PRODUCTION PROCESSES FOR EXTRUDING, DRAWING, AND HEAT TREATING THIN STEEL TEE SECTIONS

The three-phase program concerns processes for the manufacture of thin extruded, drawn, and heat treated tee shapes. In phase I, a production manufacturing process for the extrusion of 0.062-inch-thick by 20-foot-long tee shapes in AISI 4340, PH 14-8 Mo, and 18% Ni maraging steel was provided using a 1,200-ton Hydropress. The extrusion procedures, glass lubrication, temperature, and post-extrusion thermal and mechanical property tests are described. The results of Phase I show a relationship between alloy content, extrudability, and ram speed. AISI 4340 is the easiest to extrude and has the highest ram speed of the three alloys extruded. 18% Ni maraging steel is the most difficult to extrude and has the lowest ram speed during extrusion. The ram speed and extrudability of PH 14-8 Mo is between the two. A reproducible drawing process was refined in Phase II to reduce the thickness of the 20-foot-long tee extrusions to a target thickness of 0.040 inch. The success of the drawing phase of the program is primarily attributed to the invention of an adjustable draw die system that completely eliminates the necessity for 'pointing.' A process to heat treat 20-foot-long by 0.040-inch-thick extruded and drawn AISI 4340, PH 14- 8 Mo, and 18% maraging steel tee shapes was in Phase III. The heat treat response of the three alloys is adequate and exceeds the target mechanical properties for AISI 4340 and PH 14-8 Mo.