JPH0947879A - Cladding by welding method for sliding face of guide structure in machine tool and guide structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To directly execute cladding by welding on base metal with necessary minimum material by executing plasma transferred arc welding on the surface of base metal made of ferrous material of bearing main body while supplying copper alloy powder. SOLUTION: While a copper alloy powder 10 essentially made of copper is supplied to a plasma arc 11, cladding by welding is executed on the surface of a base metal 12. By generating a plasma arc 11 between the copper alloy powder 10 and tungsten electrode 13 and supplying the copper alloy powder 10, the copper alloy powder 10 is melted in the arc 11 to be cladded by welding on the surface of base metal 12. The neighborhood of arc 11 is shielded with an inert gas 16, cladding by welding is done without melting the base metal 12 in large quantity. By this method, the penetration of base metal 12 to the cladding by welding face is reduced, the prescribed performance is obtained even in the case of a thin thickness of cladding by welding.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sliding surface overlay of a guide structure in a machine tool in which a guide sliding surface of a guide portion such as a spindle of a machine tool or a table is overlay-processed by plasma transfer arc welding. A welding method and a guide structure.

[0002]

2. Description of the Related Art In machine tools, in order to support the load of a sliding table and a spindle, and guide with a minimum frictional resistance in the direction of relative movement, a static pressure type bearing or a dynamic bearing is used. A pressure type bearing is provided. Particularly, in machine tools for precision machining that require high accuracy, static pressure type bearings that exhibit excellent characteristics in terms of motion accuracy are often used.

FIG. 5 shows a conventional hydrostatic bearing pad. This is a hydrostatic bearing used as a linear guide for guiding a linear sliding motion of a table or the like in a machine tool.
A recess 2 is formed on the guide surface, and the lubricating oil is supplied to the recess 2 via the throttle 3. The mobile unit 4
The bearing is supported by the static pressure of the lubricating oil film in the bearing gap between the periphery of the recess 2 and the moving body 4.

Usually, in the design of this type of hydrostatic bearing, the selection of the material of the guide surface differs depending on whether importance is attached to rigidity or slip characteristics. When focusing on rigidity, iron-based materials are often selected, and when focusing on slip characteristics, copper-based materials are selected. Generally, in the case of a bearing material made of a copper-based single material, the rigidity of the base material often decreases, and the problem is that the amount of strain is double that of iron-based materials. Is a processed material of a copper alloy plate, and a method of sticking this plate material to a base material of an iron-based material is adopted.

Further, in order to make up for the defects of the bearing material, the guide surface is also formed by overlaying the surface of the base material. Conventionally, T
IG welding and MIG welding are applied.

On the other hand, in the dynamic pressure type bearing, the guide surface system by surface contact is the most excellent sliding surface in the past. However, in terms of performance and price, it is common to use a cheaper turkite sliding guide surface.

By the way, recently, plasma transfer arc welding has been applied to overlay processing. This plasma transferred arc welding is a welding process in which alloy powder is put into a plasma arc generated between a work piece (base material) and a tungsten electrode, which is then melted and welded to the work piece surface. It is a technology and has been applied to surface treatment and overlay processing of parts where wear resistance is particularly required. As the prior art, for example, Japanese Patent Laid-Open No. S55-512
The invention described in Japanese Patent No. 6 can be mentioned.

According to this, in the arc generated between the steel base material shielded by the inert gas and the non-consumable electrode,
By supplying the alloy steel powder mixture and overlaying it on the surface of the steel base material, it is said that it is possible to process a surface-hardened overlay layer with extremely high hardness without causing welding cracks without significantly melting the base material to be welded. There is.

[0009]

In the hydrostatic bearing, in the case of the method of sticking the plate material of the copper-based material as described above, the material of the plate material is much more expensive than general steel material. Moreover, in terms of the function required as a sliding surface, a copper-based material plate must be processed using a member with a size of several tens of millimeters, which is expensive, because it is required to be several millimeters. It has become a thing. In addition, in the case of the hydrostatic bearing of the pasting type, the compact design of the bearing structure cannot be performed and the rigidity cannot be increased, which is a factor that hinders high precision.

On the other hand, as shown in FIG. 6, TIG welding, M
When the guide slide surface is formed by overlaying the base material 5 by the overlay processing by IG welding, there is about 30% of the melt-in 7 of the overlay material from the base material, which is on the surface of the slide surface. It has the greatest drawback that it begins to precipitate and causes galling.
Further, it was difficult to firmly weld the buildup 6 and the base material 5 at the weld boundary due to the presence of the pinholes 8 and impurities.

One of the performances required for a static pressure bearing for machine tools is that it generates less heat.
In this respect, the static pressure bearing of the method in which the plate material made of the copper-based material is attached makes it easy to transfer the heat generated when the static pressure oil is sheared at the sliding speed to the machine body side, and The difference in the coefficient of linear thermal expansion between the two is a major cause of thermal displacement. This thermal displacement promotes deformation of the static pressure gap, which causes problems such as insufficient oil quantity, and also causes deterioration of oil due to heat and secular change. Furthermore, in the processing of plate materials that take thermal displacement into consideration, conventionally, there are many parts that rely on experience,
On the pasting surface of the plate material, a large number of assembling steps are required, such as using an epoxy resin as an adhesive material for pasting, or processing an O-ring groove.

On the other hand, the dynamic pressure bearing has a problem in that high rigidity is obtained when a turkey slide guide surface is adopted as the guide system. Further, the surface-contact guide surface type dynamic pressure bearing has a problem that although it is possible to obtain an excellent sliding surface, it is expensive due to the difficulty of processing and bonding.

Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art and to have excellent strength and slip characteristics as compared with the conventional method of sticking a plate material or welding overlay processing. It is to provide a guide structure for a machine tool having a static pressure sliding surface.

Another object of the present invention is to provide a machine tool guide structure which exhibits excellent performance as a dynamic pressure sliding surface of a machine tool for precision machining.

Further, another object of the present invention is to form a good sliding surface with less penetration of the base material by overlay processing without restriction of the shape, and moreover, it is suitable for automation and contributes to cost reduction. It is to provide a processing method.

[0016]

In order to achieve the above-mentioned object, the present invention provides a bearing while feeding a copper alloy powder having a composition component mainly composed of copper into a plasma arc shielded by an inert gas. It is characterized in that the sliding surface material of the bearing element is built up by performing plasma transfer arc welding on the surface of the base material made of iron-based material of the main body.

Further, according to the present invention, in a guide structure of a machine tool for providing a moving body which makes a relative sliding motion in a moving direction, a composition component mainly composed of copper is contained in a plasma arc shielded by an inert gas. The present invention is characterized by comprising a hydrostatic bearing element having a sliding surface that is overlay-processed by performing plasma transfer arc welding on a surface of a base material made of an iron-based material of a bearing body while feeding a copper alloy powder. To do.

Further, according to the present invention, in a guide structure of a machine tool for giving a guide in a moving direction to a moving body which makes a relative sliding motion, a composition component mainly composed of copper is contained in a plasma arc shielded by an inert gas. The present invention is characterized by comprising a hydrodynamic bearing element having a sliding surface that is overlay-processed by performing plasma transfer arc welding on the surface of a base material made of an iron-based material of the bearing body while feeding the copper alloy powder. To do.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a diagram showing a build-up process by plasma transfer arc welding, in which a base material 1 is fed while a copper alloy powder 10 is fed to a plasma arc 11.
2. Build up the surface of 2. In the figure, 13 is a tungsten electrode, 14 is a DC arc welding power source, and is connected so that the base material 12 serves as an anode and the tungsten electrode 13 serves as a cathode. 1
Reference numeral 5 denotes a shield gas nozzle, and an argon gas as an inert gas is jetted so as to cover the plasma arc. A supply passage for the copper alloy powder 10 is provided between the inner cylinder 17 that houses the tungsten electrode 13 and the outer cylinder 18. Therefore,
When the plasma arc 11 is generated between the base material 12 and the tungsten electrode 13 and the copper powder alloy 10 is supplied, the copper powder alloy 10 is melted in the arc and built up on the surface of the base material 12.

FIG. 2 shows an embodiment in which the pad material of the hydrostatic bearing is built up by plasma transfer arc welding. The base steel material is JIS
Using G 3101 SS400, copper powder alloy,
A copper alloy powder containing copper as a main component and having a particle size of 60 to 200 mesh shown in Table 1 was used.

[0022]

[Table 1] When using plasma transfer arc welding,
Since only the land portion 20 is built up, and as a result, the recess portion 21 can be formed in the center, the material required for the build up of the minimum sliding surface is sufficient as compared with the conventional plate material attachment method. Saves money.

Further, in the case of overlaying by plasma transfer arc welding, it is possible to combine a steel material having high strength and a copper alloy having good sliding surface characteristics with a high degree of freedom, and two types of materials can be combined. It is possible to obtain a good static pressure sliding surface by utilizing the characteristics of both.

Here, FIG. 7 is a photomicrograph of the metal structure of the weld boundary in the pad material of the hydrostatic bearing at a magnification of 200 times. Of these, FIG. 7 (a) shows a hydrostatic bearing pad material of the present invention, and FIG. 7 (b) shows a welding boundary of the material that is built up by conventional MIG welding for comparison with this. If you compare this photo, as you can see,
According to the present invention, the penetration of the base material is the conventional MIG welding,
Compared to the one that is built up by TIG welding, there are less pinholes and inclusions of impurities at the weld boundary,
It was found that the problem of peeling of the generated build-up can be solved because the welding is performed firmly on the dense surface.

In addition, since it is easy to build up thinly, the structure of the hydrostatic bearing can be made compact, and the precision and the damping can be improved as compared with the conventional pasting method.

Next, referring to FIG. 3, in a boring machine in which a boring shaft is movably provided inside a milling shaft 22, a dynamic pressure sliding surface 23 for guiding the boring shaft is formed by plasma transfer arc welding. It is an embodiment.

In this case, plasma transferred
According to arc welding, the welding torch 24 is attached to the milling shaft 22.
It is possible to carry out the overlaying by inserting it horizontally into the shaft hole, and to perform the overlaying with a high degree of freedom without being restricted by the longitudinal direction. Further, in plasma transfer arc welding, the dynamic pressure sliding surface 23 can be processed at low cost as a surface contact surface.

Although the present invention has been described above with reference to the embodiments, the present invention can be applied to static pressure sliding surfaces of various machine tools and guide mechanisms having dynamic pressure sliding surfaces. For example, as shown in FIG. 4, it is similarly effective when applied to the static pressure sliding surface 26 of the grindstone shaft 25 of the grinder.

[0029]

As is apparent from the above description, according to the invention described in claim 1, the plasma transfer arc welding allows the welding boundary to be formed on the dense base metal without causing the problem of separation. The weld boundary is firmly and firmly welded to the dense base metal so that there is no strong and firm welding, and pinholes on the sliding surface and a highly rigid sliding surface without impurities can be formed. In addition, since the thickness of the buildup can be reduced and the minimum required material can be built up directly on the base metal, there is no waste of material, there are few restrictions on processing, and welding with a large degree of freedom is possible. It is suitable for labor saving and contributes to the reduction of the processing cost of the sliding surface material of machine tools.

According to the second aspect of the present invention,
The overlay method is plasma transfer arc, and it has a good sliding surface that does not melt into the base metal due to low temperature welding, and the sliding surface formed by overlaying the steel base material is While the characteristics of the copper alloy can be utilized and the strength can be enhanced, the strain can be reduced.

Further, according to the invention described in claim 3, the dynamic pressure sliding surface becomes a surface contact guide surface which can be constructed at a low cost, and the dynamic rigidity can be improved.

[Brief description of drawings]

FIG. 1 is an explanatory view of a sliding surface build-up welding method according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of an embodiment in which the present invention is applied to a hydrostatic bearing pad.

FIG. 3 is an explanatory view of an embodiment in which the present invention is applied to a dynamic pressure sliding surface of a milling shaft.

FIG. 4 is an explanatory view of a grindstone shaft to which the present invention can be applied.

FIG. 5 is a structural explanatory view of a conventional hydrostatic bearing pad.

FIG. 6 is an explanatory view showing penetration of a base material on a sliding surface which is welded by overlay welding to a conventional base material.

FIG. 7 is a micrograph of a metallographic structure showing a weld boundary of a hydrostatic bearing pad, FIG. 7 (a) is a hydrostatic bearing pad according to the present invention, and FIG. 7 (b) is a padding conventional by MIG welding. Here is an example:

[Explanation of symbols]

 10 Copper alloy powder 11 Plasma arc 12 Base metal 13 Tungsten electrode 16 Argon gas 20 Land part 21 Recess part 22 Milling shaft 23 Dynamic pressure sliding surface 24 Welding torch 25 Grindstone shaft

Claims (3)

[Claims] 1. A plasma arc is formed on the surface of a base material made of an iron-based material of a bearing main body while feeding a copper alloy powder having a composition component mainly composed of copper into a plasma arc shielded by an inert gas.
A sliding surface overlay welding method for a guide structure in a machine tool, characterized in that the sliding surface material of a bearing element is overlay-processed by performing transfer arc welding. 2. In a guide structure of a machine tool for providing a moving body that performs relative sliding motion in a moving direction, a copper alloy powder containing copper as a main constituent in a plasma arc shielded by an inert gas. In a machine tool characterized by comprising a hydrostatic bearing element having a sliding surface that is overlay-processed by plasma transfer arc welding on the surface of a base material made of iron-based material of the bearing body while feeding Guide structure. 3. A guide structure of a machine tool for guiding a moving body which makes a relative sliding motion in a moving direction, wherein a copper alloy powder containing copper as a main component is contained in a plasma arc shielded by an inert gas. In a machine tool characterized by comprising a dynamic pressure bearing element having a sliding surface that is overlay-processed by plasma transfer arc welding on a surface of a base material made of an iron-based material of a bearing body while feeding Guide structure.