The structural characteristics, working principle, main components and welding effect of the new single-column tube-plate automatic argon arc welding machine are introduced.
Key words : single column; automatic; argon arc welder
With the continuous improvement of heat exchanger manufacturing in China, various units have put forward higher requirements on the manufacturing quality and service life of heat exchangers, and the quality of heat exchangers and the length of service life are largely Depends on the quality of the tube-plate weld. In order to improve the welding quality and reduce the labor intensity, many manufacturers have successively developed tube-plate automatic welding machines. Some manufacturers have introduced tube-plate automatic welding machines from abroad, but due to the low dimensional accuracy and assembly quality problems of domestically produced pipes, These devices, which require high quality of the pipe, are difficult to get into normal use. Our company has purchased 3 sets of internal and external tube plate automatic welding machines, which have been unable to be used normally due to positioning and power supply maintenance problems. Based on this situation, our company has independently developed a double-column tube-plate automatic welder. After more than one year of use, the effect is good, but the structure is quite cumbersome. Later, the double-column tube-plate automatic welding machine was improved, and a new type of tube-plate automatic welding machine-single column type tube-plate automatic welding machine was developed. The welding machine simplifies the structure of the former welding machine, Lightweight and flexible to move, and ensure the quality of welding. The structure, composition and working principle of the new welding machine are now introduced.
1. The basic structure and working principle of the welder
This machine adopts the gantry structure which is completely different from the hanging type used in foreign countries and has more domestic use. Instead, it adopts the column type structure, which is mainly composed of welding head, electric control box, walking device and welding power source (Tangshan Panasonic TSP-300 tungsten argon arc welding machine) is composed of 4 major components. The machine head and the control box are mounted on the operating platform, and the platform can be moved up and down by the screw under the driving of the motor, and the traveling rail is specially arranged under the base. The entire welding head can also be moved in a small range of front, rear, left and right by the adjustment of 2 handwheels. In order to make the positioning more accurate, a positioning core sleeve is specially designed at the top of the welding head. The welding speed of the machine head can also be controlled by electric control according to the diameter of the welded pipe, the thickness of the workpiece and the welding material (1.6-18.9r/s).
2. The main components of the welder
2.1 Structure of the welding head
The welding head is mainly composed of a welding gun body, a power drive and a welding machine. The gun body is equipped with a tungsten pole, a tungsten pole clamp, a shunt and a ceramic nozzle; in addition, the gun body is also provided with water, electricity and gas passages. The power drive mainly has two parts, one part is a DC motor reducer driving one pair of gears to rotate the torch; the other part is a DC motor driven drive wheel, which is used to drive the wire. The rotating machine part, that is, the rotating part is shown in Fig. 2, and the part 10 on the way is the centering core sleeve, and its function is to adjust the concentricity of the rotating track of the tungsten pole and the pipe by the taper positioning method. Due to the large error of the domestic pipe, the inner diameter deviation of the pipe is often between ±0.30mm. It is not easy to do with the inner hole positioning method, and the error is large. Therefore, with taper positioning, in the case where the tube plate surface and the machine head are straight and vertical, the taper head is used to locate the hole. As long as the tube tube burr is removed, if there is a slight error in the taper positioning, it can be jogged. Or mechanical fine-tuning to adjust until it is centered. When the part is 9, the centering rod is used to position the centering core sleeve so as not to shake; the part 8 is a conductive copper ring, which is a part of the brush, and functions to transfer the power to the tungsten pole; the part 6 is Spring wrench, its role is to adjust the centering rod to move back and forth, automatically reset by the spring.
2.2 wire feeding mechanism
The wire feeding mechanism is mainly composed of a wire feeding head, a wire feeding pipe and a wire feeding wheel. The design features of the wire feeder mechanism are mainly fixed by the clamping body and the tension spring is reset, so that the position direction of the wire feeding head is easier to control. The wire feed wheel is fixed to the rotating body and rotates together with the welding head. The wire feeding method is to use a motor to drive a single driving wheel to drive the wire.
2.3 The movement of the welder on the guide rail and the brake structure
Four wheels are mounted under the base of the welder to allow the welder to move along the guide rails, and in order to make the welder run smoothly, a rolling bearing is placed in contact with the flat side of the guide rail. In order to make the nozzle and the tungsten poles accurately aligned, the quality of the welding machine brake device is particularly important. The brake structure of the welder is shown in Fig. 4. It is mainly composed of four parts: clamping plate, brake body, DC wet electromagnet valve, lock nut and screw.
In normal times, the inner spring of the component drives the brake body and the screw to clamp the guide rail through the clamping plate, so that the welder is in a braking state. When the welding machine is to be driven, the DC wet electromagnet valve is moved to the right after being energized (see the above figure in the moving direction), and the clamping plate is moved to the right to reduce the upper distance of the two brake bodies, thereby opening the lower part of the brake body. The rail is opened and the welder begins to walk. After the power is turned off, the electromagnet is non-magnetic, and the clamping plate returns to the clamped state under the action of the internal spring of the DC electromagnet valve. The feature of this brake structure is that the welder is in a braking state when it is not walking, thereby making the positioning of the head more convenient.
3. The electrical principle of the welder
The main working part of the machine is realized by a program controller composed of integrated circuits, and its simple principle
There is one start switch on the head of the machine. Only when the starting position is reached, the program can enter the automatic control state when the switch is reset. There are five kinds of welding method selection switches for this machine. When a certain welding method is to be performed, as long as Rotate the selector switch to the desired position and the machine head can be soldered in accordance with this procedure. The nose rotates. The wire feeding motor speed control circuit is realized by various feedback and thyristor phase shifting circuits. The horizontal moving distance is controlled by the inductive counter, and each movement is 1mm, which ensures the accuracy of moving to the next weld seam after each welding. Sex (such as 36 tubes with a distance of 36mm). In addition, the "arbitrary repair welding position", the ascending and descending control, the jog and the step, and the stepping of the horizontal movement of the machine are realized by a control circuit composed of a transistor and a thyristor. The welding power supply of this machine adopts DC pulse TIG welding, and various methods and parameters can be selected and welded according to different needs.
4. Precautions during use
When using this automatic welder, in order to obtain high-quality welding performance, the pipe itself has strict quality requirements. Firstly, the elongation of the pipe is longer than the manual welding, generally 4-5mm is preferred, too long will reduce the weld penetration, the weld is not beautiful; too short will cause undercut, pipe breakage and other defects . Secondly, the cleanliness of pipes and tube sheets is relatively high. The tube sheet is preferably cleaned with an alkali or organic solution, and the tube is sanded to a metallic luster. Into the bone can not do the above requirements, the pores will appear when welding, affecting the quality of welding. The third requirement is that the groove of the tube plate should not be too large, generally the chamfer is ≤ 2mm, and the best is 1mm. If the groove is too large, it is easy to burn the tungsten rod, and if it is too small, the penetration is not enough.
5 Conclusion
To sum up, the welder has the following advantages:
a. The welding machine is easy to operate, convenient to position, and has wide applicability;
b. The cost is low, the structure of the welder is relatively simple, and it is convenient to repair compared to other welders.
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