What Are the Advantages and Disadvantages of Induction Hardening?Induction hardening is becoming increasingly popular in the manufacturing industry due to the controlled hardening offered by this technology. Improving the workpiece's various physical, mechanical, and chemical properties is beneficial.
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Understanding advantages and disadvantages of induction hardening helps to get the best result by minimizing possible defects and failures. This article will discuss all the advantages and disadvantages in depth.
How Does Induction Hardening Influence the Physical & Mechanical Properties?
The heating of the workpiece at a high temperature causes the austenite transformation, in which carbon atoms get trapped inside the crystal structure at the micro-level. The alternation of crystal structure leads to the strengthing of grain boundaries. As a result, the carbon atoms trapped inside the crystal structure increase the hardness, and the tight grain boundaries enhance the mechanical strength.
Let's examine the other hardening approaches to demonstrate that induction hardening is superior.
Other Hardening Methods
Several different methods can be used to harden metals. Let's discuss three major hardening approaches besides induction hardening, flame, furnace, and vacuum hardening.
The Furnace hardening process involves heating of workpiece into a heat treatment furnace in a controlled environment. The workpiece is heated until austenite transforms, after which a quick quenching occurs.
The furnace hardening cannot heat the workpiece as uniformly as induction hardening does. It heats all workpiece portions, while induction hardening can heat specific workpiece sections. Induction is a go-to option if you need to harden a particular portion.
Vacuum hardening involves heating the workpiece by controlling the partial pressure, followed by a quick cooling process. It is often used for high-precision parts, as it can produce tough and consistent surfaces with minimal distortion.
Like the furnace hardening, it is also incapable of heating the workpiece at a specific region. The vacuum prevents the workpiece from reacting with atmospheric gases in the air, so the result is unaffected.
Flame hardening also involves the hardening of the outer surface using a flame while maintaining the ductility of the core section. The depth capability of flame hardening ranges up to 10 mm. This process is typically used to harden small or thin parts or to harden specific areas of a more significant piece.
Since induction hardening does not use an open heating approach like flame hardening, it is more precise and does not create overheating, scaling, or decarburization damage.
What Are the Advantages of Induction Hardening?
Induction hardening offers a range of advantages over other hardening approaches. It is possible to harden a specific workpiece area with the exact penetration depth using induction hardening. Many applications require hardening the workpiece only on a particular section, which can be achieved by controlling the operational variables, such as the amount of current, heating time, and current frequency. In addition, a customized coil can be designed for the process based on specific use.
Following are the other key advantages of the induction hardening process.
- Induction hardening can heat and cool a metal component much faster than other methods, such as flame or furnace hardening.
- It customizes the hardness of the steel workpiece to the desired level.
- Induction hardening is the best approach to get uniform hardening throughout the material structure.
- It requires low manual labor and can be completely automated, depending on the requirements.
- It is generally more energy efficient than other methods, as it heats and cools the component more quickly and requires less energy to maintain the high temperatures.
- Induction hardening allows for greater control of the heating and cooling rates, which can result in a more consistent and precise hardening of the component.
- The induction hardening process minimizes the risk of defective parts and directly contributes to the hardening cost. In addition, the automation in induction hardening reduces manual labor and helps to reduce the overall cost.
Click to see the different induction hardening methods.
Click to see how to do hardening and self-tempering.
What Are the Disadvantages of Induction Hardening?
The workpiece geometry and uniform heating are linked to the main drawbacks of induction hardening. If the workpiece geometry is intricate, the region close to the induction coil gets hotter than other sections. However, using the customized induction coil according to the shape of the workpiece eliminates the possibility of uneven heating.
Cracking in the workpiece is another possible disadvantage of induction hardening. Some of the few reasons include thermal expansion, thermal stress, and uneven quenching.
Following are the other key disadvantages of the induction hardening process.
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Explore more:NPK 10 20 20: The Ultimate Guide to Boosting Your Garden's Growth- The thermal expansion caused the concentration of impurities at grain boundaries, further leading to the weak grain structure resulting in intergranular cracking.
- The rapid heating and cooling process in induction hardening can distort the hardened component. This can be a problem if the component requires precise dimensions or is prone to warping.
- The cost might be a disadvantage if we compare the installation cost of induction hardening technology with other approaches, such as flame hardening and furnace hardening.
- Induction hardening is not compatible with all types of metal and alloys. It is limited to specific grades of steel alloys. Low-carbon alloys like steel , , 12L14, and do not perform well under the induction hardening procedure.
- The steel needs to have a certain level of carbon content (> 0.40%) to obtain a significant increment in hardening level.
- It requires a high level of attention and expertise to ensure that the component is adequately heated and cooled to achieve the desired results.
- Careful control of process parameters can be time-consuming and may require frequent monitoring and adjustments during the induction hardening process.
Summing Up
Is Your 35kV Oil-Immersed Transformer Safe from Overheating Risks?There is no doubt that induction hardening is one of the practical approaches to hardening steel alloys with a specific carbon content level. It offers uniform hardening, low-energy cost, quick lead time, and several other advantages.
It also has a few disadvantages, namely the possibility of cracking and high installation costs. However, Using FOCO's sophisticated induction hardening machine makes the process cost-effective through its sustainability. Furthermore, the geometry of the workpiece and customizing the induction coil help prevent the risk of crack formation.
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What is Induction Hardening?
Induction hardening is a method of quickly and selectively hardening the surface of a metal part. A copper coil carrying a significant level of alternating current is placed near (not touching) the part. Heat is generated at, and near the surface by eddy current and hysteresis losses. Quench, usually water-based with an addition such as a polymer, is directed at the part or it is submerged. This transforms the structure to martensite, which is much harder than the prior structure.
A popular, modern type of induction hardening equipment is called a scanner. The part is held between centers, rotated, and passed through a progressive coil which provides both heat and quench. The quench is directed below the coil, so any given area of the part is rapidly cooled immediately following heating. Power level, dwell time, scan (feed) rate and other process variables are precisely controlled by a computer.
Typical Induction Hardening Materials
Typical materials include:
Benefits of Induction Hardening
Increased Wear Resistance
There is a direct correlation between hardness and wear resistance. The wear resistance of a part increases significantly with induction hardening, assuming the initial state of the material was either annealed, or treated to a softer condition.
Increased Strength & Fatigue Life due to the Soft Core & Residual Compressive Stress at the Surface
The compressive stress (usually considered a positive attribute) is a result of the hardened structure near the surface occupying slightly more volume than the core and prior structure.
Parts may be Tempered after Induction Hardening to Adjust Hardness Level, as desired
As with any process producing a martensitic structure, tempering will lower hardness while decreasing brittleness.
Deep Case with Tough Core
Typical case depth is .030' - .120' which is deeper on average than processes such as carburizing, carbonitriding, and various forms of nitriding performed at sub-critical temperatures. For certain projects such as axels, or parts which are still useful even after much material has worn away, case depth may be up to ½ inch or greater.
Selective Hardening Process with No Masking Required
Areas with post-welding or post-machining stay soft - very few other heat treat processes are able to achieve this.
Relatively Minimal Distortion
Example: a shaft 1' Ø x 40' long, which has two evenly spaced journals, each 2' long requiring support of a load and wear resistance. Induction hardening is performed on just these surfaces, a total of 4' length. With a conventional method (or if we induction hardened the entire length for that matter), there would be significantly more warpage.
Allows use of Low Cost Steels such as
The most popular steel utilized for parts to be induction hardened is . It is readily machinable, low cost, and due to a carbon content of 0.45% nominal, it may be induction hardened to 58 HRC +. It also has a relatively low risk of cracking during treatment. Other popular materials for this process are /, , , ETD150, and various cast irons.
Limitations of Induction Hardening
Requires an Induction Coil and Tooling which relates to the Part's Geometry
Since the part-to-coil coupling distance is critical to heating efficiency, the coil's size and contour must be carefully selected. While most treaters have an arsenal of basic coils to heat round shapes such as shafts, pins, rollers etc., some projects may require a custom coil, sometimes costing thousands of dollars. On medium to high volume projects, the benefit of reduced treatment cost per part may easily offset coil cost. In other cases, the engineering benefits of the process may outweigh cost concerns. Otherwise, for low volume projects the coil and tooling cost usually makes the process impractical if a new coil must be built. The part must also be supported in some manner during the treatment. Running between centers is a popular method for shaft type parts, but in many other cases custom tooling must be utilized.
Greater Likelihood of Cracking Compared to most Heat Treatment Processes
This is due to the rapid heating and quenching, also the tendency to create hot spots at features/edges such as: keyways, grooves, cross holes, threads. (Please talk to an AHT representative if you have concerns.)
Distortion with Induction Hardening
Distortion levels do tend to be greater than processes such as ion or gas nitriding, due to the rapid heat/quench and resultant martensitic transformation. That being said, induction hardening may produce less distortion than conventional heat treat, particularly when it's only applied to a selected area.
Material Limitations with Induction Hardening
Since the induction hardening process does not normally involve diffusion of carbon or other elements, the material must contain enough carbon along with other elements to provide hardenability supporting martensitic transformation to the level of hardness desired. This typically means carbon is in the 0.40%+ range, producing hardness of 56 ' 65 HRC. Lower carbon materials such as may be used with a resultant reduction in achievable hardness (40-45 HRC in this case). Steels such as , , 12L14, are typically not used due to the limited increase in hardness achievable.
Our Burton Ave Location in Waterloo, Iowa and our Cullman, Alabama location offers Induction Hardening. Request a Quote by Filling out our Form.
* Blog was updated in July to reflect our Cullman, Alabama location now having induction hardening.
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