JP3038814B2 - Electrodes for plasma arc machining - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electrode used for a plasma arc machining torch for welding or cutting a workpiece.

<Prior Art> Generally, a plasma arc processing torch is shown in FIG. 5, where 1 is a plasma electrode cooled by a fluid, and this electrode 1 is a hollow electrode base made of copper or a copper alloy. The electrode member 2 is composed of a material 2 and a high-melting-point insert 3 such as hafnium or zirconium, which is mounted in a recess at the tip of the electrode substrate 2. 4 is an electrode support member made of a conductive material for supporting the electrode 1, 5 is an insulating sleeve provided outside the electrode support member 4, 6 is a chip support member made of a conductive material provided outside the insulating sleeve 5, The torch body 7 is constituted by 4 to 6 above. Reference numeral 8 denotes a hollow chip supported at the tip of the tip support member 6, and a plasma flow ejection hole 801 is formed at the center of the tip. 9 is an insulating cup, 10 is a cooling water guide tube, and the cooling water flowing from the supply hose 11 directly cools the electrode 1 and then flows out of the torch from the drain hose 12 through the passage shown by the arrow. In the torch, while supplying power between the electrode 1 and the workpiece, an appropriate plasma arc forming fluid G such as air, oxygen, or nitrogen is ejected from the plasma ejection hole 801 of the chip 8 to generate a plasma jet. The plasma jet is used to process the workpiece.

<Problems to be Solved by the Invention> However, recently, there is a variation in electrode life from users, and there is a problem in work management. Therefore, an electrode having a life as uniform as possible has been demanded.

Therefore, when the electrode was investigated, the electrode 1
In this method, a recess having a diameter slightly smaller than the outer diameter of the insert 3 is formed in the tip of the electrode base material 2, and the columnar insert 3 is driven into the recess. In this case, the air in the distal end recess is closed as if the insert 3 was a lid, and a vacuum state was established as the insert 3 was fitted into the distal end recess,
It was found that most of the electrodes 1 in which the insert 3 was driven into the recess at the distal end and fitted had a gap between the bottom surface of the recess at the distal end and the insertion end face of the insert 3. However, due to the processing accuracy of the tip recess and the insert 3, there are some cases where the bottom surface of the tip recess and the insertion end face of the insert 3 are in contact with each other. The electrode life was shorter when an electrode having a gap between the bottom surface and the insertion end face of the insert 3, that is, when most of the electrodes were used.

Therefore, an object of the present invention is to provide an electrode for plasma arc processing having a uniform service life.

<Means for Solving the Problems> In order to achieve the above object, the configuration of the present invention is to mount a high-melting point insert in a concave portion at the tip of an electrode substrate made of copper or a copper alloy cooled by a fluid. In the electrode for plasma arc machining, the insert is sequentially subjected to nickel electroplating and noble metal plating, and the diameter of the tip recess is formed slightly larger than the diameter of the plated insert, and the tip recess is formed. The insert is driven into the space defined by the electrode base material and the insert by driving the insert through the low-melting substance so that the insert is on the release side of the tip recess. , The outer periphery of the end of the electrode base material is pressed in the center direction, and the end of the electrode base material and the insert are machined so as to be flush with each other.

<Example> Hereinafter, the present invention will be described in detail with reference to the drawings. In FIG. 1, reference numeral 2 denotes an electrode substrate made of copper or a copper alloy cooled by a fluid, and reference numeral 3 denotes an insert having a high melting point such as hafnium or zirconium, which is formed, for example, in a columnar shape. Reference numeral 21 denotes a substance having a lower melting point than that of the electrode substrate 2, and is a so-called low melting point alloy such as tin, lead, or an alloy of tin and lead. The low-melting substance 21 and the insert 3 are mounted, for example, fitted so that the insert is on the open side of the concave end. That is, in other words, the substance 21 having a low melting point is filled in a space defined by the electrode base material 2 and the insert 3.

The electrode 1 is composed of the electrode substrate 2, the substance 21 having a low melting point, and the insert 3.

In the electrode 1 having the above-described structure, the low-melting substance 21 generally has flexibility, but when the insert 3 is driven into the concave portion 201 of the electrode substrate 2 through the low-melting substance 21 to be fitted therein,
Since the sealed air corresponding to the tip recess 201 exists in a vacuum state, there are many states where the insertion end face of the insert 3 does not completely contact the low melting point material 21 and the bottom face of the tip recess 201. However, when plasma processing is performed using the electrode 1, the temperature of the tip of the insert 3 is about 1000 ° C., and the temperature of the insertion end face of the insert 3 is about 600 ° C., so that the substance 21 having a low melting point is melted. The insertion end face of the insert 3 and the bottom face of the tip recess 201 are thermally short-circuited by the molten low melting point substance 21. By the way, generally, a cooling fluid is used to form the concave portion 20 at the tip of the electrode substrate 2.
Since the bottom surface of 1 is most efficiently cooled, the insert 3 thermally short-circuited to the bottom surface via the molten low-melting substance 21 is effectively cooled. For this reason, the electrode life during which the electrode 1 is thermally stable during the plasma processing becomes constant.

Next, in FIGS. 2 (A) to 2 (F) and FIGS. 3 (A) to 3 (D), reference numeral 3 denotes a high melting point insert having a predetermined size. The insert 3 is formed in a cylindrical shape having a diameter of 1 to 3 mm and a length of 3 to 5 mm. First, the surface of the insert 3 is degreased and the oxide film is removed by a pretreatment such as electrolytic degreasing and immersion in hydrofluoric acid. Thereafter, as shown in FIG. 2B, nickel plating 1 is applied to the surface of the insert 3 by electroplating.
For example, the insert 3 is electroplated with nickel using a wood strike bath. In this case, the current density of the wood strike nickel plating is 1 to 10 A · dm ⁻² , preferably 2
~ 4A ・ dm ^-2 , the electroplating time is 10 ~ 15 minutes, the appropriate thickness of the wood strike nickel plating 41 is 0.1
2020 μm was obtained. Thereafter, as shown in FIG. 2C, the surface of the insert 3 is appropriately plated with silver. Assuming that the diameter of the insert 3 in which the nickel electroplating 41 and the silver plating 42 are sequentially applied is d, the diameter of the tip concave portion 201 formed in the electrode base material 2 made of copper or a copper alloy is d The material 21 having a low melting point and the insert 3 are inserted into the recess 201 at the tip end, which is slightly larger than d + Δd. Thereafter, as shown in FIG. 2 (E) and FIG. 3 (A), the outer periphery of the end of the electrode substrate 2 is pressed in the center direction by the pressing tools 51 to 54. By the way, the electrode substrate 2 protrudes to the tip of the electrode 1 beyond the end face of the insert 3 at the time of crimping. When the electrode 1 with the projections 202 formed thereon is used for plasma arc machining, the arc generation point on the electrode surface goes around on the projections 202, so that the electrode life is shortened. For this reason, as shown in FIG. 2 (F), after the crimping, the protruding portion 202 is removed as a next step by machining such as bite cutting or grinder processing, so that the tip of the electrode base material 2 and the insert 3 are connected to each other. Are formed so as to be flush.

As described above, since the distal end portion of the electrode base material 2 and the insert 3 are formed flush with each other, the arc generating point on the electrode surface is on the insert 3 and plasma processing is performed in a desired state.

In the electrode manufactured as described above, the nickel plating is applied to the insert 3 because the nickel is electroplated.
And the high-melting-point insert 3 made of hafnium has improved adhesion, and until the step of crimping the plated insert 3 into the tip recess 201 of the electrode substrate 2 is performed. Even if an unexpected external force acts on the plating portion, the situation that the plating peels off hardly occurs, and the adhesion between the nickel plating 41 and the insert 3 is good. Even when the outer periphery of the end portion is pressed in the center direction, the plating does not peel off from the insert 3, so that the insert 3 can be securely pressed to the concave portion 201 at the front end of the electrode substrate 2. That is, the plasma electrode 1 can be easily and reliably manufactured. Further, when the plasma electrode 1 is used, since the insert 3 is pressed against the concave portion 201 at the tip of the electrode substrate 2, even when the electrode 1 is heated, the insert 3 is held by the restraining force at the time of pressing, and the insert 3 is held. 3 never leaves, and
Since nickel plating 41 does not substantially generate oxides,
The heat generated in the insert 3 during the plasma processing is quickly transmitted to the nickel plating 41 → the silver plating 42 → the electrode substrate 2 and is sequentially taken out of the electrode by a cooling fluid for cooling the electrode substrate. As described with reference to FIG. 1, the insertion end face of the insert 3, the substance 21 having a low melting point,
Even when the bottom surface of 1 is not completely in contact, during plasma processing, the low-melting substance 21 is melted, and the bottom surface of the tip concave portion and the insert 3 are thermally short-circuited. The effective cooling of the insert 3 by the cooling fluid via the substance 21 results in the electrode being thermally stable and having a constant electrode life and a longer electrode life than in the prior art.

Conventionally, an insert of zirconium is immersed in molten zinc chloride to perform galvanization on the insert, and then immersed in molten silver to apply silver plating to the insert. It has been suggested that the inserted insert be brought into low contact with the recess at the tip of the electrode substrate by silver. In this case, an oxide film is formed on the surface of the zinc plating, and this oxide film causes heat conduction from zinc to silver. Due to the badness, the heat of the insert is not quickly transferred to the electrode substrate, and as a result, the service life of the electrode is not improved as expected.

FIG. 4 is a view showing the life of the electrode, in which the case of a conventional electrode using hafnium as an insert is indicated by a dotted line, and a low melting point substance 21 and a high melting point insert 3 is shown by a dashed line, and a high-melting-point insert in which a low-melting-point substance 21 and a predetermined plating are applied to a concave portion at the tip of the electrode substrate 2 is shown. 3 is shown by a solid line in the case of an electrode corresponding to FIG. 2 of the present invention.

As can be understood from FIG. 4, each of the electrodes corresponding to FIGS. 1 and 2 of the present invention is twice or three times as long as the use limit of the conventional electrode using hafnium, that is, the electrode life. Has also become longer.

<Plasma cutting conditions in FIG. 4> Cutting speed: 40 cm / min Cutting length: 30 cm / times Current: 120 A Material to be cut: SS41, plate thickness 16 mm Cutting time per cycle: 45 seconds FIG. FIG. 3 (D) is a crimping tool used for crimping the outer periphery of the end of the electrode base material 2 in the center direction.
It is a figure which shows the modification of 51-54, As shown in FIG.3 (B) thru | or FIG.3 (D), if the crimp surface parallel to the outer surface of the electrode 1 is formed after crimping, Since the parallel crimping surface can be used as a tool locking surface for attaching and detaching the electrode, a tool locking surface machining step after crimping can be omitted, and the electrode 1 can be manufactured at low cost. Also, the insert 3 can be zirconium.

In the above, a wood strike bath is optimal as the nickel electroplating applied to the insert 3. Despite this, if it is acceptable to reduce some conditions such as the plating speed and the adhesion of nickel plating to the insert, appropriate electroplating such as sulfamic acid bath or Watt bath should be used. Can also.

Furthermore, an insert 3 plated with nickel is plated with nickel.
Although silver plating is best in terms of heat conduction and cost, it can be plated with a so-called noble metal such as gold, platinum or rhodium.

<Effect of the Invention> As is clear from the above description, the effect of the present invention is obtained when the insertion end face of the insert, the substance having a low melting point, and the bottom surface of the tip concave portion of the electrode base material are not completely in contact. However, at the time of plasma processing, the insertion end face of the insert and the bottom surface of the tip concave portion are thermally short-circuited by the molten low-melting substance, and the insert 3 is made effective by the cooling fluid through the molten low-melting substance 21. As a result, the electrode is thermally stabilized, the electrode life becomes constant, and the electrode life becomes longer than before.

Further, in addition to the above-described effects, the present invention provides the insert in which nickel electroplating and silver plating that do not substantially generate oxides are sequentially applied to the insert, so that heat generated in the insert is applied to the electrode through the plating portion. The quick transfer to the substrate and the effective cooling of the insert ensures that the electrodes are not heated above a predetermined state, further extending the life of the electrodes.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal section of an electrode of the present invention, and FIG. 2 (A)
FIGS. 2 (F) to 2 (F) are detailed vertical cross-sectional views of each component of the electrode. 3 (A) to 3 (D) correspond to the side views of FIG. 2 (E), each showing a different modified example, and FIG. 4 shows the electrode life. FIG. 2 shows the case of the invention, and the dotted line shows the conventional case. FIG. 5 is a sectional view of a main part of a general plasma arc processing torch. DESCRIPTION OF SYMBOLS 1 ... Electrode 2 ... Electrode base material 3 ... Insert body 21 ... Low melting point substance

Continuation of the front page (56) References JP-A-50-152949 (JP, A) JP-A-2-307667 (JP, A) JP-A-2-307676 (JP, A) JP-A-60-227997 (JP) , A) JP-B-59-24919 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) B23K 10/00 B23K 35/02 H05H 1/34

Claims (1)

(57) [Claims] 1. An electrode for plasma arc processing comprising a high-melting-point insert inserted into a recess at the tip of an electrode substrate made of copper or copper alloy cooled by a fluid. The plating is sequentially performed, the diameter of the tip recess is formed slightly larger than the diameter of the plated insert, and the insert is driven into the tip recess via a low-melting substance. Is fitted so as to be on the release side of the tip concave portion, and the low-melting substance is filled in a space defined by the electrode substrate and the insert, and the outer periphery of the end portion of the electrode substrate is centered. An electrode for plasma arc machining, which is press-bonded in a direction and machined so that a tip portion of the electrode substrate and the insert are flush with each other.