WO2001055481A1

WO2001055481A1 - Power supply for discharge surface treatment and discharge surface treatment method

Info

Publication number: WO2001055481A1
Application number: PCT/JP2000/000303
Authority: WO
Inventors: Akihiro Goto; Toshio Moro
Original assignee: Mitsubishi Denki Kabushiki Kaisha
Priority date: 2000-01-24
Filing date: 2000-01-24
Publication date: 2001-08-02
Also published as: CN1344333A; CN1210128C; CH695567A5; DE10084316B4; DE10084316T1; TW483948B

Abstract

A first pulse width T1 and a first peak value Ip1 are determined so that the current density between an electrode (1) and a work (2) is in such a predetermined range that the release of an electrode material is controlled. During the first pulse width T1, after the diameter of the discharge arc column (10) reaches a sufficient value, the discharge current is increased to a second peak value Ip2 so that a predetermined amount of hard coating material is supplied by the release of the electrode material according to predetermined processing conditions during a second pulse width T2. Then a discharge is caused between the electrodes to efficiently form a hard coating (17) on the work (2). Thus the surface treatment cost is lowered and a dense hard coating (17) is formed on a work (2).

Description

Description Power supply device for discharge surface treatment and discharge surface treatment method

According to the present invention, a discharge is generated between an electrode for discharge surface treatment and a workpiece, and a hard coating made of the electrode material or a substance in which the electrode material reacts with the discharge energy by the energy of the discharge. TECHNICAL FIELD The present invention relates to a power supply device for electric discharge surface treatment and an electric discharge surface treatment method used for electric discharge surface treatment for forming a hard coating made of the following. Background art

Conventionally, techniques for forming a hard coating on the surface of a workpiece to impart corrosion resistance and wear resistance include, for example, a discharge surface disclosed in Japanese Patent Application Laid-Open No. 5-148615. There is a processing method. In this technology, primary processing (deposition processing) is performed using a green compact electrode, which is a discharge surface treatment electrode formed by mixing WC (tandustane carbide) powder and Co (cobalt) powder and compression molding. This is a method for treating the discharge surface of a metal material, which consists of two steps: performing a secondary process (remelting process) by replacing the electrode with a relatively low electrode consumption such as a copper electrode. This method can form a hard coating with strong adhesion to steel, but cannot form a hard coating with strong adhesion to sintered materials such as cemented carbide. Have difficulty.

However, according to our research, when a material that forms a hard carbide such as Ti (titanium) is used as an electrode for discharge surface treatment and a discharge is generated between the workpiece and a metal material, the process of remelting occurs. It has been found that a strong hard coating can be formed on the metal surface, which is the workpiece, without the need. This is due to the discharge This is because the exhausted electrode material reacts with C (carbon), which is a component of the working fluid, to produce TiC (titanium carbide). In addition, when a discharge is generated between a metal material as a workpiece and a compact powder electrode as a discharge surface treatment electrode made of a metal hydride such as TiH 2 (titanium hydride), T It has been found that a hard coating can be formed more quickly and with higher adhesion than when a material such as i is used. Moreover, the green compact electrode is an electrode for electrical-discharge surface treatment with a mixture of other metals or ceramics hydride such as T i H _2, when a discharge is generated between the metal material as a workpiece, the hardness It is important that hard coatings having various properties such as abrasion resistance can be quickly formed.

Such a method is disclosed, for example, in Japanese Patent Application Laid-Open No. 9-192937, and FIG. 4 is a block diagram showing an example of an apparatus used for such a discharge surface treatment. is there. In the figure, 1 is a green compact electrode which is an electrode for discharge surface treatment formed by compression molding of TiH2 powder, 2 is a workpiece, 3 is a heating tank, 4 is a working fluid, and 5 is a green compact. A switching element for switching the voltage and current applied to the electrode 1 and the workpiece 2; 6, a control means for controlling on / off of the switching element 5; 7, a power source; 8, a resistor; It is a hard coating. With this configuration, a discharge is generated between the green compact electrode 1 and the workpiece 2, and the discharge energy forms a hard coating 9 on the surface of the workpiece 2 made of steel, cemented carbide, or the like. can do. Switching element 5, control circuit 6, power supply 7, and resistor 8 This is equivalent to a discharge surface treatment power supply device that determines the discharge current pulse waveform in discharge surface treatment.

Such a conventional discharge surface treatment power supply device is basically based on a rectangular discharge current pulse, and as shown in FIG. 5, by changing the discharge current peak value I p and the pulse width T, Hard coating formed on workpiece Is to adjust the film thickness or the like.

FIG. 6 is an explanatory diagram of the adhesion of the electrode material to the workpiece, and FIG. 7 is a diagram showing changes in the current density and the diameter of the discharge arc column with the passage of time from the start of discharge. In Fig. 6, 1 is an electrode for electrical discharge surface treatment, 2 is a workpiece, 10 is a discharge arc column, 11 is an electrode component that is rapidly heated, vaporized, exploded and released, and 12 is a workpiece 2 This is the electrode component attached. Immediately after discharge has occurred, the diameter of the discharge arc column 10 is small and the current density is extremely high, as shown in (a) of FIG. 6 and FIG. Also, the electrode for electric discharge surface treatment is different from the normal electrode for electric discharge machining that performs removal machining, in which the heat conduction and the mechanical strength are deliberately reduced to improve the productivity of the surface treatment work _; As shown in (a) of the figure, when the current density is high, the portion near the discharge arc column 10 of the discharge surface treatment electrode 1 is rapidly heated, and a part of the discharge surface treatment electrode 1 is vaporized and exploded. It will be scattered around (in the machining fluid). Here, the rapidly heated, vaporized, exploded, and released electrode component 11 is rapidly cooled by the heating solution, and does not become a hard coating of the workpiece 2. On the other hand, when the current density is appropriate, as shown in FIG. 6 (b), since the diameter of the discharge arc column 10 is widened, a wide area of the discharge surface treatment electrode 1 is heated and covered. The amount of the electrode component 12 attached to the workpiece 2 increases.

Thus, in the case of a rectangular discharge current pulse waveform (for example, Fig. 5) from a conventional power supply for discharge surface treatment, even if the peak value IP of the discharge current pulse is increased in order to improve the productivity of surface treatment. In particular, immediately after the discharge, the ratio of the electrode material adhering to the workpiece is small. Therefore, the ratio of the electrode material adhering to the workpiece is about 10% to 50% by weight, and there is a problem that the surface treatment cost is increased due to the large waste of the electrode material.

In the discharge surface treatment method, the electrode material is released by the heat of the discharge, and a part of the material is melted and adhered to the surface of the workpiece as a hard film. Obedience The discharge energy has a function of releasing the electrode material and a function of melting the released material and the workpiece. Fig. 8 is a photograph of the surface of the workpiece when the discharge surface treatment was performed by a single discharge current pulse on the steel material as the workpiece. Fig. 8 (a) shows the amount of release of the electrode material. If too much, FIG. 8 (b) shows the case where the amount of the released electrode material is too small. If the release amount of the electrode material is too large ((a) in Fig. 8), the electrode material released by the discharger energy will not melt sufficiently, and a dense hard film cannot be formed on the workpiece. . If the amount of electrode material released is too small (FIG. 8 (b)), the workpiece is excessively melted, and the workpiece is removed more than the hard coating adheres. In a conventional discharge surface treatment power supply unit, the rectangular discharge current pulse waveform (for example, Fig. 5) shows that in one discharge, the discharge of the electrode material and the discharge of the electrode material and the workpiece by one rectangular discharge current pulse. It is difficult to secure an appropriate supply amount of electrode material because of simultaneous melting of the electrodes, and it is difficult to remove the workpiece due to insufficient supply of electrode material and to melt the hard coating due to excessive supply of electrode material. There is a problem that occurs. Disclosure of the invention

The present invention has been made in order to solve the above-described problems, and can reduce surface treatment costs and form a dense hard film on a workpiece. An object is to obtain a power supply device and a discharge surface treatment method.

The power supply device for electric discharge surface treatment according to the present invention is used for electric discharge surface treatment in which a discharge is generated between an electrode for electric discharge surface treatment and a workpiece and energy is used to form a hard coating on the surface of the workpiece. In the power supply device for discharge surface treatment used, the discharge current pulse is set to a first pulse width T 1 (first peak value I p 1), second pulse width T 2 (second peak value I p 2), ..., n-th pulse width Tn (peak value of η Ι ρ η) (η is an integer of 2 or more ), And the first pulse width Τ1 and the first peak value Iρ1 are set so as to be a current density between the electrodes within a predetermined range for suppressing emission of the electrode material, The k-th pulse width T k and the k-th peak value I pk (2≤k≤n, where k is an integer) are set in advance according to the desired processing conditions when the supply amount of the hard coating material due to the release of the electrode material is set. Control means for setting the values so as to be set.

The discharge surface treatment method according to the present invention is directed to a discharge surface treatment method for generating a discharge between a discharge surface treatment electrode and a workpiece, and forming a hard coating on the surface of the workpiece by energy thereof. Discharge current pulse

1 pulse width T 1 (first peak value I pi), second pulse width T 2 (second peak value I p 2), nth pulse width Tn (nth peak value I pn) (n is an integer of 2 or more), and the first pulse width T 1 and the first peak value I p 1 are defined as the distance between the electrodes within a predetermined range for suppressing the release of the electrode material. The current density is set so that the k-th pulse width T k and the k-th peak value I pk (2≤k≤n, k is an integer) are set so that the supply amount of the hard coating material by the release of the electrode material is A hard coating is formed on the surface of the workpiece by setting the value to a value set in advance in accordance with an intended processing condition.

The present invention is configured as described above, and has the following effects.

ADVANTAGE OF THE INVENTION Since the power supply device for discharge surface treatment and the discharge surface treatment method according to the present invention can efficiently make the electrode material adhere to the workpiece surface, the surface treatment cost can be reduced.

In addition, since an appropriate supply amount of the electrode material can be secured, a dense hard film can be formed on the workpiece. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a diagram showing a configuration of a power supply device for surface treatment for discharge according to an embodiment of the present invention, a voltage between electrodes, and a discharge current.

FIG. 2 is an explanatory diagram showing a state of forming a hard film on a workpiece by discharge surface treatment using the power supply device for discharge surface treatment according to the embodiment of the present invention.

FIG. 3 shows the electrode wear lengths when the discharge surface treatment was performed using the conventional power supply device for discharge surface treatment and when the discharge surface treatment was performed using the power supply device for discharge surface treatment according to the present invention. It is a figure which shows comparison of a height.

FIG. 4 is a configuration diagram showing an example of an apparatus used for discharge surface treatment. FIG. 5 is a diagram showing a gap voltage and a discharge current pulse in a conventional power supply device for surface treatment for discharge.

FIG. 6 is an explanatory diagram of the adhesion of the electrode material to the workpiece. FIG. 7 is a diagram showing changes in current density and diameter of a discharge arc column with the passage of time from the start of discharge.

FIG. 8 is a photograph of the surface of the workpiece when the discharge surface treatment was performed on the steel material by one discharge current pulse. BEST MODE FOR CARRYING OUT THE INVENTION FIG. 1 shows a power supply device for electric discharge surface treatment according to an embodiment of the present invention. FIG. 1 (a) is a configuration diagram, FIG. (B) shows the gap voltage and discharge current, and (c) in FIG. 1 shows another example of the discharge current. In FIG. 1, 1 is an electrode for electric discharge surface treatment, 2 is a workpiece, 3 is a machining tank, 4 is a machining fluid, 13 is a switching element group, and 14 is an on / off of the switching element group 13. Control means to control, 15 is power supply, 16 is resistor group, T 1 is the first pulse width, T 2 is the second pulse width, Tr is the dwell time, I pl is the first peak value, and I p 2 is the second peak value. The switching element group 13, the control means 14, the power supply 15, and the resistor group 16 correspond to a discharge surface treatment power supply device that determines a discharge current pulse waveform and the like in the discharge surface treatment.

Next, the operation will be described. The discharge surface treatment electrode 1 and the workpiece 2 are opposed to each other in the machining fluid 4, and a predetermined gap is maintained by a driving device (not shown). The peak value of the discharge current is a function of the power supply voltage of the power supply 15 and the resistance value of the resistor group 16 connected in series with the on switching element of the switching element group 13. By turning on the switching elements of the switching element group 13 connected in series to the resistors having a large resistance value in the resistor group 16 by the control means 14, the discharge surface treatment electrode 1 and the workpiece 2 are connected to each other. After a predetermined time has elapsed, discharge occurs (first peak value I p 1). After the occurrence of discharge is detected and the first pulse width T1 has elapsed, the switching element that has been turned on is turned off by the control means 14, and a resistor having a small resistance value in the resistor group 16 is turned off. The discharge current is increased by turning on the switching elements of the switching element group 13 connected in series (second peak value Ip2). Thereafter, after the second pulse width T 2 has elapsed, the control means 14 turns off all the switching elements of the switching element group 13. Further, after the elapse of the rest time Tr, the switching elements of the switching element group 13 are selectively turned on again by the control means 14. The discharge surface treatment is performed by repeating the above operations. As described above, the control of the peak value of the discharge current can be performed by the control means 14 selectively turning on and off the switching elements of the switching element group 13.

The discharge current pulse may be stepwise as shown in FIG. 1 (b), The shape may be a slope as shown in (c) of FIG. The discharge current and the slope can be increased by a method such as introducing an inductance in series with the power supply circuit of the power supply device for discharge surface treatment.

FIG. 2 is an explanatory view showing a state in which a hard film is formed on a workpiece by discharge surface treatment using a power supply device for discharge surface treatment according to an embodiment of the present invention. 2 is a workpiece, 10 is a discharge arc column, and 17 is a hard coating formed on the workpiece 2 by the method according to the present invention. (A) in FIG. 2 corresponds to the first part of the first pulse width T1 in (b) or (c) in FIG. 1, and (b) in FIG. 2 corresponds to ( b) or (c) corresponds to the last part of the first pulse width T1, and (c) in FIG. 2 corresponds to the second pulse width T2 in (b) or (c) in FIG. It corresponds to the part. In (b) or (c) of FIG. 1, the first pulse width T 1 and the first peak value I p 1 are set so as to have a current density within a predetermined range for suppressing the release of the electrode material. ((A) in FIG. 2) In the section of the first pulse width T1, the diameter of the discharge arc column 10 is made sufficiently large ((b) in FIG. 2). Next, in the state where the diameter of the discharge arc column 10 is increased, the supply amount of the hard coating material due to the discharge of the electrode material is previously determined at the second pulse width T2 according to the intended processing conditions. The switching means 13 and the like are controlled by the control means 14 so that the set value is obtained, and the discharge current is increased to a predetermined second peak value Ip2. Thus, the hard film 17 is formed efficiently (FIG. 2 (c)).

The first pulse width T1 and the first peak value Ip1, which are the current density between the electrodes within a predetermined range that suppresses the release of the electrode material, and the supply amount of the hard coating material to the workpiece are determined. The set values of the second pulse width T2 and the second peak value Ip2, which are the desired amount, are determined in advance by experiments, and the required processing speed, surface properties of the hard coating, electrode consumption, etc. It can be set according to the processing conditions. Wear. For example, the material of the electrode for discharge surface treatment and its constituent component ratio, the parameter of the electrode such as hardness, the parameter of the material of the workpiece, etc., the first pulse width T1, the second pulse width When the pulse width of the discharge current and the parameters of the peak value of T 2, the first peak value I p 1 and the second peak value IP 2 are changed, the amount of consumption of the electrode for discharge surface treatment, work Data such as the surface properties of the hard coating formed on the object and the productivity of the surface treatment work are collected in advance by experiments, and using these data, the expected processing speed, the surface properties of the hard coating, and electrode consumption The first pulse width T1 and the first peak value I1, which are the current density between the electrodes within a predetermined range that suppresses the release of the electrode material, according to the processing conditions such as Set the second pulse width T 2 and the second peak value I p 2 so that the material supply amount is the expected amount. It is sufficient.

FIG. 3 shows the electrode wear lengths when the discharge surface treatment was performed using the conventional power supply device for discharge surface treatment and when the discharge surface treatment was performed using the power supply device for discharge surface treatment according to the present invention. The comparison was made under the condition that the thickness of the hard coating formed on the workpiece was the same. In this case, the discharge current pulse from the conventional discharge surface treatment power supply device is a rectangular wave having a peak value IP of 8 A and a pulse width T of 8 s.The discharge current pulse from the discharge surface treatment power supply device according to the present invention is as follows. The first pulse width T1 is 8 s, the first peak value Ip1 is 2 A, the second pulse width T2 is 8 s, and the second peak value Ip2 is 8 A. In FIG. 3, the electrode wear length is about 500 m for the conventional discharge current pulse and about 200 m for the discharge current pulse according to the present invention. It can be seen that electrode wear can be greatly reduced.

As described above, according to the discharge surface treatment using the power supply device for discharge surface treatment according to the present invention, the electrode material can be efficiently attached to the surface of the workpiece, thereby reducing the surface treatment cost. Can be. Also, electrode materials Since a proper supply amount of the material can be secured, a dense hard film can be formed on the workpiece.

In the above description, the peak value of the discharge current may be three steps or more in two steps. Further, in each section of the pulse width, the current value of the discharge current pulse is not constant or slope-shaped, and may be a predetermined time function. Industrial applicability

INDUSTRIAL APPLICABILITY As described above, the power supply device for discharge surface treatment and the discharge surface treatment method according to the present invention are suitable for use in a surface treatment-related industry in which a hard film is formed on the surface of a workpiece.

Claims

The scope of the claims

1. In a power supply device for electric discharge surface treatment used for electric discharge surface treatment for generating a discharge between the electrode for electric discharge surface treatment and a workpiece and using the energy to form a hard film on the surface of the workpiece,

The discharge current pulse is divided into a first pulse width T 1 (first peak value I pi), a second pulse width T 2 (second peak value I p 2),. n (n is an integer greater than or equal to 2), and the first pulse width T 1 and the first peak value I p 1 are determined to suppress the release of the electrode material. And the k-th pulse width T k and the k-th peak value I pk (2≤k≤n> k is an integer) within the range of A power supply device for electric discharge treatment, characterized by comprising control means for setting the supply amount of the hard coating material to a value set in advance according to the intended processing conditions.

2. A discharge surface treatment method in which a discharge is generated between an electrode for discharge surface treatment and a workpiece and energy is used to form a hard coating on the surface of the workpiece.

The discharge current pulse is divided into a first pulse width T 1 (first peak value I pi), a second pulse width T 2 (second peak value I p 2), an n-th pulse width T n (n is an integer greater than or equal to 2), and the first pulse width T 1 and the first peak value I p 1 are determined to suppress the release of the electrode material. And the k-th pulse width T k and the k-th peak value I pk (2≤k≤n, where k is an integer) are set to be within the range of A discharge surface treatment method comprising: setting a supply amount of a hard coating material according to a predetermined value according to an intended processing condition; and forming a hard coating on the surface of the workpiece.