Hardenability of Steel - Lab Report Example

 Table of Contents Introduction……………………..…………………………………………………………… page 2 Procedure………………………………………………………………………………………. page 2 Jominy End-Quench Test 1. Introduction Jominy End-Quench test which implement Rockwell C hardness test to determine hardenability of specimens made of various steel compositions. Hardenability is the measurement of the capacity of steel when hardened in depth after quenching it from its austenitizing temperature [ CITATION Wes09 \l 3081 ] . The knowledge of hardenability of steal is essential as selection of the appropriate combination of alloy steel and heat treatment to manufacture of different components of different sizes to minimise thermal stresses and distortion is dependent on this process[ CITATION Els93 \l 3081 ]. In this experiment we are to examine four identical in dimension samples (25.4mm diameter, 101.6mm long) from different materials. 2. Equipment list Lathe Heat treatment furnace Quenching fixture with water flow Rockwell C hardness tester Calliper and steel ruler Safety clothes. 3. Procedure All samples were placed in furnace for 20 min in 850°C and then placed in quenching stand, where water flow of 24°C was applied on the bottom of the sample face. After 10min sample was cooled down in water tank and subsequently grinded. Grinding was executed on grinding machine in order to remove oxidised surface on the sample and prepare piece for Rockwell C hardness test. Figure 1: Surface grinding machine Within Surface grinding machine, sample was fixed in modular vise which was held on magnetic table which is already part of the grinding machine. Figure 2: Modular vice and magnetic table of Surface grinding machine After grinding when surface was clean and smooth, grid for measuring Rockwell hardness was applied as requested. 1.6mm in interval from 0 to 12.7 mm and 3.2 mm in interval 12.7 to 38.1 mm Figure 3: Specimen with already tested hardness Hardness was measured on Rockwell C measuring device. Hardness was measured in every interval which was previously applied on all four pieces and data recorded into table. Figure 3: Set Rockwell C measuring device The hardest part of the piece should definitely be the face of the specimen, but since there was no chance to measure hardness on same machine, portable hardness tester was used. For that purpose face was cleaned by sandpaper to prepare specimen for reasonably accurate measurement and three different measurements were taken on the face of each sample. Figure 4: Cleaned face of the sample Figure 5: Portable hardness tester Requirements 1. Tabulated data for each sample Table 1: Sample 626 distance 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 HRC 52.80 52.80 52.80 52.80 52.80 52.80 52.80 52.80 52.80 52.80 52.80 52.80 52.80 52.80 52.80 52.80 52.80 52.80 31.30 Table 2: Sample 846 distance 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 HRC 24.20 24.20 24.20 24.20 24.20 24.20 24.20 24.20 24.20 24.20 24.20 24.20 24.20 24.20 24.20 24.20 24.20 24.20 25.20 Table 3: Sample 716 distance 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 HRC 40.20 40.20 40.20 40.20 40.20 40.20 40.20 40.20 40.20 40.20 40.20 40.20 40.20 40.20 40.20 40.20 40.20 40.20 40.20 Table 4: Sample 36 distance 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 HRC 51.60 51.60 51.60 51.60 51.60 51.60 51.60 51.60 51.60 51.60 51.60 51.60 51.60 51.60 51.60 51.60 51.60 51.60 51.60 2. The Jominy curve for the samples Figure 6: a jominy curve for the samples 3. The samples contain the following alloys. a) Sample 36: This sample contains 1.80 nickel, 0.80 chromium and 0.20 molybdenum. b) Sample 626 This sample contains 0.50 nickel, 0.450 chromium and 0.15 molybdenum c) Sample 846: this is an unalloyed sample since the curve is irregular and indefinite. d) Sample 716 This sample contains 6.80 chromium Table 5 Sample no:36 Distance from the quenched end Hardness Expected microstructure Justification 0 51.0 martensite At this point the temperatures over 6000C makes it stable. 25.4 52.60 martensite It is stable at all temperatures over 6000C 50.8 52.0 martensite At this point the temperatures over 6000C makes it stable. Table 6 Sample no:626 Distance from the quenched end Hardness Expected microstructure Justification 0 52.8 martensite It is stable at all temperatures over 6000C 25.4 35.57 martensite and pearlite It is stable at all temperatures up to 4000c-6000C 50.8 31.30 martensite and pearlite It is stable at all temperatures up to 4000C-6000C Table 7 Sample no:716 Distance from the quenched end Hardness Expected microstructure Justification 0 40.20 martensite and pearlite It is stable at all temperatures up to 4000c-6000C 25.4 23.35 pearlite It is stable at all temperatures below 2000c. 50.8 12.80 pearlite It is stable at all temperatures below 2000c. Table 8: Sample no:846 Distance from the quenched end Hardness Expected microstructure Justification 0 24.0 Pearlite It is stable at all temperatures below 2000c. 25.4 28.0 pearlite It is stable at all temperatures below 2000c. 50.8 25.20 pearlite It is stable at all temperatures below 2000c. 4. Hardenability of steel helps in selecting an appropriate heat treatable engineering steel for a given application. The types of steels and their applications are: a) Carbon steels: these are used in making wood cutting tools such as axes, swords, machetes and knives. b) Alloy steel: this type of steel is used in making pipelines, auto parts and transformers c) Stainless steel: this type of steel is used in making food processing equipment, utensils, and cutlery, dental and surgical tools. d) Tool steels: these are used in making cutting and drilling equipment. 5. Radial position Equivalent distance HRC hardness Surface 3 56 ¾ radius 8 53 Mid radius 13 47 Centre 17 42.5 Oil Radial position Equivalent distance HRC hardness Surface 13 47 ¾ radius 19 41.5 Mid radius 22 38 Centre 25 36 Figure 7: hardness profiles of water and oil Read More