Breakage of Spring Steel During Manufacturing: A Metallurgical Investigation
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CASE HISTORY—PEER-REVIEWED
Breakage of Spring Steel During Manufacturing: A Metallurgical Investigation Souvik Das . Sandip Talukdar . Vikas Solanki . Anup Kumar . Goutam Mukhopadhyay
Submitted: 11 May 2020 / Accepted: 8 July 2020 ASM International 2020
Abstract Spring steel is a name given to a wide range of steels used in the manufacture of springs, prominently in automotive and industrial suspension applications. High carbon of HC82BCr grade steel is drawn in the range of 4.0–3.0 mm as per customer’s requirement for production of spring mainly in automobile components. This spring steel grade is produced from continuous cast billet of size 150 mm 9 150 mm and then hot rolled into the size of 5.5 mm diameter wire rod. Quality aspects of these spring are significant as any inherent abnormality in the material could lead to unwanted productivity losses or quality claims or sometimes serious safety issues. In this present study, spring samples broken during coiling stage were collected from plants for understanding their quality aspect and potential causes of breakage during production. Detailed microstructural investigation revealed that the root cause of breakage of the spring is related to the segregation of phosphorous and chromium in the billet which leads to the formation of martensite (brittle and less ductile) in wire rod during rolling process. This volume change due to formation of martensite increases the stress level at the interface of pearlite and martensite. During wire drawing, this increased stress level causes formation of internal crack in subsequent passes causing breakage during spring formation.
S. Das (&) V. Solanki A. Kumar G. Mukhopadhyay R&D and Scientific Services, Tata Steel Limited, Jamshedpur 831 001, India e-mail: [email protected] S. Talukdar Product Technology Group, Tata Steel Limited, Jamshedpur 831 001, India
Keywords Spring steel Productivity Segregation Breakage Martensite
Introduction Spring steel is a name given to a wide range of steels used in the manufacture of springs, prominently in automotive and industrial suspension applications. These steels are generally low-alloy manganese, medium-carbon steel or high-carbon steel with a very high yield strength (1000– 1200 MPa). This allows objects made of spring steel to return to their original shape despite significant deflection or twisting. As a general use steel, spring steel has a wide range of commercial applications. It is a common material used for manufacturing objects like springs, washers, saw blades, lock picks, antennas, and scrapers. It’s also commonly used to make lawn mower parts, the landing gear of small aircrafts, and vehicle coil springs [1, 2]. High carbon of HC82BCr grade steel wire rod is drawn in the range of 4.0–3.0 mm as per customer’s requirement. This spring steel grade is produced from continuous cast billet of size 150 mm 9 150 mm and then hot rolled into the size of 5.5 mm diameter wire rod. Mechanical descaling or pickling is carried out before drawing according to the custo
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