod and the deep hole welding groove; wherein the shielded metal arc welding in the step 2 is multi-pass welding. The method has the advantages of easy mastering of technical points, moderate welding operation difficulty, easy popularization, low welding cost and good welding seam quality.
Description
Technical Field
The invention relates to the technical field of welding, in particular to a manual deep hole welding method for a heat exchange tube and a tube plate.
Background
Due to the limitation of factors such as structure and design requirements, the box type air cooler (as shown in fig. 1) can only adopt deep hole welding for welding the tube heads between the heat exchange tubes and the tube plates, and a welding gun must transversely penetrate through a tube hole of the tube plate and go deep into the tube hole of the tube plate through a small plug hole (the diameter of the tube hole is slightly larger than that of the heat exchange tube) to carry out inner fillet welding. The connection of the heat exchange tube and the tube plate is an important link in the manufacture of the box type air cooler.
Traditional manual argon tungsten-arc welding needs to add wires, and the gun head cannot extend inwards, so that deep-hole welding of the heat exchange tube and the tube plate cannot be carried out by manual argon tungsten-arc welding. At present, a special automatic deep hole TIG (Tungsten Inert Gas) welding machine is mostly adopted to weld the heat exchange tube and the tube plate, and the welding of the automatic deep hole TIG welding machine can meet the standard and quality requirements, but has the problems of expensive equipment, extremely high assembly requirement, long welding preparation time, difficulty in wide application and the like.
In addition, the shielded metal arc welding can carry out deep hole welding theoretically, but the existing manual arc welding cannot solve the problems of defects in the welding seam of the tube head, unfused root, incomplete penetration and the like, and cannot provide qualified welding process evaluation meeting the standard, so that the manual arc welding is hindered in the practical application of deep hole welding. Therefore, purchasing a specialized automatic deep hole TIG welder remains the only option for most manufacturers.
Therefore, the deep hole welding method for the heat exchange tube and the tube plate, which is simple and feasible and meets the welding quality requirement, is urgently needed to be developed in the field.
Disclosure of Invention
The invention aims to provide a manual deep hole welding method for a heat exchange tube and a tube plate, which aims to solve the problems that in the prior art, deep hole welding equipment is large in investment, manual welding cannot meet quality requirements, and the like. The method is a manual deep hole welding method, the technical key points are easy to master, the welding operation difficulty is moderate, the popularization is easy, the welding cost is low, and the quality of a welding seam is good.
In order to realize the purpose, the technical scheme adopted by the invention is as follows:
a manual deep hole welding method for a heat exchange tube and a tube plate is characterized in that the manual deep hole welding method is used for entering from a tube box thread plugging hole at the end part of a box type air cooler to weld the heat exchange tube and the tube plate, the heat exchange tube is inserted into a tube hole of the tube plate, and the end part of the heat exchange tube is flush with one side of the tube plate, and the manual deep hole welding method comprises the following steps:
wherein, the shielded metal arc welding in the step 2 is multi-pass welding.
In an embodiment of this application, the tube sheet with groove on the heat exchange tube is single V groove, deep hole welds the groove and is big V bilateral groove.
In one embodiment of the present application, the angle of the bevel on the tube sheet is 45 ° -85 °;
the angle of the groove on the heat exchange tube is 30-45 degrees.
In one embodiment of the application, the depth of the deep hole welding groove is more than or equal to 2.0mm, and is more than or equal to the thickness of the heat exchange tube.
In one embodiment of the application, the diameter of the electrode is less than or equal to 2.6mm.
In an embodiment of the present application, in step 2, when performing shielded metal arc welding, an arc starting point is on the tube plate side in the deep hole welding slope;
welding one side of the electric arc close to the tube plate in the welding process;
the arc starting point and the arc extinguishing point are melted repeatedly in the same welding.
In an embodiment of the present application, the multiple welding in the shielded metal arc welding in step 2 at least includes backing layer welding and cover layer welding, and the thickness of the backing welding bead is controlled to be reduced when the backing layer welding is performed; and when the cover surface layer is welded, controlling a welding bead of the cover surface layer to meet the requirement of filling the size of a welding seam.
In one embodiment of the application, the time interval between two adjacent welds in the multiple welds is controlled, and the next weld is performed when the previous weld is not completely cooled.
In one embodiment of the present application, the interchannel temperature of the multi-channel welding is controlled within a range of 40 to 60 ℃.
In an embodiment of the present application, in the step 2, when performing the shielded metal arc welding:
controlling the welding speed within the range of 50 to 70mm/min;
and/or the current adopted by the electric arc welding is 70 to 100A;
and/or the voltage adopted by the electric arc welding is 20 to 30V.
Compared with the prior art, the invention has the beneficial effects that:
1. according to the manual deep hole welding method for the heat exchange tube and the tube plate, grooves are formed on the two sides of the heat exchange tube and the two sides of the tube plate to form specific deep hole welding grooves, the original groove limit angle is further expanded, the traditional fillet weld is changed into a butt weld (namely a Y-shaped butt weld), the groove (molten pool) space is expanded, and a larger space and more favorable conditions are provided for the upward floating of welding rod slag and the outward overflow of gas; the root of the welding line can be completely exposed under the electric arc, so that the electric arc burns at the root in the first time, and the complete fusion and penetration of the root of the welding line are ensured. The side of the heat exchange tube is provided with a groove, so that the wall of the heat exchange tube is thinned before welding, the heat of the electric arc for melting the tube wall is saved, the rest heat is used for fusing the root of a welding seam, the problem of low temperature of a molten pool can be solved, the root is fused better, and welding slag floats sufficiently; meanwhile, the melted metal pole on the pipe wall is prevented from flowing into the groove to block the fusion channel at the root of the groove, and the fusion penetration of the root of the welding line is further ensured.
2. In the multi-pass welding process, when the backing layer is welded, the thickness of the backing weld bead is controlled to be reduced as much as possible so as to ensure the fusion and penetration of the root of the weld; the welding bead of the subsequent welding is used for filling the size of the welding seam; when the cover surface layer is welded, the welding bead of the cover surface layer is controlled to meet the final requirement of welding seam size filling so as to fully ensure the welding seam quality.
3. The current, the voltage and the welding speed of the electric arc welding are controlled, so that the welding seam is formed, the molten slag can completely float to the surface of the welding seam from the root of the welding seam in the solidification process of a molten pool, and the fusion penetration of the root of the welding seam is ensured.
4. According to the manual deep hole welding method for the heat exchange tube and the tube plate, a deep hole welding machine is not needed, and the equipment cost is saved; compared with argon arc welding, the welding speed is higher, and the efficiency is higher; the technology is easier to master, the technical training difficulty of welders is moderate, the popularization rate is high, and the popularization and the application are easy; the leakage rate of the welded pipe head (the joint of the heat exchange pipe and the pipe plate) is low, the limit of the pulling-out force which can be born by the welded pipe head is more than 540Mpa, the lower limit value of the evaluation standard is far exceeded, and the safety is guaranteed.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a schematic structural view of one end of a box type air cooler.
FIG. 2 is a schematic structural diagram of a deep hole welding groove in the present application.
Fig. 3 is a schematic view of the structure of a weld of comparative example 2.
FIG. 4 is a schematic diagram of the tube sheet opening structure of comparative example 3; wherein a is a structural schematic diagram of the tube plate opening condition (1); b is a structural schematic diagram of the tube plate opening condition (2); c is a structural schematic diagram of the tube plate opening condition (3); d is a structural schematic diagram of the tube plate opening case (4).
Reference numerals:
1. a heat exchange pipe;
2. a tube sheet; 21. a tube hole;
3. a pipe box; 31. plugging the hole with a thread;
4. and (4) deep hole welding a groove.
Detailed Description
In the following, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive.
Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
The embodiment provides a manual deep hole welding method for a heat exchange tube and a tube plate, which is suitable for welding connection of a heat exchange tube 1 and a tube plate 2 in a box type air cooler.
Specifically, as shown in fig. 1, the heat exchange tube 1 and the tube plate 2 are welded by entering from a screwed hole 31 of a tube box 3 at the end part of the box type air cooler and traversing through a tube hole 21 of an inner cavity of the tube box 3 and extending into the tube plate 2. In the method, a heat exchange tube 1 is inserted into a tube hole 21 on a tube plate 2, and the end part of the heat exchange tube 1 is flush with one side of the tube plate 2 facing the inner cavity of a tube box 3.
The method comprises the following steps:
Respectively beveling the pipe hole 21 (facing to the pipe box 3 side) of the pipe plate 2 and the outer wall of the end part of the heat exchange pipe 1; and the groove roots on the tube plate 2 and the heat exchange tube 1 are aligned, that is, the groove depths on the tube plate 2 and the heat exchange tube 1 are equal, so that a specific deep hole welding groove 4 is formed. The welding position is changed from the traditional fillet weld to the butt weld.
And 2, carrying out shielded metal arc welding.
For manual welding rod electric arc welding, a welding rod extends into a wire blocking hole 31 on an end pipe box 3, transversely penetrates through the inner cavity of the pipe box and extends into a deep hole welding groove 4 formed between the pipe plate 2 and the heat exchange pipe 1; the arc extends from the plug hole 31 to weld the welding rod and the deep hole welding groove 4.
The shielded metal arc welding in the step 2 is semi-blind welding and is multi-pass welding, and comprises at least two welding procedures.
In one embodiment, as shown in fig. 2, the grooves on the tube plate 2 and the heat exchange tube 1 are both single V grooves, and correspondingly, the deep-hole welding groove 4 formed by the tube plate 2 and the heat exchange tube 1 correspondingly is a large V double-side groove (i.e. a Y-shaped butt seam). The V-shaped groove is arranged, so that the floating of slag and gas is facilitated.
When the deep-hole welding groove 4 is a large-V double-side groove, the angle range of the groove on the tube plate 2 is 45-85 degrees, and preferably 75-85 degrees.
The angle of the groove on the heat exchange tube 1 is smaller than or equal to that of the groove on the tube plate 2, and the angle range of the groove on the heat exchange tube 1 is 30-45 degrees, preferably 35-45 degrees.
The depth of the grooves on the tube plate 2 and the heat exchange tube 1 is consistent, the depth of the formed deep hole welding groove is more than or equal to 2.0mm, and the depth of the deep hole welding groove is related to the minimum leakage channel size required by the design and at least is more than or equal to the thickness of the heat exchange tube 1. The gap between the tube hole 21 of the tube plate 2 and the heat exchange tube 1 can meet the production standard requirement, and the deviation is below 0.15mm and can not be increased randomly.
The electrode used in this embodiment is a small diameter electrode, and is typically 2.6mm or less in diameter.
When the shielded metal arc welding is carried out, an arc starting point is arranged on the side of the tube plate 2 in the deep-hole welding groove 4; in the welding process, the electric arc is also welded as close to one side of the tube plate as possible; and the arc starting point and the arc extinguishing point are repeatedly melted in the same welding process, so that incomplete fusion and incomplete penetration at the arc starting point and the arc extinguishing point are avoided.
The arc starting point is arranged on the side of the tube plate 2, and the arc is welded on the side close to the tube plate 2 in the welding process, so that the heat exchange tube 1 is prevented from being punctured; meanwhile, the groove angle of the side of the tube plate 2 is large, slag generated by welding and melted tube plate metal are not easy to flow into the root of the welding seam, and the influence of the slag and the like on the welding quality of the root of the welding seam is better avoided.
When the heat exchange tube 1 is welded with the tube plate 2, two or more than two welding processes are adopted for welding, namely, the welding process at least comprises two welding processes of bottom layer welding and surface layer welding. Wherein, when the backing layer is welded, the thickness of the backing weld bead needs to be controlled to be reduced as much as possible so as to ensure the root of the weld joint to be fully fused and welded thoroughly; the subsequent welding bead is used for filling the deep hole welding groove 4; when the cover surface layer is welded, the welding bead of the cover surface layer needs to be controlled to meet the final filling requirement of the size of a welding seam. The thickness of the filler metal formed after welding should be greater than the depth of the deep hole welding groove 4.
In the multi-welding process, the interval time between two adjacent welding processes is not too long, and the next welding process is carried out when the previous welding process is not completely cooled. Namely, the former welding keeps certain interlayer temperature to provide preheating for the latter welding; meanwhile, the two welding processes can be better fused, and the defects are reduced.
Preferably, the inter-welding temperature (namely the interlayer temperature) is controlled within the range of 40-60 ℃, so that the better welding quality can be achieved, the welding quality of the previous welding is not influenced, the fusion between two welding layers can be ensured, and the generation of cracks in a welding zone is prevented. The inter-pass temperature refers to the lowest temperature of a preceding weld joint when a subsequent weld joint is welded in a multi-pass welding process.
Further, when carrying out shielded metal arc welding, the welding speed is controlled within the range of 50 to 70mm/mim, and preferably within the range of 60 to 70mm/min.
The current adopted by the electric arc welding is 70 to 100A, preferably 80 to 85A; the voltage for arc welding is 20 to 30V, and the preferable welding voltage is controlled within 23 to 26V.
The current, the voltage and the welding speed of the electric arc welding are controlled, the temperature and the cooling speed of a weld pool in the welding process are ensured to be proper, and the slag is further ensured to float from the root of the weld.
In conclusion, in the manual deep hole welding method for the heat exchange tube and the tube plate, the grooves are formed on the two sides of the heat exchange tube 1 and the tube plate 2 to form the specific deep hole welding groove 4, the original groove limit angle (usually the limit angle is 80 degrees) is further enlarged, the traditional fillet weld is changed into a butt weld (the groove is only formed on the side of the tube plate in the traditional welding), the groove (molten pool) space is enlarged, and a larger space is provided for the upward floating of welding rod slag and the outward overflow of gas; the root of the welding seam can be completely exposed under the electric arc, so that the electric arc burns at the root in the first time, and the complete fusion and penetration of the root of the welding seam are ensured. Wherein, a groove is opened on the side of the heat exchange tube, so that the heat exchange tube is thinned before welding, the heat of the electric arc melting tube wall is saved, and the residual heat is used for fusing the root of the welding seam; meanwhile, the melted metal pole on the pipe wall is prevented from flowing into the groove to block the fusion channel at the root of the groove, and the fusion penetration of the root of the welding line is further ensured. The leakage rate of the pipe head obtained by the method is below 3 percent, is equivalent to that of automatic argon tungsten-arc welding, and is more convenient to leak.
Experimental example 1
Taking a tube plate, wherein the material of the tube plate is Q345R, and the thickness of the tube plate is 22mm; the heat exchange tube is a stainless steel S30408 thick-wall tube with the specification of phi 25 multiplied by 3.0 mm.
A single V groove of 80 degrees is formed in the tube hole 21 on the tube plate 2, a single V groove of 45 degrees is formed in the heat exchange tube 1, and a deep hole welding groove (i.e. a large V double groove) is correspondingly formed. The depth of the deep hole welding groove is more than or equal to 2mm. The tube plate comprises 10 tube heads (joints of the tube plate and the heat exchange tubes).
The diameter of the welding rod (i.e. the filler metal) is phi 2.6mm.
Welding is performed by Shielded Metal Arc Welding (SMAW), which includes two welding processes (two welding passes can be formed). The parameters of the two welding procedures are the same, the current is 82A, the polarity is direct current reverse connection, the arc voltage is 23 to 24V, and the welding speed is 60mm/min. The temperature between the lanes was 52 ℃. The welding is performed manually by welders with better technology.
Experimental example 2
Basically the same as the experimental example 1, except that the tube hole 21 of the tube plate 2 is provided with a bevel angle of 60 °; the angle of the groove on the heat exchange tube 1 was 39 °, and the same shielded metal arc welding as in experiment 1 was performed.
Experimental example 3
Taking a tube plate, wherein the material of the tube plate is SA-516 Gr.70N, and the thickness of the tube plate is 36mm; the heat exchange tube material is SA-213 TP316L, and the specification is phi 19 multiplied by 2.0mm.
A single-V groove of 85 degrees is formed in the tube hole 21 on the tube plate 2, a single-V groove of 40 degrees is formed in the heat exchange tube 1, and a deep-hole welding groove (namely a large-V double-side groove) is correspondingly formed. The depth of the deep hole welding groove is 2mm. The tube plate comprises 10 tube heads (joints of the tube plate and the heat exchange tubes).
The diameter of the welding rod (i.e. the filler metal) is phi 2.6mm.
The welding is carried out by manual shielded metal arc welding, and comprises two welding procedures (two layers and one welding procedure can be formed). Wherein, the parameters of the first welding (namely, the welding of the bottom layer) are as follows: the current is 81A, the polarity is direct current reverse connection, the arc voltage is 23 to 24V, and the welding speed is 60mm/min. The temperature between the lanes was 46 ℃. Parameters of the second weld (i.e. cap layer weld): the current is 80A, the polarity is direct current reverse connection, the arc voltage is 23 to 24V, and the welding speed is 70mm/min.
The manual welding is performed by a welder with better technology.
Experimental example 4
The method is basically the same as the experimental example 3, except that the bevel angle formed on the pipe hole 21 of the pipe plate 2 is 45 degrees; the angle of the bevel on the heat exchange tube 1 is 45 degrees (as shown in fig. 2).
The welding is carried out by manual shielded metal arc welding, and comprises two welding procedures (two welding passes can be formed). Wherein, the parameters of the first welding are as follows: the current is 80A, the polarity is direct current reverse connection, the arc voltage is 24V, and the welding speed is 60mm/min. The temperature between the lanes was 45 ℃. Parameters of the second weld: the current is 80A, the polarity is direct current reverse connection, the arc voltage is 26V, and the welding speed is 60mm/min.
The welding is performed manually by welders with better technology.
Experimental example 5
The thickness of the tube plate is 36mm; the specification of the heat exchange tube is phi 25 multiplied by 2.5mm.
A single V groove of 75 degrees is formed in the tube hole 21 of the tube plate 2, a single V groove of 40 degrees is formed in the heat exchange tube 1, and a deep hole welding groove (i.e. a large V double groove) is correspondingly formed. The depth of the deep hole welding groove is 2mm. The tube plate comprises 10 tube heads (joints of the tube plate and the heat exchange tubes).
The size of the welding rod (i.e. the filling metal) is phi 2.6mm.
The welding is carried out by manual shielded metal arc welding, and comprises two welding procedures (two welding passes can be formed). The parameters of the two welding processes are the same, the current is 82A, the polarity is direct current reverse connection, the arc voltage is 23 to 24V, and the welding speed is 60mm/min. The temperature between the lanes was 44 ℃.
The manual welding is performed by a welder with better technology.
Experimental example 6
The method is basically the same as the experimental example 5, except that a single V groove of 85 degrees is formed on the tube hole 21 of the tube plate 2, and a single V groove of 30 degrees is formed on the heat exchange tube 1, so as to form a deep hole welding groove correspondingly. The depth of the deep hole welding groove is 2.0 to 2.22mm.
The parameters of the two welding procedures are the same, the current is 72 to 89A, the polarity is direct current reverse connection, the arc voltage is 21 to 28V, and the welding speed is 50 to 70mm/min. The temperature between the lanes was 60 ℃.
Experimental example 7
The method is basically the same as the experimental example 5, except that a single V groove of 75 degrees is formed on the tube hole 21 of the tube plate 2, and a single V groove of 45 degrees is formed on the heat exchange tube 1, so as to form a deep hole welding groove correspondingly. The depth of the deep hole welding groove is 2.0 to 2.22mm.
The parameters of the two welding processes are the same, the current is 74 to 90A, the polarity is direct current reverse connection, the arc voltage is 21 to 28V, and the welding speed is 50 to 70mm/min. The temperature between the lanes was 60 ℃.
Experimental example 8
The material of the pipe plate is Q345R, and the thickness is 20mm; the heat exchange tube is a stainless steel S30408 thick-wall tube with the specification of phi 25 multiplied by 3.0 mm.
A single-V groove of 60 degrees is formed in the tube hole 21 on the tube plate 2, a single-V groove of 45 degrees is formed in the heat exchange tube 1, and deep-hole welding grooves (namely large-V double-side grooves or Y-shaped butt seams) are correspondingly formed. The depth of the deep hole welding groove is more than or equal to 2mm. The tube plate comprises 10 tube heads (joints of the tube plate and the heat exchange tubes).
The size of the welding rod (i.e. the filling metal) is phi 2.0mm.
Welding is carried out by manual shielded metal arc welding, and comprises two welding (two welding passes can be formed). The parameters of the two welding processes are the same, the current is 80 to 100A, the polarity is direct current reverse connection, the arc voltage is 22 to 24V, and the welding speed is 60 to 70mm/min. The temperature between the lanes was 60 ℃.
The manual welding is performed by a welder with better technology.
Physical and chemical experiments:
in experimental examples 1 to 8, 2 tube heads were cut out at random from each of the welded tube heads, and the cross sections of weld joints of 16 tube heads were obtained in total and examined by macroscopic metallographic examination. The detection results show that the root parts of the welding seams of the 16 pipe heads obtained in the experimental examples 1-8 are completely fused and welded, slag inclusion, air holes and the like are avoided, and the thickness of the welding seams also meets the standard requirements. The experimental examples 1-8 show that the method for carrying out shielded metal arc welding by opening the large V double-sided groove is reasonable and successful.
And macroscopic metallographic detection is that after the pipe head is subjected to linear cutting, polishing and corrosion are carried out, and a welding line is observed by using a magnifying lens of 10 times.
Pull-off force test 2 tips from each of examples 1-8 were selected for pull-off force test. The experimental data show (original experimental data not shown) that the pull-off force limit actually endured by the weld of each tube head is over 540 Mpa. According to the standard requirements of products, the calculated pull-out force is qualified when the calculated pull-out force does not exceed the allowable pull-out force, the design calculation shows that the pull-out force of the welding line of the head of the heat exchange tube is more than or equal to about 30MPa, and the actual detection value is far greater than the design requirement.
Therefore, the welding structure obtained by the method can meet the requirements no matter from the design or the welding manufacturing perspective, and welding seams with qualified quality are welded.
Comparative example 1
The heat exchange tube extends out of the tube plate by 2mm (not less than the wall thickness of the heat exchange tube), a single V groove with the angle of 45 degrees is formed in the tube hole of the tube plate, and the depth of the groove is not less than 2mm.
The diameter of the welding rod is phi 2.6mm; the welding current is 90-100A, the arc voltage is 20-25V, the number of welding tracks is 1, and the experiment comprises 10 tube heads.
Manual stick arc welding is performed by the welder at the technical centre.
And performing macroscopic metallographic detection after the 10 pipe heads are subjected to warp cutting, observing the welding line by using 10 magnifying lenses for polishing corrosion, and detecting that the root of the welding line is 100% unfused and not welded through.
The result analysis shows that the groove is too narrow, the electrode arc per se has insufficient stiffness, and the arc cannot reach the root of the groove like the argon arc welding adopted at present under the condition of too wide arc, so that the root cannot be fused and melted through.
Comparative example 2
The method is basically the same as that of comparative example 1, except that a limit groove design is performed on the tube sheet. Comprises two auxiliary tube plates, and each auxiliary tube plate and the heat exchange tube form 10 tube heads.
Opening a single V groove of 80 degrees on the pipe holes of the secondary pipe plate (as shown in figure 3); the pipe hole of the other pair of pipe plates is provided with a single V groove with an angle of 85 degrees.
After welding, 2 tube heads (4 tube heads in total and 32 cross sections) are taken from the two pairs of tube plates at will, macroscopic metallographic detection is carried out after wire cutting, and welding seams are observed by a magnifying lens of 10 times after polishing and corrosion.
As a result, the unfused and incomplete penetration rate of the root of the weld is more than 80%, and the situation is slightly improved, but the design requirement is still not met.
Comparative example 3
The bevel angle of the comparative example 1 is too small, so that the electric arc cannot reach the root of the bevel, and the defect of incomplete fusion and incomplete penetration exists in the root of the welding line. This comparative example was further designed.
Specifically, as shown in fig. 4, the opening condition of each secondary tube plate is as follows:
(1) Opening a 2.5mm wide groove on the pipe hole on the pipe plate, wherein the angle of the outer wall of the groove is 45 degrees (see a diagram in fig. 4);
(2) Opening a groove with the width of 2.5mm on the pipe hole on the pipe plate, wherein the angle of the outer wall of the groove is 45 degrees, and adding a chamfer (see a diagram b in a figure 4) of R2.0 between the bottom of the groove and the outer wall to increase the width of the root of the groove;
(3) Opening a groove with the width of 2.5mm on the pipe hole on the pipe plate, wherein the angle of the outer wall of the groove is 60 degrees (see a c diagram in fig. 4) so as to further increase the width of the groove root;
(4) The pipe hole on the pipe plate is opened with a groove with the width of 2.5mm, the angle of the outer wall of the groove is 60 degrees, and a chamfer angle R2.0 (see a diagram d in figure 4) is added between the bottom of the groove and the outer wall so as to further increase the width of the root of the groove.
The diameter of the welding rod is phi 2.6mm; the welding current is 90-100A, the arc voltage is 20-25V, and the number of welding tracks is 1. Manual stick arc welding is performed by the welder at the technical centre.
And (4) cutting warp of the pipe head obtained after welding, performing macroscopic metallographic detection, polishing and corroding, and observing a welding seam by using a magnifying lens of 10 times. The detection result is that more than 90 percent of the root of the welding seam is not fused and is not welded through.
Analysis shows that the electric arc still can not be fused to the root of the groove, so that the root can not be fused and welded through.
From comparative examples 1 to 3, it can be seen that, no matter whether the groove is increased from 45 ° to 80 ° or even 85 °, or whether the groove is changed from a single V groove to a grooved single V groove, or even chamfered, the groove angle and width are increased, the problem of fusion and penetration of the weld root is not actually solved.
Claims (8)
1. A manual deep hole welding method for a heat exchange tube and a tube plate is characterized in that the manual deep hole welding method is used for entering from a tube box thread plugging hole at the end part of a box type air cooler to weld the heat exchange tube and the tube plate, the heat exchange tube is inserted into a tube hole of the tube plate, and the end part of the heat exchange tube is flush with one side of the tube plate, and the manual deep hole welding method comprises the following steps:
step 1, grooving: beveling the outer walls of the tube hole of the tube plate and the end part of the heat exchange tube, and aligning the root parts of the bevels on the tube plate and the heat exchange tube to form a deep hole welding bevel;
step 2, carrying out shielded metal arc welding: the welding rod extends into the deep hole welding groove from the wire plugging hole, and the electric arc extends into the welding rod and the deep hole welding groove from the wire plugging hole to weld;
wherein the content of the first and second substances,
the grooves on the tube plate and the heat exchange tube are both single-V grooves, and the deep hole welding groove is a large-V double-side groove;
the angle of the groove on the tube plate is 45-85 degrees;
the angle of the groove on the heat exchange tube is 30-45 degrees;
and the shielded metal arc welding in the step 2 is multi-pass welding.
2. The manual deep hole welding method for the heat exchange tube and the tube plate according to claim 1, wherein the depth of the deep hole welding groove is more than or equal to 2.0mm and is more than or equal to the thickness of the heat exchange tube.
3. The manual deep hole welding method for the heat exchange tube and the tube plate according to claim 1, wherein the diameter of the welding rod is less than or equal to 2.6mm.
4. The manual deep hole welding method for the heat exchange tube and the tube plate according to claim 1, wherein in the step 2, when carrying out shielded metal arc welding, an arc starting point is arranged on the side of the tube plate in the deep hole welding slope;
in the welding process, welding is carried out on one side of the electric arc close to the tube plate;
the arc starting point and the arc extinguishing point are repeatedly melted in the same welding.
5. The manual deep hole welding method for the heat exchange tube and the tube plate according to the claim 1 or 4, wherein the multiple welding of the shielded metal arc welding in the step 2 at least comprises backing layer welding and cover layer welding, and the thickness of the backing welding bead is controlled to be reduced when the backing layer welding is carried out; and controlling a welding bead of the cover layer to meet the welding seam size filling requirement when the cover layer is welded.
6. The manual deep hole welding method for the heat exchange tube and the tube plate according to claim 5, wherein the interval time between two adjacent welds in the multiple welds is controlled, and the next weld is performed when the previous weld is not completely cooled.
7. The manual deep hole welding method for the heat exchange tube and the tube plate according to claim 6, wherein the temperature among channels of the multi-channel welding is controlled within the range of 40 to 60 ℃.
8. The manual deep hole welding method for the heat exchange tube and the tube plate according to claim 1, wherein in the step 2, when carrying out shielded metal arc welding:
controlling the welding speed within the range of 50-70mm/min;
and/or the current adopted by the electric arc welding is 70 to 100A;
and/or the voltage adopted by the electric arc welding is 20 to 30V.
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