- Revolutionizing Case Depth Measurement
In less than a minute, continuous acquisition testing enables rapid and precise case depth measurement without extensive sample preparation.
Case hardness is crucial across industries, from automotive and aerospace to machinery and military applications. Traditional testing methods, however, require time-consuming sample preparation, involving cutting, mounting, and polishing, to conduct sequential micro-hardness tests. This process often takes hours from start to finish. Enter HTD®, offering groundbreaking innovations in case depth measurement.
HTD®: A New Standard in Testing
Using a Rockwell-like approach, HTD® employs continuous acquisition testing to assess metal hardness throughout the case. This provides accurate case depth results in under a minute, eliminating the need for traditional preparation steps. The HTD® applies full load testing with a force of up to 4000 kg, which allows for substantial time savings and faster process control feedback.
Benefits of Continuous Acquisition Testing
- Faster Results: Case depth is measured in under a minute.
- Reduced Sample Prep Time: No more cutting, mounting, or polishing.
- Rapid Testing: Hours-long testing is reduced to minutes.
- Enhanced Process Control: Real-time data offers immediate feedback.
In less than a minute, continuous acquisition testing enables rapid and precise case depth measurement without extensive sample preparation.
Case hardness is crucial across industries, from automotive and aerospace to machinery and military applications. Traditional testing methods, however, require time-consuming sample preparation, involving cutting, mounting, and polishing, to conduct sequential micro-hardness tests. This process often takes hours from start to finish. Enter HTD®, offering groundbreaking innovations in case depth measurement.
HTD®: A New Standard in Testing
Using a Rockwell-like approach, HTD® employs continuous acquisition testing to assess metal hardness throughout the case. This provides accurate case depth results in under a minute, eliminating the need for traditional preparation steps. The HTD® applies full load testing with a force of up to 4000 kg, which allows for substantial time savings and faster process control feedback.
Benefits of Continuous Acquisition Testing
- Faster Results: Case depth is measured in under a minute.
- Reduced Sample Prep Time: No more cutting, mounting, or polishing.
- Rapid Testing: Hours-long testing is reduced to minutes.
- Enhanced Process Control: Real-time data offers immediate feedback.
Working Principle of HTD®
Designed to measure the effective case depth of surface-hardened layers, the HTD® uses a 120° conical indenter with a tip radius of 0.2 mm.
It features a penetrator shroud to reference penetration depth and a transducer to measure displacement.
With a continuously increasing load up to 4000 kg, it gathers hardness data across multiple force levels.
A patented algorithm processes this data to determine effective case depth and generate a schematic curve of the hardened surface layer.
The absolute hardness values are converted to Vickers hardness numbers using standard conversion tables.
It features a penetrator shroud to reference penetration depth and a transducer to measure displacement.
With a continuously increasing load up to 4000 kg, it gathers hardness data across multiple force levels.
A patented algorithm processes this data to determine effective case depth and generate a schematic curve of the hardened surface layer.
The absolute hardness values are converted to Vickers hardness numbers using standard conversion tables.
The physics behind the operation
Background:
The imprint generated by HTD® does not reach the depth at which you find the effective hardness sought but is much more superficial; this is possible because the impression propagates its effects well beyond its volume, all around and under the impression itself.
The measurement on thin sheets will only be valid if the sheet thickness is 10 times the penetration depth.
The distance between adjacent impressions must be at least 3 times the diameter of the impression itself.
These rules result from the observation that the formation of the measured hardness value involves a volume of material greater than the volume of the impression itself.
It is easy to understand, therefore, that, on the surface of a heat treated material, the effect of an impression produced with low loads is essentially all in the harder surface layer, while in the case of higher loads, the volume involved in the formation of the hardness value extends to areas of material deeper than the effective hardness layer sought.
Consequently, if a curve is drawn that takes into account hardness and load during the measurement, a load-hardness curve is obtained; this curve shows that, starting from a high hardness value detected at low loads and with small indentations, the curve decreases constantly as the applied load increases.
HTD® provides this curve for each measurement made. The shape of the curve depends, among other things, on the depth and type of heat treatment.
Already in 1960, Bückle demonstrated the existence of a correlation between the stitching and the hardness value measured by the surface at the same point.
For this purpose, he divided the material under the impression made by the surface into parallel layers equal in thickness and depth to the depth of the impression.
He assigned each of these layers a weight, and the sum of the weights was 1.
This subdivision extends from 5 to 10 times the penetration depth.
By multiplying the different layers with the local hardness and adding the results, the hardness measured from the surface is obtained.
Test results
The HTD® uses the information acquired from the continuous application of the load to generate a load- penetration curve (not a single value) from each single test.
Figure #2 below provides an example of the test results.
The vertical axis is hardness measurement and the horizontal axis is the load applied.
Note the downward curve in this example illustrates that hardness declines as force (Kgf) is applied.
Figure #2 - Hardness and Force data from continuous acquisition testing (Kgf)
The data acquired is then used in a proprietary patented algorithm to calculate the effective case depth as shown in Figure #3 below. In this instance, the effective case depth is 2.95mm. Note: Vickers 513 corresponds to a hardness of Rockwell C 50.
Figure #3 - Case Depth Results and Analysis
Implications
HTD® testing allows for users to achieve test results and analysis much faster with savings of manpower, time and money. The process control opportunities are profound because information is available so much faster than with previous testing machines. Users can choose to tighten their process controls and increase their quality sampling. The test results reduce uncertainty and provide for improved supplier/customer communication while reducing waste and improving throughput. Cost savings are achieved through both reduction in sample preparation and testing time as well as reduction in product rejects.
With increasing emphasis in all industries on quality, tightening of standards and process control the HTD® is a logical value added measurement and analysis tool for commercial and captive heat treaters. It provides an opportunity to demonstrate case depth consistency and decrease uncertainty while reducing the cost and time involved in case depth measurement.
