GB2240396A

GB2240396A - Ceramic block gauge

Info

Publication number: GB2240396A
Application number: GB9001710A
Authority: GB
Inventors: Tetuo Dosuda; Yoshirou Kamata; Kinji Takizawa
Original assignee: Mitutoyo Corp
Current assignee: Mitutoyo Corp
Priority date: 1988-12-19
Filing date: 1990-01-25
Publication date: 1991-07-31
Anticipated expiration: 2010-01-25
Also published as: DE4002986A1; JPH0468561B2; JPH02165001A; GB2240396B; GB9001710D0; DE4002986C2

Abstract

A block gauge comprises a ceramic material obtained by sintering zirconium oxide as a main ingredient, 3-7% by weight of yttrium oxide and 0-20% by weight aluminium oxide. The gauge is marked, e.g. with a size, by radiating a laser beam onto the gauge in an inert atmosphere or under a reduced pressure. The inert atmosphere may be a gas of nitrogen, helium, argon, or a mixture thereof.

Description

1 BLOCK GAUGE AND METHOD OF MARKING CERAMIC MATERIAL The present invention

relates to a block gauge used as a reference gauge in precisely measuring a length and a method of marking a ceramic material used for a block gauge.

conventional block gauge is made of a metal material.

block gauge of a metal material, however, has such an insufficient corrosion resistance as to easily produce corrosion. For this reason, the handling of such a block gauge requires considerable care. For example, it is necessary to store the block gauge in a complete corrosion- preventive environment, and the block gauge must be handled with corrosion-preventive gloves on.

If corrosion is produced, the surface state of the face indicating the dimension is impaired, thereby making it impossible to secure the accurate dimension or to bring the block gauge into close contact with another block gauge, what is called wringing.

In order to enhance the corrosion resistance, it may be considered that the block gauge should be plated with, e.g., chrome Cr. A plated block gauge, however, increases the _number of manufacturing steps and is difficult to provide a i predetermined nominal dimension, thereby making the manufacture thereof complicated.

Accordingly, it is an object of the present invention to eliminate the above-described problems in the prior art and to provide a block gauge made of a corrosion-resistant material and filling all the requirements of a block gauge such as the homogeneity of a material, corrosion resistance, easy handling property, and marking of a nominal size and the like.

The present inventor first investigated a plurality of corrosionresistant materials so as to solve the problem of corrosion resistance. Among these materials, those which can fill all the requirements of a block gauge are selected and further the thus-selected corrosionresistant materials are processed by a method which is suitable thereto. Thus, the present invention has been achieved.

The present invention provides a block gauge composed of a ceramic material obtained by sintering zirconium oxide as a main ingredient, 3 to 7 wt% of yttrium oxide and 0 to 20 wt% of aluminum oxide, the ceramic material being marked by radiating a laser beam onto the portion to be marked in an inert gas atmosphere or under a reduced pressure.

The present invention also provides a method of marking a ceramic material by radiating a laser beam onto the 2 - 1 portion to be marked while maintaining the ceramic material in an inert gas atmosphere or under a reduced pressure.

The present inventor selected a ceramic material because it is a corrosion-resistant material and has a homogeneity. More particularly, a white or light yellow ceramic material is selected because it supplies a contrast to the surroundings of a job site and is distinguishable. Furthermore, as a ceramic material having a sufficient corrosion resistance, a thermal expansion coefficient substantially equal to that of a steel, which is generally an object of measurement, and a dense and homogeneous structure, and satisfying the condition that the volume does not change after sintering, a zirconia ceramic material is used which is obtained by sintering zirconium oxide ZrO 2 as the main ingredient together with 3 to 7 wt% of yttrium oxide Y 203 and 0 to 20 wt% of aluminum oxide Al 2 0 3 based on the main ingredient as adjuvants. The above-described composition produces a zirconia ceramic material in a mixed phase of a hexagonal phase and a monoclinic phase, what is called, partially stable state, thereby providing the zirconia ceramic material with both a high strength and a high toughness and securing the resistance to brittleness.

The marks placed on the block gauge such as a nominal dimension, the number of article and a trademark are preferably of a black color, which supplies a contrast to the white or light yellow zirconia ceramic material. It is necessary that the marked surface has the same or a lower height as or than the wringing surface so as to enable wringing. The present inventor solved the problems of the color of the marks and the height of the marks with respect to the wringing surface by radiating a laser beam onto the portion to be marked in an inert gas atmosphere or under a reduced pressure. As the inert gas, nitrogen N 2, helium He, argon Ar or a mixture thereof is preferable. The inert gas atmosphere is obtained by blowing the inert gas onto the portion of the zirconia ceramic material to be marked or introducing the inert gas into a sealed chamber which accommodates the zirconia ceramic material.

The reduced pressure may be a pressure of 5 to 46 mmHg.

For radiation of a laser beam, a YAG laser generating device is used in a Q switch mode. Alternatively, a CO 2 laser generating device may naturally be used.

The present invention will be explained in detail with reference to the following embodiment.

4 - h 1 1 f ZrO 2 as the main ingredient and Y 203 and Al 203 as adjuvants are pulverized to a predetermined particle diameter, and they are mixed and stirred in a uniform state.

The material in a uniform state is pressed and molded in a compact state, what is called a packed state, and heated for sintering.

The zirconia ceramic material (in the block form) obtained by sintering is cut with a diamond cutter into a rectangular parallelepiped slightly larger than a predetermined dimension.

The rectangular parallelepiped is ground into the form of a block gauge by lapping using a diamond or the like such that each surface has a predetermined flatness, each of the opposing faces secures the parallelism and the nominal dimension coincides with a predetermined dimension.

A laser beam having a frequency of 8 KHz is radiated from a YAG laser generating device onto the surface of the shaped zirconia ceramic material to be marked in a Q switch mode at an output of 10 W and at a rate of 22 mm/sec while blowing N 2 gas from an N2 gas nozzle at an angle of 30 to 60 degrees from a distance of 3 cm at a pressure of about 0.40 kg/CM2, thereby marking the surface with a nominal number, the number of article and a trademark.

The block gauge obtained in the above-described process..is composed of a zirconia ceramic material, which is free 1 from corrosion. It is therefore unnecessary to store the block gauge in a corrosion-preventive state or handle it with corrosion-preventive gloves on. In addition, the block gauge has homogeneity and there is substantially no dimensional change.

A zirconia block gauge is milk white which supplies a contrast to the surroundings of a job site sufficient to be distinguishable, so that it is substantially completely prevented from being lost.

By the laser beam irradiation under specific conditions, black marks slightly recessed in the form of a groove are obtained. The marks therefore supply a sufficient contrast to the while milk color of the substrate for being easily read. In addition, according to the abovedescribed marking method, since the flatness is maintained in each surface without producing any protrusion, there was no trouble in bringing it into close contact with another zirconia block gauge. The light-resistance test (test for a period equivalent to 10 years) was made on the marks by using a carbon arc lamp, but the marks remained as they were without any change.

The thermal expansion coefficient measured about 10 x 10-6/oC. The thermal expansion coefficient of steel is about 11.5 x 10-6/oC. Therefore, even when the temperature of the environment changes, if the object of measurement is S 1 made of a steel, the thermal expansion coefficient of a zirconia block gauge approximately follows the thermal expansion coefficient of the object of measurement, thereby preventing a large error from being produced due to a temperature change.

When the wear-resistance test was carried out by placing a zirconia block gauge on an FC surface plate (cast iron plate) and moving the block gauge a friction length of 8,000 m in a planetary state at a rate of 260 cm/min while applying a predetermined load to the block gauge, wear of about 0. 07 m was observed. in the wear-resistance tests under the same conditions, the wear of steel was about 0.7 um, and the wear of a hard metal was about 0.25 pm. That is, the zirconia block gauge has about ten times as high wear resistance as steel has, and about 3.5 times as high wear resistance as a hard metal has.

In the wear-resistance test of the zirconia block gauge, a phenomenon such as cracking, breaking and chipping was not produced and it was observed that a sufficient resistance to brittleness was maintained.

In this embodiment, if a protrusion is produced in the adjacent portion to the black and recessed groove during the marking operation by the radiation of a laser beam under specific conditions, it is possible to remove the protrusion by grinding, as desired.

t k The block gauge may be produced by cutting a zirconia ceramic material (in the form of a block) into a rectangular parallelepiped (the shape of a block gauge) slightly larger than a predetermined dimension, marking the rectangular parallelepiped zirconia ceramic material by the radiation of a laser beam under specific conditions, and thereafter grinding the zirconia ceramic material so that the nominal dimension coincides with the predetermined dimension.

As described above, a block gauge according to the present invention is advantageous in many points. It is easy to handle because the corrosion resistance is secured so much that the block gauge can be handled with bare hands, no corrosion-preventive treatment is necessary after use, and the storage of the block gauge under special conditions is unnecessary. Since the material is homogeneous, there is substantially no dimensional error. Both wear resistance and resistance to brittleness are secured. Since the substrate is of a white or light yellow color, it supplies a contrast to the surroundings of a job site and marks which are black. In addition, since the thermal expansion coefficient is close to that of steel, when the object of measurement is steel, the error due to a temperature change is greatly reduced.

Claims

1. A block gauge comprising a ceramic material obtained by sintering zirconium oxide as a main ingredient, 3 to 7 wt% of yttrium oxide and 0 to 20 wt% of aluminum oxide, said ceramic material being marked by radiating a laser beam onto the portion of said ceramic material to be marked in an inert gas atmosphere or under a reduced pressure.

2. A block gauge according to Claim 1, wherein said inert gas is one selected from the group comprising nitrogen gas, helium gas, argon gas and a mixture thereof.

3. A block gauge according to Claim 1, wherein said reduced pressure is a pressure of 5 to 46 mmHg.

4. A method of marking a ceramic material by radiating a laser beam onto the portion of said ceramic material to be marked in an inert gas atmosphere or under a reduced pressure.

5. A method of marking a ceramic material according to Claim 4, wherein said inert gas is one selected from the group comprising nitrogen gas, helium gas, argon gas and a mixture thereof.

6. A method of marking a ceramic material according to Claim 4, wherein said reduced pressure is a pressure of 5 to 46 mmHg.

9 - Published 1991 at'Me Patent Ofte. State House. 66/71 High Holborn, L4DndonWCIR47P. Further copies may be obtained from Sales Branch, Unit 6, Nine Mile Point. Cwmfelinfach, Cross Keys, Newport, NPI 7HZ. Printed by Multiplex techniques ltd, St Mary Cray. Kent-