Ultra Large Bearings: A Complete Range of Seamless Induction Heating Solutions

The Ultra Large Bearing (ULB) industry can increase the production performances by using induction heating on a full range of thermal processes. The paper presents the technological, economical, and process optimizations that can be achieved using induction heating technology in both hardening and tempering. Two different solutions are available for (seamless) race hardening: a high-power induction single shot process for small to medium size rings and induction seamless scan hardening for large sized bearings. The ultra-low frequency induction tempering process is described and compared with a traditional furnace. These technologies are presented and compared to show application ranges, specific features, metallurgical results, and efficiencies in processing and cost.

Methods of elimination of rails increased damage in the area of weld joints

Rail weld joints from electric-contact welding in stationary and fi eld conditions, as well as those from aluminothermic welding are weak points on tracks that are easily damaged compared with rails outside the weld joints. Currently, these weak points are the defects connected with lack of penetration in the welding area, burns at the points of poor contact of the rail foot with the current-carrying contact tips, or with defects of the weld joint machining after welding, as well as the local hardness reduction in areas affected by heat after welding, and local heat treatment after welding. Elimination of wide areas of reduced hardness at the weld joint points producing saddles, cracks, and chipping, and promoting rails damage next to such joints is a major challenge for increasing the serviceability of weld joints. This study introduces three avenues for elimination of increased damage of rails at weld joints including:• Improvement of technology and equipment for electriccontact welding and local heat treatment after welding in the stationary and fi eld conditions.• Development of technology and equipment for induction welding in the stationary and fi eld conditions.• Development of technology and equipment for differentiated induction tempering of rails preliminary welded in strings 800 m long.

Effect of Different Tempering Processes on Microstructure and Hardness of Q690 Steel

Q690 steel was the research object in this test. The traditional tempering and induction tempering were used in this experiment after quenching. By studying the microstructure and hardness of the sample at the two different tempering processes, it can be concluded that there are more carbide precipitations in the microstructure and the microstructure of the sample is more uniform when the tempering temperature was 450°C. For same tempering temperature, the carbide dispersion, uniformity of the microstructure and retained austenite transformation are all better in 5mm depth range to sample surface, and the hardness of the sample is lower after induction tempering. So it can be see that not only the heating up speed is faster, the energy can be saved more, but also the microstructure is more homogeneous, the mechanical property is improved greater, in a relatively short period by induction tempering rather than traditional tempering. But because of the skin effect, the microstructure distribution of the tempering layer is uneven with the increased of sample thickness, so in order to achieve the homogenizing, one of the effective methods is to improve heating affected zone according reduction the power supply frequency of induction tempering.