JPS6149566B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic welding preheating control device that preheats a part of a base material to be welded to an appropriate preheating temperature and maintains this appropriate preheating temperature.

When welding base metals, the part to be welded is generally preheated. The main purpose of this preheating is to slow down the cooling rate of the weld zone to prevent cracking and hardening of the heat-affected zone, but it also aims to balance thermal strain to reduce residual stress and welding deformation. Or to prevent insufficient penetration of welded parts, and even dehumidify.
Sometimes the purpose is to remove combustible materials. As an example of preheating, FIG. 1 shows a preheating operation for a cylindrical base material to be subjected to circumferential welding. In FIG. 1, a cylindrical base material 1 is rotatably installed with the parts to be welded against each other, a welding machine 2 is placed above the part to be welded, a main burner 3 for preheating is placed below the part to be welded, and the welding machine 2 is placed above the part to be welded. Auxiliary preheating burners 4 are installed between the main preheating burner 3 and the welding parts, respectively. Base material 1
The part to be welded is heated by the main burner 3 and the auxiliary burner 4 until it reaches an appropriate preheating temperature. When the temperature of the part to be welded reaches the appropriate preheating temperature, welding is performed using the welding machine 2.

As mentioned above, the main burner 3 and the auxiliary burner 4 are used to heat the welded part of the base metal 1 to an appropriate preheating temperature, and acetylene gas, propane gas, etc. are mainly used as the heat source. Preheating temperature control ``Adequate preheating temperature maintenance control'' relies on the experience of on-site workers and manually controls the flow rate of the heat source, so ``maintaining appropriate preheating temperature'' is difficult, and in some cases it may cause damage to the part to be welded. The temperature drops, and in extreme cases, cracks occur, and because there is no proper temperature control method, a lot of fuel is wasted. Furthermore, since the "appropriate preheating temperature" of the base material differs depending on the material and thickness of the base material, it has been difficult to ensure the "appropriate preheating temperature" by manual operation by an operator.

The present invention automatically secures and maintains an "appropriate preheating temperature," which was conventionally performed manually based on the operator's experience. The purpose of this is to shorten the time required for preheating, further reduce fuel consumption, save resources, save energy, save labor, and reduce product costs. A main burner and an auxiliary burner that move relative to each other to preheat the welded part of the base metal, a temperature detector that measures the temperature of the welded part, and an appropriate preheating temperature at which the welded part should be preheated are set. a preheating temperature setting device, a subtractor for calculating the measured temperature of the welded part measured by the temperature detector and the appropriate preheating temperature set in the preheating temperature setting device, and a calculation result by the subtractor. a regulator that outputs a valve opening command signal according to the valve opening command signal, an air flow control valve that adjusts the flow rate of air in response to the valve opening command signal from the regulator, and an air flow rate control valve that adjusts the flow rate of the air by the air flow control valve. a mixer that mixes the fuel from the fuel pipe and the fuel from the fuel pipe to generate combustion gas to be sent to the main burner and the auxiliary burner; and a combustion gas pipe that guides the combustion gas generated in the mixer to the main burner. A main burner load cutoff valve is provided and capable of cutting off the supply of combustion gas to the main burner, and a valve opening command signal from the regulator is input, and the valve opening command signal is less than or equal to a preset value. A main burner load cutoff command generator gives a cutoff command to the main burner load cutoff valve so that combustion gas is sent only to the auxiliary burner, and a valve opening command signal from the regulator adjusts the air flow rate. Even if the valve is almost closed, the opening degree of the air flow rate control valve is such that the minimum amount of combustion gas can be ensured to prevent the auxiliary burner from blowing out. A lower limiter is provided.

Next, an embodiment of the present invention is shown in the drawings, and the embodiment will be described in detail based on the drawings. FIG. 2 shows a schematic diagram of an embodiment, in which a cylindrical object is used as the base material. In Fig. 2, the base material 1 is connected to two rotating machines 5.
It is placed on the board and can be rotated in the direction of the arrow.
a welding machine 2 that performs welding above the part to be welded of the base material 1; a main burner 3 that performs preheating below the part to be welded;
Auxiliary burners 4 for preheating are installed between the welding machine 2 and the main burner 3, each facing the welded part. A temperature detector 6 is provided near the welding machine 2 to detect the temperature of the welded part to be welded,
The temperature detector 6 is connected to a subtracter 7 and sends a detection signal to the subtracter 7. A preheating temperature setter 8 is connected to the subtractor 7 and sends a preset preheating temperature as an output signal. This preheating temperature setting device 8 is a setting device that changes a suitable preheating temperature of the base material 1 in a programmatic manner, taking into consideration the dimensions, material, etc. of the base material 1. The subtractor 7 is connected to a regulator 9 that performs a regulating operation, and the regulator 9 is connected to an air pipe 12 provided in the middle of an air pipe 12 through which air is supplied by the operation of an air source 11 via a lower limiter 10. It is connected to the flow rate control valve 13. Said lower limiter 1
0 means that the opening of the air flow rate control valve 13 is below a certain value (below the blowout limit of the auxiliary burner 4, that is, below the minimum stable combustion range). Air fed into the mixer 14 and the mixer 1 from the fuel source 16
A fuel mixture (combustion gas) is generated by mixing an appropriate amount of fuel sucked in according to the amount of air in the mixer 14 through a fuel pipe 15 connected to the fuel pipe 15 connected to the mixer 14. The mixer 14 is configured to guide the mixture to the main burners 3 and 4 as a heating source through a mixture pipe (combustion gas pipe) 17 and mixture pipes (combustion gas pipes) 17a and 17b that branch from the mixture pipe 17. It's getting old. The regulator 9 also connects the mixture pipe 17a to the main burner 3 via a main burner load cutoff command generator (hereinafter abbreviated as cutoff command generator) 18.
The main burner load cutoff valve 19 is connected to the main burner load cutoff valve 19 provided in the The mixture pipe 17b connected to the auxiliary burner 4 is also provided with an auxiliary burner load cutoff valve 20.

Next, the preheating temperature control of the base material 1 will be explained with reference to FIGS. 3a, 3b, and 3c, which show mutual changes between time and base material temperature, time and valve opening degree, and time and burner load. In FIG. 3a, the horizontal axis indicates time h, and the vertical axis indicates temperature °C. In the figure, a indicates a change in the "preheating temperature set value", and b indicates a change in the "preheating temperature". Figure 3b
, the horizontal axis represents time h, and the vertical axis represents the valve opening percentage of the main burner load cutoff valve 19 and the air flow control valve 13. In the figure, c represents the change in the valve opening degree of the main burner load cutoff valve 19. , d indicate changes in the valve opening degree of the air flow rate control valve 13. In Figure 3c, the horizontal axis is time h
, the vertical axis indicates the burner load percentage of the main burner 3 and the auxiliary burner 4, and in the figure, e indicates a change in the burner load of the main burner 3, and f indicates a change in the burner load of the auxiliary burner 4.

In the "preheating temperature setter" 8, the preheating temperature of the base material 1 is programmed with respect to changes over time, as shown by a in FIG. 3a. The welded portion of the base material 1 is preheated with this "preheating temperature set value" a as a target. At the start of preheating, the main burner load cutoff valve 19 and air flow control valve 13 are fully open as shown in Fig. 3b, so the base metal 1 is welded at 100% burner load of the main burner 3 and auxiliary burner 4. section is preheated. The temperature of the heated portion of the base material 1 to be welded is detected by a temperature detector 6, and a temperature detection signal is sent to a subtracter 7. The "preheating temperature set value" a as shown in FIG. 3a is also sent to the subtracter 7 from the "preheating temperature set value" 8 as an output signal, and calculation is performed between it and the previous temperature detection signal. At this time, if the temperature detection signal is smaller than the output signal which is the "preheating temperature set value" a, the output of the subtractor 7 becomes positive, and the output (valve opening command signal) of the regulator (for example, PID regulator) 9 is The opening degree of the air flow control valve 13 is increased via the lower limiter 10. The opening degree of the air flow rate control valve 13 increases, and the air flow from the air source 11 to the air pipe 1 increases.
2. When the air flow rate flowing through the air flow control valve 13 to the mixer 14 increases, the amount of fuel sucked into the mixer 14 from the fuel source 16 through the fuel pipe 15 increases, and the mixture pipe 17 and the mixture Piping 17a
The air-fuel mixture and air-fuel mixture pipe 17 lead to the main burner 3 through the air-fuel mixture pipe 17b, and the auxiliary burner 4 through the air-fuel mixture pipe 17b.
The load on the main burner 3 and the auxiliary burner 4 increases due to the increase in the air-fuel mixture flowing to the main burner 3 and the auxiliary burner 4. As a result,
The amount of heat given to the base material 1 increases, and as shown in Figure 3 a and b.
The rate of increase in base material temperature increases as shown in .

Due to the above action, when the temperature detection signal of the temperature detector 6 approaches the "preheating temperature set value" a, which is the output of the "preheating temperature setting device" 8, the absolute value of the temperature signal difference created by the subtractor 7 becomes smaller. , the valve opening command signal, which is the output of the regulator 9, becomes smaller. When the valve opening command signal becomes smaller, the valve opening of the air flow control valve 13 becomes smaller as shown by d in FIG. 3b, and the main burner 3 and auxiliary burner 4 The amount of air-fuel mixture sent to the base material decreases, and the rate of increase in base material temperature decreases. As the valve opening command signal to the air flow control valve 13 becomes smaller, the main burner 3 and the auxiliary burner 4
If the burner load becomes too small, the risk of burner misfire or backfire increases, so the value of the valve opening command signal, which is the output of the regulator 9, should be set to a certain value (for example, 20%).
When the following occurs, a main burner load cutoff signal is sent from the cutoff command generator 18 to the main burner load cutoff valve 19, and the main burner load cutoff valve 19, which had been fully open until then, is switched off as shown in c in Fig. 3b. The burner load of the auxiliary burner 4 is increased by completely closing the air-fuel mixture from the mixer 14 to the auxiliary burner 4.
As shown in Figure c, the combustion is stabilized by raising the temperature relatively. The operation of the control system after cutting off the burner load on the main burner 3 is the same as when both the main and auxiliary burners 3 and 4 are loaded, but the difference is that only the auxiliary burner 4 is controlled. The part to be welded of the base metal 1 is continued to be heated only by the auxiliary burner 4, and when the temperature detection signal by the temperature detector 6 sufficiently approaches the "preheating temperature set value" a, which is the output of the "preheating temperature set value" 8, the adjustment is performed. As the value of the valve opening command signal output from the mixer 9 becomes smaller, the valve opening of the air flow control valve 13 also becomes smaller as shown in FIG. The possibility of misfire or backfire of the auxiliary burner 4 increases slightly. In order to prevent this, the lower limit limiter 10 provided between the regulator 9 and the air flow control valve 13 operates so that the value of the valve opening command signal is below a certain value (below the blowout limit of the auxiliary burner 4). In other words, by setting a lower limit value for the opening degree of the air flow rate control valve 13 as shown in g in Fig. 3b, the allowable minimum flow rate of the air-fuel mixture to the auxiliary burner 4 is set. secure. The lower limit of the burner load of the auxiliary burner 4 is indicated by g' in FIG. 3c.

As explained below with reference to examples, the automatic welding preheating control device of the present invention detects the temperature of the part to be welded of the base material, and compares this detected value with a preset "preheating temperature setting value". Based on the calculation result, a valve opening command signal is issued to adjust the opening of the air flow control valve, and the flow rate of the air-fuel mixture to the main burner and auxiliary burner that performs preheating is adjusted. The temperature of the part to be welded should be brought close to the preheating temperature, and if the flow rate of the mixture to the main burner and auxiliary burner becomes small, the supply of the mixture to the main burner will be cut off.
The air-fuel mixture is fed only to the auxiliary burner, and when the air-fuel mixture flow rate becomes smaller, the minimum allowable amount of air-fuel mixture is fed to the auxiliary burner. The preheating work is not limited to butt welding of cylindrical objects as shown in the example shown, but is also applicable to butt welding of flat plates, welding of cylindrical objects in the axial direction, and welding of flat plates and cylindrical objects as shown in FIGS. 4, 5, and 6. This can be applied to preheating work such as welding. Figures 4, 5, and 6 show the arrangement of the main burner, auxiliary burner, and welding machine with respect to the base metal in each case. In Figure 4, 1a is a flat plate that is the base metal, 2a is a welding machine, and 3a is the main burner,
4a is an auxiliary burner, 1b is a cylindrical base material, 2b is a welding machine, 3b is a main burner, 4
b is an auxiliary burner, in Fig. 6, 1c is a flat plate, 1d is a cylindrical object, 2c is a welding machine, 3c is a main burner, 4
c is an auxiliary burner.

Furthermore, in the embodiment shown in FIG.
Although the base material 1 is rotated by the welding mechanism, the welding machine 2, main burner 3, and auxiliary burner 4 may be moved along the welded part. Even if the base material is not a cylindrical object, it is possible to move the welding machine, main burner, and auxiliary burner to perform preheating and welding.

As described above with reference to the embodiments, the automatic welding preheating control device of the present invention includes a main burner that preheats the temperature of the part to be welded of the base material to follow a preset "appropriate preheating temperature"; The mixture flow rate to the auxiliary burner is controlled, and when the heating of the part to be welded progresses and the mixture flow rate decreases, the mixture is sent only to the auxiliary burner for preheating, and the mixture flow rate to the auxiliary burner is Since the temperature does not exceed a certain level, the time required to raise the temperature of the part to be welded can be shortened, and preheating can be performed efficiently, making it possible to save fuel.
Moreover, safe preheating work can be performed without the risk of misfire or backfire. Furthermore, since an appropriate preheating temperature of the welded part can be maintained, the quality of the welded product can be improved.

[Brief explanation of the drawing]

Fig. 1 is a schematic perspective view showing a conventional preheating operation, Fig. 2 is a schematic diagram showing an embodiment of the present invention, and Figs. Graphs showing changes in material temperature, changes in valve opening over time, and changes in burner load over time, and Figures 4, 5, and 6 show the positional relationships of the main burner, auxiliary burner, and welding machine when the base material is changed. FIG. In the drawing, 1 is the base material, 2 is the welding machine, 3 is the main burner, 4 is the auxiliary burner, 6 is the temperature detector, 7 is the subtractor, 8 is the "preheating temperature setter", 10 is the lower limit limiter, and 13 is the Air flow control valve, 14, mixer, 18
1 is a main burner load cutoff command generator, and 19 is a main burner load cutoff valve.

Claims (1)

[Scope of Claims] 1. A main burner and an auxiliary burner that move relative to the base material to preheat the welded part of the base metal, a temperature detector that measures the temperature of the welded part, and the welded part a preheating temperature measuring device to which an appropriate preheating temperature is set to preheat the area; and a preheating temperature measuring device that performs calculation between the measured temperature of the welded part measured by the temperature detector and the appropriate preheating temperature set in the preheating temperature setting. a controller that outputs a valve opening command signal according to the calculation result of the subtracter; and an air flow rate control valve that adjusts the flow rate of air in response to the valve opening command signal from the controller. a mixer that mixes air whose flow rate is adjusted by the air flow rate control valve and fuel from the fuel pipe to generate combustion gas to be sent to the main burner and the auxiliary burner; a main burner load cutoff valve that is installed in a combustion gas pipe that leads gas to the main burner and can cut off the supply of combustion gas to the main burner; a valve opening command signal from the regulator is input;
and a main burner load cutoff command generator that gives a cutoff command to the main burner load cutoff valve so that combustion gas is sent only to the auxiliary burner when the valve opening command signal becomes equal to or less than a preset value; Even if the value of the valve opening command signal from the regulator becomes such that the air flow control valve is almost closed, the opening of the air flow control valve ensures a minimum amount of combustion gas that can prevent the auxiliary burner from blowing out. 1. An automatic welding preheating control device, comprising: a lower limit limiter provided between the regulator and the air flow control valve to control the air flow rate so as not to fall below a possible level.