On Hot Metal Gas Forming Process

Abstract

Hot Metal Gas Forming (HMGF) is a new metal forming process jointly developed by 15 automotive/aerospace companies/suppliers and one university under NIST-Advanced Technology Program [1, 2]. The primary goals of this program are (1) to achieve enhanced formability for automotive steels and aluminum alloys at high speeds, and (2) to reduce manufacturing cost. The technical approach is to develop a gas forming process that forms tubular components at elevated temperatures inside ceramic dies. During the forming, 1) a tubular workpiece is placed into the ceramic die cavity, then is rapidly heated to above 0.6Tm (melting temperature in K) by a set of induction coils that are embedded behind the ceramic die outer surfaces; 2) The two tube ends are sealed and a gas pressure is applied inside the bube; and 3) The metal fill the die cavity under combined internal gas pressure and optional axial feeding. After forming the workpiece is transferred to a cooling station for possible on-line heat treatment. For many steels and heat-treatable aluminum alloys the mechanical properties can be improved through controlled cooling rate after forming. In this presentation, the results on the elevated-temperature tensile behaviors and formability of several commonly used automotive aluminum alloys and steels will be presented. The microstructural evolution and its effect on the formability and post-forming properties will also be discussed. Two types of tube in-die forming 0processes have been studied: (1)tube expansion from 2 inche to 3 inch in diameter; (2) tube forming from round to squared sections. Based on laboratory that can perform continuous operation at a cycle time less than 30 seconds. Current activities in implementation of this new metal forming method for manufacturing vehicle chassis components will be described.