JPS6358079B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coating method for coating a core wire with flux when automatically producing coated welding rods.

In the coated welding rod manufacturing process, a wet-kneaded flux adjusted to the desired composition is applied around the core wire, and then sent to a drying process to be dried and, if necessary, fired to form a coated welding rod. However, in this coating process, it is necessary that the flux be coated uniformly around the core wire with sufficient adhesion strength, but in practice various problems are encountered. This will be explained based on FIG. 1, which shows an overview of flux coating.Flux 2 is shown in the figure, which is obtained by selectively mixing powders of various metal oxides, silicate compounds, carbonates, etc., and then kneading them with water glass and wet-mixing them. However, a cylindrical molded product is formed using a molding machine, and a plurality of the molded products are placed in series on the receiving plate 4 of the coating machine 1. This is made into one lot, pushed into the flux cylinder 5 by the piston 6 of the hydraulic cylinder 7 (the flux shows this pushed state in the figure), pressurized and pushed out from the die 9 of the die head 8, and at the same time, The core wires 3 are supplied one by one from the core wire feeder to a die head 8 via a guide 10, and are extruded from the die head with the flux 2 of a constant thickness coated around the core wires. The supply of the core wire 3 is carried out sequentially and continuously until the pressure extrusion of the flux 2 for one lot is completed, and when the extrusion limit is reached, as shown in FIG. , the piston 6 returns to the starting position and receives the flux of the next lot waiting on the side of the receiving plate 4 onto the receiving plate 4, and repeats the above-mentioned pressure extrusion operation again. The core wire supply operation is interrupted from the completion of extrusion of one lot of flux to the start of extrusion of the next lot of flux, but, of course, the shorter the interruption time, the higher the operating rate of the apparatus and the higher the productivity. However, when the piston 6 is moved back at high speed for the purpose of shortening the interruption time, air cannot flow in from the air vent groove 11 in time, creating a vacuum state and the residual flux peeling off from the inner wall of the die head, following the piston and causing the same flow. It becomes collapsed as shown in Figure C. When the flux of the next lot is received on the receiving plate 4 and pressed again with the piston 6 in such a state, air tends to accumulate between the current flux molded product and the flux residue from the previous time, and this air cannot escape through the air vent groove 11. It is easily compressed and mixed into the flux. If air is present in the flux, good pressure bonding cannot be achieved when the flux 2 is applied around the core wire 3 by the die 9, and it becomes difficult to form a coating with a uniform thickness. Furthermore, as the surrounding pressure of the coated welding rod passing through the die 9 and coming out of the coating machine changes drastically from high pressure to atmospheric pressure, the air in the coated flux layer expands rapidly, causing the flux layer to peel off,
This will cause cracks in the coating.

In the end, in the past, if the piston retraction speed was slowed, the interruption time would become longer, leading to a decrease in the coating machine operating rate, and if the retraction speed was increased, defective welding rods would occur, reducing the coating yield. Ta.

The present invention was devised in view of the above-mentioned drawbacks of conventional devices, and when the flux extrusion piston finishes extruding flux and retreats, the piston head and the residual flux are separated for a short period of time (1 to 5 minutes).
The piston is retreated at a low speed for a period of seconds), and while the piston is retreating at a low speed, an air bleed valve is opened to allow air to flow into the flux cylinder to prevent the generation of a vacuum state,
Also, by reducing the adhesive force between the piston and the residual flux, the final pressed state is maintained without breaking the residual flux in the die block, and the air vent valve is opened during the next flux filling and extrusion to prevent air from entering the flux. , it became possible to successfully apply flux coating to the core wire. Examples will be described below.

2 and 3 show embodiments of the invention,
The same parts as in FIG. 1 are given the same reference numerals. In Fig. 2, 14 is a solenoid valve that opens and closes the air hole 5a provided in the flux cylinder 5, 15 and 16 are motors that drive the hydraulic pumps 17 and 18, 19 is a check valve, 20 is an oil tank, and 21 is an electromagnetic switch. Valve, PS1 is a switch operated by hydraulic pressure inside the pipe, 23 is piston 6
This is a limit switch that detects the forward limit of the engine.
In Fig. 3, Pb3A is a push button switch for starting the motors 15 and 16, Pb3B is a push button switch for stopping the same,
Pb36 is the push button switch for advancing the piston 6, Pb37
is the reverse push button switch. start switch
Close Pb3A and relay RM3 and delay relay
TM3 is energized, contact RM3'(' indicates the contact of the relay) closes and holds itself, and energizes the electromagnetic contactors M3Y, M1Y of motors 15, 16 and delay relay TM1. Therefore, the low pressure pump motor 15 and the high pressure pump motor 16 are Y
Activated by wiring and delayed relay TM3 after a predetermined time.
TM1 operates and switches its contacts TM3' and TM1', de-energizes the magnetic contactors M3Y and M1Y, and M3
Δ and M1Δ are energized to cause the motors 15 and 16 to enter the operating state with the Δ connection. Note that Th3 and Th1 are thermal relay contacts for protection. Next, when the forward push button switch Pb36 is pressed, the relay R36 is energized, the contact R36' is closed, and the solenoid SOL1a of the electromagnetic switching valve 21 is energized, and the switching valve is connected to the piping _l1 where pressure oil is supplied to the piping l. ₂ is switched so that it is connected to the oil tank 20. Therefore, the piston 6 moves forward, pushing the flux compact into the cylinder 2 and pressing it. When the flux in the cylinder reaches a predetermined pressure due to the pressure, the core wire begins to be supplied to the core wire guide 10, and coating begins.

When the piston 6 reaches its forward limit and one cycle of painting is completed, this is detected by the limit switch 23. That is, the switch 23 closes at the forward limit of the piston 6 and energizes the relay R15.
Contact R15' of relay R15 opens and closes to deenergize relay R36 and relay R37, and closes contact R37' to energize solenoid SOL1b of electromagnetic switching valve 21. Therefore, the switching valve switches to connect the pipe _l2 to the pressure oil and the pipe _l1 to the oil tank, and the piston 6 starts to retreat. At this time, relay
1Δ is energized. For this reason, the low pressure large capacity pump 17
The motor 15 of is stopped, and the piston 6 is retracted at low speed only by the motor 16 of the high-pressure, small-capacity pump 18. In addition, timers TO2 and TO1 start operating by energizing relay R37 and closing contact R37', and after a predetermined time, contact TO1' of timer TO1 closes, relay XO2 is energized, contact XO2' opens, and the solenoid SOL1b is deenergized, the pressure oil supply is stopped, and the retraction of the piston 6 is temporarily stopped. The changeover switch PS1 responds to the hydraulic pressure in the pipe _l1 , and when the hydraulic pressure is high and therefore during painting, it switches to the contact on the right side of the drawing, and when the oil pressure drops after painting, it switches to the contact on the left side of the drawing, so the solenoid valve No. 14 solenoid 2a is energized and the solenoid valve opens air hole 2a. This air hole 2a is provided in the flux cylinder 5 so as to be located at the contact surface between the tip of the piston 6 and the residual flux in the die head 8 at the forward limit, so that when the piston 6 starts to retreat,
Air is allowed to flow into the created gap to prevent the creation of a vacuum. Moreover, since the piston 6 moves back at a slow speed and then stops, sufficient air can flow in, and there is no residual flux collapse as shown in FIG. 1C.

When relay XO2 is energized and contact XO2' is opened, relay XO1 is deenergized and contact XO1' is closed to start motor 16. Also a timer
When TO2 opens contact TO2' after a predetermined time, the timer
TO1 and relay XO2 are deenergized and contact XO
2' is closed and the solenoid SOL1b is energized, so that the piston 6 is moved back at high speed by the high pressure pump 18 and the low pressure pump 17. Therefore, although the piston 6 temporarily slows down and stops when retracting, most of the remaining piston 6 retracts at high speed, so the overall time required is short and the operating rate is improved.

The push button switches Pb36 and Pb37 are used to manually move the piston 6 forward and backward, and the push button switch Pb38 is used to stop it. Note that the circuit shown in Figure 3 uses many locking contacts,
Since these are well-known security techniques, detailed explanations will be omitted.

As explained above, according to the present invention, it is possible to prevent cracking of the welding rod coating due to air intrusion caused by the collapse of flux remaining in the die block by a simple means, and improve the yield of coated welding rod production. In addition, the work of removing defects by the operator can be omitted, which greatly contributes to improving productivity.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of flux coating procedures and problems, and FIGS. 2 and 3 are piping diagrams and wiring diagrams showing embodiments of the present invention. In the drawing, 1 is an automatic coating machine, 2 is a flux, 3 is a core wire of a coated welding rod, 6 is a flux pressing piston, 5 is a flux cylinder, 5a is an air hole,
17 and 18 are hydraulic pumps, 15 and 16 are drive motors thereof, and 21 is a switching valve.

Claims (1)

[Claims] 1. In a coating method for coated welding rods using an automatic coating machine, after a predetermined amount of flux in a flux cylinder is coated on a core wire supplied from a separate process by advancing a flux press piston, the flux press piston and the flux 1. A method for coating a coated welding rod, which comprises causing air to flow into a boundary between the electrode and the welding rod, at the same time retracting a press piston at a low speed for a predetermined short period of time, and then retracting the press piston at a high speed.