Everything You Need To Know To Find The Best Digital Rockwell Hardness Testing Machine

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It is an established notion in the field of manufacturing that a certain object is just as good as the materials it is made of. As such, production specialists need to make sure that every component, material, and material treatment used to build a certain device or machine is going to be strong and durable.

This is where the Rockwell Hardness test comes into play since it was specifically designed to measure the durability of a material. The system is designed for testing in accordance to ASTM E18 standard. But before you decide to invest on a Rockwell Hardness Tester, there are a few things about the test that you need to understand first.

What is the Rockwell Hardness Test?

The Rockwell Hardness Test is actually one of several tests aimed to gauge a material&#;s compatibility as a component to an object based on their strength and durability. The other tests in the series include the the Knoop, Brinell, and Vickers methods.

The concept of the Rockwell Hardness test is essentially similar to its counterparts. A sample material is fed on to either a digital or manual Rockwell hardness tester which would then drop a set load ending with an indenter on the surface. Then, the strength of the material will be determined by the nature of the indentation left on the sample.

However, the Rockwell method differs greatly from the Knoop, Vickers, and Brinell methods in one aspect. Where the others measure strength by the size or width of the indentation left, the Rockwell method measures strength through depth. The rationale behind the Rockwell method is that the durability of a material is better gauged on its ability to maintain structural integrity from damages that are not merely superficial. This is why the method is commonly used in the fields of metallurgy and engineering, where the integrity of a material cannot be simply observed at a surface level.

How is the Test Conducted?

As was stated, the Rockwell hardness test is essentially similar to other methods in the sense that strength is gauged through applying load on to a material. How the Rockwell test goes about doing this, however, is different.

First, a minor load is applied to the surface which determines the zero position. Once the zero position is established, a heavier major load is then applied to the material which causes the indentation.

At the same time, the minor load is maintained all throughout the test. Some variations of the test would require that the major load remain on the material until it the indent it has made is deep enough.

Once the major load is removed, the depth of the penetration starting from the zero position is then measured. As with all hardness tests, the strength of the material is inversely proportional to the damage it sustained. As such, under the Rockwell method, materials tend to rate higher at the hardness scale if the indentation left on them is closer to the surface.

Why is the Rockwell Method Reliable?

In some cases, gauging the strength of materials through Rockwell Hardness Tester is preferable. This is due to a number of advantages as listed below.

1. No Material Preparation is Required

In some tests, the sample material has to be buffed, ground, cut up, and polished in order to get the most accurate of readings. Essentially, tests like the Knoop and Vickers method need for the sample surface to be as flat as possible with little to no variation.

In the Rockwell method, since the depth of the indentation is being measured, there is no need for the sample to undergo different processes to make the test accurate. This is also why the Rockwell method is used when testing unrefined materials like ore.

2. No Optical Evaluation

With the Rockwell method, the value of the hardness is directly readable since most hardness testers using this method don&#;t use diagonal scales to measure hardness. This is quite true if you opt for a digital Rockwell Hardness tester as the values are immediately displayed on screen after a few seconds of processing.

With the absence of optical evaluation, the chances of the operator making an error on the readings are greatly reduced.

3. Cost-Effective

Since Rockwell hardness testers do not need to be equipped with elaborate optical evaluation systems, they have rather short test cycles. This would allow for a more efficient testing process where operators can quickly move through one specimen to another.

Add to this the fact that Rockwell testers are considerably inexpensive compared to other instruments, the Rockwell method makes for a rather cost-effective process. And this is not the only way the Rockwell method helps its operators save up on costs.

4. Non-Destructive Nature

Despite the fact that the test leaves a sizeable indent on the material, the Rockwell method is a non-destructive and non-invasive process. After every test, the specimen itself can still be used for other purposes.

This means that the Rockwell method can effectively help its operators reduce their waste. If your workshop also processes raw materials, this could help in reducing operational costs.

How Accurate is the Rockwell Hardness Tester System?

The RockGen Rockwell Hardness Testing System was designed to test the hardness level of metal based on the indentation they leave on a tested material according to the Rockwell scale. The machine is capable of measuring the resolution of a material to a 0.001&#;. NextGen&#;s Rockwell hardness testers are guaranteed to provide one of the absolute highest accuracies on the market. The Rockwell Hardness Testing measurement is calculated by first applying the preliminary force test called a preload for a specified period of time called a dwell time.

After the specified period of time, an additional load, also known as the major load, will be applied. Now the total force has been applied and the measurements of the depth of the indentation are taken from the reference point to the final depth of the penetrator after it has undergone its major load. The distances between the two imprints are known as the Rockwell Hardness Values.

How Many Tests Are There for the Rockwell Regular Test Scales?

The Rockwell Hardness Tester has many different scales depending on the application of the tester on different materials. There is a total of 30 Rockwell hardness scales available to use for hardness testing and hardness value. The Rockwell Regular Scales Testing use a preload of 10kgf and a major load of 50kgf, 100kgf, or 150kgf. The Superficial Rockwell scales are for materials that are thin as 0.15mm or 0. inches and that use a preload of 3kgf and a major load of either 15kgf, 30kgf, or 45kgf.

What Are the Limitations of the Rockwell Testing Systems?

The Rockwell Testing systems depend on the material that is being tested including the hardness, thickness, indentation positioning, and scale limitations on the materials that are being tested. The material being tested must be at least 10x thicker than the indentation that the Rockwell indentation is going to be when it is made of the material.

NextGen&#;s Rockwell Hardness Testers are amongst the leading Rockwell Manufacturing machines and can provide you with all of the options your company needs including the Rockwell Twin Digital Testing machines. The Twin model is among the most popular products we have allowing the operator to test both Rockwell regular and Rockwell superficial scales on a single instrument. Enjoy the benefits of Rockwell hardness testing and the unprecedented accuracy it provides.

In Conclusion

Despite its advantages, the Rockwell method is not exactly applicable at all instances. However, it does not mean that a Rockwell Hardness Tester will not yield considerably accurate measurements which should help any workshop.

This is why it is important that you should find a rather reputable manufacturer who can then provide you with a well-build Rockwell tester. If calibrated right, these instruments can help you improve the quality of your facility&#;s output while reducing waste.

To learn more, contact us today.

Understanding the different hardness testing types and systems can be useful to determine an optimal solution. Hardness testing functionality has evolved and now users can dial into world-class caliber instrumentation which more closely aligns with their applications at hand.

 

Hardness Testing Defined

Contact us to discuss your requirements of Digital Rockwell Hardness Testing Machine. Our experienced sales team can help you identify the options that best suit your needs.

One of the most common indentation hardness tests used today is the Rockwell hardness test, and although less widespread, the Brinell and Vickers hardness tests are also utilized. The majority of indentation hardness tests measure the deformation that occurs when the material being tested is penetrated with an indenter. Two levels of force are applied to the indenter at specified rates and dwell times when performing a Rockwell hardness test. This is different than the Brinell and Vickers tests, where the size of the indentation is measured after the indentation process. The Rockwell hardness of the material is based on the difference in the depth of the indenter at two specific times during the testing cycle. The value of hardness is calculated using a formula that was derived to yield a number falling within an arbitrarily defined range of numbers known as a Rockwell hardness scale.

 

Regardless of the Rockwell scale or indenter being used, the overall Rockwell test procedure is the same. The indenter is brought into contact with the material to be tested, and a preliminary force (a.k.a. the minor load) is applied to the indenter. The preliminary force is usually held constant for a set period of time (dwell time), after which the depth of indentation is measured. After the measurement is made, an additional amount of force is applied at a set rate to increase the applied force to the total force level (a.k.a. the major load). The total force is held constant for a set time period, after which the additional force is removed, returning to the preliminary force level. After holding the preliminary force constant for a set time period, the depth of indentation is measured a second time, followed by the removal of the indenter from the test material. To calculate the Rockwell hardness number, the measured difference between the first and second indentation depth measurements, "h", is used.

If using an older Rockwell hardness systems, the operator may have to manually control most or all of the test procedure steps. The majority of today's newer machines automatically perform the entire test. Also, when leaving a mark or indentation is not an option, non-destructive ultrasonic technology can be used.

If using an older Rockwell hardness systems, the operator may have to manually control most or all of the test procedure steps. The majority of today's newer machines automatically perform the entire test. Also, when leaving a mark or indentation is not an option, non-destructive ultrasonic technology can be used.

 

Rockwell Hardness     

When testing the hardness of carbon steel, alloy steel, cast iron, non-ferrous metals and engineering plastics, Digital Rockwell Benchtop Hardness Testers can be used to directly measure in the most popular regular Rockwell hardness scales and can quickly convert that hardness value into HB, HV, HK and many other scales. Desirable hardness tester features include the ability to obtain ultra precise results, a wide measuring range, and scale/ selectable test force capabilities. Also, automatic main test force loading/unloading, a high resolution digital display and USB data storage are all very advantageous.

A user-friendly touchscreen interface can speed operations and the ability to use USB output to a flash drive is excellent for data mobility. There are options to apply the weight load such as on digital systems that use weights to apply the load or use a closed loop load cell to apply the weight load. The latter affords greater precision and repeatability. With a weight loaded system, the level of the machine is of great importance, so that the weights drop correctly. This is a less critical matter when using a load cell system.

Conforming to ASTM E-18 Superficial Rockwell Hardness standards, hardness testers in this category offer excellent repeatability in all Superficial Rockwell Hardness scales. Superficial Rockwell hardness testing is designed for very thin and soft workpieces. The systems are ideally suited for a wide range of environments including inspection labs, heat treat facilities, tool rooms, workshops and laboratories. For more versatility, twin hardness testers are capable of testing in all of the regular Rockwell and Superficial Rockwell hardness scales.

Dolphin nose systems allow for the hardness testing of inner, as well as exterior, diameters. The systems are generally larger in size than other Bench Rockwell systems, offering greater testing heights and depths. Dolphin nose models offer a manual handle that activates the preload system, or an advanced Auto Z-axis preload system. Using the Auto Z-axis preload system, after placing the workpiece in testing position, the operator only needs to press the start button for the machine to complete the testing process.

Brinell Hardness

Brinell hardness testing is commonly used for very large, porous testing of less hard metals, such as castings. Benchtop systems available today can handle the most popular Brinell hardness applications, and incorporate the latest innovative closed-loop technology. A test load is applied via a closed-loop control unit with a load cell to apply weight loads up to 3,000kg, a DC motor and an electronic measurement and control unit. The result is highly accurate Brinell hardness measurements at all test loads up to 0.5%. A common load overshoot or undershoot, also known as traditional dead weight or open-loop, system is eliminated. The absence of mechanical weights not only eliminates friction problems but also makes the equipment less sensitive to misalignments caused by vibrations. The systems are ideal for laboratories, workshops, tool rooms and inspection labs.

 

Software driven digital optical systems offer advantages over manual microscopes that are supplied with several hardness testing machines. Connected to a PC, laptop or tablet, the operator can push a single button to take automatic and instant measurements. All graphics can be saved, along with test results, in either word or excel formats.

 

Vickers/ Knoop Hardness

Micro Vickers/ Knoop Hardness Testers are cost-effective options in Vickers hardness applications, that are ideal for those who do not perform high volume testing each day. Testing is done on extremely thin/small workpieces, and often used for checking the hardness of layers, or platings and coatings on small parts in a laboratory environment. A high level of preparation is needed for such testing, including but not limited to, a high degree of polishing.

 

There are three types of turret control including a basic manual turret for changing from optics to indentation and back to optics for measuring. A second type incorporates an automatic turret, giving operators greater freedom to change the turret position by a button on the tester keypad. The most popular Vickers/Knoop Hardness Testers have a turret control option using software to control the entire test with a one-click process using calibrated auto edge detection. Precision video and measurement software also allows for clicking of the indent edges in software, then deriving a hardness reading on screen. 

Designed for the accurate hardness testing of small precision parts, thin materials, case-hardened layers and all sorts of steel components, Macro Vickers Hardness Testers utilize larger weight loads of up to 50kg. This type of test bridges the gap between the superficial Rockwell and micro Vickers machines. These systems have a manual turret.

 

Shore Testers (Durometers)

Shore Portable Hardness Testers are targeted for testing materials such as rubber, soft plastics and leather, and versions are also available for the testing of hard plastics such as bowling balls and hard hats. Electronic Durometers for measuring Shore A and Shore D values are designed to fit comfortably and firmly in a user's hand. A large LED display and simple 3 button control make this device easy to use.

 

 Portable Hardness Testers

There are two popular digital methods of portable hardness testing. The first is "Dynamic Impact", based on the Leeb principle of hardness, developed by DietMar Leeb in the 's. A spring loaded impact body is thrust to the test surface, affecting rebound. Initial thrust and rebound speed is measured in a non-contact mode, and is calculated as a Leeb hardness value and then automatically converted to Rockwell C, B, Brinell, Vickers and Shore Values. Also, the portable benefit means the tester can be brought to the workpiece, which is especially useful when testing large and/ or cumbersome parts. This method has resulted in efficient, fast and accurate portable hardness testing results.

 

However, when a mark or indentation on the workpiece must be avoided, ultrasonic testing is a great solution. Advanced Non-Destructive Portable Hardness Testers utilize ultrasonics with Ultrasonic Contact Impedance (UCI) technology, enabling a portable hardness tester to test special surfaces on small and thin workpieces without marking the surface. These units can test metals as thin as 2mm throughout all scales, hard or soft. UCI technology is available on both manual and motorized systems. The motorized probe systems are used for very thin testing of coatings and platings, or surfaces with a very high polish finish.

 

UCI is based on a 136 degree diamond at the end of a vibrating rod being depressed into the test surface at a fixed load. The difference in Ultrasonic vibration frequency is then calculated into a hardness value. The UCI test procedure is slower than the Dynamic Impact style, however the UCI method has the advantages of being non-destructive and able to test thin and small work parts.

 

Previously, destructive indentations made on such sample pieces meant the garbage heap for those tested. Using ultrasonics, this is no longer the outcome. These systems have an open architecture and can be calibrated to read any metal, in any hardness scale, with reference samples to perform initial calibration. Ultrasonic portable hardness testing is ideal for applications such as bearings, pistons and valves, among many others. Key industries for this type of testing include aerospace, automotive and medical parts as well as knife blade manufacturing, to name just a few. 

 

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