JPH0260435B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD OF THE INVENTION The present invention relates to electric arc welding, and more particularly to an electric arc capacitor discharge percution stud welding process, also referred to as the Vang welding process. The electric arc capacitor discharge percution stud welding method of the present invention can be applied to the production of welded structures in general engineering, shipbuilding, equipment manufacturing and civil engineering. [Prior Art] Widely known electric arc capacitor discharge percution welding (“Avtomaticheskaya”) for welding studs to metal sheets, plates and other components.
svarka” Magazine, No. 9, 1973, “Naukova
Dumka”/Kiev/, NAChvertko,
“Udarnaya Kondeusatornaya svarka shpilek
In order to ensure reliable generation of an electric arc between the ends of the studs and the component, the ends of the studs are ridged by cold upsetting. The length and diameter of this raised part are determined by the main diameter of the stud and the material of each part to be welded.The shape of the raised part at the end of the stud to be welded is wedge-shaped, conical, etc. shape, etc. The action of the spring mechanism places the raised portion of the stud on the surface of the member.
When a bank of capacitors, previously charged to the required voltage, is electrically connected to the stud and member, welding current begins to flow through the raised portion of the stud and the member. When the value of the discharge current of the capacitor bank reaches its maximum value, the ridge is explosively evaporated due to the high current density within the ridge (up to 10 ⁶ A/cm ² ). Because of the high temperature of the metal vaporization, the gap from the stud to the part is ionized and an electric arc is ignited, forming an arc in the vapors of the stud and part being welded. The length of the electric arc and the arc time depend on the length and diameter of the raised portion of the stud. The end of the stud and the underlying member surface melt. The action of the spring mechanism brings the end of the stud closer to the workpiece so as to gradually extinguish the length of the electric arc, and when the end of the stud is introduced into the molten metal of the workpiece, the electric arc The arc is extinguished. The welding cycle is complete when the molten metal is completely solidified. The formation of the raised part at the end of the stud is relatively complicated, since the length and diameter of the raised part need to be relatively accurate in order to properly repeat the operation to produce a welded joint with good quality. It's work. Another widely known method is the automatic arc welding of curved butt joints with V-grooves of varying width using consumable electrodes (SU, A, 941052). This method is a gas shielded DC welding method. First, an electric arc is ignited between the electrode and the welding structure. While the arc is ignited, the electrode is moved along the weld line while being vibrated across the weld line. The voltage of the welding arc is measured during welding, and as the electrode approaches the edge of the structure to be welded and the length of the arc gap changes, the measured value is 10-20% of the predetermined value. % decrease and this variation lasts between 0.025 and 0.1 s, the movement of the electrode is reversed. As a result, the electrode is guided along the weld line with sufficient precision so that the varying width groove of the weld structure is uniformly filled with metal over its entire width.
When individual beats are deposited (the welding operation is repeated several times), the speed of welding is automatically varied. It is only possible to reverse the movement of the electrodes in accordance with the voltage fluctuations of the electric arc when the fluctuations are in the range of 10% to 20%. This is because if the voltage of the electric arc drops more than this, the welding operation will be adversely affected. The process is delayed due to the 0.025-0.1s delay in sending the command to reverse the movement of the electrodes. The more widely known electric arc capacitor discharge percution stud welding method (Thyssen
Technische Berichte, No. 2, 1982, A.Frings
et al., “Lichtbogenbolzenschweissen und
Kaltgewalzten Stahlfeinblechen”, pp.161～
170) is the step of pre-positioning the stud on the member;
Retract (retract) the stud to be welded from the part.
and the steps of igniting an auxiliary electric arc therebetween and moving the stud toward the workpiece by means of a spring mechanism in the welding head. After sustaining the auxiliary arc for a predetermined period of time, the discharge of the capacitor or capacitor bank is initiated to direct the welding current through the stud and workpiece, melting the end surface of the stud and the underlying workpiece surface. At the expiration of a predetermined arc time of the welding electric arc, the stud is introduced into the molten metal of the part. The stud and member to be welded are then held together or butted together to form a welded joint. In this process, the timing of discharge of the capacitor bank is determined by the time of movement of the stud relative to the component, so a specially designed high precision gauge is required. However, in this method, the operation of the spring mechanism of the welding head is not performed in a sufficiently stable state, so that the operation of butting the stud against the member cannot be repeated sufficiently. The resiliency of the welding head spring mechanism must be adjusted because the mass of the spring mechanism varies as the diameter of the stud changes. [Problems to be Solved by the Invention] An object of the present invention is to provide an electric arc capacitor that increases the efficiency factor of welding work and expands the range of stud diameters that can be welded by setting the discharge start time of the capacitor in advance. An object of the present invention is to provide a method for welding a discharge percution stud. [Means for Solving the Problems] The above object is the process of pre-positioning a stud on a member, retracting (retracting) the stud from the member and forming a stud between the end of the stud and the member. igniting an auxiliary electric arc, moving the stud toward the member, discharging a capacitor between the end of the stud and the member, and placing the stud into the molten metal of the member. an electric arc capacitor discharge percussion welding method comprising the steps of: introducing the stud to the member 4; and abutting and joining the end of the stud to the member 4 to form a weld; The voltage drop across the auxiliary electric arc is measured when the stud is in position, the sum of the electrode coupling voltage drops at the end of the stud and the member is subtracted from the measured value, and the resulting voltage drop value is This is achieved by the electric arc capacitor discharge percution stud welding method of the present invention, which is characterized in that discharge of the capacitor starts when the voltage drop value varies by 10% to 90%. The electric arc capacitor discharge percution stud welding method of the present invention can increase the efficiency factor of the welding operation by extending the arc time of the welding electric arc, thereby expanding the range of studs that can be welded. be able to. [Embodiments] The present invention will be further described below with reference to the accompanying drawings, with reference to embodiments in electric arc capacitor discharge percution stud welding. The electric arc capacitor discharge percution stud welding method of the present invention is carried out as follows. In FIG. 1, a stud 1, held by a gripping device 2 of a welding head (not shown), is pre-positioned by its end 3 onto a member 4. In order to ignite the auxiliary electric arc, a current is supplied through a series connected thyristor switch 5 and a current source 6. A series connected thyristor switch 7, a capacitor bank 8 and a current source 9 are present to supply the current for igniting the welding arc. A voltage measuring circuit 10 connected in parallel between the gap between the end 3 of the stud 1 and the member 4 is connected to the thyristor switches 5 and 7. Turn on the thyristor switch 5 connected to the current source 6. The stud 11 is retracted (retracted) from the part 4 by the electromagnet 11 of the welding head and an auxiliary electric arc is ignited between the end 3 of the stud 1 and the part 4. The arc gap between the end 3 of the stud 1 and the member 4 is ionized by the auxiliary electric arc. When the stud 1 is fully retracted (retracted) from the member 4, the electromagnet 11 is deenergized, the auxiliary electric arc remains ignited, and the welding head spring mechanism (not shown) moves the stud 1. Member 4 (first
2a). As stud 1 is moving from time t ₀ towards member 4, the voltage drop across the auxiliary electric arc is measured and from this measurement the electrode coupling voltage drop at end 3 of stud 1 and member 4 can be determined. The sum is subtracted to obtain a value corresponding to the voltage drop U ₁ (FIG. 2) in the auxiliary electric arc column. This value is directly proportional to the length of the auxiliary arc, L ₁ (Fig. 2a), which is equal to the distance between end 3 of stud 1 and member 4; Discharging of the capacitor bank 8 (FIG. 1) begins when a predetermined voltage drop U ₂ corresponding to the distance L ₂ between the capacitor bank 8 and the member 4 is reached. The predetermined voltage drop U ₂ depends on the charging voltage of the capacitor bank 8, the diameter of the studs 1 to be welded and the power cable (not shown) connecting the current source 9 of the welding current through the capacitor bank 8 to the welding head (not shown). is selected according to the inductance of The distance L ₁ corresponds to the voltage drop U ₁ (second b
Figure) is determined by the relative value of the decrease. Voltage
When the decrease in U ₁ reaches a value U ₂ which is proportional to the length L ₂ (time t ₁ ), the voltage measuring circuit 10 sends a signal to switch on the thyristor switch 7 connected to the capacitor bank 8 . The capacitor bank 8, previously charged by the current source 9, discharges in the gap between the end 3 of the stud 1 and the member 4, which was previously ionized by the auxiliary electric arc (FIG. 2c). In this way, capacitor bank 8 (second d
The welding electric arc is maintained by the discharge current shown in Figure). The respective surfaces of the end 3 of the stud 1 and the member 4 to be welded are melted by this current, and the pressure of the metal vapor in the arc gap causes a spring (not shown) in a spring mechanism (not shown) of the welding head. ), the stud ₁ enters the molten metal of the part 4, and in this way the stud 1 and the part 4 to be welded are butted together. The welding arc is extinguished and a weld is formed between the end 3 of the stud 1 and the member 4. The discharge current of the capacitor bank 8 flowing through the welded joint between the end 3 of the stud 1 and the member 4 decreases exponentially. The welding cycle ends when the metal in the weld has solidified. In carrying out the method of the invention, the distance from the end 3 of the stud 1 to the member 4 is measured from the relative reduction in voltage drop across the auxiliary electric arc column. That is, the above arc is used as an independent measurement medium. Arc voltage is determined from Ireton's formula below. U ₃ =a+bL (1) where "a" is the sum of the electrode coupling voltage drops, i.e. the sum of the anode and cathode voltage drops at end 3 and member 4 of stud 1, and this value is particularly important for electric arcs. is independent of the length (the absolute value of the electrode coupling voltage drop is 10-17V). “b” is a proportionality coefficient that depends on external conditions, welding current value and electric arc length (NA
Kaptsov, “Elektricheskie yavleniya v.
gazakh i v vakuume”, 1950,
Gosudarstvennoe Izdatel'stvo Tekhnicheskoi
i Teoreticheskoi Literatury／Moscow−
Leningrad/, p.524). When the welding current begins to flow at the time when the voltage of the auxiliary electric arc reaches the predetermined value U ₄ , the length of the arc gap, that is, the distance from the end 3 of the stud 1 to the member 4, becomes equal to L ₂ in the following formula: . L ₂ = U ₄ -a/b (2) U ₄ = kU ₀ (3) Then, k = U ₄ /U ₀ (4) Here, U ₀ is the end of stud 1 when it is pulled in the most. is the voltage drop across the electric arc corresponding to the distance from section 4. Substituting equation (1) into equation (3), U ₄ =k(bL ₀ +a) (5) where L ₀ is the length of the electric arc when stud 1 is at its maximum distance from member 4. Substituting equation (5) into equation (2) yields the following equation. L ₂ = U ₄ - a/b = kL ₀ - (1-k) a/b (6) The value of the voltage drop at the auxiliary electric arc column is U ₁ = U ₃ - a = bL, but Then, k=U ₂ /U ₁ =bL ₁ /bL ₀ =L ₁ /L ₀ ;L ₁ =kL ₀ (7) where U ₁ is the force from member 4 of stud 1 at its most retracted position. is the voltage drop in the electric arc column, corresponding to the maximum distance, and U ₂ is the voltage drop in the electric arc when the welding current of the capacitor discharge begins to flow. As can be clearly seen from equation (7), the voltage drop across the electric arc is measured while the stud 1 is moving towards the member 4, and the electrode coupling voltage drop is subtracted from the value thus measured. and the obtained value is compared with the predetermined voltage drop value, then
The dependence of these values on external factors is offset. The time at which the welding current supplied by the discharge of the capacitor bank 8 begins to flow is set such that upon contact between the end 3 of the stud 1 and the member 4, the respective surfaces are completely melted. Should. If the discharge of the capacitor bank 8 is delayed, sufficient time will not be given for the weld to completely melt and the quality of the welded joint will deteriorate.
Moreover, in this case the energy stored in the capacitor bank 8 is wasted due to the occurrence of a short circuit upon contact between the end 3 of the stud 1 and the member 4. Conversely, if the capacitor bank 8 starts discharging too early, the end 3 of the stud 1
The quality of the welded joint is still poor because the two come into contact at a time when the current flowing through the surface of the member 4 and the surface of the member 4 is insufficient to maintain them in a molten state. The level of voltage drop across the auxiliary electric arc column when the welding current supplied by the discharge of the capacitor bank 8 should begin to flow is the level at which the initially measured stud 1 is fully retracted from the member 4. in the range of 10% to 90% of the initial voltage, which in practice ensures that the welding current at any time of the movement of the stud 1 towards the part 4 and at any distance between the stud 1 and the part 4 can start flowing. The voltage drop on the auxiliary electric arc supplied with direct current is 16-40V. Lower limit like this
16V is close to the sum of the voltage drops of 10-17V across each electrode or end 3 of stud 1 and member 4. The variation of the voltage drop in the auxiliary electric arc column when the welding current begins to flow shall not be less than 10% of the above initial voltage. If it is less than 10%, welding arc will not occur and the end 3 of the stud 1 and the member 4 will be welded.
There is a risk of a short circuit occurring in the gap between the On the contrary, the upper limit of the fluctuation of the voltage drop of the auxiliary electric arc when the welding current starts flowing is determined by the initial voltage value.
The reason for setting it to 90% is that the welding arc is generated with high reliability and is defined by the maximum recommended value of the arc time which depends on the maximum length of the welding arc that can continue stably and with high reliability. In practice, the maximum length of the auxiliary electric arc is 3 to 5 mm. The maximum arc time of welding current depends on the inductance of the welding circuit including the power supply cable, and is 6 to 8 ms.
It is. Table 1 shows examples of electric arc capacitor discharge percution stud welding.

〔Effect of the invention〕

The electric arc capacitor discharge percution stud welding method of the present invention reduces the total labor input for welding work, significantly improves welding productivity, expands the work area by increasing the length of the power cable, and saves power. You can save money.

[Brief explanation of the drawing]

FIG. 1 is a block unit circuit diagram of an apparatus capable of carrying out an electric arc capacitor discharge percussion stud welding method according to an embodiment of the present invention. Figures 2a, 2b, 2c and 2d are lines showing the movement of the stud relative to the member, the voltage of the auxiliary electric arc column, the capacitor voltage, and the welding arc current versus time, respectively, in a method embodying the invention; It is a diagram. DESCRIPTION OF SYMBOLS 1...Stud, 2...Welding head gripping device, 3...End of stud 1, 4...Member, 5,
7...Thyristor switch, 6,9...Current source, 8...Capacitor bank, 10...Voltage measurement circuit, 11...Welding head electromagnet.

Claims (1)

[Claims] 1 pre-positioning the stud 1 on the member 4,
retracting the stud 1 from the member 4 and igniting an auxiliary electric arc between the end 3 of the stud 1 and the member 4; moving the stud 1 towards the member 4; 8 between the end 3 of the stud 1 and the member 4, introducing the stud 1 into the molten metal of the member 4, and discharging the stud 1 between the end 3 of the stud 1 and the member 4. In an electric arc capacitor discharge percussion welding method including a step of butting and joining members 4 to form a welded part, the stud 1 is attached to the member 4.
The voltage drop across the auxiliary electric arc is measured as it moves towards the stud 1, and the sum of the electrode coupling voltage drops at the end 3 of the stud 1 and the member 4 is subtracted from the measured value to obtain the obtained value. An electric arc capacitor discharge percution stud welding method, characterized in that discharge of the capacitor 8 starts when the obtained voltage drop value fluctuates by 10% to 90% of the initially obtained voltage drop value.