Abstract

Hardenability is the ability of steel to harden with depth and it is commonly measured using the Jominy end-quench testing. During the testing, an end-quenching apparatus is needed. This study deals with the design, fabrication and testing of the apparatus. The design of the apparatus was based on the standards of ASTM A255-10, all dimensions were based on the standard specimen. From the design of the quenching chamber where the quenching occurs to the frame, reservoir and drainage tanks, the quenchant channel to the pump needed to transport the quenchant to the battery needed to power the pump. The materials were well selected to provide optimum performance while considering their costs. All the parts were fabricated individually according to A255-10 standards and dimensions of the design, assembled together and then painted to avoid corrosion and improve its aesthetics. The testing of the apparatus was carried out using a Leeb testing machine which was done according to the Jominy end quench testing standards and it was carried out with three specimens of same compositions and quenched with different quenchants: water, brine solutions of 3.5% and 5% salt content. Necessary parameters for the efficiency of the apparatus and the hardenability curves were noted during the testing in order to calculate the efficiency and obtain the hardenability curves of the specimens. Specimen quenched with water had a hardness of 465 and 373HL; specimen quenched with brine solution of 3.5% had a hardness of 578 and 376 HL which appeared to have the highest hardenability and specimen quenched with brine solution of 5% had a hardness of 448 and 395 HL 2 mm and 100 mm respectively from their quenched ends. The efficiency of the specimen was estimated to be 77.5%. Hardness values were highest at the quenched end and decreased along the depth of the specimens. The incorporation of a DC power source helped to tackled power failures that may occur during quenching process.

Key words: hardness, quenchants, Jominy specimen, quench test, hardenability