열간압연용 아다마이트 워크롤의 고온 가공성 평가

Abstract

Adamite cast steel with carbon contents ranging from 1.4% to 2.0% is used as work roll for the edger roll and the 4Hi work roll in the roughing mill, the front roll in the finishing mill, and the section rolling mill. Recent trends in development of rolling technology require the improvement of the properties of the work roll itself in direct contact with the rolled sheet as the rolling force and speed increase by lowing the temperature of the rolled sheet to increase the production of rolling and reduce energy consumption. Conventional adamite cast steel rolls when used for a long period have the negative effect on the production of rolling due to the generation of spalling on the surface and the disposal of service life because of reduced the strength and weakening high wear resistance. Hence, previous studies are being conducted to increase the service life of adamite cast steel rolls, one of the various methods is to improve properties through hot forging. The aim of this study is investigating the applicability of hot forging to improve properties and service life of adamite cast steel manufactured by the casting process. A gleeble thermal-mechanical test was performed to evaluate hot workability of adamite cast steel by applying hot forging. A gleeble test was performed under the two heating temperatures. In the first condition, adamite cast steel was heated to the temperature of 1200℃ and then rapidly cooled to the test temperature of 1100℃, 1000℃, 900℃ and 800℃, and the strain was compressed to 50% under all the test temperatures, and the strain rate of 1.0s-1, 0.1s-1, 0.01s-1 and 0.001s-1 was performed differently. In the second condition, adamite cast steel was heated to the temperature of 1100℃ and then rapidly cooled to the test temperature of 1100℃, 1000℃, 900℃ and 800℃, and the strain was compressed to 50% under all the test temperatures, and the strain rate of 1.0s-1, 0.1s-1, 0.01s-1 and 0.001s-1 was performed differently the same as the first condition. Instability maps were obtained using the flow stress-strain curves derived from a gleeble test, evaluation of hot workability and the stable forming conditions were derived through the microstructural analysis at the cross sections of the hot compressed specimens. From the above experimental investigation, we could be obtained conclusions as follow; In the heating temperature of 1200℃ at the strain of 50%, the stable hot forming conditions are derived from the forming temperature range of 1020-880℃ regardless of strain rates. In the heating temperature of 1100℃ at the strain of 50%, the stable hot forming conditions are derived from the forming temperature range of 1040-870℃ regardless of strain rates.