material case-hardening furnace: Einsatzhärteofen {m} case-hardening furnace: Zementierofen {m} [Einsatzhärten] material tech. Laser hardening is particularly suitable for areas that are very difficult to access, such as Direct hardening is a special case hardening process. Carbon and ammonia are diffused into the surface layers. 19,000 Pound double helical pinion shaft carburized to an effective case depth of 0.250" being quenched into 20,000 gallons of agitated, warm oil. While the current density in a conductor cross-section is constant with direct current, with alternating current the current density increases with increasing frequency in the outer areas and decreases inside. The toughness (ductility) of steels increases with decreasing carbon content, as then less brittle cementite is found in the microstructure. Flame hardening is also generally inferior to induction hardening and laser hardening in terms of accuracy (adjustment of the hardening depth). More information about this in the privacy policy. The hardening depth is controlled by the feed rate! technique in which the metal surface is reinforced by the adding of a fine layer at the top of another metal alloy that is generally more durable Carburising with a carburising medium (e.g. The surface of the specimen to … This generally also applies to the other surface hardening processes, as the unhardened core provides sufficient toughness. In the high-frequency range of up to several megahertz, even hardening depth of only a few tenths of a millimeter can be achieved. tech. In these cases hardening can be used as a possible heat treatment. However, crankshafts or camshafts are usually also surface-hardened after quenching and tempering. Engineering Applications and Design Engineering Materials. Case hardening 1. The hardening depth is controlled by the frequency of the alternating current! The term face hardening is also used to describe this technique, when discussing modern armour. Depending on the application, different surface hardening methods have developed. For screws and fasteners, case-hardening is achieved by a simple heat treatment consisting of heating and then quenching. Case-hardening involves packing the low-carbon iron within a substance high in carbon, then heating this pack to encourage carbon migration into the surface of the iron. This does not have the beneficial effect of encouraging CO production and it can also introduce phosphorus as an impurity into the steel alloy. The layer thicknesses range from 0.1 mm to 1 mm. case hardening depth translation german, English - German dictionary, meaning, see also 'case conference',attaché case',basket case',cartridge case', example of … This website uses cookies. The enormous thermal output of the diode laser of several kilowatts results in a temperature just below the melting point in a very short time! On ground parts case depth … Due to the relatively low surface hardening temperatures, however, the lower-carbon core is not completely austenitized, so that no completely martensitic core structure is formed after quenching. Adding an easily decomposed carbonate "energiser" such as barium carbonate breaks down to BaO + CO2 and this encourages the reaction. In order to harden even such thin-walled workpieces only on their surface in the range of a few tenths of a millimetre, so-called induction hardening can be used. 2), case depth (Fig. Case hardening produces a hard and wear-resistent edge area and a tough core. Hillfoot stock a wide range of case hardening steel grades ready for processing and delivery when you need them. Nitride forming elements must be present for this method to work; these elements include chromium, molybdenum, and aluminum. For this reason, it may only make sense to harden the surface of a workpiece so that the component core still retains its toughness (partial hardening). After carburizing, the workpiece is first cooled slowly and then reheated to core hardening temperature or cooled to core hardening temperature immediately after carburizing. The case-hardening depth is approximately 2 mm and the hardness is 57-62 HRC by single-shot hardening. Both carbon and alloy steels are suitable for case-hardening; typically mild steels are used, with low carbon content, usually less than 0.3% (see plain-carbon steel for more information). Examples include firing pins and rifle bolt faces, or engine camshafts. The hardness is achieved by the formation of nitrides. These diffuse from the enriched surface layer into the core. after a slow cooling from the reheated state (single and double quench hardening) or. Case-hardening or surface hardening is the process of hardening the surface of a metal object while allowing the metal deeper underneath to remain soft, thus forming a thin layer of harder metal (called the "case") at the surface. Flame or induction hardening are processes in which the surface of the steel is heated very rapidly to high temperatures (by direct application of an oxy-gas flame, or by induction heating) then cooled rapidly, generally using water; this creates a "case" of martensite on the surface. Transport to the surface of the steel was as gaseous carbon monoxide, generated by the breakdown of the carburising compound and the oxygen packed into the sealed box. Bone contains some carbonates but is mainly calcium phosphate (as hydroxylapatite). However, the depth of hardening is ultimately limited by the inability of carbon to diffuse deeply into solid steel, and a typical depth of surface hardening with this method is up to 1.5 mm. The carbon then diffuses into the surface layer, where it leads to an enrichment of the carbon content to a hardenable level of about 0.8 % carbon, while the core remains low in carbon. How does nitriding differ from all other surface hardening methods? The quenching required for this can be either done. Although oxygen is required for this process it is re-circulated through the CO cycle and so can be carried out inside a sealed box. Carbon itself is solid at case-hardening temperatures and so is immobile. C F Typical case depth Case hardness, HRC Typical base metals Process characteristics Carburizing Pack Diffused carbon 815–1090 1500–2000 125 mm–1.5 mm (5–60 mils) 50–63(a) Low-carbon steels, low-carbon alloy steel Low equipment costs; difﬁcult to control case depth accurately Gas Diffused carbon 815–980 1500–1800 75 mm–1.5 mm Steels without carbon can’t be hard During carburizing the carbon content is increased and now you get a hard surface and a tough core. Packing low carbon steel parts with a carbonaceous material and heating for some time diffuses carbon into the outer layers. The disadvantage, however, is the simultaneously decreasing toughness or embrittlement of the steel, which can lead to unforeseeable material failure. With induction hardening, the workpiece is heated by induced eddy currents. In this case, the temperature control is preferably adapted to the desired core properties in order to achieve optimum core properties. With small geometries, this can lead to undesired full hardening over the entire cross-section. Typical hardening depths with laser hardening are in the range of 0.1 mm to 2 mm. However, components such as toothed wheels must combine both contradictory properties: For such applications case hardening is suitable, which is generally structured as follows: In case hardening, a low-carbon steel (case hardening steel) with a maximum of 0.2 % carbon is first exposed to a carbon-containing environment. Nitriding is therefore not one of the classical surface hardening methods by means of microstructure transformation. We are specialist for large case hardening Depth! A carbon content of 0.3–0.6 wt% C is needed for this type of hardening. If components are to be very tough, they must inevitably be relatively low in carbon. Older formulations of these compounds contain potentially toxic cyanide compounds, while the more recent types such as Cherry Red do not.[3][4]. At 1450°F the case is only .005" (.13mm) after 1 hour but .016" (.4mm) at 1600°F after the same time. The nitride layer also improves corrosion resistance. It is also important to distinguish between total case depth and effective case depth. What are the advantages of induction hardening compared to flame hardening? Nitriding requires special steels containing nitride-forming alloying elements, so-called nitriding steels (e.g. Nitriding is used in particular to improve the fatigue strength of dynamically stressed components! In addition, no (toxic) exhaust gases are produced during induction hardening compared to flame hardening. Laser hardening is particularly suitable for areas that are very difficult to access, such as tapped holes. Übersetzung für "case hardening depth" im Englisch-Deutsch Wörterbuch dictindustry - mit Forum und Beispielen. With case hardening, low-carbon steels are first enriched with carbon in the surface layer (carburisation) and then quenched! Larger surface layers have to be scanned line by line with the laser. Residual ferrite is to be expected in the core. Case colouring refers to this pattern and is commonly encountered as a decorative finish on firearms. Single quench hardening specifically influences the properties of the surface (surface hardening) or the core (core hardening)! Carbonitriding is similar to cyaniding except a gaseous atmosphere of ammonia and hydrocarbons is used instead of sodium cyanide. This in turn leads to a constantly changing magnetic field around the electrode, which penetrates into the adjacent workpiece and generates eddy currents due to the induction effect (“secondary coil”). 1.) In this case, the hardening temperature is preferably adapted to the desired properties of the surface layer in order to achieve optimum surface properties. Specified case depth should have a tolerance of .005 min. If you continue to use this website, we will assume your consent and we will only use personalized ads that may be of interest to you. With laser hardening, the surface is heated by a laser beam and quenched by heat dissipation in the workpiece (self quenching)! 4 case-hardened depths of the M3.75 gears made of 17CrNiMo6-4 The Barkhausen signals obtained show, depending on the case-hardened depth, 3 more or less pronounced peaks. Above all, the increase in fatigue strength makes case hardening very interesting for dynamically stressed components such as gears or drive shafts. The thickness of the hardened layer is referred to as the case depth. However, due to the permanent change in temperature, the hardness distortion in this double quench hardening is relatively high. The result of the hardening process is controlled by four factors: Carburizing is a process used to case-harden steel with a carbon content between 0.1 and 0.3 wt% C. In this process steel is introduced to a carbon rich environment at elevated temperatures for a certain amount of time, and then quenched so that the carbon is locked in the structure; one of the simpler procedures is repeatedly to heat a part with an acetylene torch set with a fuel-rich flame and quench it in a carbon-rich fluid such as oil. The hardening depth can be kept very low! Case depth is typically measured as “total” or “effective”. case hardening depth: Einsatzhärtungstiefe {f} case-hardening carburizer: Zementationsmittel {n} [Einsatzhärten] ind. It is a common knowledge fallacy that case-hardening was done with bone but this is misleading. Case hardening a gearbox components creates a hard outer-shell and a pliable inner layer. 900 °C are necessary. What are single-quench hardening, double-quench hardening and direct hardening? Carburizing depths of 0.1 to about 5 mm can be economically achieved with this method. specify case depth and hardness that is required. The effective case depth is typically about two-thirds to three-fourths the total case depth. In such cases nitride hardening (nitriding) can provide a remedy, which does not require any microstructural transformation. 3. (In some cases, the depth … Expensive alloy steels can only be nitrided and are used. This austenitized state at about 750 °C is then quenched to achieve the desired martensite formation in the surface layer. tive case depth and provide different values for recommended case depth. Typical hardening depths with laser hardening are in the range of 0.1 mm to 2 mm. However, these do not represent any weaknesses but increase the fatigue strength of the component to a special degree due to the residual compressive stresses caused! The surface hardening processes explained so far all have in common that the hard surface layer is achieved by a martensitic microstructure. For theft prevention, lock shackles and chains are often case-hardened to resist cutting, whilst remaining less brittle inside to resist impact. Since alloying elements generally reduce the critical cooling rate, deeper surface layers can be hardened with high-alloy steels. For which steels is case hardening suitable and what are the mechanical properties of case hardened components? What are the characteristics of surface-hardened workpieces? It is suitable for steels that tend to form coarse grains during carburizing or for components that still require intermediate machining before hardening. Induction hardening can be easily automated and is suitable for complex geometries, especially in mass production! This is usually used at a low to medium hardening depth. 50 mm, depending on focusing and process control. The hardened layer is called the case. Under the critical temperature the workpiece's microstructure does not convert to an austenitic phase, but stays in the ferritic phase, which is why it is called ferritic nitrocarburization. Hardened steel parts are typically used in rotating applications where high wear resistance and strength is required. In these cases, the surfaces requiring the hardness may be hardened selectively, leaving the bulk of the part in its original tough state. A high-frequency alternating current is generated in a copper tool electrode (“primary coil”) which is adapted to the shape of the workpiece to be hardened. As a guideline, the carbon content should be at least 0.3 % for hardening. Shallow cases only 0.002 - 0.005", and deep cases, up to 0.350" have been specified and readily achieved. 3), the desired case proﬁle, and cost. Why does laser hardening not require quenching with water? The process embraces carburizing, nitriding, … In this process, the steel is cooled slowly after carburizing. How is the depth of the hardening layer controlled during flame hardening? No quenching is done after nitriding. Although bone was used, the main carbon donor was hoof and horn. Case hardening depth is defined as the depth below the surface where the hardness decreased to 550 HV. These very large eddy currents of up to several thousand amperes per square millimeter lead to heating of the workpiece. [2] Flame or induction hardening are processes in which the surface of the steel is heated very rapidly to high temperatures (by direct application of an oxy-gas flame, or by induction heating) then cooled rapidly, generally using water; this creates a "case" of martensite on the surface. Nitriding heats the steel part to 482–621 °C (900–1,150 °F) in an atmosphere of ammonia gas and dissociated ammonia. This is collectively known as a carburizing pack. Toothed wheels are typical cases where surface hardening is used. It is less complex than hardening and tempering. Because a very high hardness can be achieved at the surface during induction hardening, high residual stresses can occur. After the surface layer has been carburized to the desired hardenable level, the actual hardening process takes place, whereby the relatively low-carbon core is slightly quenched and tempered. This is why the process is also referred to as surface hardening or single quench hardening from surface hardening temperature. The pack is put inside a hot furnace for a variable length of time. Case hardening may be defined as a process for hardening a ferrous material in such a manner that the surface layer, known as the case, is substantially harder than the remaining material, known as the core. Viele übersetzte Beispielsätze mit "case hardening" – Deutsch-Englisch Wörterbuch und Suchmaschine für Millionen von Deutsch-Übersetzungen. The frequencies to be adjusted therefore depend on the thicknesses of the hardness layers to be achieved. Single and double quench hardening is usually carried out on steels with a tendency to coarse grain formation, as a recrystallisation effect occurs during the $$\gamma$$-$$\alpha$$-transformations! The fact that heat is mainly generated on the surface rather than inside the material is due to another physical phenomenon, the so-called skin effect. 10 times greater. With laser hardening, only small surfaces can be hardened economically. Destructive material testing & non-destructive testing (NDT), Fundamental equation of planetary gears (Willis equation). With flame hardening, a burner flame is passed over the workpiece surface to be hardened, which is then austenitized. For case hardened parts, the part’s end use dictates which heat treatment process and case depth measurement is specified. Normally the hardness of case after hardening and low temperature tempering is 58 to 64 HRC (VPN 570-690). Under inert gas, oxidation of the surface can even be completely prevented. The steel darkens significantly, and shows a mottled pattern of black, blue, and purple caused by the various compounds formed from impurities in the bone and charcoal. Such components are characterised by their high surface hardness combined with a very tough core (since low-carbon content)! This also results in relatively simple control of the hardening depth. This can increase the … Compared to single and double quench hardening, direct hardening is less time-consuming and energy-intensive and therefore less expensive, since reheating is not necessary. Cyaniding results in the formation of layer of thickness ranging from 0.25 mm to 0.75 mm. Also, unlike other processes it requires only … The thickness of the hardened surface layer depends on the speed at which the burner flames are moved over the workpiece surface (called feed). There are several methods of case hardening for gears, including vacuum carburizing, atmosphere carburizing, and induction hardening. 2. A heating period of a few hours might form a high-carbon layer about one millimeter thick. These mild steels are not normally hardenable due to the low quantity of carbon, so the surface of the steel is chemically altered to increase the hardenability. Due to the lower carbon content, however, higher temperatures of approx. This requires a high design tooling effort in advance so that induction hardening is economical, especially in automated production lines with high batch sizes. The $$\gamma$$-$$\alpha$$-transformations cause a recrystallisation effect, which leads to grain refinement of the coarsely grown grains during carburisation. 34CrAlMo5). The reheating during single and double quench hardening makes these processes relatively energy- and time-intensive and therefore expensive. The shaft is the same dimensions as example 1 (30 x 500 mm). The laser spot covers a track width of 1 to approx. While the surface hardness increases strongly due to the nitrides formed, the properties of the component core remain unaffected, as the nitrides only form on the surface. In the medium frequency range from 1 kHz to about 10 kHz, hardening depth of about 5 to 1 mm can be achieved. According to additional analyses, the central peak, with a dominant amplitude, is principally related to the structure of the core, and is thus called the "bainite" peak. This has the advantage that the scaling is relatively low and the post-processing effort is reduced accordingly. Case hardening is a simple method of hardening steel. case hardening depth [DIN ISO 15787:2010] Einsatzhärtungstiefe-Härtetiefe {f} [Abk. Depending on the temperature in the surface layer or in the core, either the surface layer properties or the core properties of the workpiece can be specifically influenced during quenching. Surface hardening is used to produce a hard and wear-resistant surface layer on steel workpieces, while the toughness in the core is largely retained. case hardening depth [DIN ISO 15787:2010] The longer the package is held at the high temperature, the deeper the carbon will diffuse into the surface. This techniques is used for steels with a low carbon content. In principle, a combination of core and surface hardening is also possible. In the production of bearing components, manufacturers know it is important to control the case depth … Case hardening is a simple approach that hardens the surface of a material by infusing elements into the metal. In such circumstances, case-hardening can produce a component that will not fracture (because of the soft core that can absorb stresses without cracking), but also provides adequate wear resistance on the hardened surface. Case hardening for high surface hardness. 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