With increasingly tight tolerance ranges, rectification of steel is becoming increasingly important. It is comparable to bending. Rectification cannot be used to restore the initial state of the workpiece. Various procedures are available.

 

There are now electromechanical and hydraulically powered rectification benches that operate under computer control. This is particularly advantageous for series production. At Härtha, we use a manual straightening press .

 

Requirements

The objective behind steel rectification is to ensure compliance with a specified tolerance range for warping. Before, during, and after rectification, the component geometry and the deviations are measured manually or using an NC system. If the shape deviation of series production parts is always the same, a fixed deformation can be set without the need for measurements.
 

 

Circular rectification

Circular rectification refers to various methods for rectifying round components. Deviations are measured by means of sensors during rotation. It is important that these sensors make contact with the component throughout the measurement. Circular rectification is differentiated into rolling rectification and bending rectification.

Rolling rectification

Rolling rectification is most commonly used early in the manufacturing process of components, for example for blanks after forging. It is intended to achieve flatness in the material and reduce tensions. This type of circular rectification usually impacts the entire component.

Bending rectification

Bending rectification is intended to eliminate existing deviations by means of a targeted correction. This requires measurement of the component’s geometry and of concentricity deviations. Only then can the workpiece be correctly positioned in the rectification press. Next, the bending stroke is performed by the press. This can be done manually or using an NC system.

High-frequency hammering

High-frequency hammering is suitable, for example, for welds or for increasing the service life of components. This rectification method makes it possible to treat deformations and residual stresses in specific areas of the component. Particularly high dimensional stability can be achieved.

Moulding rectification

Moulding rectification is suitable for components that are not rotationally symmetrical, such as aluminium castings. This requires that the measuring device is calibrated to a target value. Rectification is performed by bending.
 
INFO: Rectification of pipes
The production of pipes often brings about straightness deviations which need to be rectified. In the past, the straightness of pipes was determined subjectively by visual judgement. Today, pipes often need to meet highly specific requirements. For example, a 1-metre pipe must have a straightness deviation no greater than 0.2 mm. The permissible deviations increase accordingly with the length of the pipes. These stringent requirements require the use of state-of-the-art rectification machines.

 

Rectification can be applied wherever warping occurs on steel parts – whether during thermal or mechanical metalworking. Warping can also occur during the use of workpieces. Rectification is suitable for all types of steel - from non-alloy construction steel to quenched and tempered special steel.

 

 

Depending on the procedure, rectification offers the following advantages:

 

• Great dimensional stability
• Optimum flatness
• Suitable for different component geometries
• Suitable for different types of steel

 

 

Would you like to commission our services for rectifying your workpieces made of steel, stainless steel or aluminium? Then we will first need the following information about your workpiece:

 

• Material designation
• Hardness
• Heat treatments
• Weight and quantity
• Dimensions

 

 

Refer to our location overview to find the Härtha location closest to you, and to learn which processes we offer besides the rectification of steel.

 

 

A deep cryogenic treatment makes sense only for materials containing residual austenite at room temperature. Although primarily applied on high-alloy ledeburitic tool steels, it is also used for eutectoid tool steels. In the case of non-alloy and low-alloy steels, residual austenite forms only when the carbon content is at least 0.5%.

 

A deep cryogenic treatment is usually applied after hardening. However, because of the high risk of cracking during the cryogenic treatment, this now increasingly takes place after the first tempering treatment. The objective of this process is to eliminate dispersed η-carbide particles. However, this effect has not been proven conclusively.

 

It depends on the material whether the residual austenite content should be stabilised by repeated tempering or by deep cryogenic treatment.

 

 

Steels Subjected to deep cryogenic treatment are also hardened, and they achieve dimensional stability. This is achieved by cooling to a temperature between -90 °C and -196 °C. At these temperatures, the residual austenite in the material is converted to martensite.

 

Unless the residual austenite content is reduced, it may cause changes in the microstructure and volume of the component during subsequent use. The reason for this is the soft residual austenite, which becomes converted to the harder martensite over a number of weeks. The deep cryogenic treatment of steel prevents this slow gradual change in dimensional stability. This is especially important for precision components and high-precision tools.

 

INFO: Cryogenic methods
The development of various methods has made it possible to achieve ever lower temperatures during deep cryogenic treatments. Air is cooled down as low as -60 °C in deep-freeze chests or cabinets. Temperatures can be lowered far below -60 °C by means of mixtures of alcohol, dry ice, and liquefied gas. Finally, the use of liquid nitrogen and liquid helium allows cryogenic treatment down to -196 °C and -269 °C respectively.

 

 

What happens during deep cryogenic treatment?

In deep cryogenic treatment, the cooling process after hardening is extended, in order to accelerate the rate of conversion from austenite to martensite. For this purpose, the component is generally cooled to -90 °C. To achieve an even higher conversion rate, the material can also be cooled over an extended period to as low as –196 °C. This step is followed by at least one tempering cycle.

 

This procedure transforms the previously heterogeneous microstructure into a homogeneous lattice structure. This reduces residual stresses in the microstructure. Finally, hardness and wear resistance are increased because of the higher martensite content.

 

 

 

Cryogenic treatment is primarily intended to prevent slow gradual changes in dimensional stability and offers the following advantages:

 

• Consolidation of dimensional stability
• Reduction of residual stresses
• Reduced wear thanks to increased wear resistance
• Suitable for automation, and reproducible
• Ideal for precision tools

 

 

Basic requirements for deep cryogenic treatment are a carbon content of at least 0.5 % and a sufficient content of alloying elements with a martensite finish temperature (Mf) below 30 °C. All steels that meet these requirements are suitable for cryogenic treatment. Examples are:

 

• Ledeburitic chromium steels (e.g. 1.2080, 1.2379, 1.2436)
• High-speed steels
• Eutectoid tool steels (e.g. 1.2842)

 

 

Our deep cryogenic equipment has the following dimensions:
1,150 x 750 x 600 mm/500 kg

 

 

Refer to our interactive location overview to learn which Härtha locations offer deep cryogenic treatment of steel.

 

 

Would you like to subject your components to hardening and deep cryogenic treatment at our company? We will gladly provide you with a proposal. Please tell us the material designation, dimensions, weight, and quantity of workpieces to be treated.

 

 

The magnetic powder crack test begins with the magnetisation of the workpiece. This creates field lines that run parallel to the workpiece surface. Cracks on the surface cause the field lines to escape, and then to re-enter after the defect location. As a result, magnetic poles form at the crack, and these create a stray magnetic field.

During the magnetisation, a powder composed of iron oxide mixed with fluorescent dye particles is scattered across the component, or washed over it in the form of an aqueous suspension. The iron powder now collects at the magnetic poles of the defective areas. In a dark room, even the finest cracks will become easily visible under UV light.

 

The procedure is suitable for irregularities on or close to the surface – hidden cracks with a depth of up to approx. 1 mm can be detected. This testing method can detect only cracks that run transversely to the field lines. Defects that run parallel to the field lines do not interfere with the field lines, and do not produce a stray magnetic field.

 

Different magnetisation methods allow the generation of field lines longitudinal and transverse to the field lines of the component surface, allowing testing for longitudinal and transverse cracks. These methods are field and current flow magnetisation, as well as combined magnetisation. Very large components can be magnetised in sections. The systems used for magnetisation must not be operated by people wearing a cardiac pacemaker.

 

Current flow

During current flow magnetisation, a current is transmitted through the component, generating a ring-shaped magnetic field around the component surface. The field lines travel transverse to the component surface. This allows the detection of cracks in the longitudinal direction by means of iron powder.

 

Field flow

During field flow magnetisation, the current does not pass through the component itself. Instead, the component is clamped into a U-shaped iron yoke . There are electric coils on both legs of the yoke. This creates a magnetic field longitudinal to the component surface and reveals transverse cracks with the help of iron powder.

Combined magnetisation

If the crack orientation cannot be predicted, the current and field flow methods can be carried out one after the other or in combination at the same time. For this purpose, the test specimen is clamped into an iron yoke with coils while, at the same time, a current is transmitted through the workpiece. This process is particularly useful for large quantities.

 

Magnetic particle testing is basically suitable for all types of magnetisable materials. It is used, for example, for safety components in automotive engineering or for welds on pipelines.

 

The flux test is used for the automated inspection of such simple mass-produced components as rods or bolts. However, complex components with irregular geometry, such as crankshafts, springs, or brake discs, are equally suitable for a magnetic particle crack test. The same applies to some extent to rough surfaces.

 

Background

The production, processing, and use of steel causes the formation of cracks. Processes typically leading to cracking include casting, rolling, welding, and bending. If the crack formation remains untreated, the crack will progress from the surface to the inside of the component, and may cause a breakage. Magnetic powder crack testing can be used to check the component for cracks after each processing step.

 

 

Magnetic powder crack testing is used for the quality assurance of workpieces, and offers the following advantages:

 

• Fast and convenient process
• Reproducible
• Reliable according to DIN regulations
• Even hairline cracks and hidden cracks (just below the surface) become clearly visible
• No need for surface treatment
• Can also be applied to components with complicated shapes and large sizes
• Suitable for stationary and mobile use

 

 

DIN EN ISO 9934-1 Non-destructive testing — Magnetic particle testing — Part 1: General principles

 

DIN EN ISO 17638 Non-destructive testing of welds - Magnetic particle testing

 

DIN EN ISO 1369 Founding – Magnetic particle testing

 

DIN EN ISO 10228-1 Non-destructive testing of steel forgings – Part 1: Magnetic particle testing

 

DIN EN ISO 10839-5 Non-destructive testing of steel pipes - Part 5: Magnetic particle testing of seamless and welded ferromagnetic steel pipes for the detection of surface defects

 

ASME Section V Article 7 & 25 Magnetic Particle Examination

 

ASME Section VIII

 

DIN 25435-2, In-service inspections for primary coolant circuit components of light water reactors – Part 2: Magnetic particle and penetrant testing

 

DIN EN 1330-7, Non-destructive testing - Terminology – Terminology – Part 7: Terms used in magnetic particle testing

 

DIN EN 1369, Founding – Magnetic particle testing

 

DIN EN 10228-1, Non-destructive testing of steel forgings – Part 1: Magnetic particle testing

 

DIN EN 10246-12, Non-destructive testing of steel pipes – Part 12: Magnetic particle inspection of seamless and welded ferromagnetic steel pipes for the detection of surface defects

 

DIN EN 10246-18, Non-destructive testing of steel pipes – Part 18: Magnetic particle inspection of the tube ends of seamless and welded ferromagnetic steel tubes for the detection of laminar imperfections

 

DIN EN ISO 3059, Non-destructive testing – Penetrant testing and magnetic particle testing – Viewing conditions

 

DIN EN ISO 9934-1, Non-destructive testing – Magnetic particle testing – Part 1: General principles

 

DIN EN ISO 9934-2, Non-destructive testing – Magnetic particle testing – Part 2: Detection media

 

DIN EN ISO 9934-3, Non-destructive testing – Magnetic particle testing – Part 3: Equipment

 

DIN EN ISO 17638, Non-destructive testing of welds – Magnetic particle testing

 

DIN EN ISO 23278, Non-destructive testing of welds – Magnetic particle testing – Acceptance levels

 

DIN CEN/TR 16638, Non-destructive testing – Penetrant and magnetic particle testing using blue light

 

 

Refer to our interactive location overview to find the locations closest to you that offer procedures for testing and metalworking.

 

 

Are you interested in a magnetic powder crack test? Our specialists will be happy to advise you on test procedures that are suitable for your components. Firstly, please tell us the material designation and dimensions, as well as the weight and quantity of the workpieces to be tested.

 

 

Blast cleaning is suitable for the most diverse requirements for the surface quality of metallic workpieces, because the grain sizes and blasting agents are selected specifically to produce the desired result. The pressure can be regulated individually as well. It is mostly in the low pressure range between 0.5 bar and 5 bar.

 

The blasting agent is blasted onto the workpiece surface in a special chamber. Through blasting impact at high speed, all contamination and residues from previous treatments of the metal are removed.

 

Fine blasting is often a manual process. In contrast, in order to process a large number of units automatically and at consistent parameters, industrial sandblasting is usually performed by CNC-controlled sandblasting systems.

 

INFO:
The ever stricter requirements imposed on industrial components have caused blast cleaning to be developed from sandblasting. After much continuous refinement, the process is now ideally suited for removing rust, paint, and old coats of material from workpieces, and for smoothing metallic surfaces.

 

Blast cleaning provides a variety of advantages:

 

• Refinement of steels that have lost their corrosion resistance during heat treatment or because of manufacturing processes
• More environmentally friendly than pickling
• Suitable for a wide variety of materials
• Refined matt appearance
• Longer working life for tools and die casting moulds

 

 

The blasting agent is selected to suit each specific area of application and the properties of the component. A good choice for stainless steel, for instance, is corundum, which is ferrite-free and rather soft. Conversely, a coarser blasting agent might be appropriate for workpieces with thick walls.

 

The agents can be categorised as follows:

 

• Glass beads for smoothing and hardening surfaces, as well as for releasing tensile stress at weld seams
• Hard cast iron for paint removal
• Steel grit for rust removal
• Steel shot for removing coats of material
• Corundum for descaling and cleaning highly contaminated surfaces

 

 

Possible applications

Examples of blast cleaning applications include removal of coatings, descaling, rust removal, and smoothing. These steps are part of important processes in metalworking. It is furthermore possible to blast a wide variety of materials for cleaning, including aluminium, titanium, stainless steel, and non-ferrous metals.

 

Consequently, blast cleaning is used across a wide range of industries, for example in medical engineering and electronics, as well as in the automotive and furniture industries.

 

Since fine blasting can be executed with utmost precision and coordination, it is also used for engravings.

 

 

Maximum workpiece size: 1,350 x 900 x 600 mm/200 kg

 

 

Would you like to engage our services for blast cleaning your components? We would be happy to send you a proposal. We will require the following information first:

 

• Material designation
• Weight
• Dimensions
• Quantity

 

 

The HÄRTHA hardening plants operate in various locations in Germany, Italy, and the Netherlands. Refer to our interactive location overview to find a location close to you that will blast clean your workpieces.

 

 

Different methods of material analysis can be used to examine a variety of materials. At Härtha, we use optical emission spectroscopy to analyse iron-based materials.

 

The metal analysis can serve the following functions:

• Identification of unknown types of materials
• Testing the delivery quality of a material
• Testing a material against DIN standards
• Determination of reasons for excessive wear
• Determination of material quality
• Exclusion of material mix-ups

 

Optical Emission Spectroscopy (OES)

Optical emission spectroscopy is also known as arc-spark OES or spark OES. It is used to determine grades of steel, and is carried out using a OES spectrometer, also known as a spark spectrometer. The device displays the emission spectrum of chemical substances.

 

As soon as a material or component passes through the spark stand, it generates an arc or spark discharge. The contact between spark and material causes the sample material to evaporate. The atoms and ions released in the process are excited to radiation state. This emitted radiation is passed through optical systems and separated into its spectral components.

 

This results in light waves of different length that are typical of the individual elements. Measurement of these different wavelengths makes it possible to clearly identify and quantify the elements or ingredients contained in a material.

 

Stationary and mobile devices

Both stationary and mobile devices are available for material analysis. At Härtha, we use both types of devices. As well as giving us the ability to react flexibly, we can easily perform exact analyses - even of large and bulky workpieces.

 

Cost of material analysis

The costs incurred for a material analysis vary with the type of analysis and the workpiece to be examined. In a metal analysis using an OES spectrometer, the number of measuring points decides the costs.

 

 

A key advantage of material analysis is the speed of the process. What is more, as a non-destructive testing method, material analysis also has no effect on the properties of the workpiece.

 

Knowing the material properties exactly allows compliance with legal testing and safety requirements, as well as efficient use of resources by repairing components. The result is a cost-saving alternative to new purchases.

 

 

Material analysis can be used in various metal processing processes. Refer to our interactive location overview to find out where we offer each process.

 

The hardness test is a depth difference method that measures the resistance of the material to permanent deformation. For this purpose, a penetrator is pressed onto the material with a specific test force. The resulting penetration depth or the permanent impression in the test specimen is then measured, and the hardness value of the metal is calculated.

The different types of hardness tests are distinguished, on the one hand, by the shape and material of the penetrator. This body is usually made of steel, carbide, or diamond, and generally possesses a pyramidal, conical, or spherical shape. In addition, other distinguishing characteristics are the size and type of the load. The tests are furthermore categorised into static tests with a constant load, and dynamic tests with an impact load.

The most widely used methods are the standardised static hardness tests as per Rockwell, Vickers, and Brinell. The use of these standard methods produces values that are internationally consistent and comparable.

Rockwell hardness test

The Rockwell test provides a fast method for testing the hardness of metals, and produces values that can be read directly. While primarily suitable as a rapid test and for large material samples, this method is also used for more thorough tests such as the Jominy end-quench test.

In the Rockwell hardness test, a diamond cone is pressed into the material as a penetrator – initially with a preliminary force to avoid errors due to unclean surfaces, and then with the testing force. The resulting penetration depth determines the Rockwell hardness.

The measurement units HR and HRC are commonly used. HR stands for Hardness/Hardness Rockwell, while C stands for Cone – in addition to indicating the procedure, HRC thus also specifies the test head and the hardness scale.

 

Vickers hardness test

Generally suitable for all solid materials, the Vickers hardness test is also used in the metal industry, for example to control the quality of welds and edge layers. It can be used in both the macro and the micro range if the surface is ground flat.

During a Vickers hardness test, a symmetrical diamond pyramid is used as a test head which, under the application of the test force, leaves an impression in the material under application of the test force.

The diagonals of this impression are measured optically and are used to determine the Vickers hardness (HV).

Knoop hardness test

The Knoop hardness test is used mainly for brittle materials such as ceramics, and for coatings. An asymmetric pyramidal diamond serves as the test head, and presses down on the material with a slight force to prevent cracking, allowing penetration into thin layers. The Knoop hardness (HK) is derived from the optical measurement of the long diagonals.

Brinell hardness test

The oldest common method for hardness testing is the Brinell test. It was developed by Johan August Brinell as early as 1900. The Brinell hardness test is suitable for materials with an inhomogeneous or coarse particle size distribution, and for large samples, because this test method creates a rather large impression. A ball made of tungsten carbide is used as the penetrator. Accordingly, the acronym HBW (Hardness Brinell Tungsten Carbide Ball Indenter) is used as the measurement unit.

Which of the four methods for hardness testing is used depends primarily on the type of material, hardness, and treatments of the workpiece. Other factors are the homogeneity of the structure and the size of the component.

It is important that the section of the material to be tested is representative of the entire workpiece. If the microstructure is particularly heterogeneous, the test area must be correspondingly large.

The choice of hardness testing can furthermore depend on standards as well as the number of samples and the required accuracy of the test result.

The result for the hardness derives from different parameters that vary with the selected hardness test. In addition to the distinction between static and dynamic hardness testing, the static methods are further divided into depth measurement methods and optical measurement methods.

Dynamic hardness testing

During dynamic hardness tests, the force exerted by the test head is applied abruptly. The Leeb rebound method (ISO 16589), for example, is performed by shooting a sphere at the material to be tested, and then measuring the height of the rebound.

Another example is the UCI method (DIN 50159-1), which is short for Ultrasonic Contact Impedance. This method measures the resonance displacement of an ultrasonic vibration rod, which results from the contact of the test head with the material surface.

Depth measurement methods

The Rockwell method (HR) is a depth measurement method standardised as per ISO 6508. Brinell (HBT) and Vickers (HVT) can also be measured by depth. However, these procedures are not standardised. It is common to all procedures that they measure the test head's depth of penetration.

Optical measurement methods

Brinell (ISO 6506), Knoop (ISO 4545) and Vickers (ISO 6507) take measurements using optical measurement methods based on norms and standards. These methods measure the impression size that the test head leaves behind in the material. This measurement is followed by the calculation of the hardness based on a formula.

The test force applied during the hardness test is defined as the force with which the penetrator acts on the material to be tested. The greater the impression remaining in the material, the greater the accuracy of the measurement. For testing, it is therefore advisable to always use the maximum permissible test force.

Test forces are officially specified in Newton (N), but are often measured internally in gramme force (gf), kilogramme force (kgf) or pond (p). 1 kgf equals 1,000 p or 9.81 N. Above and below 1 kgf the hardness test is classified as a macrohardness test, and below this value it is a microhardness test.

Only proper procedure ensures the accuracy and reproducibility of hardness tests. As a general rule, if the test force is low then an exact result usually requires consideration of more parameters. The following factors must be taken into account:

• A controlled environment (temperature, humidity, vibrations, etc.)
• Calibration of the test device
• No impurities on the material or test device
• The test device and the test head respectively must be aligned horizontal and perpendicular to the material surface
• The material sample must be fixed stably in place
• Constant lighting conditions are important for optical measurement methods

 

In many cases, the execution of a hardness test requires the surface to be prepared accordingly. This preparation can involve chemical, electrochemical, or mechanical processes. It is important that the properties of the material surface to be tested remain unchanged.

The quality of the surface preparation has a direct effect on the accuracy of the test result. Which method is suitable depends on the condition of the material surface and on the type of hardness test, the penetrator used, and the test force.

Preparation is not necessarily required for a macrohardness test (test force above 1 kgf). Fine grinding will suffice in most cases. In contrast, the surface to be subjected to a microhardness test (test force below 1 kgf) must be polished mechanically or by means of electrolysis. The objective is a clearly visible edge for the optical measurement of the impression.

Deformations during preparation

Deformations can occur during sampling and must be polished – with an accuracy of 6.3 μm to 1 μm, depending on the planned test force. The lower the test force, the lower the number of permissible deformations. Below 300 gf, the surface must be free of deformations or damage.

Depending on the planned hardness test, the following steps may be necessary for surface preparation:

Hardness testing method	Surface preparation
Rockwell (macrohardness test)	No surface preparation, grinding
Brinell (macrohardness test)	Grinding, polishing or lapping
Vickers (macrohardness test)	Grinding
Vickers (microhardness test)	Mechanical, polishing electropolishing
Knoop (microhardness test)	High-gloss polishing, electropolishing

 

The hardness test plays a major role in the quality assurance applied by various industries, as it can often be carried out in a nearly non-destructive manner.

The metal industry in particular commonly relies on this testing method , for example as a means to examine welds or verify the success of heat treatments and surface finishes. In addition, the hardness test is also of relevance in the area of positive material identification (PMI).

 

 

At Härtha, we use hardness tests for quality assurance at all locations. Refer to our interactive location overview to also learn the metal processing processes which we offer at locations near you.

 

Sample preparation forms an integral part of metallography and is the basis of the microscopic examination of solid materials. Sample preparation is comprised of several steps, with a number of procedures available. To ensure that the sample is not corrupted and that its original properties are preserved, it is always vital to apply the correct procedure.

 

The appropriate metallographic process

Each step of sample preparation requires the selection of suitable chemical and physical procedures, with appropriate consumables. A thorough knowledge of physics and chemistry is a basic prerequisite for every metallographer or material tester.

 

The decision about the appropriate preparation procedures must be based on the characteristics of the workpiece. These essentially include the nature of the workpiece, the type of material, and the treatments to which the workpiece has been subjected.

 

For example, wet abrasive cutting is a good choice for titanium workpieces, while vacuum infiltration is suitable for particularly porous materials. Classification into material groups can assist in the selection of suitable procedures.

 

Preparatory steps at a glance

Preparatory step	Possible procedures
Sampling	Cutting
	Sawing Wet
	Cutting
Sample fixation	Hot embedding
	Cold embedding
	Vacuum infiltration
Grinding	Manual
	Semi-automatic
	Fully automatic
Polishing	Manual
	Semi-automatic
	Fully automatic
	Electrolysis
Etching	Immersion
	Colour etching

 

Potential errors and quality inspection

Errors can occur at every step of the sample preparation and must be investigated with targeted quality control. Only if no errors are detected can the next step be performed. Possible errors include:

• Deformation
• Cracking
• Pitting
• Changes in the microstructure
• Detachment of coatings
• Smearing
• Scratches and gouges
• Detachment of phases
• Overetching

 

 

 

 

The actual analysis is performed as soon as the sample has been successfully prepared. For this, the microstructure is examined under the digital microscope. The desired microstructure does not necessarily have to be of the highest quality. The analysis determines a quality that is sufficient for the specific use of the workpiece.

 

 

Metallography is used for quality assurance in all branches of the metal industry. The areas of application include:

 

• Determination of layer thicknesses
• Microstructural analysis
• Procedure tests (e.g. heat treatments)
• Inspection of the particle size distribution in the event of damage
• Monitoring of series production parts
• Inspection of semi-finished products and cast iron parts
• Assessment of weld seams

 

 

A workpiece is to undergo metallographic analysis following its carburisation. The drawing specification specifies the carburisation depth and the absence of residual austenite. These values must now be verified.

 

Maintaining the right temperature throughout the entire sample preparation is essential. The process begins with the request for the sample. Cooling with water during the cutting process keeps the sample from being impaired by heat generation.

 

The next step is the cold or warm embedding of the sample. Since the risk of fissure formation is greater during cold embedding, this example uses hot embedding with a hot embedding agent, which can be used at temperatures as low as 150°C. The temperature during hot embedding must not exceed 180 °C, as any residual austenite may otherwise be converted to martensite. This would falsely qualify the sample as conforming, even though this is not true for the component.

 

If the quality control result is satisfactory, the sample is subjected to grinding and polishing. The carburised zone is made visible by means of etching. As the last step, a microhardness test checks the carburisation depth as per the DIN requirement.

 

 

 

At our Härtha hardening plant we offer metallography as a means to assure the quality of our metalworking processes. Refer to our interactive location overview to find out the processes offered at each location.