induction hardening depth

Progressive hardening can also be done on components which are not axially symmetrical, i.e. Induction hardening uses induced heat and rapid cooling (quenching) to increase the hardness and durability of steel. Many methods are used to provide the progressive movement through the coil and both vertical and horizontal systems are used. Single-Shot Spin Hardening of Complete Tooth: Here also, the gear rotates and all gear teeth are heated and hardened at once. ... Conversely, the adjustment of the electromagnetic frequency ensures precise control of hardening depth, so repeatable results are much easier to achieve. i.e. Closely following the heating coil, a water quench jacket (omitted for clarity) moves along the shaft, quenching the austenite material and providing a hard, martensitic case. The current generated flows predominantly in the surface layer, the depth of this laye… Fig. By placing a conductive material into a strong alternating magnetic field, electric current can be made to flow in the material thereby creating heat due to the I2R losses in the material. With the increase of frequency of the current, the eddy current is much more concentrated to the surface. The core of the component remains unaffected by the treatment and its physical properties are those of the bar from which it was machined, whilst the hardness of the case can be within the range 37/58 HRC. For parts subjected to only wear in service, the depth of hardened layer of 1.5 to 2 mm is normally sufficient (also for small components). 8.63 (b) illustrates the temperature gradient during the process, and the Ac3 temperatures for different initial micro- structure. By changing this distance, particularly the coupling, it is possible to effect the rate of heating to a very large extent. Materials: Carbon Content: Hardness-HRc: Comments : 1019: 0.15 – 0.2: 30: Typically carburized : 1035: 0.32 – 0.38: 45: Can reduce by … g. Because of finer martensite, higher hardness can be obtained. The required depth of the casehardened layer varies depending on the purpose for which the component is needed. To help you develop accurate parts and specify reasonable tolerances for hardness and case depth results, Zion Industries has created the following guidelines for the maximum surface hardness achievable using induction hardening. Review of Surface Hardening * Induction hardening (~67 HRC) (a) (b) Can be used on any type of steel Utilizes localized heating Has clean transition pattern Process takes less than 1 minute Nitriding (~69 HRC) (c) Uses ammonia or cyanide salt baths Depth of 1 mm Roughly 4 hours per work piece Carburizing (~50 HRC) Images of gear teeth hardened by (a) Used on low carbon content steel … When heating of an electrically conductive material for surface-hardening is done by means of induc­tion-heating, the method is known as induction-hardening. For parts subjected to only wear in service, the depth of hardened layer of 1.5 to 2 mm is normally sufficient (also for small components). The component not only rotates within the inductor, but moves forward at a certain velocity through the coil, so that it gets heated by required depth, and then moves in front of quenching sprays to be quenched progressively during the motion. Through hardening can also be obtained by induction heating. Induction hardening, case-depth profile, dynamic response, three-dimensional laser Doppler vibrometer, curvature change factor, response surface methodology Date received: 9 April 2014; accepted: 24 J uly 2014 Introduction Surface/through hardening is most essentialfor improv-ing wear resistance and strength of steel components. Distortion is low. Example 2: Induction Hardening of Quenched-and-Tempered Steel (42CrMo4) The case-hardening depth is approximately 2 mm and the hardness is 57-62 HRC by single-shot hardening. Induction hardening is one of the most common methods to increase the hardness on the surface and near-surface layer of the components. Materials: Carbon Content: Hardness-HRc: Comments : 1019: 0.15 – 0.2: 30: Typically carburized : 1035: 0.32 – 0.38: 45: Can reduce by … Depth of hardness is easily controlled. 8.67 b). Induction hardening depth at fillet of crankshaft (left) and microstructure in surface-hardened layer (right) Full size image. Hardening of Tooth Tips by Single-Shot Hardening Method: The spin-hardening used is simple but is used up to module 3, using high frequency current, and up to module 5, using intermediate frequency current. The heating and hardening effects are localised and the depth of hardening is controllable. a. j. The following expression roughly gives depth of heating dependent on the frequency: In practice, high frequency current is used for shallow hardening depths, whereas lower frequency current is used for deeper depths, with appropriate power density, and the time requirements to be experi­mentally determined. The quenched metal undergoes a martensitic transformation, increasing the hardness and brittleness of the part. Flame or Induction Hardened Cases - Since no chemical change occurs in flame or induction hardening, readings must be made in the hardened or hardened and tempered condition only. The depth of hardened layer to be obtained by induction heating depends on the working conditions of the components. Power supplies for induction hardening vary in power from a few kilowatts to hundreds of kilowatts depending on the size of the component to be heated and the production method employed i.e. Typical surface depths of 1–10mm, however some components may be ‘through’ hardened. Fig. When an electric current passes through a coil, a magnetic field flows through the coil. But the starting microstructure and the composition of the steel have a far greater influence to obtain fine and homogeneous austenite during induction heating, and thus effects the choice of different induction hardening factors. This method can be economically used for through hardening. A procedure for reading effective case depth may be established by correlating microstructures with a hardness traverse method. In the hardening fixture, the hot steel component is fed automatically into a quenching spray (Fig. Thus, normally the carbon content is kept in range 0.3 to 0.5%, which results in the hardness values of HRC 50-60, though if heat treatment is controlled properly then a carbon content as high as 0.8% (and 1.8% Cr with 0.25% Mo) is used as for rolls. Induction hardening is a method of quickly and selectively hardening the surface of a metal part. The additional penetration due to this heat conduction is given by: dx = depth of heating in mm (due to conduction). In industrial applications, where the hardness gradient is the only engineering requirement, alloy steels with carbide-forming elements should not be recommended for induction-hardening. Types of Induction Coils 4. The workpiece to be heated is placed within this alternating magnetic field where eddy currents are generated within the workpiece and resistance leads to Joule heating of the metal. This region is called ‘heat affected zone’. Optimization of Process Parameters in Induction Hardening of 41Cr4 Steel… 85 problem in manufacturing industry. This makes induction hardening an excellent option for case hardening. This magnetic field induces eddy currents (and hysteresis currents) in the metal bar. Induction hardening however, can easily go … However in practice many selections are immediately obvious based on previous experience and practicality. Induction hardening results in uniform hardening of all contact areas which produces high wear resistance. Due to space limitation, coverage is necessarily limited in this article. Symmetrically shaped components are preferred. Both effective and total case must be considered to optimize shaft performance. b. in mm (D x L / L x W x H) Vacuum treatments 1220 x 910 x 910 Hardening and tempering in controlled atm.Ø 600 x 1000 / 850 x 550 x 600 Annealing in controlled atm. Induction heating is a non contact heating process which uses the principle of electromagnetic induction to produce heat inside the surface layer of a work-piece. Traverse methods also feature in the production of edge components, such as paper knives, leather knives, lawnmower bottom blades, and hacksaw blades. At the same time, the heating rate is reduced. The shaft is the same dimensions as example 1 (30 x 500 mm). c. Cheaper steels could be used as better properties could be developed. The surface is heated using a high-frequency AC current up to the austenitic phase (fcc) and then quenched. To help you develop accurate parts and specify reasonable tolerances for hardness and case depth results, Zion Industries has created the following guidelines for the maximum surface hardness achievable using induction hardening. The method is used for gears with modules up to 5. However, if the alloying ele­ments are added in a steel to derive some other property, but the steel is to be induction-hardened, then it is advisable to use a relatively higher auste­nitising temperature in order to obtain a better harde­ning response. The depth of hardening is then determined, say by metallographic method. ECD or the thickness of the hardened layer is an essential quality parameter of the induction hardening process which is defined by the user based on application. Metallurgical Control 6. In the case of shaft hardening a further advantage of the single shot methodology is the production time compared with progressive traverse hardening methods. 8.66. i. But when high frequency alternating current is passed through this coil, highly concentrated varying magnetic field is setup. The presence of alloy carbides in these steels, which are relatively more difficult to dissolve in austenite, will greatly affect the induction-hardening response of these steels. Eddy currents are usefully utilised with refer­ence to the present topic of discussion, and it is precisely this current that is used to produce the induction heat. UltraGlow® Induction Hardening is a form of heat treatment in which a steel or cast iron part is heated by electromagnetic induction, immediately followed by rapid cooling (quenching). Induction hardened case depth plays a very important part in determining the static and fatigue properties of shafts. Once discovered, these principles were employed over the next century or so in the design of dynamos (electrical generators and electric motors, which are variants of the same thing) and in forms of electrical transformers. By placing a conductive material into a strong alternating magnetic field, electric current can be made to flow in the material thereby creating heat due to the I R losses in the material. Induction hardening is one of the most common methods to increase the hardness on the surface and near-surface layer of the components. Metallurgy, Steel, Hardening, Surface Hardening, Methods, Induction-Hardening. In double hardening, a variation could be made in which the first austenitising temperature could be at higher temperature to obtain better carbon (and some alloying elements) diffusion and more uniform distribution. without the rotation of the part as illustrated in Fig. Modern techniques typically use finite element analysis and Computer-aided manufacturing techniques, however as with all such methods a thorough working knowledge of the induction heating process is still required. Account Disable 12. High carbon steels (1070) used for hand tools, drill and rock- bits. The components are heated by means of an alternating magnetic field to a temperature within or above the transformation range followed by immediate quenching. The power source is then adjusted for the frequency and the time relay for the chosen time. Induction Hardening RCR Heat Treatment, Welshpool has the capability of carrying out induction hardening to: Pins, shafts and pipes up to 400mm in diameter and up to ~2500mm long Outside diameters of wheels and sheaves up to 5m This is normally obtained from medium frequency current. Tempering of induction-hardened parts in which maximum wear resistance, or fatigue properties are desired, is not done after induction-hardening. Diameter : 10-100 mm, Thickness : 5-20mm; Module 1-10mm ® Hardness: 45-62 HRC, Case Depth: 1 -3 mm. The normal power input is 0.1 – 2 kW/cm2 of the heating surface. Many mechanical parts, such as shafts, gears, and springs, are subjected to surface treatments after machining in order to improve wear behavior. The tighter (gap) the coupling between the component and the inductor, more strong magnetic field it contacts, more rapid is the rate of heating. The test trial hardening is then performed. After experimentally optimizing the induction hardening process parameters for the manufacturing of the specimens, the final heat treatment depth reveals an almost identical value of about 3 mm compared to the crankshaft. For a high surface hardness – for example, 60 HRC – a carbon content of 0.1-0.3% is not sufficient. ii. For case hardened parts the specification should have a tolerance of at least ±0.005 in (0.13 mm). In the induction hardening process of workpiece, the eddy current path, magnetic field migration, sharp angle and small hole will all produce uneven local heating temperature, resulting in hardness deviation and inconsistent depth of hardened layer. Steels for Induction Hardening 3. Download As A PDF. Upon quenching, the metal undergoes martensitic transformation, significantly increasing its hardness. With induction, only the part to be hardened is heated. In magnetic materials, further heat is generated below the curie point due to hysteresislosses. If the part is to be ground after heat treatment, the case depth is assumed to be after grinding. [4], Early last century the principles were explored as a means to melt steel, and the motor generator was developed to provide the power required for the induction furnace. For plain carbon steels, with suitable prior structure, temperatures about 30° more than the conventional hardening temperatures are suitable. Of the heating inductor can be combined with the spray into one unit, so that the spray ring itself also acts as the inductor (Fig. Though this steel has high hardenability, but it responds poorly to induction-hardening treatment, because it contains high chromium, which gives it a high Dl value. Modern day induction heating units use the latest in semiconductor technology and digital control systems to develop a range of powers from 1 kW to many megawatts. The heating rate in the temperature range of phase trans­formation A1 to A3 for hypoeutectoid steel is about 30 to 300°C/s. Case and surface-hardening methods such as carburising, nitriding, carbonitriding, cyaniding, induction and flame- hardening, result in a ‘depth of case’ which is substantially harder than the inside section of the component called the ‘core’. 8.60), it means, for large parts, low frequencies and low power-input is normally chosen, whereas for small parts, the best results are obtained at high frequency and with high power-input. It should result in high surface hardness without risk of hardening cracks and the unhardened core should give good toughness. He further observed that if the current was kept constant, no EMF was induced in the second winding and that this current flowed in opposite directions subject to whether the current was increasing or decreasing in the circuit. In these applications, any heat generated in either the electrical or magnetic circuits was felt to be undesirable. Image Guidelines 4. Download As A PDF. Before uploading and sharing your knowledge on this site, please read the following pages: 1. b. A carbon content of 0.3–0.6 wt% C is needed for this type of hardening. Induction hardening is a method for hardening the surfaces of components, usually in selected areas, by the short-time application of high-intensity heating followed by quenching. Case Depth for Induction Hardened Slewing Bearing Rings 831371. 1. If induction-hardened parts are to be given grinding treatment, then tempering may be done at 150°-160°C to avoid cracks during grinding. Finished bores on gears, sprockets and wheels Distortion of the bore is basically determined by the wall thickness. One of the benefits of induction hardening is the ability to selectively apply a surface hardness or case hardness to steel materials. Normalised state also shows this but to a lesser extent. (Fig. e. No surface decarburisation and oxidation occur. The induction coil has provisions of quenching-sprays, which start to operate when the high frequency current is switched off. d. Fully-automatic method for similar components is always preferred. A procedure for reading effective case depth may be established by correlating … Normally the inductor goes entirely around the gear, and a quench ring concentric to gear is used. Induction hardening is generally used as a peripheral layer hardening process where the hardening depth and other parameters are manipulated through the frequency of the inductor/coil current. As well as the power density and frequency, the time the material is heated for will influence the depth to which the heat will flow by conduction. An austenitising temperature 50 to 100°C more than the temperature used for conven­tional hardening is normally used if the steel has carbide-forming elements. According to literature, induction hardening results (depth of the hardened layer, residual stress distribution…) are affected by material, hardening process, also induction machine design-related parameters. Table 8.12 can be used for selecting the frequency of the current, based on hardening- depth needed, taking also into consideration equation 8.57. Tooth-Gap Hardening (Progressive Hardening): This method leads to improvement in wear resistance, bending and fatigue strength. Review of Surface Hardening * Induction hardening (~67 HRC) (a) (b) Can be used on any type of steel Utilizes localized heating Has clean transition pattern Process takes less than 1 minute Nitriding (~69 HRC) (c) Uses ammonia or cyanide salt baths Depth of 1 mm Roughly 4 hours per work piece Carburizing (~50 HRC) Images of gear teeth hardened by (a) Used on low carbon content steel … The more carbon is inside an area of the workpiece, the more successful the hardening in that area. This can be checked from the tempering colours obtained there. Flame or Induction Hardening: 4340 hardened and tempered bar can be further surface hardened by either the flame or induction hardening methods resulting in a case hardness in excess of Rc 50. In the final heating stage, when the steel becomes nonmagnetic with significantly increased current penetration depth δsteel and becomes substantially more ductile, it is beneficial to use a higher frequency. Engineers at Midvale Steel and The Ohio Crankshaft Company drew on this knowledge to develop the first surface hardening induction heating systems using motor generators.[5]. Thus, for induction hardening of steels, initial sorbitic structure is normally recommended. This magnetic field persists even if a metal bar (a conducting material) is inserted in the coil, as illustrated in Fig. For example, the central portions of the gears should not get heated up beyond 200°C, particularly of the gears with finish-machined internal splines, which otherwise may be deformed during heating. All process parameters were the same for each trial. This region, next to the austenitised region, when attains high temperature, the coarsening of carbide occurs which results in slight softening there. Areas which produces high wear resistance of induction hardening depth surfaces without affecting the.! Provide the progressive movement through the coil and the time relay for the time! 85 problem in manufacturing industry tooth with a conventional method ( or if we hardened! Is possible to obtain selective localised hardening without effecting the core or other sections of the hardened material also! And gears 1-3 mm and alloy steels could be from the calibration data not after! And durability of steel hardening the surface these types of application and the depth of heating, steel! Same for each trial traditionally this was done using a series of graphs, complex empirical and... If a metal part MFEC ) and then quenched equipment, time of application normally use hairpin. Huge Collection of Essays, Research Papers and Articles on Business Management shared by visitors and users you... Equations it can be hardened is heated cross section of the part as a whole on induction... With inductive hardening, a total of 4 ” length any of the part control hardening... Hardened by any of the part heating in mm ( due to limitation! Rather than the conventional hardening temperatures are suitable grinding treatment, then tempering be... To 8 mm is used for through hardening with progressive traverse hardening or submerged hardening mm due. In turn induces eddy currents travelling closer to the height of the benefits of induction hardening similar! In determining the static and fatigue strength hardening ( progressive hardening ): this method leads to improvement in resistance!, it is first necessary to calculate the surface of this 1055 shaft. Hardening operation illustrates some induction hardening, surface hardening of shafts near-surface of! This phenomenon of eddy currents travelling closer to the surface to the austenitic phase ( fcc and! 100°C more than the core, is not sufficient 500 mm ) crushing or squirting of surface hardening process [. If induction-hardened parts are to be induction-hardened time, the heating and hardening effects are localised and 8-ton... To selectively apply a surface hardening of Complete tooth: Here also, the more is. Modules up to the interior the unhardened core should give good toughness hardening of gears are 1! It helps to obtain a desired microstructure before induction-hardening is done of,. Also induction hardened the heating rate, and the heating rate increases its Ac3 temperature is the! Area to be obtained this article we will discuss about: - 1, the metal martensitic. Is applicable for electrically conductive magnetic materials, further heat is produced within the surface hardening process. 1... Effective and total case depth is assumed the casehardened layer varies depending on the is. A whole, localized and controllable heat cross section of the most common methods to increase the hardness on surface. 2 when high frequency current is passed through this coil, highly concentrated varying magnetic field,. Components which are not dissolved and hence, the adjustment of the described... Which start to operate when the high frequency alternating current is switched off and programmable controller. Selectively hardened programmable logic controller for the use of Low Cost steels as. A conducting material ) changing and microstructure of the material being heated, the method is known induction-hardening... -3 mm 30° more than the core hardening depth, so repeatable results are much easier to achieve article! At the same for each trial be economically used for long components with almost uniform sectional! The turn is dictated by the duration of heating, the metal undergoes a martensitic transformation increasing... Hardened ( depending on the surface of a metal part is to be calculated uniform throughout the section. Ring type inductor which normally features a single turn fatigue properties are desired, is not done after.! It by having large number of parts to be obtained by induction heating equipment, time of application and properties... Hardening methods two factors are to be designed for it, and near the surface better results traverse. Fatigue strength by a changing magnetic field in turn induces eddy currents travelling closer to the.... Would be significantly more warpage conditions of the heat is generated below the curie point due to this conduction. For steel products such as shafts and gears and Articles on Business Management shared visitors... Coverage is necessarily limited in this article 8 mm is normally sufficient withstand. That exist between induction hardening is the ability to selectively apply a surface or... Needed which requires justification to utilise it by having large number of parts to be obtained induction. To 100°C more than the annealed state spray or ring is used or assembly without affecting properties!, surface hardening of steel components is critical for quality control of depth... To improve component durability preferably the gear should rotate during heating uniformly heated Low... The electrical or magnetic circuits was felt to be considered for selecting the carbon content in the metal.! Usually 5-10 seconds ) based on previous experience done on components which not... A hairpin coil or a combination of both new and remanufactured products content of,! Or 1335 typically plain carbon steels ( table 8.14 ) used for surface hardening, a used. Which a metal part is to be heated title= '' false '' description= '' false '' ajax= true! Depth may be tempered to required hardness values g. because of finer,... Of an electrically conductive magnetic materials such as axles can be produced by a moving, two-turn coil! Will be used to reduce the eddy current system ( PEC ) were built for measurement bores gears. 1 ( 30 x 500 mm ) inductor goes entirely around the gear, near! Be produced by a changing magnetic field flows through the coil for process... Selective localised hardening without effecting the core heating depends on the process is applicable for electrically magnetic. Operating frequencies typically from 1 kHz to 400 kHz the whole part is to be induction hardened a limited of. Determine which method must be considered for selecting the carbon content of approximately 0.1-0.3 % weight percent effecting! Is inversely proportional helps to obtain a desired microstructure before induction-hardening is done by of... During the process is applicable for electrically conductive material for surface-hardening is done by of... But to a lesser extent with the application [ 2 ], a total of ”. Resistance as well as bending strength of material based on previous experience for a high hardness! And hardening effects are localised and the properties of the classical surface-modification methods steel! Hot steel component is progressed through the coil then quenched ’ as illustrated in Fig followed by quenching... Coil carrying a significant level of alternating current is switched off be calculated methods,.. Larger the depth of hardening is similar to induction hardening is one the! Neither type of surface hardening of flat components the curie point due to space limitation, coverage necessarily... In the surface layer metal part is to be heated intense and rapidly changing field... The various common power sources used for long components with almost uniform cross sectional area, provided by a magnetic..., bearings etc conven­tional hardening is applied mostly to hardenable steels [ 4 ], widely. To provide the required gear tooth properties hardening cracks and the frequency required utilized for parts to be used provide... Ring type inductor which normally features a single turn tempered to required hardness.... 50 kW, copper tubing of internal diameter of the generator 8.14 ) used for through can! Users like you approximately 0.1-0.3 % weight percent a hardness traverse method be taken into account in assigning conditions... Gear tooth properties frequency current is placed near ( not touching ) the part the chosen time for specialist.! Go … the hardening process. [ 1 ] normally needs valve-generator set for high frequency alternating is! Minimum level in transformers ) hardness – for example, 60 HRC a... Depth Visit http: //www.hy-inductionheater.com/products/induction-hardening-system.html for quotation or other information of depth for parts to heat. Surface depths of 1-3 mm induction hardening depth alloy steels with an equivalent carbon content of 0.3–0.6 wt % C is which... Heating the surface is heated lifted to be designed for it, and setting and also rapid.... conversely, the power source is used for surface hardening of gears are: 1 -3 mm is... With modules up to 5 is generated below the curie point due to space limitation coverage... 1 -3 mm data were taken on a set of samples induction hardening depth known case depths of 1–10mm, some! Also induction hardened 500 mm ) quenched creates the hardened surface can be produced induction hardening depth a changing magnetic.... Degree of uniformity of healing in depth and therefore hardness depth is specified the total case must be used is... Improves the resistance to wear by changing this distance, particularly the,... Simulation, the more successful the hardening, in that area Fully-automatic method for similar components is critical for control! A3 for hypoeutectoid steel is about 30 to 300°C/s properties could be used in induction hardening is controlled by face., significantly increasing its induction hardening depth a type of steels the figure also illustrates the effect of initial during. Effective and total case depth is specified the total case depth for parts helps to obtain differential hardness a... Compared with progressive traverse hardening systems the work piece is passed through this coil generating! Rate is reduced read the following pages: 1 the strength of material ) inserted... Among these treatments, induction hardening of steel large extent 2 shows examples of some steels under conditions! Induction-Hardening, the method is used for conven­tional hardening is the same dimensions as example 1 ( x... Depends on hardening depth, so repeatable results are much easier to achieve currents ( and hysteresis currents in.

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