Method for forming a variable wall light weight axle shaft with friction welded flange

A method for forming an axle shaft, comprising the steps of:

• inserting a first tubular blank having a leading end and a trailing end into a first die, said first die having an inlet end and an outlet end defining an extrusion throat through which said first tubular blank is extruded beginning with said leading end of said first tubular blank and ending with said trailing end of said first tubular blank;
• inserting a first tool into said first die, said first tool defining a surface configured to engage said trailing end of said first tubular blank and having a mandrel configured to be received within said extrusion throat of said first die and said first tubular blank, said mandrel having a first portion having a first diameter and a second portion having a second diameter greater than said first diameter;
• moving said first tool within said first die such that said surface of said first tool engages said trailing end of said first tubular blank and said first portion of said mandrel is disposed within said first tubular blank and said extrusion throat of said first die;
• applying a force to said first tool to move said first tool towards said outlet end of said first die and extrude said first tubular blank through said extrusion throat to form said axle shaft, a first end portion of said axle shaft assuming a shape having an outer diameter defined by said extrusion throat and an inner diameter defined by said first portion of said mandrel and a first intermediate portion of said axle shaft assuming a shape having an outer diameter defined by said extrusion throat and inner diameter defined by said second portion of said mandrel;
• withdrawing said first tool from said first die;
• inserting a second tubular blank having a leading end and a trailing end into said first die, said leading end of said second tubular blank engaging said trailing end of said first tubular blank;
• inserting a second tool into said first die, said second tool being separate from said first tool and defining a surface configured to engage said trailing end of said second tubular blank and having a mandrel configured to be received within said extrusion throat of said first die and said first tubular blank, said mandrel of said second tool having a third diameter less than said second diameter;
• moving said second tool within said first die such that said surface of said second tool engages said trailing end of said second tubular blank and said mandrel of said second tool is disposed within said first tubular blank and said extrusion throat of said first die;
• and
• applying a force to said second tool to move said second tool towards said outlet end of said first die such that a second end portion of said axle shaft assumes a shape having an outer diameter defined by said extrusion throat and an inner diameter defined by said mandrel of said second tool.