Welding die and welding method for titanium welded pipe

Abstract

The invention relates to the technical field of metal material processing. The invention provides a welding die and a welding method for a titanium welded pipe, the die comprises a welding roller, the welding roller comprises a welding upper roller and a welding lower roller, the welding upper roller is connected with the welding lower roller through a bolt, the welding upper roller is provided with a first arc groove, and the welding lower roller is provided with a second arc groove; the first arc groove and the second arc groove are connected or disconnected along with attachment or separation of the upper welding roller and the lower welding roller. According to the welding mold and the welding method for the titanium welded pipe, the structural arrangement of the welding roller can be optimized, the friction force between the mold and a titanium belt is reduced, and the surface quality of the prepared titanium belt is improved; in addition, the fitting degree between the welding roller and the titanium belt to be welded can be improved, the clamping stability between the welding roller and the titanium belt is enhanced, the problem that the welding effect is poor due to the fact that the two sides of the titanium belt slightly swing in the welding process is avoided, and the welding quality of the titanium welded pipe is improved.

Description

Technical Field

[0001] The invention relates to the technical field of metal material processing, and in particular to a welding die and a welding method for a titanium welded pipe. Background Art

[0002] At present, titanium welded pipes made of pure titanium cold-rolled strips are usually used as heat exchange tubes and condenser tubes, and are widely used in condensers and condensers of equipment such as seawater desalination, coastal power stations and nuclear power plants. Among them, thin-walled small and medium-diameter titanium welded pipes are widely used. They are made by cold-rolled titanium strips that are gradually cold-bent and deformed through forming dies and then clamped and welded in a welding box with a pair of welding rollers.

[0003] At present, the titanium welded tube welding roller molds are all made of mold copper (such as TS4), which has a high raw material cost. In addition, when the surface hardness of the titanium strip is lower than 120HV or the transverse yield strength exceeds 410MPa, the copper mold is easy to produce adhesive wear with the titanium strip, resulting in friction marks on the surface of the titanium welded tube. In addition, the hole shape of the current welding roller adopts a single-segment arc design, and the radius of the arc is the radius of the finished tube. Since the titanium strip is not a perfect circle after being cold-bent by the forming die, the single-segment arc design does not fit the contour of the titanium strip, and the two sides of the titanium strip will swing slightly during welding. When the titanium strip swings, the weld morphology fluctuates. For ultra-thin welded pipes below 0.4mm, such fluctuations will cause the weld strength to fail to meet the standard. Therefore, it is of great significance to study how to improve the stability of the clamping between the mold and the titanium strip to be welded, and avoid the slight swing of the two sides of the titanium strip during welding, resulting in poor welding effect.

[0004] Patent CN104308551B mentions a copper alloy sheath preparation device and preparation method for a special through-ground wire for a high-speed railway. In the device, the welding gun of the welding device is set at the seventh horizontal roller. According to the patent, from the first horizontal roller to the fourth horizontal roller, the groove depth of the annular groove decreases one by one, the arc length of the upper arc in the generatrix of the annular groove increases one by one, and the arc length of the lower arc shortens one by one, so that the effect of gradually deforming the whole circle can be achieved. And the preparation method of the copper alloy sheath disclosed in the patent, by selecting the preparation steps of copper alloy strip-scraping-first stage deformation into a U-shaped shape-second stage deformation circle-third stage deformation: forming and welding-fourth stage deformation: sizing after welding, it can achieve the effect of reducing surface damage and facilitating welding. However, since the seventh horizontal roller in the patent is an integrated setting, the preparation cost is relatively high, and through the preparation method, the copper alloy strip can be processed accordingly, but the required titanium strip processing and treatment cannot be achieved. Summary of the invention

[0005] In view of this, the present invention aims to propose a welding mold and a welding method for titanium welded pipes, so as to solve the problems in the prior art that titanium strips with a surface hardness lower than 120HV or a transverse yield strength exceeding 410MPa are prone to surface wear marks during molding, or even pickling titanium strips; and the titanium strips are prone to slight swinging during welding of ultra-thin welded pipes; thereby optimizing the structural setting of the welding roller, reducing the friction between the mold and the titanium strip, improving the surface quality of the prepared titanium strip, and reducing the wear of the titanium strip; and also improving the fit between the welding roller and the titanium strip to be welded, enhancing the stability of the clamping between the welding roller and the titanium strip, avoiding slight swinging of the two sides of the titanium strip during welding, which in turn causes the problem of poor welding effect, and improving the welding quality of the titanium welded pipe.

[0006] To achieve the above object, the technical solution of the present invention is achieved as follows: The present invention relates to a welding mold and a welding method for a titanium welded pipe. The welding mold for the titanium welded pipe comprises welding rollers, which comprise an upper welding roller and a lower welding roller. The upper welding roller is connected to the lower welding roller via a latch. The upper welding roller is provided with a first circular arc groove, and the lower welding roller is provided with a second circular arc groove. The first circular arc groove and the second circular arc groove are connected or disconnected as the upper welding roller and the lower welding roller are fitted or separated.

[0007] Furthermore, the welding mold also includes a forming section mold, a sizing section mold and a sizing section mold; the titanium strip is sequentially passed through the forming section mold, welding roller, sizing section mold and sizing section mold to prepare the required titanium welded pipe.

[0008] Furthermore, the radius of the first arc groove is recorded as R1, the radius of the second arc groove is recorded as R2, and R1<R2.

[0009] Furthermore, the material of the welding upper roller is mold copper.

[0010] Furthermore, the material of the welding lower roller is bakelite.

[0011] Furthermore, the nominal radius of the titanium welded pipe is recorded as R, R1=R.

[0012] Furthermore, R2=R+R0; R0 is the radius deviation value, and R0 is a positive number.

[0013] A titanium welded pipe welding method, wherein the titanium welded pipe welding roller is used during the welding process, and the method comprises the following steps: Step 1: Cleaning the titanium strip: Select the required titanium strip and clean it in the cleaning device using a high-pressure air gun; Step 2: Threading and debugging: Under the action of the pulling force of the steel wire at the first speed V1, the cleaned titanium strip is firstly roller-formed by the mold roller in the forming section mold; then, the titanium strip after roller forming is welded by the welding roller; finally, the welded titanium strip is roughly sized to obtain a semi-finished titanium tube; Step 3: Annealing: Place the semi-finished titanium tube into an annealing furnace, maintain the annealing temperature of the annealing furnace at T°C, and the annealing speed at V2; after the preset annealing time t, the semi-finished titanium tube is taken out of the furnace; Step 4: Precision sizing: After the semi-finished titanium tube enters the precision sizing die, the precision sizing die is pressed down one by one, and the downward pressure of the flat roller and the vertical roller is adjusted according to the tube diameter data of the diameter gauge. After reaching the preset tolerance required for the titanium welded tube, the finished titanium welded tube is prepared.

[0014] Furthermore, the type of titanium strip in step one includes any one of an acid-washed titanium strip and a low-roughness titanium strip, and the titanium strip selected in step one is not limited by surface hardness and transverse yield strength.

[0015] Furthermore, in step three, the annealing temperature T is set to 620°C.

[0016] Compared with the prior art, the welding mold and welding method of a titanium welded pipe described in the present invention have the following beneficial effects: By setting the welding roller, the structural setting of the welding roller can be optimized, the friction between the mold and the titanium strip can be reduced, the surface quality of the prepared titanium strip can be improved, and the wear of the titanium strip can be reduced; the fit between the welding roller and the titanium strip to be welded can be improved, the clamping stability between the welding roller and the titanium strip can be enhanced, and the problem of poor welding effect caused by slight swinging of the two sides of the titanium strip during welding can be avoided. By setting the welding method, the efficiency of titanium welded pipe preparation can be effectively improved, the cost of titanium welded pipe preparation can be reduced, and the quality of titanium welded pipe welding can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings, which constitute part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention. In the accompanying drawings: Figure 1 This is a schematic diagram of the appearance of a qualified titanium welded pipe prepared in Example 1; Figure 2 This is a schematic diagram of the appearance of a qualified titanium welded pipe prepared from a high yield strength titanium strip in Example 2; Figure 3 This is a schematic diagram of the structure of a split welding roller with two arc segments in the present invention; Figure 4 It is a schematic diagram of the structure of a welding roller containing a single arc in the prior art.

[0018] Explanation of reference numerals: 1. welding upper roller; 2. welding lower roller. DETAILED DESCRIPTION

[0019] The inventive concepts of the present disclosure will be described below using terms commonly used by those skilled in the art to convey the essence of their work to other persons skilled in the art. However, these inventive concepts can be embodied in many different forms and should not be considered limited to the embodiments described herein.

[0020] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0021] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0022] In order to solve the problem that titanium strips with surface hardness lower than 120HV or transverse yield strength exceeding 410MPa, or even pickled titanium strips are prone to surface wear marks during molding in the prior art, and that titanium strips are prone to slight swings during welding of ultra-thin welded pipes, this embodiment proposes a welding mold and a welding method for titanium welded pipes. The welding mold for a titanium welded pipe comprises a welding roller, the welding roller comprises a welding upper roller 1 and a welding lower roller 2, the welding upper roller 1 is connected to the welding lower roller 2 by a latch, a first arc groove is provided at one end of the welding upper roller 1, a second arc groove is provided at one end of the welding lower roller 2, and the other ends of the welding upper roller 1 and the welding lower roller 2 are both smooth and flat surfaces; the first arc groove and the second arc groove are connected or disconnected as the welding upper roller 1 and the welding lower roller 2 are fitted or separated.

[0023] Through the setting of the split welding roller, the structural setting of the welding roller can be optimized, the friction between the mold and the titanium strip can be reduced, the surface quality of the prepared titanium strip can be improved, and the wear of the titanium strip can be reduced; it can also improve the fit between the welding roller and the titanium strip to be welded, enhance the clamping stability between the welding roller and the titanium strip, and avoid slight swinging of the two sides of the titanium strip during welding, thereby causing the problem of poor welding effect.

[0024] Among them, the first arc groove is connected to the second arc groove to form a semicircular hole shape, and the inner wall of the semicircular hole is attached to or separated from the outer wall of the titanium welded tube, which is used to provide support for the welding of the titanium welded tube. The first arc groove is arranged at one end of the welding upper roller 1 close to the welding lower roller 2, and the second arc groove is arranged at one end of the welding lower roller 2 facing the welding upper roller 1. The radius of the first arc groove is recorded as R1, and the radius of the second arc groove is recorded as R2, and R1<R2. In addition, the material of the welding upper roller 1 is mold copper. The material of the welding lower roller 2 is bakelite. At least one pin is set. In this embodiment, one pin is set. The copper is mold copper TS4.

[0025] Different from the bolt connection method used in the previous composite mold, the present application adopts a single latch to connect the copper part and the bakelite part, without drilling and tapping on the two parts of the mold, which greatly improves the efficiency of preparing the welding roller. The welding roller is a passive roller with a small holding force, so this latch fixation can meet the strength requirements of the mold repair. Therefore, through the setting of a single latch, it is possible to achieve the fixation between the welding upper roller 1 and the welding lower roller 2 without drilling and screwing, which can simplify the structure of the welding roller, improve the preparation efficiency of the welding roller, and simplify the preparation complexity of the welding roller. In addition, since the welding upper roller 1 is at the top of the welding roller and is very close to the weld pool and the arc, the welding upper roller 1 adopts the setting of mold copper, which can meet the material's need to withstand high temperatures above 600°C, and can also avoid the influence of thermal damage on the welding roller, thereby improving the service life of the welding roller. In addition, since the welding lower roller 2 is at the bottom of the welding roller, far away from the weld molten pool and the arc, it only needs to withstand a temperature of 300°C. Therefore, the welding lower roller 2 is made of bakelite material, which can not only meet the heat resistance temperature required by the bottom of the welding roller, but also reduce the manufacturing cost of the bottom of the welding roller, and can also pave the way for the welding upper roller 1 and the welding lower roller 2 to be connected by a single pin, thereby greatly reducing the preparation cost of the welding roller and improving the preparation efficiency of the welding roller.

[0026] The nominal radius of the finished titanium welded pipe is recorded as R, R1=R, R2=R+R0; R0 is the radius deviation value, R0 is a positive number; the specific value of R0 is set as required. In this embodiment, R0 is 1.5 mm.

[0027] Due to the process characteristics of cold bending of titanium strip, the titanium strip is not a perfect circle during welding, but an ellipse with a slightly larger lower part. Therefore, the previous single-segment arc hole shape is not suitable for the actual situation. The titanium strip and the mold do not fit together during welding, so the weld morphology is not stable when making ultra-thin welded pipes. Different from the single-segment arc groove used in the prior art, the radius of the arc is the nominal radius of the finished welded pipe, which easily causes the titanium strip to swing when the arc groove clamps the finished welded pipe for welding; the semi-circular hole groove formed by splicing two arcs in this application has a higher fit with the titanium strip during welding, which is beneficial to increase the stability of the titanium welded pipe welding process, the hole shape of the welding roller is more in line with the titanium strip, the edge of the titanium strip is stable during welding, the welding quality is high, and the weld strength is strong. It is also beneficial to reduce the excess friction between the titanium strip and the welding roller, and the service life of the welding roller is greatly increased.

[0028] The welding die also includes a forming section die, a first sizing section die and a second sizing section die; the titanium strip is sequentially passed through the forming section die, the welding roller, the first sizing section die and the second sizing section die to prepare the required titanium welded pipe. The welding roller is arranged between the forming section die and the first sizing section die; the semi-finished titanium pipe between the first sizing section die and the second sizing section die is annealed.

[0029] The present invention uses bakelite as a raw material to make a titanium welded pipe forming section mold, which can be used to support the welding of different titanium strips to produce titanium welded pipes, and is suitable for the welding of pickled titanium strips and low-roughness titanium strips; in addition, since the market price of bakelite is much lower than mold copper, and the molding accuracy and life of bakelite molds are consistent with the life of copper molds, it is better than engineering plastic molds. At the same time, bakelite is easier to turn, and the mold processing cycle is further reduced; the manufacturing cost and cycle of the titanium welded pipe forming section mold are reduced; therefore, it is beneficial to increase the service life of the mold on the basis of reducing the mold cost; it also has the effect of excellent surface quality of the prepared product, which is beneficial to the large-scale industrialized stable production of titanium welded pipes.

[0030] A titanium welded pipe welding method, wherein the titanium welded pipe welding roller is used during the welding process, and the method comprises the following steps: Step 1: Cleaning the titanium strip: Select the required titanium strip and clean it with a high-pressure air gun in the cleaning device to remove the debris and small titanium chips on the surface of the titanium strip; Step 2: Threading and debugging: Under the action of the pulling force of the steel wire at the first speed V1, the cleaned titanium strip is firstly roller-formed by the mold roller in the forming section mold; then, the titanium strip after roller forming is welded by the welding roller; finally, the welded titanium strip is roughly sized to obtain a semi-finished titanium tube; Step 3: Annealing: Place the semi-finished titanium tube into an annealing furnace, maintain the annealing temperature of the annealing furnace at T°C, and the annealing speed at V2; after the preset annealing time t, the semi-finished titanium tube is taken out of the furnace; Step 4: Precision sizing: After the semi-finished titanium tube enters the precision sizing die, the precision sizing die is pressed down one by one, and the downward pressure of the flat roller and the vertical roller is adjusted according to the tube diameter data of the diameter gauge. After reaching the preset tolerance required for the titanium welded tube, the finished titanium welded tube is prepared.

[0031] The type of titanium strip in step 1 includes any one of pickled titanium strip and low roughness titanium strip, and the titanium strip selected in step 1 is not limited by surface hardness and transverse yield strength; in step 3, the annealing speed is V2=V1; the specific values ​​of V1 and V2 are set as required. In this embodiment, the annealing temperature T is 620°C, and the actual annealing temperature T is set as required.

[0032] Different from the previous situation where titanium strips with surface hardness lower than 120HV or transverse yield strength higher than 410MPa could not be used for welded pipe production, titanium strip manufacturers for welded pipes must use titanium strips with higher surface hardness and lower yield strength. The production process of this type of titanium strip is complex, has high requirements on the raw material composition and annealing process, and is costly. Through the setting of the method, the present invention enables titanium strips with low hardness and high yield strength to be used for large-scale production of welded pipes, and titanium strip manufacturers for welded pipes can choose cheaper and more readily available titanium strips to produce titanium strips for welded pipes. It can also effectively improve the efficiency of titanium welded pipe preparation, reduce the cost of titanium welded pipe preparation, and improve the quality of titanium welded pipe welding. It is conducive to breaking through the restrictions on the surface hardness and yield strength of titanium strips for welded pipes, breaking through the restrictions on the surface state of titanium strips, and realizing the production of titanium welded pipes from pickled titanium strips, and the requirements for cold-rolled titanium strip production equipment can be further reduced.

[0033] Step 2 includes: Step S21: belt threading and debugging: under the action of the pulling force of the steel wire at the first speed V1, the cleaned titanium belt is firstly roller-formed by the mold roller in the forming section mold; Step S22: adjusting welding parameters according to the required requirements; and welding the edges of the roll-formed titanium strip through welding rollers; Step S23: The welded titanium strip is roughly sized to obtain a semi-finished titanium tube.

[0034] Through the action of steel wire pulling, the preparation efficiency of titanium welded pipes can be effectively improved, the control of the preparation cycle of titanium welded pipes can be improved, the preparation cost of titanium welded pipes can be effectively reduced, and the reliability of the preparation of titanium welded pipes can be improved. It can avoid the placement deviation during the transportation and movement of titanium welded pipes, resulting in the deviation of the welding position, and can effectively improve the stability and safety of titanium welded pipe welding.

[0035] Example 1

[0036] A titanium strip with a grade of Gr1, a surface hardness of 119HV0.5, a transverse yield strength of 300MPa, a bright surface, a strip thickness of 0.5mm, and a strip width of 78.5mm is selected to prepare a titanium welded pipe, wherein the welding roller mold specification is 25mm, and the welding roller is a split welding roller made of bakelite and copper. The titanium welded pipe is prepared by the following method. The method comprises the following steps: Step 1: Cleaning of titanium strip: Before the titanium strip enters the forming mold, it first enters the cleaning device and uses a high-pressure air gun to remove debris and small titanium chips on its surface.

[0037] Step 2: Wire threading and debugging: Use steel wire to pull the front end of the titanium strip through the forming section die one by one, and press the die roller down to form it. Adjust the welding parameters so that the strip edge is welded and then enters the rough sizing to prepare the semi-finished titanium tube.

[0038] Step 3: The semi-finished titanium tube enters the annealing furnace, the annealing temperature is set at 620°C, the annealing speed is consistent with the main line speed, and then leaves the annealing furnace.

[0039] Step 4: After entering the precision sizing, press down the precision sizing dies one by one, adjust the pressing amount of the flat roll and the vertical roll according to the pipe diameter data of the diameter gauge, and finally reach the set tolerance. The surface quality of the finished titanium welded pipe is as follows Figure 1 As shown, all standard requirements are fully met.

[0040] Example 2

[0041] The preparation method is the same as that in Example 1, except that a titanium strip with a grade of Gr2, a surface hardness of 157HV0.5, a transverse yield strength of 418MPa, a bright surface, a strip thickness of 0.5mm, and a strip width of 80.5mm is used to prepare the titanium welded pipe, wherein the welding roller mold specification is 25.4mm, and the welding roller is a split welding roller made of bakelite and copper.

[0042] The surface quality of the finished titanium welded pipe is as follows: Figure 2 As shown, all standard requirements are fully met.

[0043] Example 3

[0044] The preparation method is the same as that in Example 1, except that a titanium strip with a grade of Gr2, a surface hardness of 165HV0.5, a transverse yield strength of 377MPa, a bright surface, a strip thickness of 0.5mm, and a strip width of 59.5mm is used to prepare the titanium welded pipe, wherein the welding roller mold specification is 19mm, and the welding roller is a split welding roller made of bakelite and copper.

[0045] The surface quality of the finished titanium welded pipe meets the relevant requirements of the American standard.

[0046] Through the settings of Examples 1-3, it can be seen that the welding roller mold in the present invention can be used to produce welded pipes and ultra-thin welded pipes for titanium strips with low hardness or transverse yield strength exceeding 410MPa, and the welding roller in the present invention has the characteristics of low cost and high life. The surface quality, dimensional accuracy and weld morphology of the titanium welded pipes prepared by the welding method described in the present invention meet the requirements of national standards, American standards and high-end customer enterprise standards, and can meet the requirements of most titanium welded pipe manufacturers. In addition, the technology of the present application can achieve large-scale stable production.

[0047] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A titanium welded pipe welding die, characterized in that: The welding roller comprises a welding upper roller (1) and a welding lower roller (2), the welding upper roller (1) being connected to the welding lower roller (2) via a latch, the welding upper roller (1) being provided with a first circular arc groove, the welding lower roller (2) being provided with a second circular arc groove, the first circular arc groove and the second circular arc groove being connected or disconnected as the welding upper roller (1) and the welding lower roller (2) are attached or separated; The first arc groove and the second arc groove are connected to form a semicircular hole, and the inner wall of the semicircular hole is attached to or separated from the outer wall of the titanium welded pipe; the material of the welding upper roller (1) is mold copper, and the material of the welding lower roller (2) is bakelite; In addition, the nominal radius of the titanium welded pipe is recorded as R, the radius of the first arc groove is recorded as R1, and the radius of the second arc groove is recorded as R2, R1=R; R2=R+R0; R0 is the radius deviation value, and R0 is a positive number.

2. A titanium welded pipe welding die according to claim 1, characterized in that: The welding mold also includes a forming section mold, a sizing section mold and a sizing section mold; the titanium strip is sequentially passed through the forming section mold, the welding roller, the sizing section mold and the sizing section mold to prepare the required titanium welded pipe.

3. The titanium welded pipe welding mold according to claim 1, characterized in that: The R1<R2.

4. A titanium welded pipe welding method, characterized in that: The method, during the welding process, uses a titanium welded pipe welding roller as claimed in any one of claims 1 to 3, and the method comprises the following steps: Step 1: Cleaning the titanium strip: Select the required titanium strip and clean it in the cleaning device using a high-pressure air gun; Step 2: Threading and debugging: Under the action of the pulling force of the steel wire at the first speed V1, the cleaned titanium strip is firstly roller-formed by the mold roller in the forming section mold; then, the titanium strip after roller forming is welded by the welding roller; finally, the welded titanium strip is roughly sized to obtain a semi-finished titanium tube; Step 3: Annealing: Place the semi-finished titanium tube into an annealing furnace, maintain the annealing temperature of the annealing furnace at T°C, and the annealing speed at V2; after the preset annealing time t, the semi-finished titanium tube is taken out of the furnace; Step 4: Precision sizing: After the semi-finished titanium tube enters the precision sizing die, the precision sizing die is pressed down one by one, and the downward pressure of the flat roller and the vertical roller is adjusted according to the tube diameter data of the diameter gauge. After reaching the preset tolerance required for the titanium welded tube, the finished titanium welded tube is prepared.

5. The titanium welded pipe welding method according to claim 4, characterized in that: The type of titanium strip in step one includes any one of pickled titanium strip and low roughness titanium strip, and the titanium strip selected in step one is not limited by surface hardness and transverse yield strength.

6. The titanium welded pipe welding method according to claim 4, characterized in that: In the step 3, the annealing temperature T is 620°C.

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