Cold Rolling Mill — STF Steel

A steel manufacturer suffered continuous bearing failures at its cold rolling mill. NSK's application review determined that highly contaminated operating conditions were causing unexpected failures; bearing life was only 3–4 months. To combat residual contamination in the lubricant, NSK STF (Super Tough Steel) spherical roller bearings made from super-hardened steel were recommended. After a four-month trial, laboratory examination showed a remaining service life of 29–50 months; the customer now replaces the bearings once a year during planned maintenance.

• Cold rolling mill — 1 machine; initially 3–4 months service life
• Highly contaminated operating conditions
• Grease sample analysis revealed contamination as the cause of failure
• NSK solution: long-life Super Tough Steel (STF) Spherical Roller Bearings
• Service life extended from 3–4 months to 29–50 months (10 times the initial life)
• Unexpected stoppages eliminated; bearings replaced during planned annual maintenance

Technical Features: STF (Super Tough Steel) Spherical Roller Bearings

• Special material; innovative heat treatment technology
• Better performing standard bearing steel
• TF, NTF, HTF, STF, WTF — a material family for the needs of every environment
• Up to 10 times more service life with contaminated lubricating oil
• Up to twice the service life with clean lubrication
• Up to 4 times the service life at 160°C
• Wear rate less than one third; 40% improvement in seizure strength