Tempering pdf

It is because the strength and toughness could be increased through thermal mechanical treatment that it is chosen to be construction material[3]. Armor material is used as shots protection.

Tempering is required to produce ductile and wear resistant material[4]. Tempering aims to increase ductility and reduce brittle by reducing hardness level[5]. Besides iron and nickel content, lateritic steel also contains manganese which will affect the steel weldability, surface hardness, and corrosion resistance[7]. Generally, lateritic steel is used as the main material in piping system, hydroelectric power plant, petrochemical, also nuclear power industry because of its life-time, corrosion resistance, coating easiness, and low-cost[6].

Tempering process is required to increase ductility, reduce brittle, and increase wear resistance. Temperature of the tempering treatment will decrease hardness level of the materials[5].

The aim of this study to obtained and analysis phase transformation from tempering temperature, timing, cooling rate, and steel composition including combined carbon level, also residual element are some variables which affect the micro structure and mechanical properties of tempered steel[8]. Then the steel plate specimen quenched using water and oil quench media, also normalizing. And also aims to increase ductility, tensile strength, and impact toughness properties[10].

The result of metallography using nital etchants showed a formation of microstructure from the tempering process is martensite and retained austensite on figure 1[11][12]. Martensite phase will affect the rising of hardness and tensile strength level of the material. However, internal stress which happened during the martensite phase formation could decrease ductility and material resistance.

One of the tempering process objectives is to increase impact toughness level;the low temperature in tempering process could cause brittle to the martensite which formed through the tempering process. It is called tempered martensite embrittlement. Retained austenite was found on A1, A2, QO, and U2 specimens can be affected the secondary hardening phenomenon. Retained austenite on A1 and A2 specimens could be affect non-linear of yield stress and ultimate tensile stress.

The microstructure of ferrite and pearlite as in the as cast material is owned by specimens QU, U1, and U2 because the specimen is quenched with an air cooling medium where the air cooling rate is very low, the result of microstructure from austenite to ferrite and pearlite phase.

Hardness Test Result 70 Hardness Test Result The type of media cooling determines the rate of cooling and the higher the heat propagation coefficient, a higher cooling rate will affect the resulting hardness value [8].

Tensile Strength Test Result In Figure 4 it can be analyzed that after quenching process the tensile stress will be increase, and also the tensile strength will increase too as a result of the initial phase change of austenite and then turn into a harder martensite [9]. This is as a result of martensite formation process in line with the presence of distortion which will rapidly increase the strength and hardness of the material, but the internal stress that arises in the process of martensite formation can lead to decreased ductility and resistance significantly.

The above data also indicates that tempering temperature has an effect on tensile strength properties significantly. Elongation Test Result The Elongation may also be affected by the tempering process, if tempering temperature rises then elongation will also rise [13]. However, the data result with the oil cooling will be effect the elongation, for the medium cooling rate allows the material to have high carbide density in the ferrite phase, which can disrupt the formability of the material so that the elongation decreases too.

The impact resistance level increased alongside the increment of tempering temperature [9]. Figure 6 gives us information regarding impact resistance level. They are all related that martensite phase which caused by the heat treatment was showing distortion. That was affect decreasing impact value seems like secondary hardening phenomenon where is steel contains carbide formed element such as Cr, Mo, V, dan W [13].

Tensile strength was optimal through air quenched relatively, with or without tempering treatment. He and J. Herbirowo and B. Jena et al. Impact Eng. Martempering process using oil- and water-based quenchants at lower temperature is adopted in this work. The test samples were evaluated for hardness, distortion, and wear under accelerated simulated tests.

The results show that although both hardness and wear resistances were lower compared to the austempering, they met the design intent. Also the wear rate of martempered samples was more consistent which may provide advantages for maintenance purposes.

High precision machining such as hard turning changes the surface and the material properties of steel alloys. A sliding block-on-cylinder wear tester was used for the purpose of testing the wear performance of AISI bearing steel.

The effect of microstructure on the wear performance of hard-turned steel showed that the white layer and overtempered martensite OTM had a higher wear resistance than martensite.

The wear mechanism dependence on the surface hardness was attributed to this increase in wear performance. The near-surface residual stress of the material was shown to become more compressive as the material wore down. The applied normal loads affected the surface roughness, residual stresses, and, in turn, the wear performance of the material. The chemical composition of the investigated steel is determined by optical emission spectrometer and shown in Table 1. Dry sliding test is conducted on pin disc apparatus against EN32 steel disc having hardness of Hv to measure coefficient of friction based on standard ASTM G The images were captured in a metallurgical microscope from prepared samples to study the microstructure changes.

Figure 1 a shows the microstructure of annealed specimen, which consists of small black dots with good distribution. These black dots are interpreted as carbide present in the structure.

The structure of the martempered sample Figure 1 b is completely covered with carbides and has a very rich density of these all over the surface. The sample has good number of carbides but occurs only in some areas. The above samples have different microstructures and their hardness varies with amount of carbides. The samples which were annealed have fewer carbides with massive pearlite compared to remaining samples and as such it is least hard as the carbides are retained in solution.

Martempered sample has a microstructure rich with carbide or martensite which is the hardest steel structure. This is evident from the structures observed which shows the density of carbide. As expected with reference from the microstructure test, the martempered sample is the hardest because of conversion of austenite into martensite structure. As the soaking time increases the conversion time and conversion of austenite into bainite increase and the conversion of martensite decreases as such the hardness decreases.

The annealed sample exhibits the least hardness among the tested samples for the hardness. Impact strength of all the specimens obtained from Izod impact test is shown in Figure 3. The moderate impact strength was observed for annealed sample.

Martempered sample shows least impact strength due to formation of martensite. Austempered samples impact strength was improved because of the presence of bainite and it is observed that impact strength was improved with soaking time in austempering. After the experiments were conducted in the prescribed procedure, the weight loss for every reading was noted till a steady or nearer to steady state arrived.

The wear rate is given by weight loss for one min. Variation of weight loss for each minute with constant speed of rotation is measured and average weight loss is calculated. From weight loss, wear rate for each minute and average wear rate are calculated and presented in Figure 4. The result clearly indicates that the martempered sample has the least wear rate. Annealed sample has the more wear rate compared to other samples. This shows that the martempered sample is having good wear resistance followed by the austempered samples.

This also indirectly indicates the hardness acquired by the sample in the heat treatment process. The weight loss of heat treated samples with respect to time in dry sliding test is measured.

The average wear rate of heat treated samples with respect to time in dry sliding test is presented in Figure 5. The bar graph clearly indicates that the most effected pin is annealed when compared to all the pins and the least effected is martempered. The annealed pin had a burr formation at the end which was kept on the tungsten disc. This indicates that a lot of heat was formed at the end which deformed the portion of that end plastically. Also this suggests that the material was more ductile than that of the remaining samples.

The pin on disc experiment was done till steady friction value was obtained. After every reading, the friction value for each sample was measured and also the average friction coefficient value Figure 6 was calculated. It is observed that average friction value is less for annealed one and increased in martempered and austempered samples. AISI steel was subjected to various heat treatments for enhancing the material properties.

From the present study the following conclusions are drawn. Hardness increased three times with martempering process. The impact strength increased with soaking time in austempered samples up to certain level. Based on the functional requirement, the choice can be made among the heat-treated AISI steels.

Bourithis and J. Pdf Abstract The mechanical properties of steel decide its applicability for a particular condition. Introduction The knowledge of materials and their properties is of great significance for a production engineer. Pdf Download Adobe Reader Jetley [10] reported improvement in wear properties of aircraft brake steel rotors by martempering.

Experimentation The chemical composition of the investigated steel is determined by optical emission spectrometer and shown in Table 1.