예열공정이 적용된 롤 포밍 공정에서 고장력강판의 스프링 백 영향 연구

Abstract

In this study, roll forming process studied the new convergence process that combines the pre-heating process. The forming shape of the roll forming process is V-shape and materials of forming sheet are high tensile steel, aluminum alloy, magnesium alloy and titanium alloy. Roll forming process applied to the pre-heating process was used to the Taguchi's experimental method and forming sheet was pre-heated using a butane gas torch and a plasma gas torch. Roll forming process experiment at room temperature used high tension steel (SPFH 590) and variables of the roll forming experiment are forming speed and roll gap. Forming speed has a small influence to spring-back phenomenon. But the roll gap affects a greater influence to her spring-back phenomenon more than forming speed. Temperature characteristics experiment of pre-heating devices unit was used for a butane gas torch and a plasma gas torch. The temperature of the flame of gas torch was measured using an infrared thermal imaging camera. The length of the flame was calculated by converting the temperature data from the infrared thermal imaging camera. After identifying the characteristics of the flame, distance between the pre-heating device and the forming sheet determined in accordance with the pre-heating device. Roll forming process applied to the pre-heating process was evaluated for formability by the FEM simulation and roll forming experiment. Method of FEM simulation was thermal-structure interaction analysis applied to moving heat source that moved along the center line of the forming sheet. And spring-back analysis was performed static analysis using thermal-structure interaction analysis result. As a result, the spring-back value is measured at the measuring point of the forming sheet according to the various temperatures. Spring-back effect of the pre-heating temperature was characterized as not significant. The roll forming experiment was calculated SN ratio obtained by using the spring-back value. The main effect for SN ratios is derived by using the SN ratio. According to the analysis results of the formed sheet, spring-back effect of the pre-heating process was characterized as not significant. However, in ANOVA results, preheated forming sheet has been reduced to the buckling phenomenon. And forming the sheet is formed into a consistent cross-section shape, so product quality is determined to be improved. The material of the metal sheet experiment is a titanium alloy, magnesium alloy and aluminum alloy. Experimental method of titanium alloys is equal to the high tension steel experiment. Titanium alloys were lower than the high strength steel formability. Experiment of an aluminum alloy and a magnesium alloy is applied to Taguchi experimentation. But experimental results of the alloy sheets were generated cracks. Because of the time for supplying thermal energy by gas torch is short. FEM simulation of the roll forming process analyzes the close cross-section shape and the tube shape process. Analysis of the tube shape was obtained the spring-back value corresponding to the number of roll passes. Analysis of the close cross-section was analyzed formability according to the roll gap.