JPS5825884A - High frequency welding method for electric welded pipe - Google Patents

Abstract

PURPOSE:To obviate welding defects in the stage of producing an electric welded steel pipe with a high frequency welding method by welding a steel plate while controlling weld heat input and the rate of upsetting so as to maintain the adequate melting rate of pipe edges and the rising angle of metal flow. CONSTITUTION:In the stage of producing an electric welded steel pipe by forming a steel plate to a pipe shape, and welding the edge parts of a V shape by high frequency induction heating, a bead width and a bead height 1' are measured with an image sensor camera 1, and the thickness of the plate and a pipe forming speed are measured with measuring devices 2, 3, and are inputted via an arithmetic circuit 4 to a comparator 7, which compares the bead width and the bead height with reference set values. In accordance with the results thereof, the source voltage is controlled 10, whereby the weld heat input is kept constant. The bead width and bead height at optimum rates of upsetting with respect to the pipe forming speed and the thickness of the plate are compared with reference values in a comparator 9, and in accordance with the results thereof, the rate of upsetting is controlled 11 during welding, whereby weld defects such as cold wells and penetrators are obviated.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a high frequency S* method for electric resistance welded steel pipes, so f! III! This paper proposes a new method for performing high-wave welding while controlling human heat and up heat input.

In the production of ERW steel pipes, the high-waste wave S* method, which utilizes properties unique to high-frequency currents called skin effect and proximity effect, is widely adopted, and it is well suited for high-speed heating because it enables efficient heating. There are advantages to doing so. One of the important things in this high frequency welding method is the management of heat and upset amount. Conventionally, methods for controlling welding heat input and upset amount have mainly been based on visual observation of the molten steel in the weld zone by an operator, or manual control based on the temperature of the discharged bead of the V-shaped edge after a squeeze roll. I was adjusting the input. In the case of such conventional technology, there are individual differences and limitations in the responsiveness to changes in the surface temperature and color of molten steel due to changes in plate thickness or pipe forming speed, depending on the operator. Welding defects called welding defects may occur. In addition, as another conventional technology, welding heat input and upset amount can be automatically adjusted by adjusting the plate voltage, current, grid current, etc. of the oscillator.
1# has been proposed. This method has poor accuracy and is not practical due to heat loss in the oscillator, transmission circuit, and pipes.

In this way, it has been pointed out that in the past, there was a lack of understanding of the flIII phenomenon correctly.The purpose of this invention is to provide a solution to this problem, and its gist is When heat welding is performed by passing a high-frequency current through the V-shaped edge of an open pipe, the actual measured values of the bead width and bead height, which fluctuate depending on the pipe manufacturing speed and plate thickness, are compared with those standard settings. By comparing, the power supply voltage is controlled to keep the welding heat input constant, and the pipe forming speed after the change, the bead radius and peed height at the optimum upset amount corresponding to the plate thickness are used as standards. The upset amount is controlled by comparing the measured values of the bead radius and bead height before and after the change with the standard. Let me explain with reference.

This invention is based on S input heat (amount of edge melting before upsetting)
Even if the amount of upset by the squeeze roll is controlled correctly, welding defects such as penetrators and cracks will occur if the amount of upset by the squeeze roll reaches 7. This was devised based on the knowledge that if the input of human heat is inappropriate, the upset amount control will end in failure.

Generally, during AT, if the amount of edge melting immediately before upset is insufficient, it will result in poor fusion (cold weld), and if the melting is excessive, the so-called @Jdans! i1g
Penetrators may occur due to a state called elephant. Therefore, in order to obtain a good weld, it is necessary to optimize the welding heat input, that is, the amount of edge melting immediately before upsetting. However, even if the IMTFI immediately before the upset is appropriate, if the amount of upset is inappropriate, defects may occur. Normally, this upset discharges the V-shaped molten steel along with oxides and t! The purpose of this is to obtain a III-contact portion with no upsetting defects, and the stronger the upset, the better.On the other hand, if the upsetting is too strong, the metal flow will rise too much and the Charpy impact properties will deteriorate. Therefore, it is important to upset the metal flow rise angle to an appropriate value.

From the above, what is necessary when making pipes is to adjust the welding heat input to obtain an appropriate melt width, and to perform upsetting at an appropriate amount depending on the molten state of the edge before upsetting. The present invention is a developed high-frequency welding method that finally meets this need.

That is, in the present invention, reference values for the bead width and bead height are set in advance, and these are compared with the actually measured bead radius and bead height, which change with changes in pipe forming conditions such as pipe forming speed and plate thickness. By comparison, the IE source voltage is set to 111 m so that both are constant, and the welding heat input is kept constant. Then, after the operation or after the operation, the bead width corresponding to the i/1a upset amount when the pipe forming speed and plate thickness are changed, with respect to the calculated and stored upset amount corresponding to the reference value,
While determining the bead height, welding is performed by controlling the amount of upset by comparing the bead height with actual measurements.

In this way, change the fusion heat input and upset amount control#
Bead #I, which will be removed later, is based on the bead height.
The reason for this is that it accurately shows changes in pipe-making conditions and the amount of change is easy and accurate.

1st. The figure below shows the pipe forming speed when the melting state of the V-shaped edge before the squeeze roll is optimized.

It shows the relationship between the skin length difference upset amount and bead width, build thickness, or metal flow rising angle when the plate thickness is changed. By detecting the pipe forming speed, plate thickness, bead width or bead height from these figures,
It can be seen that the metal y a -rise angle of the welded portion can be easily estimated, and that this makes it easy to control the amount of upset.

In addition, from this time, the maximum aIil length difference upset for the optimum metal 7o-rise angle (for example, 60°),
Furthermore, it is also possible to find the bead width and bead height of j&-.

For example, as shown in Figure 2, when the edge is kept in the optimal melting and heating state, the plate thickness changes from 1-no-shi to 1-1, j111-II.
When the thickness is increased to
to 7.0 as. At that time, the bead width is j
, the height should be 3.9111m, and the bead height should be 2.7 to 3.
．． Increased to 6 seagulls. Therefore, the amount of edge melting is 11
11! If the upset amount is controlled so that the bead height is 3.6 mm under the i-shaped structure, a predetermined metal 70 rise angle and a good welded portion of the five seams can be obtained. however,
The idea is to adjust the amount of heat input 'e so that the amount of edge melting is optimized.

@J-j diagram shows pipe forming speed 21 m/m: tn I plate thickness // M.

tj in advance to the optimum value of the preset amount for the difference in length at a bead coefficient of 1.7! In this state, the change in the amount of one length difference upset is shown when only the heat coefficient, plate thickness and pipe forming speed are changed at the other conditions tt. The fluctuations in these figures are completely different when the initial settings of the squeeze roll are kept constant, and when the plate thickness and pipe forming speed change.

If you know the bead 4&, you can set the optimal +4 length difference upset amount to make the metal 70-rise angle appropriate for defect-free mwI, and also set the pipe edge melt amount appropriately to eliminate defects. The welding heat input can be controlled to a constant value of 1W by comparing the reference set values of the bead width and bead height with the actual I1g value.

The vehicle body welding control method of the present invention based on such knowledge will be described with reference to FIG. 5.

θd in Figure 6 is the ideal metal 70-rise angle.

Points M and B are respectively plate thickness tm, 1B (1A<1B)
This point indicates the value of the circumferential length difference upset amount and bead height under the ideal welding condition. 1. , 1B curves are respectively mu,
It shows the changes in the height and rise angle of metal 70 when changing the 11% pigeon length difference upset filter with the heat input at point B constant. ) film, pipe making speed v * tfE contact heat input
・Pmu is a company that manufactures pipes at Pmu. Assuming that the plate thickness changes to tB at a certain point,
In order to perform ideal welding, it is necessary to set the circumferential length difference upset amount to IB1B1 welding total heat HPB・"PB.In the present invention, first, the ideal heat input* is determined according to this plate thickness change. The amount of heat input is controlled to m-x, and then the metal 70-rising angle force θ is applied.

The amount of upset is controlled so that

That is, in Fig. 6, the plate thickness tA at point C, the amount of upset 1m, the tube making speed V, the welding heat input 1pm・I,...
), if the plate thickness increases to tB, the welding heat input is set to 1 cPB/mmPH, but from the relationship to ( in the same figure), the bead height is set to hr. It is better to increase the welding heat input.As is obvious from Part J and the reference figure, the larger the welding heat input, the larger the difference in upset amount, and even if the welder has the same passion, the plate thickness will increase. As the circumferential length difference upset amount becomes smaller as it becomes thicker, the actual circumferential length difference upset amount becomes 11 in the figure, but as mentioned above, the change in the peripheral length difference upset amount due to welding heat input and the change due to plate thickness is Since they cancel each other out, 1t can be regarded as almost the same value as 1A.After controlling the welding heat input so that the bead height becomes hr, the upset amount is controlled so that the bead height becomes hB. An ideal welded part with a metal flow rise angle of θ can be obtained.

On the other hand, Figure @7 is a schematic control diagram of the present #111 welding method when the plate thickness is constant and the pipe forming speed changes from V to vB, and the same process as in Figure 4 is performed.

@r#A is a control path diagram of the method of the present invention described above.

First, the image sensor 1 detects the bead width or bead height 11 before the pipe forming conditions change, and the plate thickness measuring device λ and the pipe forming station I! tf! The plate thickness and pipe forming speed are detected by A-meter J.

These are input into an arithmetic circuit to obtain a lil length difference upset amount to be used as a reference value, and this is manually stored in the control circuit 5. By inputting the memorized noise difference upset amount, the plate thickness changed by pipe forming, and the pipe forming speed into the calculation circuit j, for example, calculate the bead height corresponding to h/A in Fig. 4 (~). Comparison-Route 7 shows both the bead height and bead height before the voltage change determined by the image sensor-camera, and the reference speed and bead height hm determined by Calculation-Route 2 by hand. , these values are compared, and the voltage is controlled by the power supply voltage control circuit 10 so that the difference becomes zero.

On the other hand, the plate thickness and pipe forming speed that have changed due to pipe forming are manually input to the calculation circuit t, and the bead height corresponding to hB in Figure 1 (-) is calculated and determined. Bead width and bead height determined by I and bead radius and bead height hB determined by calculation circuit l
These values are compared and the upset amount is controlled using a 7-set #circuit so that the difference becomes zero. In addition, the opener contacts S and S2 are ON when normal (the outputs of comparison circuits 7 and 9 are zero).
.

It is turned off. For example, in the event of an abnormality such as a change in plate thickness, the output of the comparison circuit 7 changes from zero to a positive or negative value, and returns to the original zero as the heat input decreases, but at that moment it opens and closes! ! Contacts S and S2 are O]['F
, turns on. Although the output of the comparator circuit D shows positive and negative values, the amount of upset is set to mm so that the output becomes zero. At the moment the output of comparison circuit D becomes zero, #!
The MIalI points S and S are the original ON and O, respectively.
It has returned to the state of FF. All such operation control is performed by the switch control circuit/λ. Also, in the upset amount control circuit l/, comparison I! l! It is necessary to rotate the key according to the output of l path 9! Amount Upset Vary the amount.

Figure 1llK9 shows an image sensor used in implementing the present invention.
Shows camera placement. As shown in the figure, place the image sensor-camera 4iQ directly above the bead immediately after the stylus roll.
At the position QM or the position oo■ right next to the bead, the scanning 11/J was arranged to be perpendicular to the welding line.

The sensor output waveform of the image sensor camera I is obtained according to the heating and melting state as shown in Figure @10. This waveform is sliced at an appropriate level by one calculation path of the image sensor and camera, and the welding heat input and upset amount are calculated by using the electrical signal corresponding to the slice width.
Ta.

As a result, according to the present invention, it becomes possible to quantitatively understand changes in the metal 70 rise angle during pipe making, and appropriate upsetting can be conveniently performed in accordance with changes in pipe making conditions, compared to conventional methods. There are no welding defects such as welding ($) L, -1- or cold welds.

The present invention can be applied not only to the manufacturing of ERW pipes, but also to the high electrical resistance and induction welding of steel plates, ll [#, etc.] at public expense.

[Brief explanation of the drawing]

Figure #I1 and Happy Figure on the Bgi side are Figure 41 which shows the relationship between the bureau difference upset amount, bead width, bead height a) and metal flow rise angle [b), and Figure 3 is the heat coefficient and waste! Figure 5 is a diagram showing the relationship between the difference upset amount and the plate thickness. 1Ii
l! Figure 114 and Figure 7 are diagrams showing the relationship between negative and negative, Figure 1 is a circuit diagram of the welding control method of the present invention, and Figure 9 is a diagram showing the relationship between negative and negative.
The figure is a layout diagram of the image sensor-camera in a state in which the present invention is implemented, and FIG. 7Q is an output waveform diagram of the image sensor-camera. l...Image sensor camera //...Bead width. Bead height value, 2...Plate thickness measuring device, 3...Pipe forming speed measuring device, D...Arithmetic circuit (perimeter difference upset amount),!
...Memory path, 1... Arithmetic circuit, 7... Comparison circuit, l... Arithmetic circuit (bead width, height), D... Comparison circuit, 10... Welding heat input control Circuit, ll... Upset amount control circuit □ circuit, 12... Switch control 11gl circuit. -(Jgμ)B6. 91-α tlV (non-one V'
Zesu, (-,,1 (H(41atsuk)II-^,λolx-atzuIll
(a) Fig. 6<b> (b) Fig. 8-'' 1: Fig. 9 13゜width/, 6 5: ■ Fig. 1θ

Claims (1)

[Claims] L: A bead width that changes depending on the pipe manufacturing speed and plate thickness when heat welding is performed by passing a high frequency current through the V-shaped edge of an open pipe. By comparing the measured value of the bead height with those reference setting values, the IK# voltage is controlled to keep the Mll large heat input constant, and the optimum upset amount corresponding to the pipe forming speed and plate thickness after all changes is determined. The S & S for electric resistance welded steel pipes is characterized in that the amount of upset is controlled by comparing the measured values of the bead radius and bead height before and after their changes with the bead width and bead height as standards. Local wave welding method.