U.R.B. ® BEARINGS FORGING & TURNING OF RACES:
For getting better soundness in steel and higher compressive strength, U.R.B. outer and inner ring races are forged. Hot forging is done after heating a standard length of SAE 52100 STEEL Bar in one furnace followed by forging it using different dies to get desired shape of outer or inner rings.
U.R.B. ® BEARINGS HEAT TREATMENT DURING FORGING AND TURNING:
After forging has been completed, all the forged outer / inner rings are taken up for Spheroidized Annealing Treatment which is one of the most important heat treatment prior to turning. After spheroidized annealing process, the forged steel will acquire spheroidized carbides in the matrix of ferrite. And it is considered to be the best microstructure before the turning process. After this treatment will make it very easy for turning of outer or inner rings to the specified dimensions on the CNC machines.
Likewise, for rollers / balls, the SAE 52100 WIRE RODS COILS are taken up for Spheroidized Heat Treatment in a Bell Type Annealing Furnace under controlled a heat treatment cycle. This is followed by cold heading operation to get balls or rollers as per specified size and shape as per the dies used for the operation.
Fine dispersion of Spheroidal Carbides in the matrix of Ferrite – called a Spherodized Microstructure
After heading, balls / rollers are taken up for rough barreling process where all edges and sharp corners will be removed and become smooth. And surface finish also gets improved. This is followed by the Balls / Rollers being taken up for hardening in Rotary Retort Type Heat Treatment Furnace followed by tempering in forced air circulation tempering furnaces.
U.R.B. ® BEARINGS HEAT TREATMENT PROCESS:
For achieving higher hardness to get maximum wear resistance of outer / inner rings / rollers / balls the material is taken up for hardening operation in the suitable heat treatment furnaces.
For hardening of Outer and Inner Rings for Ball Bearings and Taper Roller Bearings of smaller sizes and for hardening of balls and taper rollers, conventional hardening after heating the races above austenitizing temperature followed by oil quenching in standard furnaces like shaker hearth furnaces with protective atmosphere inside the chamber to avoid decarburization of the rings [depletion of carbon from the material surface due to oxygen]. Following type of microstructure will be achieved consisting of undissolved carbides particles with tempered martensite. Tempered Martensite and dispersion of carbide particles remain undissolved during austenization.
Whereas for hardening of Outer and Inner Rings for Ball Bearings and Taper Roller Bearings of Medium sizes, MARQUENCHING is done in specially designed salt bath furnaces Following type of microstructure will be achieved consisting of undissolved carbides particles with tempered martensite.
Tempered Martensite, Retained Austenite and Undissolved Carbide Particles are seen in the Microstructure.
And for hardening big size races / rollers especially for Spherical Roller Bearings Races and Rollers, BAINITIC HARDENING is done which will keep the material hard as well as more ductile which can withstand high impact load during actual working. Following type of Bainitic Microstructure has been achieved after this treatment which is having special property of low chance of cracks, high ductility, high resistance to impact loads and high rolling contact fatigue life resulting in high over all life of the bearings in the actual use.
Bainitic Microstructure – SAE 52100 Bearing Steel – after Bainitic Heat Treatment . Spheroidal Carbide Particles in Lower Bainite with some Retained Austenite are seen in the Microstructure.
