Manufacturing method of integral type hydraulic support push rod produced by Q890-grade super-thick steel plate and integral type hydraulic support push rod

Abstract

The invention provides a manufacturing method of an integral type hydraulic support push rod produced by a Q890-grade extra-thick steel plate and the integral type hydraulic support push rod, the push rod is disassembled into a structure comprising a push rod body, a push rod head and a push rod tail, the push rod head and the push rod tail are die forgings, the push rod body is an integral cutting piece, and the push rod body is an integral cutting piece; the push rod head and the push rod tail are welded with the head end and the tail end of the push rod body into a whole, a box type structure of a traditional push rod is changed, meanwhile, the number of parts of the push rod is greatly reduced, the performance of the push rod is improved, meanwhile, the production process is simplified, and the production efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of hydraulic supports, in particular to a manufacturing method of an integral hydraulic support push rod produced by using a Q890 grade extra thick steel plate and the integral hydraulic support push rod. Background Art

[0002] Hydraulic support is the main equipment for coal mining. In addition to supporting the mine, it can also use hydraulic devices to move the scraper conveyor and itself horizontally.

[0003] Among them, the push rod is one of the key components of the hydraulic support, which plays the role of connecting the hydraulic support body and the scraper conveyor. It has the characteristics of large welding volume, poor service conditions, large load-bearing capacity, and complex force.

[0004] At present, the push rod is mainly welded by high-strength steel parts such as main reinforcement, main reinforcement plate, reinforcement plate, cover plate, etc. All parts on the push rod are connected by welding, and the weld forms are mainly fillet welds and groove welds. The groove weld is formed between the 40° groove of the main reinforcement plate and the cover plate, and the fillet weld is formed between the main reinforcement plate and the bottom plate.

[0005] The traditional push rod is a box-type structure, which is welded from high-strength steel plates of Q690 level and below. The plate thickness is mostly 20, 25, and 30 mm. The production process is: cutting → assembly → base welding → filling and cover welding → flame correction → painting. The details of the process plan are shown below.

[0006] Step (1) Cutting: Use a cutting machine to cut the parts of the push rod, and use a grinding machine to grind the parts with welds to reveal the metallic luster; Step (2) Assembly: Mark the position lines of the main reinforcement, rib plate and other parts on the bottom plate, use the tooling to place the main reinforcement and rib plate on the bottom plate, adjust the position of each part, and use ER50-6 welding wire to perform single-layer single-pass manual positioning welding at the position required by the process; Step (3) Welding: Fix the push rod on the welding platform, first perform manual welding for overall base, then use the robot to perform filling and cover welding in sequence, and after the cover plate groove is filled, start a 5mm fillet weld on the main reinforcement side; Step (4) Flame calibration: Use a flame spray gun to bake the deformed position until the deformation is corrected to within the tolerance range; Step (5) Spray paint: Spray paint on the push rod according to the process requirements.

[0007] Traditional putters currently have the following problems: First, the box-type structure has limited load-bearing capacity, especially in the weld area, where stress is concentrated and there are many defects. Accidents such as weld cracking and parent material breakage often occur during service. Second, the box-type push rod has many types and quantities of parts, and the overall production efficiency is low. In addition, the box-type push rod is assembled from multiple parts, including main ribs, bottom plates, cover plates and other slender parts, and the cover plate needs to be sunk 5mm between the main rib plates, which makes assembly difficult. Third, when welding the cover plate, there is a 2mm blunt edge at the root of the weld. If the welding parameters are too large, it will cause welding through, and if the welding parameters are too low, the root will not be fused, and the welding quality is difficult to guarantee. Fourth, there are many long welds between the main rib plate of the push rod and the bottom plate and cover plate. The welding amount is large and the welding deformation is serious. Flame correction is required, which causes local tempering of the steel plate and reduces the strength.

[0008] The above problems are caused by the structural form and manufacturing problems of the traditional hydraulic support push rod. Therefore, it is necessary to improve both the structure and manufacturing of the hydraulic support.

[0009] In order to solve the above problems, people have been seeking an ideal technical solution. Summary of the invention

[0010] The purpose of the present invention is to address the deficiencies of the prior art and thereby provide a method for manufacturing an integral hydraulic support push rod produced using Q890 grade extra thick steel plates with high drying efficiency and reasonable space occupancy and an integral hydraulic support push rod.

[0011] In order to achieve the above object, the technical scheme adopted by the present invention is: a method for manufacturing an integral hydraulic support push rod produced by using Q890 grade extra thick steel plate, the push rod is disassembled into a structure including a push rod body, a push rod head and a push rod tail, the push rod head and the push rod tail are die forgings, the push rod body is an integral cutting part, and the push rod head and the push rod tail are welded to the head and tail ends of the push rod body as a whole; Made by the following steps: Step 1. Cutting: Select a Q890 grade steel plate with a thickness of ≥100mm, draw a line on the steel plate according to the outer contour of the push rod, set a U-shaped opening at the tail end of the push rod body, leave anti-deformation reinforcement at the U-shaped opening, and the area enclosed by the anti-deformation reinforcement and the U-shaped opening is the internal groove. Determine the internal perforation position in the internal groove as the internal cutting starting point, and determine the external cutting starting point at the edge of the steel plate corresponding to the extension line of one side of the outer contour of the push rod; Preheat the steel plate as a whole, first pierce the inner perforation position, then preheat the perforation position, take the inner perforation position as the cutting starting point, and use a flame cutting machine to cut out the inner groove as a whole in a symmetrical cutting manner from both sides of the steel plate; Use a flame cutting machine to cut symmetrically from both sides of the steel plate from the outer cutting starting point of the steel plate, and cut out a complete push rod body along the outer contour of the push rod body; Step 2. Cutting the bevel: Place the cut push rod body on a fixed workbench, use a plasma cutter to cut the edge of the internal groove of the push rod body to form a groove with a set depth and angle, and then cut the groove on the outer periphery of the push rod body; After cutting is completed and cooled to below the set temperature, the anti-deformation reinforcement is cut and removed, and all grooves and reinforcement removal areas are polished to see the metallic luster; Step 3. Assembly: Relying on the shape positioning tooling, the push rod head and the push rod tail are placed in the corresponding positions of the push rod body, wherein the push rod head and the front end of the push rod body are in L-shaped contact, which is a butt welding structure, and the push rod tail is sunk into the U-shaped opening at the rear end of the push rod body, which is an embedded welding structure; after the assembly is completed, the positioning welding position is marked, and the positioning welding is performed after preheating; Step 4. Preheat: Preheat the workpiece as a whole to the set temperature; Step 5. Base welding: Use the robot welding platform to perform base welding on the entire push rod weld, and select the large-capacity deep welding mode; Step 6) Filling and capping welding: Continue to use the robot welding platform to perform symmetrical filling and capping welding on the weld positions to fill the groove welds; Step 7. Cool, heat, keep warm, and slowly cool to room temperature.

[0012] Based on the above, in step 1), a plurality of push rod bodies are cut synchronously from the whole steel plate, and the close sides of two adjacent push rod bodies share the same weld.

[0013] Based on the above, the overall preheating temperature of the steel plate is 100°C-150°C, the preheating temperature for the internal groove perforation is 100°C-150°C, the perforation tool is a flame gun, the perforation preheating time is ≥13min, and the perforation speed is 0.05-0.1m / mim.

[0014] Based on the above, the cutting gas for internal groove cutting is natural gas, the combustion-supporting gas is oxygen, the oxygen pressure is 0.8-0.9MPa, and the cutting speed is 0.25-0.3m / min; the cutting gas for the outer contour of the push rod is natural gas, the combustion-supporting gas is oxygen, the oxygen pressure is 0.8-0.9MPa, and the cutting speed is 0.05-0.1m / min. The cutting speed after introducing the steel plate is 0.25-0.3m / min.

[0015] Based on the above, in step 2, the groove depth of the inner groove edge is ≥25mm, the angle is between 30°-40°, the cutting speed of the groove is 0.6-0.8m / min, and after cutting, it is cooled to below 50°C before cutting the anti-deformation reinforcement.

[0016] Based on the above, in step 3, the preheating temperature of the tack welding position is 60°C -80°C, the preheating length range is 600-800mm, the tack welding is manual welding, the tack welding uses ER76-G φ1.4mm welding wire, the welding current is 300-320A, the voltage is 29-31V, the welding speed is 350-400mm / min, the length of each tack welding section is 300-500mm, the interval is 300-400mm, and the height is 4-5mm.

[0017] Based on the above, in step 4, the preheating temperature is 100-150°C; in step 7, the cooling process adopts slow cooling to 100°C, the temperature is raised to 350°C by a torch, the heat is kept warm by wrapping with asbestos cloth, and slowly cooled to room temperature.

[0018] Based on the above, in step 5, Ar+20%CO2 mixed gas shielded welding is used, ER96-G φ1.6mm diameter solid welding wire; welding parameters: welding current 300-340A, voltage 28-30V, welding speed 40-45cm / min, shielding gas flow 15-20L / min, overall preheating 100-150℃ before welding; the welding gun of the welding robot is pointed to bisect the grooves on both sides and form an angle of 70° with the welding direction.

[0019] Based on the above, in step 6, the welding adopts Ar+20%CO2 mixed gas shielded welding, ER96-G φ1.6mm diameter solid welding wire; filling and covering parameters: welding current 340-380A, voltage 29-31V, wire feeding speed 7-8m / min, welding speed 40-45cm / min, lateral sinusoidal oscillation of the end of the welding wire 1-4mm, welding wire dry extension 20-25mm, shielding gas flow 20-25L / min.

[0020] An integrated hydraulic support push rod comprises a push rod body, a push rod head and a push rod tail; The push rod body is a solid steel material obtained by integrally cutting a Q890 grade steel plate with a thickness of ≥100 mm; The head end of the push rod body and the push rod head are joined in an L-shaped manner and a groove is left, and then fixed together by welding; A U-shaped opening is arranged at the tail end of the push rod body, and the push rod tail is embedded in the U-shaped opening and assembled with the push rod body. After a groove is arranged at the assembly position, the push rod tail is fixed together by welding.

[0021] The present invention has outstanding substantive features and significant progress compared to the prior art. Specifically, the present invention has the following advantages: (1) The number of push rod parts has been reduced, production efficiency has been improved, and the difficulty of production organization has been reduced. The integrated push rod optimizes the original box-type push rod's main plate, bottom plate, and cover plate into one part, significantly reducing the number of push rod parts; (2) Innovatively proposed the cutting method and process of S890 grade high-strength and extra-thick plates. By formulating perforation parameters, optimizing the number of perforations, and formulating the cutting sequence, the previous idea of ​​gradually cutting parts on the steel plate was changed. Innovatively proposed to first perforate the entire plate, then cut the inner groove as a whole, and finally perforate the edge of the steel plate to cut the shape piece by piece. The method of cutting the shape in the same line was adopted, which reduced the number of perforations to the greatest extent, greatly improved the cutting efficiency, and effectively reduced the cutting deformation. (3) Reduced assembly difficulty, improved assembly efficiency and accuracy. The assembly of the box-type push rod requires marking and positioning, and the cover plate needs to be sunk 5mm between the main ribs, which makes assembly difficult. The assembly of the integral push rod structure only relies on the shape positioning, which makes assembly efficient and accurate. (4) Improved welding quality and reduced welding difficulty. When welding the push rod cover plate of the box-type structure, it is easy to have welding penetration or root failure, while the integral push rod structure will not have welding penetration and the base welding adopts a large penetration mode, which increases the welding penetration and improves the welding quality; (5) Small welding deformation, eliminating the flame correction process. The integral push rod only needs to weld the welds at the connection between the push rod head, push rod tail and push rod body, with small welding deformation and no need for flame correction. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a top view of the overall structural schematic diagram of the integral hydraulic support push rod in the present invention.

[0023] Figure 2 It is a front view of the overall structural schematic diagram of the integral hydraulic support push rod in the present invention.

[0024] Figure 3 It is a circuit diagram of the push rod body cutting in the present invention.

[0025] Figure 4 It is a structural diagram of a single push rod body in the blanking stage of the present invention.

[0026] Figure 5 It is a contour diagram of a single push rod body after the groove is cut and the anti-deformation reinforcement is removed in the present invention.

[0027] Figure 6 It is a schematic structural diagram of a putter head in the present invention.

[0028] Figure 7It is a structural schematic diagram of the putter tail in the present invention.

[0029] In the figure: 1. putter head; 2. putter body; 3. putter tail; 4. steel plate; 5. perforation; 6. cutting line; 7. anti-deformation reinforcement; 8. internal groove; 9. bevel. DETAILED DESCRIPTION

[0030] The technical solution of the present invention is further described in detail below through specific implementation methods.

[0031] like Figure 1-Figure 7 As shown, the integral push rod is mainly welded together by a push rod head 1, a push rod tail 3, and a push rod body 2. The push rod body 2 is a Q890 grade steel plate with a thickness of more than 100 mm. The push rod head 1 and the push rod tail 3 are high-strength die forgings, and the welds are mainly groove welds.

[0032] The push rod body 2 is a solid elongated rectangular structure, wherein the side connected to the push rod head 1 is a rectangular structure, and the side connected to the push rod tail 3 is a U-shaped hollow structure with an open end. The push rod head 1 and the push rod body 2 are butt-welded structures; the push rod tail 3 is sunk into the hollow part of the push rod body 2, and is an embedded welding structure. The edges of the connection between the push rod head 1, the push rod tail 3 and the push rod body 2 all have a 25mm deep 30° single V-shaped groove, and after assembly, a 25mm deep 60° double V-shaped groove is formed.

[0033] Process flow: cutting → assembly → base welding → filling and cover welding → slow cooling after welding → painting Step (1) Cutting: Use a flame cutting machine to cut according to the drawing, and reserve a 30mm wide anti-deformation tie rod at the open end of the push rod body 2 to form an internal groove 8 in the push rod body 2. Flame cutting process and parameters: Use a CNC flame cutting machine to preheat the steel plate to be cut as a whole, the preheating temperature is 100-150℃, and after reaching the preheating temperature, use a flame gun to cut.

[0034] Cutting core innovation: 1. Cut the internal groove 8 first: first use a flame gun to punch all the internal starting points on the Q890 extra-thick steel plate 4: the starting point is 50mm away from the inner edge of the steel plate to be cut, the preheating time for the punching 5 is 13min, and then punch at a speed of 0.05-0.1m / mim after preheating. After completion, use two flame guns for symmetrical cutting. The cutting gas is natural gas, the combustion-supporting gas is oxygen, the oxygen pressure is 0.8-0.9MPa, and the cutting speed is 0.25-0.3m / min.

[0035] 2. Cutting the shape: Use two flame guns to start symmetrical cutting at the two edges of the steel plate at the same time, cut the shape of the push rod body along the steel plate lead-in line, and cut the edges of the two adjacent push rod bodies on the same line. No more perforation is required in the middle. The speed of the flame gun leading the steel plate from the edge is 0.05-0.1m / min, and the cutting speed after leading the steel plate is 0.25-0.3m / min. (See the attached for the overall cutting sequence.) Figure 3 The cutting workpiece and sequence diagram in the figure, the arrow in the figure indicates the cutting direction, and the sequence number 6 in the figure is the cutting line) Step (2) Cutting the groove Place the push rod body 2 on a fixed workbench, first use a plasma cutting robot to cut a 25mm deep 30° groove 9 on the edge of the internal groove of the push rod body 2, and then cut the groove 9 on the outer periphery of the push rod body, with a cutting speed of 0.6-0.8m / min; after the groove cutting is completed, wait for the workpiece to cool to below 50°C, and then cut the anti-deformation reinforcement 7 at the internal groove. After cutting, grind the groove and anti-deformation reinforcement 7 to reveal the metallic luster.

[0036] Step (3) Assembly: Relying on the shape positioning, the push rod head 1 and the push rod tail 3 are placed in the corresponding position of the push rod body 2, the positions of each part are adjusted, and the positioning welding position is marked. Before welding, the positioning welding position is preheated to 60-80℃, the preheating length range is 600-800mm, and the positioning welding is performed manually. The positioning welding uses ER76-G φ1.4mm welding wire, the welding current is 300-320A, the voltage is 29-31V, the welding speed is 350-400mm / min, the length of each positioning welding section is 300-500mm, the interval is 300-400mm, and the height is 4-5mm.

[0037] Step (4) preheating: placing the workpiece in a preheating furnace and preheating to 100-150°C; Step (5) Base welding: Place the push rod on the robot welding platform, use the welding robot to perform the base welding on the push rod weld, select the large penetration mode, use Ar+20%CO2 mixed gas shielded welding, ER96-G φ1.6mm diameter solid wire. Welding parameters: welding current 300-340A, voltage 28-30V, welding speed 40-45cm / min, shielding gas flow 15-20L / min, preheating 100-150℃ before welding. The robot's welding gun points to the groove that divides the two sides equally and forms an angle of 70° with the welding direction.

[0038] Step (6) Filling and capping welding: Immediately after the base welding, the welding robot is used to perform symmetrical filling and capping welding to fill the groove weld. The welding adopts Ar+20%CO2 mixed gas shielded welding and ER96-G φ1.6mm diameter solid welding wire. Filling and capping parameters: welding current 340-380A, voltage 29-31V, wire feeding speed 7-8m / min, welding speed 40-45cm / min, horizontal sinusoidal swing of the wire end 1-4mm, wire dry extension 20-25mm, shielding gas flow 20-25L / min.

[0039] Step (7) Slow cooling after welding: After welding, it is naturally cooled to 100℃, and then baked to 350℃ with a torch. When the temperature is reached, the heating is stopped and asbestos cloth is used to keep it warm and slowly cooled to room temperature.

[0040] Step (8) Spray paint Spray paint on the push rod according to the process requirements.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or some technical features can be replaced by equivalents without departing from the spirit of the technical solution of the present invention, which should be included in the scope of the technical solution for protection of the present invention.

Claims

1. A method for manufacturing an integral hydraulic support push rod produced with Q890 grade extra thick steel plate, characterized in that: The push rod is disassembled into a structure including a push rod body, a push rod head and a push rod tail, wherein the push rod head and the push rod tail are die forgings, the push rod body is an integral cutting piece, and the push rod head and the push rod tail are welded to the front and rear ends of the push rod body as a whole; Made by the following steps: Step 1. Cutting: Select a Q890 grade steel plate with a thickness of ≥100mm, draw a line on the steel plate according to the outer contour of the push rod, set a U-shaped opening at the tail end of the push rod body, leave anti-deformation reinforcement at the U-shaped opening, and the area enclosed by the anti-deformation reinforcement and the U-shaped opening is the internal groove. Determine the internal perforation position in the internal groove as the internal cutting starting point, and determine the external cutting starting point at the edge of the steel plate corresponding to the extension line of one side of the outer contour of the push rod; Preheat the steel plate as a whole, first pierce the inner perforation position, then preheat the perforation position, take the inner perforation position as the cutting starting point, and use a flame cutting machine to cut out the inner groove as a whole in a symmetrical cutting manner from both sides of the steel plate; Use a flame cutting machine to cut symmetrically from both sides of the steel plate from the outer cutting starting point of the steel plate, and cut out a complete push rod body along the outer contour of the push rod body; Step 2. Cutting the bevel: Place the cut push rod body on a fixed workbench, use a plasma cutter to cut the edge of the internal groove of the push rod body to form a groove with a set depth and angle, and then cut the groove on the outer periphery of the push rod body; After cutting is completed and cooled to below the set temperature, the anti-deformation reinforcement is cut and removed, and all grooves and reinforcement removal areas are polished to see the metallic luster; Step 3. Assembly: Relying on the shape positioning tooling, the push rod head and the push rod tail are placed in the corresponding positions of the push rod body, wherein the push rod head and the front end of the push rod body are in L-shaped contact, which is a butt welding structure, and the push rod tail is sunk into the U-shaped opening at the rear end of the push rod body, which is an embedded welding structure; After assembly is completed, mark the tack welding position and perform tack welding after preheating; Step 4. Preheat: Preheat the workpiece as a whole to the set temperature; Step 5. Base welding: Use the robot welding platform to perform base welding on the entire weld of the push rod, and select the high penetration welding mode; Step 6) Filling and capping welding: Continue to use the robot welding platform to perform symmetrical filling and capping welding on the weld positions to fill the groove welds; Step 7. Cool, heat, keep warm, and slowly cool to room temperature.

2. The method for manufacturing an integral hydraulic support push rod produced by using Q890 grade extra thick steel plate according to claim 1 is characterized in that: In step 1), a plurality of push rod bodies are cut synchronously from a whole steel plate, and the close sides of two adjacent push rod bodies share the same weld.

3. The method for manufacturing an integral hydraulic support push rod produced by using Q890 grade extra thick steel plate according to claim 1 or 2, characterized in that: The overall preheating temperature of the steel plate is 100°C -150°C, the preheating temperature for internal groove perforation is 100°C -150°C, the perforation tool is a flame gun, the perforation preheating time is ≥13min, and the perforation speed is 0.05-0.1m / mim.

4. The method for manufacturing an integral hydraulic support push rod produced by using Q890 grade extra thick steel plate according to claim 3 is characterized in that: The cutting gas for internal groove cutting is natural gas, the combustion-supporting gas is oxygen, the oxygen pressure is 0.8-0.9MPa, and the cutting speed is 0.25-0.3m / min; The cutting gas for the outer contour of the push rod is natural gas, the combustion-supporting gas is oxygen, the oxygen pressure is 0.8-0.9MPa, the cutting speed is 0.05-0.1m / min, and the cutting speed after the steel plate is introduced is 0.25-0.3m / min.

5. The method for manufacturing an integral hydraulic support push rod produced by using Q890 grade extra thick steel plate according to claim 4 is characterized in that: In step 2, the groove depth of the inner groove edge is ≥25mm, the angle is between 30°-40°, the cutting speed of the groove is 0.6-0.8m / min, and after cutting, it is cooled to below 50°C before cutting the anti-deformation reinforcement.

6. The method for manufacturing an integral hydraulic support push rod produced by using Q890 grade extra thick steel plate according to claim 5 is characterized in that: In step 3, the preheating temperature of the tack welding position is 60°C -80°C, the preheating length range is 600-800mm, the tack welding is manual welding, the tack welding uses ER76-G φ1.4mm welding wire, the welding current is 300-320A, the voltage is 29-31V, the welding speed is 350-400mm / min, the length of each tack welding section is 300-500mm, the interval is 300-400mm, and the height is 4-5mm.

7. The method for manufacturing an integral hydraulic support push rod produced by using Q890 grade extra thick steel plate according to claim 6 is characterized in that: In step 4, the preheating temperature is 100-150°C; in step 7, the cooling process adopts slow cooling to 100°C, the temperature is raised to 350°C by a torch, the heat is kept warm by wrapping with asbestos cloth, and the temperature is slowly cooled to room temperature.

8. The method for manufacturing an integral hydraulic support push rod produced by using Q890 grade extra thick steel plate according to claim 7 is characterized in that: In step 5, Ar+20%CO2 mixed gas shielded welding is used, ER96-G φ1.6mm diameter solid welding wire; welding parameters: welding current 300-340A, voltage 28-30V, welding speed 40-45cm / min, shielding gas flow 15-20L / min, overall preheating 100-150℃ before welding; the welding gun of the welding robot is pointed to bisect the grooves on both sides and form an angle of 70° with the welding direction.

9. The method for manufacturing an integral hydraulic support push rod produced by using Q890 grade extra thick steel plate according to claim 8, characterized in that: In step 6, the welding adopts Ar+20%CO2 mixed gas shielded welding, ER96-G φ1.6mm diameter solid welding wire; filling and capping parameters: welding current 340-380A, voltage 29-31V, wire feeding speed 7-8m / min, welding speed 40-45cm / min, lateral sinusoidal oscillation of the end of the welding wire 1-4mm, welding wire dry extension 20-25mm, shielding gas flow 20-25L / min.

10. An integrated hydraulic support push rod, characterized in that: It is manufactured by the manufacturing method of the integral hydraulic support push rod produced by using Q890 grade extra thick steel plate as described in any one of claims 1 to 9; It includes the putter body, the putter head and the putter tail; The push rod body is a solid steel material obtained by integrally cutting a Q890 grade steel plate with a thickness of ≥100 mm; The head end of the push rod body and the push rod head are joined in an L-shape and grooved, and then fixed together by welding; A U-shaped opening is arranged at the tail end of the push rod body, and the push rod tail is embedded in the U-shaped opening and assembled with the push rod body. After a groove is arranged at the assembly position, the push rod tail is fixed together by welding.

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