A special: title discussion I special and special, complete sets of welding equipment steel sign capacitor storage spot welding machine development bookmark0 Guan Gonghu, Wu Gaobiao, Shao Chunbo bookmark1 Taizhou University School of Mathematics and Information Engineering, Zhejiang Linhai 317000) hardware components and software components. The spot welding machine has a simple control circuit and is convenient to operate, and can be used for the end face of the bar and the welding of the wire sign hanging piece. Improve the grade of the tag, more effectively prevent the card change and drop. Through production practice, the machine runs stably and reliably, and the welding effect is good.
0 In the steel production, manufacturers need to fix the signs to indicate the manufacturer, specifications, grades, quality, flood season and other relevant parameters of the steel. Especially in the production of wire and bar, the existing tag technology mainly uses wire or steel band bundling, end stud welding and so on. Although the method of using wire or steel strapping is low in cost, the signage is easy to lose during the handling process, and the counterfeit manufacturer is provided with a counterfeit opportunity. At the same time, the bundles of bars are generally placed in the process of production, sale and storage. The signs are buried in the raft and the relevant parameters of the signs are unrecognizable, and it is difficult to correct once the errors are posted. For the end stud welding, the welding nail is first placed in the welding machine, and the sign is hung on the welding nail. The tip arc is used to weld the sign to the surface of the base material by using an instantaneous arc. The weakness of this method is to specially prepare the welding nails, which increases the cost and working hours. The capacitor energy storage spot welder we developed uses an exclusive lanyard, puts a label on it, and welds the lanyard to the end face of the bar; or hangs the lanyard through the wire and then welds the lanyard. This can well meet the needs of the wire and bar produced by the steel mill, does not blacken and damage the signage, and is convenient for research on MCU development and automatic welding control.
Capacity (unit: F); U is the charging voltage (unit V). When soldering, the welding heat is adjusted by adjusting the charging voltage of the capacitor.
The main circuit of the capacitor energy storage spot welder is mainly composed of a charging circuit and a discharging circuit as shown. The crystal tubes VTi, VT2 and VDi~V4 form a charging circuit. After the 220V single-phase AC power is stepped down by the transformer T, it is controlled by two anti-parallel VTi and VT2, and then the full bridge rectifier circuit composed of VDiWD4 converts the alternating current into direct current to charge the capacitor group C, when the capacitor voltage reaches the given value. After that, turn off the charging circuit. The charging current satisfies the formula (2) 1: one special: the discussion and special, the complete set of welding design fee. In this charging mode, the charging current impact value at the beginning of charging is very large, under the condition of a certain power supply voltage, only through Increasing the current limiting resistor of the charging circuit to reduce the inrush current, but this inevitably increases the charging time constant T=RC, which is not conducive to high-speed recharging. At the same time, since the power consumption on the resistor is greater than the energy stored on the capacitor, the charging efficiency is low. Therefore, the use of current limiting charging overcomes the disadvantage of using current limiting resistors. Here VTi and VT2 act as both an electronic switch and a charge current.
The discharge circuit is composed of a crystal tube VT3, and the energy stored in the capacitor group is heated and welded by the VT3. Potentiometer RP: adjusts the capacitor charging voltage, which is indicated by the voltmeter V. At the same time, the voltage is compared to a given voltage by the comparator and then sent to the microcontroller. When the capacitor is charged to a given voltage, it passes through two anti-parallel VTi and The VT2 crystal tube cuts off the charging circuit. The trigger timing of the discharge transistor V3 is controlled by software timing to ensure that the charging circuit and the discharge circuit work independently, avoiding the phenomenon of straight-through. The switch K and the resistor R constitute a discharge circuit, which acts as a discharge during the stop of the welder or the regulation of the charging voltage.
2 single-chip control system 21 hardware system microcontroller hardware system composition as shown. It consists of single-chip AT89C51H, synchronization signal, welding switch, capacitor voltage acquisition, charge/discharge trigger signal, etc. All input and output signals of the single-chip microcomputer are isolated by optical diaphragm.
The synchronization signal is obtained by passing the 50Hz sinusoidal alternating current into a positive half wave of 100Hz by bridge rectification, and then comparing with the comparator to obtain a synchronization pulse of the zero crossing point. In the current-limited charging process, phase shift charging starts from 180°, ensuring that the initial charging current is not excessive and reduces the impact on the capacitor. As the capacitor voltage increases, the phase shift angle gradually decreases, ensuring a constant charging current. The collected capacitor voltage is compared with a given voltage by the comparator to obtain a charging voltage signal, which is sent to the AT89C51 of the single chip microcomputer, and when the signal is received, the charging signal is stopped. When the welding switch is pressed, the AT89C51 sends a discharge trigger signal, which discharges the energy stored in the capacitor through the workpiece and turns it into a welding process. The sampling signal of the protection circuit is also from the sampling circuit of the charging voltage. This signal is compared with a certain reference voltage. When the charging voltage reaches the specified limit voltage, the protection circuit acts immediately to realize the protection function and is indicated by the indicator light.
The main program flow of the 22 software system software system is as shown. The software design fully considers the timing of the microcontroller and the powerful functions of direct I/O port operation. It adopts modular structure programming, and mainly consists of subroutines such as current charging, discharging and alarm. The entry and exit of each block and the occupation of internal registers are clearly defined, and the combination can be separately debugged to have strong versatility.
A special: topic discussion I special and special, complete sets of welding equipment surfacing and its process requirements are: After the microcontroller power-on reset, the initialization module becomes the initialization of the timer and special registers; then start current-limiting charging, when the capacitor When the charging voltage reaches a given voltage, the charging is terminated. When welding, the welding grabs the workpiece, presses the welding switch, and discharges the capacitor. The next round of charging can only be carried out after the welding switch has been released. If the welding is released and pressed against the workpiece after the welding switch is released, there is a possibility that the charge and discharge circuit will pass through. At this time, when the charging voltage of the capacitor does not reach a given voltage for a long time, the charging circuit is sealed and an alarm indication is given.
This can well overcome the charge-discharge loop through phenomenon.
3 anti-interference measures anti-jamming technology of single-chip microcomputer has been the key link of its application. 2234. Hardware, the use of switching power supply can form a strong suppression of high-frequency common mode interference, metal box shielding measures can hinder space electromagnetic interference, but grounding Must be reliable; optical isolation can separate the main circuit ground from the analog ground of the microcontroller.
In terms of software, the software traps and fault-tolerant techniques of instruction redundancy are adopted; the signal output channel adopts repeated output to improve the anti-interference ability of the digital signal.
4 The production and evaluation of the steel sign capacitor energy storage spot welding machine, the capacity of the capacity of Zhang Yong, Yang Siqian, Bai Gang, and other 30000WS capacitor energy storage welding machine microcomputer control system. Electric Welder, 2001, 31 (3): 25-26, 46. Zhou Haobin, Sun Huizhu, Ma Xiaomei A circuit design for a new capacitor energy storage welder. Journal of Welding, 2006 (11): Li Chaoqing. Principle and interface technology of single-chip microcomputer M. Beijing: Beijing University of Aeronautics and Astronautics Press, 1994. Prevent cracking and peeling of surfacing layer. The weld metal after surfacing has high hardness and low plasticity. Especially when the metal composition of the surfacing metal is relatively different from the basic metal composition, the linear expansion coefficient of the metal is large, which causes considerable internal stress, so that the surfacing layer is piled up. In the cooling process after welding, cracks and peeling of the weld overlay layer are easily generated (the metal of the weld overlay layer is peeled off from the substrate). The main way to prevent is to reduce the welding stress during surfacing. The specific measures are: overall preheating of the weldment or reasonable local preheating, or by using the isolation layer surfacing method, that is, the plasticity is good first, the strength is not High ordinary welding rods or stainless steel welding rods are used for bottom welding to isolate the surfacing layer from the base metal.
Prevent the hardness of the weld overlay from meeting the requirements. The hardness of the weld overlay is obtained by the alloy composition of the weld overlay, and the alloy composition is derived from the weld material (solder, wire, flux) rather than the parent metal. Therefore, when surfacing, it is desirable to have a shallow depth of fusion and a small fusion ratio, so it is not suitable to use a large current. Due to the dilution of the base metal to the weld metal, the hardness of the first layer is often low, and the hardness of the remaining layers is gradually increased. Generally, the hardness does not change substantially after the third layer.
Prevent deformation of surfacing parts. When welding the surface of a slender shaft and a cylindrical part having a large diameter and a small wall thickness, it is considered to prevent deformation after welding.
1 process requirements for surfacing.
Welding to increase or restore the size of the weldment, or to obtain a deposited metal with special properties on the surface of the weldment is referred to as surfacing. For different purposes, surfacing can be divided into the following four types: cladding surfacing. When the surface of the weldment is in contact with the corrosive medium, in order to make the surface corrosion-resistant, a filler metal layer of a certain thickness is deposited on the carbon steel or alloy steel base material.
Hardfacing. A surfacing layer used to reduce abrasive wear, impact, corrosion, and cavitation on the surface of the weldment.
Thickened surfacing. Weld metal is added to the weldment surface, joint green or previously welded metal to restore the required dimensions of the component.
Separation layer surfacing. When welding dissimilar materials or materials with special requirements, in order to ensure the joint quality and performance, a certain layer of metal layer which is previously deposited on the surface of the base material (or the groove surface) is called a separator. The process of depositing the isolation layer is called the isolation layer surfacing.
3 Surfacing welding is characterized in that it does not connect two separate parts to one, but only welds a layer of deposited metal on the surface of the weldment, so the process
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