JPH0820351B2 - Ultra-precision hardness standard piece - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a standard piece for hardness measurement using a light load of 10 gf or less, and in particular, a standard for making highly reliable and precise hardness measurement. The present invention relates to an ultraprecision hardness standard piece made of a metal single crystal that can be This hardness standard piece is used for electronic device parts such as IC, LSI, thin film by PVD, CVD, optical fiber,
With the advent of advanced technology materials such as carbon fiber and other fiber materials, hardness standard pieces that can be used as criteria for quantification in the (ultra) light load dynamic hardness test method have recently attracted attention as a hardness evaluation method for these materials. It is provided.

Background of the Invention Hardness (hardness) is defined as a measure of the magnitude of resistance when it is subjected to deformation in a minimal region by another object, and is one of the properties of a material. It shows simply. Therefore, the hardness test is one of the material tests that have been widely used in the metal and other fields. As hardness,
It is well known that indentation hardness (Brinell, Meyer, Rockwell, Vickers hardness), dynamic hardness (Shore hardness) and scratch hardness (Martens method) are used depending on the situation. Among them, the indentation hardness is generally widely adopted. For the indentation hardness, the hardness is measured from the shape and size of the indentation generated by applying compression to the sample surface with the indenter.

Since the hardness measurement is a comparative measurement, it is necessary to prepare a standard for the comparison and constantly perform the verification using a standard piece according to the measuring machine. This reference piece is called a hardness standard piece.

Conventional technology and its problems The indentation hardness is measured by pressing the indenter against the surface of the hardness standard piece at a constant speed and a constant load, and determining the hardness from the size of the indentation produced thereby. The size of the indentation varies from measurement to measurement and its width is large. So usually,
When one hardness is calculated, the operation is repeated 20 to 50 times, and the average value and the standard deviation are used for comparison.

The cause of this variation is divided into the factor of the measuring method itself and that of the hardness standard piece. Most of the factors due to the hardness standard pieces are considered to be due to the nonuniformity of the standard pieces. For example, a conventional hardness standard piece is made of carbon steel, and its hardness is changed by various heat treatments. Therefore, there are misorientations of crystal grains, crystal grain boundaries, inclusions, etc., which cause variations.

Apart from the above problem of variation in conventional hardness standard pieces,
The conventional hardness test method has a large load for making an indentation (10 gf to 3000 kgf) and is not suitable as a standard piece for hardness test of thin films and other new materials. To make matters worse, the conventional hardness standard pieces show large variations as the load for making the indentation becomes smaller. As mentioned at the beginning, as a new hardness evaluation method for high-tech materials, the dynamic hardness test method under ultra-light load has begun to attract attention. The dynamic hardness test method is an attempt to develop a conventional hardness test method in which the size and hardness of an indentation are in a one-to-one correspondence with each other to obtain the relationship between displacement and load when an indentation occurs. is there. At that time, if the load at the time of indentation becomes small, the indentation naturally becomes small, and more local hardness is evaluated. Therefore, the unevenness of the crystal grain boundaries, inclusions, and surface processing state of the hardness standard piece causes the variation range of the measurement result to be more serious than before. The ultra-light load hardness test is currently only positioned as a qualitative test method. However, as the need for quantification becomes apparent, it is certain that standardization and quantification will proceed in the near future. To that end, mechanical problems of the testing machine (refining,
It is indispensable to develop a hardness standard piece that can technically meet the requirements in addition to solving the problem (higher sensitivity, etc.). In other words, the quantification is possible only by the existence of the ultra-precision hardness standard piece, which can be the standard measure for the hardness measurement of ultra-small loads. At the present time, a hardness standard piece corresponding to that has not been obtained.

As described above, the development of a new hardness standard piece in place of the conventional hardness standard piece from the two aspects enables more reliable hardness measurement of various materials.

OBJECT OF THE INVENTION Based on the above recognition, the present invention provides: 1. A hardness standard piece for hardness measurement using a light load of 10 gf or less, which can correspond to the quantification of an ultra-micro hardness measurement method; and (2) An object of the present invention is to provide a hardness standard piece in which the cause of the measurement variation of the hardness standard piece in the conventional hardness measuring method is eliminated as much as possible.

SUMMARY OF THE INVENTION The present inventors have conceived to use a metal single crystal as a hardness standard piece capable of satisfying the above object. High-purity metal single crystals do not have inhomogeneities that cause variations in measurement such as grain boundaries, inclusions, and segregation, have a certain crystal orientation, and have the surface at the level required as a hardness standard piece. Since the technique for polishing is established as described above, it is a material that is exactly used as a hardness standard piece.

Based on this finding, the present invention provides an ultra-precision hardness standard piece for hardness measurement using a light load of 10 gf or less, characterized in that the material of the hardness standard piece is a metal single crystal. Here, the term "metal" is used to include metal elements and alloys.

Description of Examples With the progress of metal / alloy single crystallization techniques such as the Britzmann method, copper, copper alloys (for example, alloys having a wide α solid solution region such as Cu-Ni and Cu-Mn), and relatively large amounts of molybdenum, etc. Techniques for producing single crystal ingots have been established.

According to the invention, for example, a disk-shaped small piece is cut out from such a metal single crystal, and the surface thereof is polished. At present, metal surface polishing technology has advanced extremely highly,
It has become possible to create a super-mirror surface required for optical mirrors, far exceeding the level conventionally required for hardness standard pieces. The flatness required for the hardness standard piece can be easily established by emery polishing, buffing, or the like.

Further, as the surface polishing method, it is preferable to use electric discharge machining, electrolytic polishing, chemical polishing, or the like, which is known as a polishing method that does not leave a processed layer on the surface. By ordinary cutting or mechanical polishing, a layer in which plastic deformation has occurred remains on the surface of the workpiece, and the layer has a high internal strain and is generally hard. The hardness changes depending on the thickness and hardness of this layer. Further, this layer is thermally unstable, and when measuring the high temperature hardness in the recrystallization temperature range, recrystallization occurs in the standard piece and the single crystal is not only polycrystallized, but the hardness also changes. Will end up. A standard piece having a conventional quenching structure cannot deal with such a standard piece having a hardness at a high temperature.

The metal single crystal in the form of a disk or the like whose surface has been polished in this way is used as an extremely high-precision hardness standard piece because it is non-uniform or does not exist on the surface. The hardness standard piece requires hardness variability over several stages,
It is possible to prepare a group of hardness standard pieces having a hardness difference from a small hardness to a large hardness according to needs depending on the kind of metal, alloying and orientation difference.

Next, the accuracy comparison results of the commercially available hardness standard piece and the hardness standard piece of the present invention will be shown. The results when the load is 200 gf are also shown for comparative reference.

Note 2: Hardness measuring tester Akashi Seisakusho MVK, load holding time 15 seconds Note 3: The hardness standard piece of the present invention is a small crystal (15 × 15 mm) from a single crystal ingot (φ50 × 120 mm) manufactured by the Britzmann method.
A small piece is cut out into about 10 mm and embedded in a polishing resin, and then the surface is polished by emery polishing and buffing.

Furthermore, in order to see the trend under light load, load 1 gf
In order to compare the commercial product with the product of the present invention, a comparative test was conducted in the same manner as above: The following evaluation is obtained from these results.

1. Metal single crystal hardness standard piece has little load dependence. In the case of a single crystal, the fluctuation rate is 3.33% at a load of 1 to 10 to 200 gf
~ 3.73% ~ 4.27%, especially 1 ~ 10gf, 3.33% ~ 3.73%
There is only a narrow width of 1 to 10 to 200 gf for commercial products
11.6% to 5.43 to 1.38%, especially 1 to 10 gf is 11.6%
It has a wide width of% -5.43% and a large absolute amount.

2.The smaller the load is, the smaller the absolute value of the fluctuation rate (and deviation) of the metal single crystal hardness standard specimen becomes, whereas the commercially available products have the opposite fluctuation rate (deviation) at light loads below 10 gf. Increase significantly. That is, although those of the present invention are suitable for light loads,
Commercial products have poor reliability at light loads. With PVD and CVD thin films that cannot be used with large loads, commercial products cannot be used.

As described above, the present invention is based on the unique idea of using a metal single crystal as a hardness standard piece. According to the present invention, it is possible to accurately evaluate materials such as conventional metals and new materials.

Effects of the Invention 1. Providing a hardness standard piece for hardness measurement using a light load of 10 gf or less, which is suitable for ultra-fine dynamic hardness measurement, and makes a great step forward in its quantification.

2. Hardness with less variation than the conventional hardness standard piece can be obtained, so it is possible to carry out highly reliable hardness verification with a small number of measurements.

3. Can be used as a high temperature standard piece.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References Japanese Patent Publication No. 52-30457 (JP, B2) 11th World Conf Non dest Test 1985, Vol. 13 (1985) KELLEY DR, JOHNS ON CE, LASHMORE DS (National Bureau of Standards, MD, USA), Production and verification of microhardness standard made by electroforming, P. 2022-2029

Claims (1)

[Claims] 1. An ultraprecision hardness standard piece for hardness measurement using a light load of 10 gf or less, characterized in that the material of the hardness standard piece is a metal single crystal.