JP4825094B2 - Resistance welding method and resistance welding apparatus for high carbon steel - Google Patents

Description

  The present invention relates to a resistance welding method and a resistance welding apparatus suitable for resistance welding of high carbon steel, in particular, high carbon-high chromium steel that has been carburized and quenched to the inside.

  Capacitor-type resistance welding is a welding method in which good welding results can be obtained by discharging electrical energy stored in an energy storage capacitor between workpieces in a very short period and flowing it as a pulsed welding current. Widely known. In such welding, unlike the AC welding in which an alternating current is passed over several cycles, usually only the weld and a small area around it are rapidly heated in a very short time, and in a natural state. It is cooled rapidly. In the case of such rapid heating and rapid cooling, if these workpieces are made of high carbon steel having a high carbon content, or high carbon steel whose surface is carburized, the hardness of the welded portion increases and becomes brittle. It is known that the mechanical strength is greatly reduced.

Therefore, conventionally, after applying a pulse welding current between the workpieces while applying a pressure between the workpieces, an AC current is passed over several tens of cycles, for example, 20 to 30 cycles. It is disclosed that heat treatment is performed and the welded portion is tempered to return the hardness to an allowable value or less to suppress a decrease in strength. However, when post-heat treatment is performed by passing an alternating current, the heat generation time becomes longer, so the temperature of the work to be welded becomes high in a wide range, which causes discoloration of the work to be welded, thermal distortion, wear of the welding electrode. Etc., and the welding quality was reduced. As a method for solving this problem, a high-carbon steel is obtained in which high welding quality can be obtained by flowing a first pulsed welding current and then tempering with a single second pulsed welding current. A resistance welding method is also disclosed (see, for example, Patent Document 1).
JP 2000-326076 A

  The resistance welding method disclosed in the above-mentioned Patent Document 1 is very effective when resistance welding is performed on high carbon steel whose surface is carburized and quenched and low carbon steel which is a normal steel material. High weld strength can be obtained without causing discoloration or thermal distortion of the weldment. However, for example, a high carbon-high chromium steel material called SUJ in the JIS standard has been carburized and quenched to the inside, so even with the resistance welding method disclosed in the above-mentioned Patent Document 1. There is a problem that the welding strength between the high carbon-high chromium steel material and the low carbon steel is greatly reduced compared to the welding strength of the high carbon steel whose surface is carburized and quenched. The same applies to a method as described above, for example, a resistance welding method in which an alternating current is applied for several tens of cycles, for example, 20 to 30 cycles after a single pulse welding current is passed between workpieces. However, the welding strength cannot be improved. In other words, in resistance welding of high-carbon steel that has been carburized and quenched to the inside, the welding strength during welding of high-carbon steel whose surface has been carburized and quenched has not reached its level, regardless of the appearance problem. It was.

  The present invention provides a first work piece made of a high carbon steel material that has been carburized to the inside by a resistance welding method that has been widely used without using a high-cost welding device such as a laser welding device. It is possible to easily resistance weld a low carbon steel, a high carbon steel whose surface is carburized and hardened, or a second work piece made of a high carbon steel material which has been carburized to the inside. It is an object of the present invention to provide a resistance welding method and a resistance welding apparatus that can be greatly improved.

1st invention energizes a welding current in the state which applied the pressure between the 1st to-be-welded object which consists of a high carbon steel by which the carburizing hardening process was carried out to the inside, and a 2nd to-be-welded object. A high-carbon steel resistance welding method for welding the first work piece and the second work piece, between the first work piece and the second work piece. a first bonding step of performing the first bonding to flow a single first pulsed welding current I1, after a cooling time Tc from the energization of said first pulsed welding current, the first Shi stream of the second pulsed welding current I2 of a single 80 to 130% of the peak value of the peak value of the pulsed welding current between said first object to be welded and the second object to be welded a second bonding step of performing a second round junction of Te, after energizing the second pulsed welding current I2, the first pulse-like Longer than the energization time of the energization time 及 beauty said second pulsed welding current I2 of contact currents I1, smaller than the peak value of the first pulsed welding current I1 and the second pulsed welding current I2 A resistance welding method for high carbon steel, comprising sequentially performing a third joining step of energizing a peak AC welding current i between the first workpiece and the second workpiece. provide.

According to a second aspect of the present invention, there is provided a charging circuit to which electric power from an AC power source is input, an energy storage capacitor charged by the electric power from the AC power source through the charging circuit, a first primary winding, a welding transformer having a second primary winding and a secondary winding, a first switch circuit for discharging the stored energy storage capacitor charges through the first primary winding, A second switch circuit that receives power from the AC power source and is connected in parallel with the second primary winding, and is carburized and quenched from the secondary winding to the inside. A resistance welding apparatus for high carbon steel that performs resistance welding by passing a welding current between a first workpiece to be welded that is carbon steel and a second workpiece to be welded. The energy storage capacitor reaches the first set voltage value. After being charged, the first switch circuit is energized the first pulsed welding current I1 of the single between the object to be welded of the ON to the first object to be welded 2 1 The first switch circuit is turned off after the second joining, and then the first storage circuit is charged with a cooling time after the energy storage capacitor is charged to the second set voltage value by the charging operation of the charging circuit. It is turned on again later, and a single second having a peak value of 80 to 130% of the peak value of the first pulse welding current is between the first workpiece and the second workpiece. of a pulsed welding current I2 is turned off after the second time joining is energized, the second switch circuit is turned on after the second off of the first switch circuit, the first Energizing time of the pulsed welding current I1 and the second pulsed welding current AC welding current i having a peak value smaller than the peak value of the first pulsed welding current I1 and the second pulsed welding current I2 is applied from the AC power source to the welding transformer for a time longer than the energizing time of I2. There is provided a high-carbon steel resistance welding apparatus characterized in that a third joining is performed between the first workpiece and the second workpiece via a wire .

According to a third aspect of the present invention, a first charging circuit to which power from an AC power source is input, a first energy storage capacitor that is charged by power from the AC power source through the first charging circuit, A second charging circuit to which electric power from the AC power source is input; a second energy storage capacitor to be charged by electric power from the AC power source via the second charging circuit; and the first energy. A first switch circuit for discharging the charge stored in the storage capacitor via the first primary winding; and the charge stored in the second energy storage capacitor as the first energy. a third switching circuit for discharging through a common said first primary winding similar to the storage capacitor, wherein the power from the AC power supply is input, and said second primary winding Connected in parallel That a second switch circuit, the welding from the secondary winding, a first object to be welded is a high carbon steel that is carburized quenching the inside, between the second object to be welded A resistance welding apparatus for high carbon steel that conducts resistance welding by passing an electric current, and after the first energy storage capacitor is charged to a first set voltage by a charging operation of the first charging circuit, The first switch circuit is turned on to discharge the stored charge of the first energy storage capacitor, thereby providing a single first between the first workpiece and the second workpiece. The first energy storage capacitor was charged to the second set voltage by the charging operation of the second charging circuit. Later, the third switch circuit is cooled. By discharging the charges accumulated in the second energy storage capacitor is turned on after the lapse of time, between the first object to be welded and the second object to be welded, the first pulsed welding A second pulse welding current I2 having a peak value of 80 to 130% of the current peak value is energized and turned off after the second joining, and the second switch circuit 3 is turned on after the switch circuit 3 is turned off, and the first pulse welding current I1 is longer than the energization time of the first pulse welding current I1 and the energization time of the second pulse welding current I2. And an AC welding current i having a peak value smaller than the peak value of the second pulse-shaped welding current I2 from the AC power source through the welding transformer, the first workpiece and the second workpiece. performing the third junction of which conductible between A high carbon steel resistance welding apparatus characterized by the above.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the first primary winding common to the first charging circuit and the second charging circuit connected in parallel with each other is the first first winding. The high carbon steel resistance welding apparatus is characterized in that the stored charges of the first energy storage capacitor and the second energy storage capacitor are discharged with opposite polarities.

According to the first aspect of the present invention, the welding strength of the high carbon steel that has been carburized and quenched to the inside can be improved by a simple joining method without requiring a special structure projection. Also, high carbon steel that has been carburized and quenched to the inside can be more stably resistance-welded with high welding strength.

According to the second aspect of the invention, high carbon steel that has been carburized and quenched to the inside can be obtained easily and relatively economically without the need for a special structure projection, and can achieve the desired high welding strength. Resistance welding equipment can be provided.

According to the third aspect of the present invention, the high carbon steel that has been carburized and quenched to the inside can be provided with a desired large welding strength in a short welding cycle without the need for a special structure projection. A resistance welding apparatus can be provided.

According to the fourth aspect of the invention, in addition to the effects obtained by the third aspect of the invention, since the welding transformer is not polarized, the carburizing and quenching process is performed to the inside without applying any special bias excitation suppressing means. It is possible to provide a resistance welding apparatus capable of stably resistance welding high carbon steel.

[Embodiment 1]
A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a view for explaining a resistance welding method for high carbon steel according to the present invention, and shows a welding current. FIG. 2 is a view showing a first embodiment of a resistance welding apparatus for realizing the resistance welding method for high carbon steel according to the present invention. FIG. 3 is a view showing a welding electrode and an object to be welded. FIG. 4 is a diagram showing an example of a switch circuit that can change the polarity of the discharge current. In FIG. 2, an AC power source 1 is a commercial AC power source or an AC generator, and a charging circuit 2 composed of a rectifier circuit having a control function is connected to the AC power source 1. The output of the charging circuit 2 is connected to an energy storage capacitor 3 formed by connecting a plurality of electrolytic capacitors in series and parallel. The energy storage capacitor 3 passes through the first switch circuit 4 and the first 1 of the welding transformer 5. It is connected to the next winding 5A. The details of the first switch circuit 4 are not shown, but from a thyristor or IGBT that is turned on / off by a drive signal, or a high-current semiconductor switch such as a transistor and a controller that controls the on / off time of the switch according to a predetermined sequence. Become.

  The welding transformer 5 has a second primary winding 5 </ b> B, and the second primary winding 5 </ b> B is connected to the AC power source 1 through the second switch circuit 6. The second switch circuit 6 has the same configuration as that of the first switch circuit 4, but the ON / OFF time is different from that of the first switch circuit 4, and the ON / OFF operation thereof will be described later. The welding transformer 5 includes a secondary winding 5C having a number of turns of about 1 to 2 turns, which is significantly smaller than the number of primary windings 5A and 5B. Welding electrodes 7 and 8 are connected to the secondary winding 5C. During welding, the first workpiece W1 and the second workpiece W2 are sandwiched between the welding electrodes 7 and 8, A pressurizing mechanism (not shown) pressurizes the welding electrodes 7 and 8 to pressurize the first workpiece W1 and the second workpiece W2. Since the pressurizing mechanism is a general mechanism, it is not shown and will not be described. However, the pressurizing force P as shown in FIG. 1 can be applied between the welding electrodes 7 and 8. Is something.

  Here, the first workpiece W1 is made of a high carbon-high chromium steel material that cannot obtain the desired welding strength by the conventional resistance welding method, and the second workpiece W2 is made of ordinary low carbon steel. Become. The first work piece W1 made of a high carbon-high chromium steel material called SUJ in the JIS standard is carburized and quenched from the surface to the inside at least as compared with the high carbon steel subjected to surface carburizing and quenching. It has been done. High carbon-high chromium steel is a material used for bearings such as radial bearings and thrust bearings, and has high hardness and very high wear resistance. Each of the first and second switch circuits 4 and 6 is a high-power semiconductor switch, and a common control circuit for controlling on / off of the high-power semiconductor switch in a predetermined sequence may be provided. . Further, the first and second switch circuits 4 and 6 may be inverter circuits.

  Before describing the present invention, specific examples of the welding electrodes 7 and 8 and the first workpiece W1 and the second workpiece W2 will be described with reference to FIG. In FIG. 3 (A), the first workpiece W1 is a round bar made of a high carbon-high chromium steel material called SUJ in the JIS standard, for example, and the tip portion is shown in cross section. A general ring projection A is formed on the front end surface. The second workpiece W2 is made of low carbon steel or high carbon steel whose surface is carburized and quenched. Although not shown in detail in the drawing, the upper welding electrode 7 has a general structure in which a plurality of, for example, the vertical welding direction is equally divided into three parts, and these three gripping portions 7A, 7B (other ones) Are not shown in the figure because they are shaded), the inner surfaces of the three gripping portions are reduced or expanded in diameter, thereby gripping or releasing the first workpiece W1. A second workpiece W2 is placed on the welding electrode 8 on the lower side, and the welding electrode 7 welds the first workpiece W1 with the ring projection A facing downward. The electrode 7 is lowered or the welding electrode 8 is raised, and the ring projection A of the first workpiece W1 comes into contact with the upper surface of the second workpiece W2. Then, a pressure mechanism (not shown) is operated to apply a pressure P as shown in FIG. 1 between the welding electrode 7 and the welding electrode 8. Note that the projection is not limited to the ring projection, and may be another general projection.

  The first workpiece W1 shown in FIG. 3B is a round bar made of the above-mentioned high carbon-high chromium steel having a spherical surface B at the tip, and the tip of the spherical surface B is at the second workpiece. It is in contact with the upper surface of the weldment W2. In the case of the first workpiece W1, the tip of the spherical surface B plays a role of projection. The welding electrode 7 has the same structure as that shown in FIG. The second workpiece W2 is a round bar made of a metal material such as low carbon steel, and the central surface area of the upper end surface is at least flat, and the spherical surface of the first workpiece W1 is formed on the flat surface. B comes into contact. The lower welding electrode 8 has the same structure as the welding electrode 7, for example, three gripping portions 8 </ b> A and 8 </ b> B equally divided in the vertical direction (the other one is not shown because it is shaded). .). As with the welding electrode 7, the welding electrode 8 grips and releases the second workpiece W <b> 2 by performing an expansion / contraction operation with a reduced diameter. Even if the first workpiece W1 is a ball such as a ball bearing ball, resistance welding can be performed in the same manner. Although not illustrated, in this case, as an example, the welding electrode 7 has a hemispherical recess that can accommodate the upper half of the ball, and a suction port or magnet that can hold the ball is attracted to the hemispherical recess. Have. Alternatively, the lower welding electrode 8 may have the aforementioned hemispherical recess, and the lower welding electrode 8 may hold the ball.

  Further, according to the resistance welding method of the present invention, the high-carbon steel material of another shape made of high-carbon steel in which the first workpiece W1 is carburized and quenched deeply into the inside made of high-carbon-high-chromium steel material or the like. Even so, if a general projection is formed at the welding location of the first workpiece W1 or the second workpiece W2, a significantly higher welding strength can be obtained compared to the conventional resistance welding method. be able to. However, when the second workpiece W2 is made of a metal material whose hardness is considerably lower than that of the first workpiece W1, a projection is formed on the first workpiece W1 made of the above-mentioned high carbon steel material. It is preferable. In this case, since the projection is likely to bite into the second workpiece W2 during resistance welding, a larger welding strength can be obtained compared to the reverse case.

  Next, the resistance welding method according to the present invention will be described while explaining the welding operation. First, the charging circuit 2 rectifies AC power from the AC power source 1 and converts it into DC power, and charges the energy storage capacitor 3 to the first set voltage. This 1st setting voltage is 400-450V, for example. The charging circuit 2 is either turned on only for a predetermined time or turned off when a voltage detector (not shown) detects that the charging voltage of the energy storage capacitor 3 has reached the first set voltage. There may be. When the charge voltage of the energy storage capacitor 3 reaches the first set voltage value, the first switch circuit 4 is turned on, and the charge of the energy storage capacitor 3 is discharged to discharge the first transformer 4 for welding. A pulsed welding current is passed through the primary winding 5A. This welding current is the current I1 shown in FIG. 1, for example, having a current peak value of tens of thousands to hundreds of thousands of amperes and a pulse width of 10 to 100 milliseconds. As shown in FIG. 1, the pulse welding current I1 is energized while the pressure P between the welding electrodes increases substantially linearly, and the first joining step is performed. By controlling the value of the charging voltage of the energy storage capacitor 3 by the operation of the charging circuit 2, the peak value of the first pulse welding current I1 and the peak value of the second pulse welding current I2 to be described later are obtained. Can be adjusted.

  In this first joining step, a large current is passed through the work piece in a very short time, and the first joining is performed. Therefore, as with other resistance welding methods, quenching is performed at the time of joining. Compared with AC resistance welding, the welded portion and the narrow range around it are only high in temperature, and the range quenched at the joined portion is significantly narrow, but the joined portion is brittle and the welding strength is low. Here, the first switch circuit 4 is turned off after a predetermined on-time has elapsed, and stops the discharge of the accumulated charge in the energy storage capacitor 3. For example, if the off time is set so that the first switch circuit 4 is turned off when the welding current I1 decreases to a current value of about several tens of percent of the peak value that does not contribute much to welding, the energy storage is performed. A certain amount of electric charge remains in the capacitor 3, and the start time of the next second bonding step can be advanced. Here, immediately after the first switch circuit 4 is turned off, the charging circuit 2 starts an on operation and starts charging the energy storage capacitor 3.

  Next, a second joining step is performed immediately after the first cooling time Tc1 after the first pulse welding current I1 is energized. The first cooling time Tc1 is a time required for the welded portion plasticized (softened) to be solidified by energization with the pulsed welding current I1, and improves the joining effect in the second joining step. The first cooling time Tc1 is required so that the quenching process is not performed. However, in order to make the second pulsed welding current I2 as small as possible, the first cooling time Tc1 is the minimum necessary since the temperature is sufficiently high immediately after hardening of the welded portion because the temperature is sufficiently high. Preferably there is. However, in the first embodiment, after the first pulsed welding current I1 is passed, the energy storage capacitor 3 must be charged to the second set voltage value. Therefore, in the first embodiment, the energy storage capacitor 3 is Since the time required to charge to the second set voltage value is required even at the minimum, the first cooling time Tc cannot be shorter than the minimum time.

  When the first switch circuit 4 is turned off, the charging circuit 2 is turned on to start charging the energy storage capacitor 3. Then, when the energy storage capacitor 3 is charged to substantially the second set voltage value and the first cooling time Tc1 has elapsed, the first switch circuit 4 is turned on, and the stored charge in the energy storage capacitor 3 is discharged. . As a result, a single second pulse welding current I2 flows between the welding electrodes 7 and 8 to which the pressure P is continuously applied. This single pulsed welding current I2 has a peak value of 80 to 130% of the peak value of the pulsed welding current I1, and is similar to the waveform of the pulsed welding current I1. As described above, there is a tendency that the peak value of the second pulsed welding current I2 needs to be increased as time elapses immediately after hardening of the welded portion. As a result, the peak value of the pulsed welding current I2 is preferably in the range of about 80% to 130% of the peak value of the pulsed welding current I2.

  When the peak value of the pulse-shaped welding current I2 is smaller than about 80% of the peak value of the pulse-shaped welding current I1, the welding strength cannot be sufficiently improved even if the third joining step described later is performed. The cause of this is that tempering is not performed at the joint between the first workpiece W1 and the second workpiece W2 made of high carbon-high chromium steel, and the first workpiece W1 and the second workpiece W1. That is, the substantial joint depth at the joint portion with the work piece W2 is not finely adjusted. On the other hand, when the peak value of the second pulsed welding current I2 becomes larger than about 130% of the peak value of the first pulsed welding current I1, the first workpiece W1 and the second workpiece W2 are welded. The joint depth of the joint is substantially improved, and both metals are compatible with each other at the joint surface. However, since the energy injected into the joint is too large, quenching is performed, and the hardness of the joint increases again. It becomes brittle, and this causes a decrease in the weld strength overall.

  I will explain this point in more detail. Comparing before and after the first joining step, the first workpiece W1 and the second workpiece W2 are in contact with each other before the first joining step. However, the contact resistance is zero after the first joining step. Therefore, since the resistance of the joint portion between the first workpiece W1 and the second workpiece W2 is only the resistance of the material, the resistance is naturally smaller after the first joining step. Become. Therefore, even if the second pulsed welding current I2 having the same peak value as the first pulsed welding current I1 is supplied in the second joining step, the heat generation at the joined portion is the first time. It becomes smaller than in the joining process. Therefore, the second pulse welding current I2 may be larger than the peak value of the first pulse welding current I1, but if the second pulse welding current I2 is too large, the joint is quenched. Is called. Therefore, the welding strength is not lowered comprehensively in consideration of the degree of increase in hardness due to the quenching and the fine adjustment of the substantial joining depth of the joined portion accompanying the increase in the second pulsed welding current I2. From the results of various experiments, the upper limit of the pulsed welding current I2 is approximately 130% of the peak value of the first pulsed welding current I1.

  However, in the resistance welding of the first workpiece W1 and the second workpiece W2 made of high carbon steel that has been carburized to the inside, such as a high carbon-high chromium steel material, the aforementioned first welding is performed. Even if the 1st and 2nd welding processes are performed, it is only about 2/3 from a little over half of the welding strength when high carbon steel and low carbon steel whose surfaces are carburized under the same conditions are resistance welded. Yes, the expected weld strength cannot be obtained. Accordingly, in the present invention, after the second bonding step described above, the third bonding step is performed after the second cooling time Tc2. In the second joining step, the first switch circuit 4 is turned off and the second pulse circuit welding current I2 is turned on. After the second cooling time Tc2 has passed, the second switch circuit 6 is turned on. Then, the third joining step is performed. When the second switch circuit 6 is turned on, an alternating current flows from the AC power source 1 through the switch circuit 6 through the second primary winding 5B of the welding transformer 5, and the number of turns and the secondary winding of the second primary winding 5B. An alternating current determined by a ratio to the number of turns of the winding 5C flows through the first workpiece W1 and the second workpiece W2 as the third AC welding current i.

  The energizing period of the third AC welding current i is significantly longer than the energizing periods of the first pulsed welding current I1 and the second pulsed welding current I2, for example, 10 to 30 cycles of the commercial frequency, that is, 200 ~ 600 milliseconds. The peak value of the third AC welding current i is significantly smaller than the first and second pulse welding currents I1 and I2. Accordingly, the temperature is gradually increased as compared with the first and second joining steps, the wide range of the first workpiece W1 and the second workpiece W2 becomes high temperature, and the joining portion is Although the tempering is sufficiently performed and the quality is deteriorated in appearance, since the materials of the first workpiece W1 and the second workpiece W2 are sufficiently compatible with each other, the welding strength of the joint is greatly increased. To improve. When the welding strength after the second joining step is compared with the welding strength after the third joining step, for example, the high carbon steel whose welding strength has increased to about 1.9 times and whose surface has been carburized. The desired weld strength was comparable to that of low carbon steel. Here, the second bonding step is omitted, and a cooling time of various lengths is provided after the first bonding step, so that the bonding strength is almost improved even if an alternating current is applied in various energization periods. There wasn't.

  As the resistance welding method, the same welding result can be obtained even if the first pulsed welding current I1 and the second pulsed welding current I2 are the same polarity or different polarity. It is preferable to have a polarity conversion function without worrying about partial excitation of the transformer. The switch circuit 4 shown in FIG. 4 is an example of a circuit having a polarity changing function, which is composed of the control type semiconductor switch elements 4A to 4D as described above. As shown in FIG. 1, when the first pulse welding current I1 and the second pulse welding current I2 are passed through the first primary winding 5A of the welding transformer 5 with the same polarity, the welding transformer Since the magnetic core 5 is strongly excited in one direction, partial excitation may occur, and the welding apparatus may not operate normally. In order to prevent or alleviate the partial excitation phenomenon of the welding transformer 5, the direction in which the first pulsed welding current I1 and the second pulsed welding current I2 flow through the first primary winding 5A is reversed. do it. In the switch circuit 4 shown in FIG. 4, for example, the semiconductor switch elements 4 </ b> A and 4 </ b> B are turned on in the first joining process, and the semiconductor switch elements 4 </ b> C and 4 </ b> D are turned on in pairs in the second joining process. Pulse-shaped welding currents I1 and I2 in opposite directions can be alternately passed through the first primary winding 5A of the transformer 5 for use. Thus, by alternately supplying pulsed welding currents I1 and I2 having different polarities to the primary winding 5A, the magnetic flux of the magnetic core of the welding transformer 5 is almost zero or fixed for each of the first and second joining processes. Therefore, a special reset circuit for preventing or mitigating the partial excitation phenomenon becomes unnecessary. In FIG. 4, 4X is a controller that operates the semiconductor switch elements 4A to 4D in a predetermined sequence as described above.

[Embodiment 2]
Although the configuration is complicated as compared with the resistance welding apparatus according to the first embodiment, the first cooling time Tc1 shown in FIG. 1 is required without being influenced by the charging time of the energy storage capacitor as compared with the first embodiment. A second embodiment of the resistance welding circuit that can be shortened to the initial limit will be described with reference to FIGS. In FIG. 5, the same symbols as those used in FIG. 2 indicate members having the same names. Since the resistance welding method is almost the same as the method described in the first embodiment, it will not be described in detail. In the second embodiment, in addition to the first charging circuit 2, the second charging circuit 10, the second energy storage capacitor 11 that is charged by the charging operation of the second charging circuit 10, and the second energy storage capacitor And a third switch circuit 12 for discharging the 11 charged charges. The second charging circuit 10 and the second energy storage added to the first power feeding circuit 20 including the first charging circuit 2, the first energy storage capacitor 3, and the first switch circuit 4. The second power feeding circuit 30 including the capacitor 11 for use and the third switch circuit 12 is arranged in parallel.

  Next, the operation of the resistance welding apparatus according to the second embodiment will be described. Since the operation of the first power supply circuit 20 is almost the same as that of the first embodiment, detailed description thereof is omitted. However, the charge charged in the first energy storage capacitor 3 is welded by turning on the first switch circuit 4. It is emitted to the first primary winding 5A of the transformer 5 for use in the arrow direction a1. As a result, the first pulse welding current I1 shown in FIG. 1 flows through the welding electrode 7, the first and second workpieces W1 and W2 and the welding electrode 8, and the first joining step is performed. Is called. At this time, the second power supply circuit 30 is charged in advance so that the second energy storage capacitor 11 has the second set voltage value before the cooling time Tc1 elapses. Therefore, the second energy storage capacitor 11 is always charged to the second set voltage value after the first pulsed welding current I1 is applied and before the cooling time Tc1 elapses. Therefore, the cooling time Tc1 is necessary. Even if it is as short as possible, when the third switch circuit 12 is turned on, the second pulsed welding current I2 having a predetermined peak value is applied to the first and second workpieces W1 and W2 immediately after the cooling time Tc1 has elapsed. Can be energized to perform the second bonding step.

  At this time, when the third switch circuit 12 is turned on, the electric charge of the second energy storage capacitor 11 is discharged through the first primary winding 5A of the welding transformer 5 in the direction of the arrow a2 opposite to the arrow a1. The Therefore, if the first pulsed welding current I1 is positive, the second pulsed welding current I2 is negative. Therefore, as described above, the first and second pulsed welding currents I1, The magnetic core of the welding transformer 5 is not excited only in one direction by I2, and the welding transformer 5 is not biased. For this reason, the first switch circuit 4 and the third switch circuit 12 do not have to have a circuit configuration having a polarity switching function as shown in FIG. 4, so that the number of semiconductor switch elements can be reduced, and the drive sequence The cost can be reduced and the reliability can be improved.

  Then, after the energization of the second pulsed welding current I2, the second switch circuit 6 is turned on immediately after the second cooling time Tc2 has elapsed, and the AC welding current i is switched between the welding electrodes 7 and 8 for a predetermined time. The first and second workpieces W1 and W2 in between are energized to perform the second joining step. Also with this resistance welding apparatus, resistance welding is performed between the first workpiece W1 made of the above-described high-carbon steel material and the second workpiece W2 made of low-carbon steel or high-carbon steel whose surface is carburized. As with the first embodiment, satisfactory weld strength was obtained. In this resistance welding apparatus, a first power supply circuit 20 for supplying the first pulsed welding current I1 and a second power supply circuit 30 for supplying the second pulsed welding current I2 are separately provided. Since it is provided, the peak value and accumulated energy of the first pulsed welding current I1 and the second pulsed welding current I2 can be determined arbitrarily and arbitrarily, and the cycle time of the welding process can be shortened, More optimal resistance welding can be performed, and higher welding strength can be obtained.

  In the second embodiment, in order to shorten the cycle time of the welding process, the first charging circuit 2 can start the on operation immediately after the first switch circuit 4 is turned off, and the second charging is performed. It is desirable that the circuit 10 is sequenced so that the ON operation can be started immediately after the third switch circuit 12 is turned OFF. Although not shown, a third primary winding wound in the opposite polarity to the first primary winding 5A is provided in the welding transformer 5, and a second energy storage is provided in the third primary winding. The accumulated charge in the capacitor 11 may be discharged. In the first and second embodiments described above, the switch circuits 4 and 6 and the switch circuit 12 are described as including the semiconductor switch elements and the controller that drives them. However, the switch circuits 4 and 6 and the switch circuit 12 are Each of them may be composed of a semiconductor switch element and a snubber circuit, and a control circuit that controls these semiconductor switch elements in common, that is, in a comprehensive manner, separately from the switch circuits 4 and 6 and the switch circuit 12 may be provided.

  In the first and second embodiments described above, the first workpiece W1 is made of a high carbon steel material that has been carburized and quenched to the inside, and the second workpiece W2 is low carbon steel or the surface is carburized. Although it explained as what consists of the made high carbon steel, even if it consists of high carbon steel materials in which the 2nd work piece W2 is carburized deeply to the inside similar to the 1st work piece W1. Good. In this case, since both the first workpiece and the second workpiece are made of high carbon steel that has been carburized and quenched to the inside, the first workpiece W1 and the second workpiece are welded. A metal member made of low-carbon steel is interposed between the welded product W2 and sandwiched between the first and second workpieces to be welded. By sequentially performing the joining process, it becomes possible to resistance-weld the first and second workpieces made of the above-mentioned high carbon steel material with the desired welding strength. In the first and second embodiments, since the first to third joining steps are performed in a state where the pressure P between the electrodes is continuously applied, the workpiece can be prevented from being deformed due to thermal strain, and the like. Moreover, since the plastic fluidized high carbon steel and the plastic fluidized low carbon steel are more compatible with each other at the joint, the welding strength is further increased.

It is a figure for demonstrating the resistance welding method of the high carbon steel which concerns on this invention. It is a figure which shows Embodiment 1 of the resistance welding apparatus which can implement | achieve the resistance welding method which concerns on this invention. It is a figure which shows an example of the welding electrode for implementing the resistance welding method of the high carbon steel which concerns on this invention, and a to-be-welded object. It is a figure which shows a specific example of the switch circuit used for the resistance welding apparatus which concerns on this invention. It is a figure which shows Embodiment 2 of the resistance welding apparatus which can implement | achieve the resistance welding method which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... AC power supply 2 ... 1st charging circuit 3 ... 1st energy storage capacitor 4 ... 1st switch circuit 5 ... Welding transformer 5A, 5B ... For welding First, second primary winding 5C of transformer 5 ... Secondary winding 6 of welding transformer 5 ... Second switch circuit 7, 8 ... Welding electrode 10 ... Second Charging circuit 11 ... second energy storage capacitor 12 ... third switch circuit 20 ... first feeding circuit 30 ... second feeding circuit W1, W2 ... first, first 2 to-be-welded object I1 ... 1st pulse-shaped welding current I2 ... 2nd pulse-shaped welding current i ... AC welding current Tc1 ... first cooling time Tc2 ... second cooling time P: Pressure between welding electrodes

Claims (4)

A welding current is applied with pressure applied between the first work piece made of high carbon steel that has been carburized and quenched to the inside, and the second work piece, and the first work piece is energized. met method of the resistance welding high carbon steel welding weldment and said second object to be welded,
A first bonding step of performing the first bonding to flow the first pulsed welding current I1 of the single between the first object to be welded and the second object to be welded,
A single second pulsed welding current I2 having a peak value of 80 to 130% of the peak value of the first pulsed welding current after elapse of the cooling time Tc from the energization of the first pulsed welding current. a second bonding step of performing a second round junction to flow between the first object to be welded and the second object to be welded,
Wherein the second pulsed welding current I2 after energization, said first pulsed welding current longer than the energization time of the energization time 及 beauty said second pulsed welding current I2 of I1, the first pulse A first AC welding current i having a peak value smaller than the peak value of the second welding current I1 and the second pulse welding current I2 is energized between the first workpiece and the second workpiece . 3. A high-carbon steel resistance welding method characterized by sequentially performing the joining step 3. A charging circuit to which electric power from an AC power source is input; an energy storage capacitor to be charged by the electric power from the AC power source through the charging circuit; a first primary winding and a second primary winding; and a welding transformer having a secondary winding, a first switch circuit for discharging the charge stored in the energy storage capacitor through the first primary winding, the power from the AC power source And a second switch circuit connected in parallel with the second primary winding, and is a high carbon steel that is carburized and quenched from the secondary winding to the inside. A high-carbon steel resistance welding apparatus that conducts resistance welding by passing a welding current between the workpiece and the second workpiece,
After the energy storage capacitor is charged to the first set voltage value by the charging operation of the charging circuit, the first switch circuit is turned on, and the first workpiece and the second workpiece are Between the first pulse welding current I1 during the first and the first joining is performed ,
Next, after the energy storage capacitor is charged to the second set voltage value by the charging operation of the charging circuit, the first switch circuit is turned on again after the cooling time has elapsed and the first covered circuit is turned on. between the weldments and the second object to be welded, by energizing the single second pulsed welding current I2 80 to 130% of the peak value of the peak value of the first pulsed welding current Turn off after the second bonding ,
The second switch circuit is turned on after the second turn-off of the first switch circuit, and the energization time of the first pulsed welding current I1 and the energization time of the second pulsed welding current I2 For a longer time, an AC welding current i having a peak value smaller than the peak values of the first pulsed welding current I1 and the second pulsed welding current I2 is supplied from the AC power source through the welding transformer. A high-carbon steel resistance welding apparatus , wherein a third joining is performed between the first work piece and the second work piece . A first charging circuit to which power from an AC power source is input; a first energy storage capacitor that is charged by power from the AC power source via the first charging circuit; and power from the AC power source. Is stored in the second energy storage capacitor, the second energy storage capacitor charged by the power from the AC power supply via the second charging circuit, and the first energy storage capacitor. The first switch circuit for discharging the charged charge through the first primary winding and the charge stored in the second energy storage capacitor in the same manner as the first energy storage capacitor a third switching circuit for discharging through a common said first primary winding, the power from the AC power supply is inputted and connected in parallel with said second primary winding 2 Sui A welding current is passed between the first workpiece to be welded and the second workpiece to be carburized and quenched from the secondary winding to the inside. A resistance welding apparatus for high carbon steel that performs resistance welding,
After the first energy storage capacitor is charged to the first set voltage by the charging operation of the first charging circuit, the first switch circuit is turned on to store the first energy storage capacitor. After discharging a charge, a first first pulsed welding current I1 is applied between the first workpiece and the second workpiece to perform the first joining. Turn off,
After the second energy storage capacitor is charged to the second set voltage by the charging operation of the second charging circuit, the third switch circuit is turned on after the elapse of the cooling time to turn on the second energy. By discharging the stored charge of the storage capacitor, a peak value of 80 to 130% of the peak value of the first pulse welding current between the first workpiece and the second workpiece. off the single second pulsed welding current I2 after the second round junction energized,
The second switch circuit is turned on after the third switch circuit is turned off, and is longer than the energizing time of the first pulse welding current I1 and the energizing time of the second pulse welding current I2. The AC welding current i having a peak value smaller than the peak values of the first pulsed welding current I1 and the second pulsed welding current I2 is supplied from the AC power source through the welding transformer. welded a second resistance welding apparatus with a high carbon steel and performing a third junction of which conductible between the object to be welded. In claim 3,
The first energy storage capacitor and the second energy storage capacitor with respect to the common first primary winding in which the first charging circuit and the second charging circuit are respectively connected in parallel. The high carbon steel resistance welding apparatus is characterized in that the accumulated charges of each are discharged with opposite polarities.

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