Standard Blocks For Hardness / Catalog

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To control various industrial hardness testers, it is important to control all related factors, including indentors, static and dynamic loads, indentation measurement, and test pieces. Hardness blocks allow overall control of these complicated factors in the field. Therefore, it is imperative that uniform test surface characteristics test blocks, their main factors of secular change are eliminated, and, if possible, their materials are similar to the quality of the sample.

Especially, our test blocks are "the most accurate, reliable test blocks" under severe condition required for each hardness testing method, and then, the standard value has been calibrated with the standard that exceed any other national or international specification in the pursuit of the world highest accurate standard for the industrial use.

Our company, established in 1939, is the first manufacturer of standard hardness test blocks in Japan and has maintained its reputation as the best and the foremost company in this field of the world.

1-1 Material selection, manufacturing process

Table 1 shows specifications of test blocks and their materials. To maintain one highly uniform test surface, the strict quality control of material selection must be needed for each test method. Our blocks are first cut from plate material, then, machined to a round disc shape. This enables significantly more constant heat treatment, and processing because plate material generally has no sectional area, and is not affected by center segregation.

After heat treatment has been finished, to achieve the most accurate and consistent commercially available in the world, first, a custom built, ultra-high precision grinding machine is used to remove the micro decarburized layer caused by heat treatment. Care is taken so that the surface is not adversely affected, which could result in surface hardness irregularities. Then the blocks are lapped. Even the underside of each block is lapped to insure precision parallel faces. The blocks undergo a polishing process, followed by wet buffing. Routine microscopic structure inspection is performed across the finished test surface for possible variations caused in process. Before the calibration process begins, surface roughness, parallelness, and flatness are. carefully controlled

1-2 Calibration procedure

Each 20 - lot batch is thoroughly treated, processed, and calibrated in one group. Each block is marked with its actual variation, based on analysis of 10 hardness readings taken on two axes across the surface. These measurements are fed into a computer for statistical calculation of mean and variation on each axis, and then a total for the block. A typical calibration certificate with each test block is printed out. Complete information is supplied to control the manufacturing process and QC program in each test block.

1-3 Standardized testers, and testing conditions

Our standardized testers used to determine standard value and variation, are more accurately controlled and corrected, based on the world's highest accurate standard, and also testing conditions are stable and fixed to prevent any drift in accuracy.

2-1 Choice of test blocks

To check the stability of tester used in calibration, test block should be chosen according to calibration requirements. Normally tester should be verified at least 3 ranges in high, middle, and low ranges of scales which a tester is being used, (e.g 60, 50, 30,or 20 HRC), if possible, many ranges (e.g. HS at 10 range intervals). Routine inspection should be performed with blocks of the above mentioned ranges or the high frequency ranges in use.

2-2 Notes

(1) The tester must be under an adequate inspection standards, and the various elements (penetrator, loading, measuring apparatus, etc.) must be confirmed to be accurate.

(2) Next, the manufacturing number, date, scale, actual variation inscribed near the perimeter of blocks should be checked up with the calibration certificate issued with each test block. The warranty period for our blocks is three (3) years from the date of calibration.

Scratches, deposits, indentations on the underside of each block, reprocessing, and heating are to be in part responsible for wider variation in hardness, so every discretion must be taken in dealing with blocks and anvils .

(3) Desirable testing conditions, loading speed, holding time, indenting force, and temperature, are to operate a tester under a daily working condition. Subject to the note designed by tester's manufactures.

(4)To calibrate a test block, 5 hardness readings should be normally taken on the working surface, 3 readings at least, 10 (9) readings to achieve higher level of accuracy, and calculate x, and R in measuring score.

(5) Measuring spots should be equally disposed over the working surface so as to represent the hardness of the block.

(6) A X-R controlling method made out through many measurements over a long period can be more useful to take an accurate measurement.

(7) Possible operator difference in HV indentation measurements can be minimized by reducing the intervals of the reticles of the eye piece to several ｵm. In addition, more than one operator or measuring system should be used to comparatively measure the same indentation to ensure the accuracy of measurements.

(8) A tester should not be adjusted if the test results are not within the appropriate tolerance specified in Table 2 . In such a case, directly inspect the load, indenter, and measuring device for the causes of error to be eliminated. Adjusting a tester within the tolerance of its standard value is not meaningful except for special circumstances. Any adjustments that ignore the specifications of testers or testing conditions are not recommended.

Test blocks can be generally used to verify the accuracy, the reliability, and the adjustment of each tester. Table 2 shows the tolerance, and the variation of testers and test blocks, based on Japanese Industrial Standard (JIS).

Our blocks fully satisfy the tolerance of standard values and variations specified by ISO and other foreign standards, but care should be taken over the test conditions used. Our blocks are perfectly in accordance with the relevant JIS for hardness tests.

The secular change of all our blocks is eliminated through sufficient heat treatment process. Due to work hardening near and around the perimeter of indentations, the usable test area is limited, such as JIS standard prescribes to us 4d (d= diameter of the indentation) space between indentations.

Shown below is an example of the guideline on working surface divided into 5 parts. To make the maximum use of a block, indentations should be made evenly over the test surface. For this purpose, we recommend dividing the working surface as shown below. For the durable limits specified in Table 3, reduce the numbers to half if the highest accuracy is required.