Sapphire watch glass hardness test

Sapphire mirror is a kind of crystal mirror synthesized by artificial compression. Its advantage is high density and not easy to scratch. The hardness of the sapphire glass mirror is second only to the hardness of diamond, with a hardness of 2200-2300 (seven times the hardness of steel) and a Mohs hardness of 9, which has good hardness, good optical permeability, low friction, high temperature resistance, and better than crystal Glass mirror and synthetic glass mirror have higher wear resistance. Using it as a watch mirror, its sealing, strength and shock resistance are better than other materials. Therefore, the sapphire mirror has become an identifier for top watches. Of course, its high price is also expected.

If it is a regular brand watch, the sapphire glass will generally be printed on the dial or back cover of the watch, indicated in English SAPPHIRE or Sapphire Crystal. But it also has shortcomings, that is, it is not shockproof, and it is not suitable for improper operations such as bumps, heavy pressures, and heavy falls. Like glass, it is brittle and easily broken. Therefore, once the sapphire mirror is broken, the maintenance costs incurred will be very expensive, because the watchmaker must carefully check to ensure that no sapphire debris is left in the movement before replacing the lens. In addition, it is a powerful fingerprint collector, so it needs to be wiped frequently to be bright.

As an important factor in the quality assurance of top-level watches, whether the hardness of sapphire is qualified has become a question worthy of attention. There are two commonly used testing methods for sapphire hardness: 1) Mohs hardness test 2) Micro Vickers hardness test

1. Mohs hardness test

Mohs hardness, also known as Mohs hardness (Mohs hardness), represents a standard of mineral hardness. It was first proposed by German mineralogist Frederich Mohs in 1812. The depth of the scratches measured is divided into ten levels to express the hardness: talc 1 (the smallest hardness), gypsum 2, calcite 3, fluorite 4, apatite 5, orthoclase (feldspar; orthoclase; periclase) 6, quartz (quartz) 7, topaz (topaz) 8, corundum (corundum) 9, diamond (diamond) 10.

Mohs hardness pen test method:

1) Indirect target estimation method

The hardness of the gemstone can be reflected in the smoothness of the facets and the sharpness of the edges after processing. Under a magnifying glass, you can see that the facets of the gems of the hardness size are smooth, flat, and sharp. The indirect visual inspection method is a non-destructive approximate hardness identification method.

2) Direct measurement method

This method is based on the mutual engraving comparison between the gem mineral to be measured and the standard hardness mineral. In 1982, German mineralogist Moss proposed a standard mineral, its grades are: talc-1, gypsum-2, calcite-3, fluorite-4, apatite-5, orthoclase-6, quartz- 7, Topaz-8, corundum-9, diamond-10. The hardness gap between corundum and diamond is the largest.

3) Use skills and precautions
3.1 Indirectly estimate the hardness of the sample first;
3.2 Find an inconspicuous place and use a hardness pen lower than the visual hardness of 1 to 2 to mark the sample. If it does not move, it means that the hardness of the sample is higher than that of the hardness pen, and then use a higher hardness pen to mark Repeat the operation. If there are only slight traces, the hardness of the sample is equivalent to the hardness of the hardness pen. Then use a higher hardness pen to mark and repeat the operation. If there are traces, the hardness of the sample is lower than this hardness. The hardness of the pen, the hardness of the tested sample or its range can be judged at this time;
3.3 Pay attention to the scoring intensity to be moderate, neither too light nor too heavy
3.4 Because the direct scoring method to determine the hardness is damaging to gems, it is generally not allowed to use this method on finished gems.

To sum up, the Mohs hardness test can easily determine the hardness range of sapphire, but it cannot get an accurate hardness value, and the scribing force and the depth of the scratch during operation are difficult to grasp, so the sapphire glass lens The test generally adopts the micro Vickers test method.

2. Micro Vickers hardness test

Vickers hardness refers to the use of a diamond pyramid indenter with an angle of 136 degrees between the opposing surfaces, which is pressed into the surface of the test sample under the action of a specified test force, and the load is removed after a fixed period of time to measure the surface pressure of the sample. Diagonal length d of the mark, and then calculate the indentation surface area, and finally calculate the average pressure on the indentation surface area, which is the Vickers hardness value of the metal, which is represented by the symbol HV. In actual measurement, manual calculation is not required, but the machine will directly and automatically measure the hardness value of the measured material.

The micro hardness tester is the abbreviation of the micro Vickers hardness tester. The Vickers hardness tester whose maximum test force does not exceed 1000gf is collectively called the micro Vickers hardness tester. Because the test force is small, the indentation left on the sample after the test is difficult to see with the naked eye, so many people attribute the microhardness test to a non-destructive test.

Steps:

1) Put the sample on the workbench

2) Set the test force (10gf-1000gf provide 8 levels of test force for selection), full charge time (1-99 seconds optional, generally set within 8-10 seconds)

3) Turn the screw lifting handwheel to focus until the surface structure of the sample can be seen clearly in the eyepiece

4) Click the \"Start\" button on the touch screen, the machine will automatically test, and the turret will automatically return to the measurement objective lens position after the test is completed

After the pressing is completed, there will be a diamond-shaped indentation on the surface of the sample, and the hardness tester will automatically turn to the total zoomThe 400X objective lens measures the length of the diagonal line of the indentation. The eyepiece of the Ebisu digital display Vickers hardness tester is equipped with a high-precision encoder, which does not require manual calculation and reading. When the diagonal line is pressed, just click the encoder button, and the machine Automatically read the length of the indentation diagonal, the machine automatically calculates the hardness value, convenient and quick operation

5) Measure the diagonal length of the indentation, the machine automatically calculates the hardness value of the sample

The digital display micro Vickers hardness tester produced by Yibipu Electromechanical Equipment has the following advantages:

1. The latest domestic exclusive design, reasonable structure and novel appearance

2. High degree of automation, automatic turret design (objective lens-indenter automatic switching) and main test force automatic loading-holding-unloading, which effectively guarantees the accuracy of test results and greatly improves work efficiency

3. Data storage function: the host chip has a high-speed storage function, which can store 100 sets of test data at the same time

4. Simple operation: The high-performance digital display micrometer eyepiece is equipped with an encoder, and the length of the diagonal line of the indentation is automatically displayed on the screen with just one touch of the encoder button. It is effective without manually reading the data and then inputting it. To avoid human error

5. One machine with two functions, high cost performance: with HV/HK (Vickers hardness, Knoop hardness) test function, the machine reserves the Knoop hardness test function, if the customer needs to test the material Knoop hardness value, just replace it Just press the head

6. The display is more intuitive: equipped with a 5.6-inch LCD touch screen, which can display the test method, test force, indentation length, holding time, test times, conversion scale, date and time more intuitively on the large screen

7. The cast aluminum shell is cast and formed at one time, and the structure is more stable and not deformed compared with the traditional welding process

8. The surface adopts automobile baking paint process, which is more shiny and scratch resistant than traditional spray paint, and it is still bright as new after many years of use.

9. The platform lifting adopts the ball positioning system, which is more stable than traditional screw lifting and easier focusing

10. Built-in thermal printer, test results can be printed at any time

11. The optical channel is reserved on the top, which can be connected to the CCD camera and our hardness measurement and analysis software to connect to the computer to measure and analyze the indentation and export the report, which is convenient for customers to archive for a long time.

12. Quality automatic judgment function, users can set the qualified hardness value range of the product before the test. Once the quality of the product exceeds the set qualified range, the machine will automatically alarm, which is convenient and practical.

In addition, after equipped with our professional Vickers hardness measurement and analysis software, it can directly communicate with the computer. Perform measurement and analysis on the computer, export detailed test reports, etc.

The main function

One. Automatic measurement: the system automatically finds the apex of the indentation, measures the diagonal length and calculates the hardness value;

two. Hardening curve: the user manually enters the depth of the test point, the software automatically draws the hardening curve and calculates the hardening layer depth. For convenience, users can save multiple depth points to a template file for recall during testing;

three. Hardness value conversion, correction, and effective verification: The system can convert the measured micro Vickers hardness value into other hardness values ​​such as HB, HR, etc.; it can correct the measured value of a spherical cylindrical sample; it can be effective on the measured value of the sample verification;

four. Data statistics: automatically calculate the average value, variance, Cp, Cpk and other statistical values ​​of measured hardness;

Fives. Automatic alarm: automatically mark out the upper and lower limits;

six. Test report: Automatically generate WORD or EXCEL document report; user can customize report format; standard format includes every single hardness measurement value, statistical value, indentation image, and hardening curve, etc.;

Seven. Data storage: the original measurement data and measurement images can be saved to a file;

Eight. Knoop hardness and fracture toughness: the software can be set to measure Knoop hardness or fracture toughness;

nine. Other functions: including general functions such as: image capture, video capture, image processing, geometric size measurement, document annotation, album management, and fixed-magnification printing.