Gear Material And Heat Treatment.pdf

GEAR MATERIALS AND HEAT TREATMENTS IOP. > Gear Knowledge > The ABC's of Gears - B > Gear Materials and Heat Tr...

GEAR MATERIALS AND HEAT TREATMENTS IOP. > Gear Knowledge > The ABC's of Gears - B > Gear Materials and Heat Treatments 6. Gear Materials and Heat Treatments IIt is essential to selectproper materials and heat treatments in accordance with the intended application of the gear. Since gears are applied for various usages, such as industrial machinery, electric/ electronic devices, household goods and toys, and composed of many kinds of materials, we like to introduce typical materials and their heal treatment methods. 6seTypes of Gear Materials S45C (Carbon Steel for Structural Machine Usage) S45C is one of the most commonly used steel, containing moderate amounts of carbon (0.45% ).S45C is easily obtainable and is used in the production Sput gears, helical gears, gear racks, bevel gears and worm gears. Heat Treatment and Hardness Heat Treatment Hardness None 194HB less than Thermal Refining 225- 260HB Induclion Hardening 45- 55HRC SCM440 (Chrome-molybdenum Alloy Steel) An alloy steel containing moderate amounts of carbon (0.40% It also contains chrome I molybdenum. SCM440 has more strength than S45C and is us ). with thermal-refining or induction-hardening treatment for producing gears. Heat Treatment and Hardness Heat Treatment Hardness rmal Refining 225-26OHB Induction Hardening 45-60HRC sCM415 (Chrome-molybdenumAlloy Steel) SCM415 is one of the most commonly used low-carbon alloy steel (C 0.15%). = Generally, is carburized for use. It has more strength than S45C or it SCM440. Surface hardness should be between 55 and 60OHRC for use. SUS303 (Stainless Steel :18Cr-8Ni Stainless Steel) Since is called "stainless steel", is a rust-resistant steel. This authentic stainless steel is basically non-magnetic. Most commonly used for gears in it it applications where rust contamination is undesirable, such as in food-processing machinery. There is a similar stainless steel called SUs304 which has more corrosion resistance than SUS303. Copper Alloy Casting Frequently used as a material for worm wheels. Phosphor bronze casting (CAC502)or aluminum-bronze casting(CAC702) are commonly used. For mati worms, metals such iron as S45C/SCM44/SCM415 are used. To prevent galling / seizure by slippage, different materials are used for each of the paired worm and worm wheel, 6-2 Heat Treatments This webeile uces cookies toimprove your comvenienco. you continue to use this website with its current sotings, you are agreeing to our use If of cookies. Please referto the privacy policy for detals. View Accept Prvacy Policy httns:/khkgears.net/newlgear knowledgelabcs_of gears-b/Gear Materials_and_Heat Treatrmernts.html 1/3 Fig. 6.4 Carbon layer by carburizing What is Nitriding? This website uses cookies to improve your convenlence. if you continue to use this website with ts current setings. you are agreeing to our se of cookies. Please efer to tha privacy polcy for details. View Accept Privacy Poicy knowledge/abcs gears-b/Gear Materials and Heat Treatrments.html 2/3 btne:/khkgears.netnewlgear of  Gear Materials and Heat Treatments |KHK áng,tempering must be applied to give toughness back to the steel, that might become brittle. Quenching cannot harden genuine steel, quenching can Work for steel containing more than 0.35% carbon. sat is Thermal Refining ? Thermal Refining is a heat treatment applied to adjust hardness/ strength / toughness of steel. This treatment involves quenching machining is and tempering. Since applied to products after thermal refining, the hardness should not be raised too high in quenching. What is Induction Hardening ? Induction Hardening is a heat treatment performed to harden the surface of the steel containing carbon more than 0.35%, such as S45C or SCM440. For gear products, induction hardening is effective to harden tooth areas including tooth surface and the tip, however, the root may not be hardened in some cases. The precision of gears declines by induction hardening. To encourage the gear accuracy, grinding must be applied. Fig 6.1 Quenching Machine Gear High FrequenCy inductor (Co) Fig. 6.2 Heating Coil (Gear and High frequency inductor (coil) What is Carburizing ? Carburizing is a heat treatment perforned to harden only the surface of low-carbon steel. The surface, in which carbon is present and penetrated the surface, gets especially hardened. Inner malerial structure (with low-carbon C=0.15%)is also hardened by some level of carburizing, however, is not a: it hard as the surface. The precision of carburized gears declines by 1 grade or so, due to deformatiorn (dimensional change) or distortion. To encourage th gear accuracy, grinding is essential. Fig. 6.3 Carburizing Furnace Fig. 6.4 Carbon layer by carburizing What is Nitriding? re Nebsite uses cookies toimprove your convenience. you continue to use this website with ts current settings. you are aoroeing to our use of If cockies. Please efer to he privacy policy for detalls. View Accept Privacy Poicy 2/3 netinew/aear knowledgelabcs_of_ gears-b/Gear Materials_and_Heat_Treatrments.html  Gear Materials and Heat Treatments gears transmit power, both tooth flanks are in sliding contact and rolling contact. In other words, the pressure which the tooth flank get is | KHK he pressure when a cylinder slides while rolling on a flat surface. The tooth flank needs to have durability against such presSure. Wer,some rigid materials such as ceramic are vulnerable to impacts and break easily. Bending force is frequently applied to the dedendum and imp be generated when gears start moving. The material of gear needs to be tenacious in order to achieve high durability against external forces and mpact. Therefore, gears need to be hard on the outside and tenacious inside just like a Japanese sword. Heat treating is the method to give such characteristics Types of heat treatment for gears are 1.Carburizing 2. Induction hardening 3. Nitriding Let's see the details and characteristics of each type. 1. Carburizing A typical treatment made for gears of low-carbon steel like S15CK. After being penetrated by "carbon" just like the name,the metal surface is quenched and tempered to harden. The thickness of the hardened layer is 0.2mm to 2mm depending on gear size. In the past, people used to cover metal with crushed carbon before sealing and heating. In Europe, products were dipped in molten sodium cyanide-base inorganic salts at high temperature, but the toxicity of sodium cyanide was a problem. Currently, gas carburization in which products are heated in carbor dioxide gas, methane, propane and steam are mainly used. Although the gas carburization is expensive because large special equiprnent is needed, a large volume of products can be processed effectively. Carburizing is usually performed after gear is cut and gear teeth are formed. After that, tooth surface is lapped and ground to finish. 2. Induction hardening Anical treatment for gears made of medium-carbon steel like S45C. eddy current flows by electromagnetic induction when the metal gear, wound with wire, is electrified. The induction hardening takes advantage of the property of the eddy current which concentrates at the metal surface and heats metal. As the common method for induction hardening, the electric current is applied to the wired coil overlaid on the gear tooth formed by cutting. Induction hardening varies in be processed at once compared to other methods like carburizing. On the othe the precision widely and fewer products can hand, this method is suited to process products with gear and axis integrated or large gears because the gear tooth can be hardened partially. 3. Nitriding Frequently used for gears made of steel which contains chrome or molybdenum. Among the various kinds of steel which are suitable for nitriding, aluminum-containing steel produces particularly a powerful effect and are called "nitride steel. In nitration, gears are heated in nitrogen gas to form a layer of iron nitride of 0.1 mm to 1mm thickness on the gear surface. The nitriding can give hardness higher than carburizing and induction hardening, but the layer hardened by nitriding is thinner than other heat treatments Meanwhile, the temperature necessary for nitriding is relatively low, 500 to 600 degrees Celsius. In contrast, products need to be heated up to 800 degre Celsius in carburizing and induction hardening. Therefore, nitriding causes no quenching cracks or distortion unlike other heat treatments. Generally, the nitriding is caried out in the final step of processing gears as doesn't cause deformation and gives high hardness. it Related links: Materials for Gears and Heat Treatment Gear Materials Kohara Gear industry Co., Ltd, 13-17 Nakacho Kawaguchi-shi Saitama-ken, 332-0022 Japan TEL+81 48 254 1744FAX +1 48 254 1765 Copyright 2021 Kohara Gear industry Co.Ltd. Al Rights Reserved. ie wabsile uses cookles tG Improve your conventence. If yoDu continue to use ihis websile with its current setings, you are agreeing to our Use of sokies. Please refer to tha privacy poicy for datais. Accept View Prvacy Poley tnewlaear knowledgelabcs of agears-b/Ges