Hot forming seamless elbow machine

This machine utilizes a combination of axial pushing, localized medium-frequency heating, and a bull-horn mandrel to simultaneously expand and bend pipes in a single operation. Starting with straight pipes smaller in diameter than the finished elbow, the hot pushing process directly produces rough elbows through simultaneous expansion and bending.

The process follows the law of constant metal volume: under axial push from the rear, the pipe billet moves forward and is rapidly heated to plastic temperature (850-1100°C) by a medium-frequency induction coil. The heat-softened steel pipe passes over a stationary horn-shaped mandrel, which gradually thickens with a curved arc, forcing simultaneous circumferential expansion and axial bending.

• Outer arc undergoes stretching
• Inner arc experiences compression
• Metal flow compensates wall thickness
• Final elbow shape is achieved

1. Material Preparation: Cut seamless steel pipes to calculated length with inner diameter smaller than finished elbow; apply graphite high-temperature lubricant to inner walls to reduce friction and prevent mandrel scratching.
2. Material Loading and Clamping: Insert pipe billet onto fixed horn mandrel; rear end held against pipe billet by movable frame push plate; front end of mandrel locked onto fixed frame.
3. Induction Heating: Position medium-frequency induction coil at horn mandrel entrance to perform localized rapid circumferential heating on the section about to enter deformation zone.
4. Extrusion Forming (Core Operation): Hydraulic/servo-driven push plate pushes pipe billet forward at uniform speed; heated section slides along horn mandrel, simultaneously expanding inner diameter while bending according to mandrel curvature.
5. Mandrel Removal: After entire elbow passes through sizing section, formed elbow is detached from horn mandrel.
6. Post-Processing: Thermal shaping, heat treatment (normalizing/tempering, mandatory for alloy steels), grooving, non-destructive testing, and sandblasting.

• Extrusion Main Machine: Fixed frame, movable push plate, hydraulic/servo propulsion system
• Forming Tools: Horn mandrel + mandrel rod (forming die)
• Heating System: Medium-frequency power supply + water-cooled induction heating coil
• Support Systems: Cooling system, temperature measurement system, control system