Hot Metal Extrusion

Hot metal extrusion forces heated billets through a die to create long, constant cross-section profiles in hard-to-form alloys at high production rates.

Overview

Hot metal extrusion pushes a heated metal billet through a shaped die to produce long parts with a constant cross section. Working above recrystallization temperature lowers flow stress, enabling high reduction ratios, complex profiles, and forming of alloys that are too hard or brittle for cold extrusion. This process is common for structural profiles, tubes, rails, and heat-dissipating shapes where grain flow and mechanical properties matter.

Use hot extrusion when you need medium-to-high production volumes of prismatic shapes in materials like steel, titanium, or high-strength aluminum alloys. Expect good dimensional consistency on profile geometry but looser tolerances than machining, with die marks and scale that may require secondary finishing on critical surfaces. Tooling cost is significant, so it favors repeated runs and families of parts that share a common profile. The tradeoff: excellent material utilization and mechanical properties, but less flexibility for late design changes and limited detail along the length beyond what the die can form.

Common Materials

  • Aluminum 6061
  • Aluminum 6063
  • Carbon steel
  • Stainless steel 304
  • Copper
  • Titanium

Tolerances

±0.005" to ±0.010" on profile dimensions, looser on twist, straightness, and runout

Applications

  • Structural aluminum or steel profiles
  • Hollow tubes and pipes with custom cross sections
  • Heat sink and cooling profiles
  • Automotive bumper beams and crash members
  • Rail and track profiles
  • Aerospace stiffeners and stringers

When to Choose Hot Metal Extrusion

Choose hot metal extrusion for long, constant cross-section parts in medium to high volumes, especially in alloys that are difficult to cold work. It fits best when you need good mechanical properties, efficient material use, and are willing to invest in dedicated dies for repeat production. Use it when most of the part’s value is defined by the profile, not by intricate features along its length.

vs Cold Metal Extrusion

Choose hot metal extrusion when working with high-strength or low-ductility alloys, or when you need high reduction ratios that would require excessive force at room temperature. Hot extrusion reduces forming loads and springback, but at the cost of looser tolerances and more surface oxidation than cold extrusion.

vs CNC machining

Choose hot metal extrusion when the part is primarily a constant cross-section shape and material removal from bar stock would waste time and material. Use extrusion to create the near-net profile, then machine only critical features and interfaces to tighten tolerances where needed.

vs Metal casting

Choose hot metal extrusion when you want better mechanical properties, directional grain flow, and fewer internal defects than typical castings. It works well for linear shapes where a constant profile is acceptable and the cost of casting tooling does not buy you useful 3D complexity.

vs Hot forging

Choose hot metal extrusion when you need long, prismatic parts rather than discrete 3D shapes. Forging suits bulkier, localized geometry; extrusion is more efficient for continuous profiles and complex cross sections extending over length.

vs Metal 3D printing

Choose hot metal extrusion for production quantities of simple, prismatic profiles where unit cost and throughput matter more than extreme geometric freedom. 3D printing is better for low-volume, highly complex shapes; extrusion wins on cost per part when the geometry can be defined by a 2D cross section.

Design Considerations

  • Design a constant cross section along length; any changes in section require secondary operations or assemblies
  • Use generous corner radii and avoid sharp internal corners to reduce die stress and improve metal flow
  • Keep wall thicknesses as uniform as possible and avoid very thin sections relative to overall size to prevent defects and die breakage
  • Specify realistic tolerances and clearly mark critical-to-function dimensions that may need post-extrusion machining
  • Control symmetry and balance of the profile to reduce twist, bow, and uneven cooling distortion
  • Call out grain direction and any required heat treatment so the shop can align extrusion, cooling, and post-processing to meet properties