The Hardness And Roll Specification Committee is foucsed on standardizing the industry in using the equotip hardness tester not only in the ordering of rolls but also in the daily testing of rolls as they go through their life in the mill.
SOP FOR THE CALIBRATION AND USE OF THE EQUOTIP HARDNESS TESTER
1.1 This procedure covers the calibration and use of the PROCEQ Equotip hardness tester.
1.2 This procedure is applicable to both the original instrument and the new upgraded model.
1.3 This procedure covers the use of the Equotip tester equipped with a D-type impact device.
2. DESCRIPTION OF APPARATUS
2.1 PROCEQ Equotip hardness tester
2.2 D-type impact device
2.3 Standardized test block manufactured by PROCEQ
3. INSPECTION OF THE EQUOTIP HARDNESS INSTRUMENT PRIOR TO USE
3.1 Before an Equotip hardness instrument is used, the instrument shall be examined to insure the following:
3.1.1 The batteries in the indicating device are not dead. Faulty batteries must be replaced prior to use.
3.1.2 The impact device is clean. A round brush is provided with the instrument to clean the bore of the device.
3.1.3 The impact body is free from all foreign matter.
3.1.4 The spherical tip of the impact body is free from cracks, spalls, or deformed areas.
4. STANDARDIZATION OF INSTRUMENT
4.1 A standard test block produced by PROCEQ shall be placed on a solid base such as a lathe bed.
4.2 The Equotip instrument shall be verified by making three or more impacts on the test block. Impacts shall be no closer than 1/8" from each other, and no closer than 1/4" from an edge of the block.
4.3 The instrument shall be considered verified if the average of 3 to 5 impact readings fall with the +/- 6 Ld units of the reference value of the standard block. Any instrument not verified may not be used for testing without repair and reverification.
4.4 An instrument shall be verified prior to checking rolls. During testing, the instrument shall be reverified after each 100 impacts. The instrument shall be reverified at any time that abnormal readings are obtained.
5. TEST PROCEDURE
5.1 Test locations
5.1.1 Roll hardnesses shall be checked at each end of the roll body and at mid length on one random longitudinal line. 5.2 Surface finish
5.2.1 The test surface shall be carefully prepared to remove any alterations in hardness caused by heating during grinding or by work hardening during machining. Any paint, scale, pits, or other surface coatings shall be completely removed. The surface shall be ground to a finish equal to, or finer than, a 100 grit abrasive.
5.3.1 To perform a hardness test, the impact device is connected to the indicator device, the instrument turned on and the impact device cocked. To cock the impact device, the charging tube is depressed until contact is felt and then allowed to slowly return to the starting position. The impact body is now in its loaded and cocked position. The impact device is placed on the roll surface and held firmly with one hand. Trigger the impact body by exerting a slight pressure on the release button. The Ld number is read on the indicator device. This completes one hardness test. For additional tests, the impact device shall be removed from the surface before recocking.
5.3.2 To prevent errors resulting from misalignment, the impact device must be held snugly against, and perpendicular to, the surface of the roll. 5.3.3 The impact device is calibrated for use in the down vertical direction. For use at 45, 90 or 180 degrees from the down vertical plane, hardness values can be determined using the correction table contained in the instruction manual, or in the case of the new model, it can be programmed for each direction.
5.3.4 The minimum distance between any two impact spots shall not be less than 1/8". No impact spot shall be impacted more than once.
5.3.5 Hardness in Ld units is displayed on the electronic screen.
5.3.6 Five impacts in an area shall constitute the minimum number of tests (on iron rolls ten impacts are preferred). The hardness of the area shall be the arithmetic average of the individual readings in the area.
5.3.7 Each area shall be reported separately. A grand average of all impact values may not be used for determining the hardness of a roll.
6.1 There is no direct correlation between Equotip Ld hardness values and hardness values obtained from any other method. This includes the conversions built into the new Equotip instrument. Any conversions are, at best, approximations, and conversions should be avoided except when special agreements have been made between the buyer and seller.
Donald E. Van Inwegen P.E. ROLL SERVICES INCORPORATED Revised: 3/25/93 Item 4.3 Revised 9/6/96 Item 6.1 Revised 12/20/96
The following are suggested methods and equipment that have been found to be useful. They are not intended to be part of the procedure but merely guidelines that may be followed. The equipment listed is some that is currently utilized by various mills and roll suppliers. Other equipment can be used provided that a proper surface is prepared.
1. When taking a hardness the impact device should be held near the bottom with one hand, and the release button activated with the other hand. This procedure seems to provide the most stable situation.
2. On rolls that have machined passes the hardness should be taken on the collar with the largest diameter.
3. For informational purposes hardnesses can be taken, when feasible, at the bottom of the passes.
4. On new rolls, surface preparation is usually carried out in two steps. The first step is rough grinding. This is done for both as-cast surfaces and rough-machined surfaces to remove any effects from casting or any work hardening caused by machining. As a rule, a .030" stock removal will assure a proper condition. The second step is final grinding with a finer grit abrasive to provide a suitable surface roughness for hardness testing.
5. For rolls that have been in service hardness should be checked on a remachined surface. In this case final grinding with a 100 grit abrasive is usually adequate.
6. All grinding operations must produce a flat area large enough to accomodate the base of the impact device. Concave areas will give incorrect results.
7. Electric powered grinders are preferred since air driven grinders operate at too high an RPM.
8. Grinding wheels or discs should have a "soft" bond. Hard bonds tend to "load up" and glaze causing overheating of the area being ground.
9. Final surface preparation is usually carried out using 100 grit discs, sleeves, belts, or flapper wheels. These consumable items should be changed frequently so that the abrasive particles are always sharp. Dull or worn out abrasives will tend to work harden the surface being prepared. 10. EQUIPMENT 10.1 Rough grinding
10.1.1 Industrial 90 degree Electric Grinder Norton Norzon-3, cup wheel Size 4/3" X 2" X 5/8" - 11 Grade 3NZ 1634-Q5B
10.1.2 Industrial 4" Electric Disc Grinder 4" Disc 24 grit, N hardness Example: Metabo A24-N-BF-80
10.2 Final grinding 10.2.1 Makita Belt Sander Model 9030 100 grit belt 10.2.2 Industrial Air Grinder 100 grit sleeves
Donald E. Van Inwegen P.E. ROLL SERVICES INCORPORATED Revised 1/8/93