Bi-Material Billet Forging for Weight Reduction
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Solution Overview
Problem
Current gear manufacturing methods generate significant scrap steel and carbon footprint, and are costly and inefficient due to high flow stresses and die failures, especially when forging large gears with multiple tooth cavities.
Innovation Solution
A method involving the formation of a bi-material billet with a steel shell and a lightweight core, where the core is in a liquid or solid state during forging, allowing for netshape forging with reduced material waste and improved fuel efficiency by using high-frequency induction heating and multi-blow indexed forging to produce gears with uniform steel thickness and reduced weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional metal-removing machining processes are used to manufacture gears, then gears can be produced with precise dimensions, but significant scrap steel is generated and carbon footprint increases
Solution Approach 1:
The invention changes the fundamental manufacturing parameter from subtractive machining to additive forging, transforming the material removal process into a material formation process. This allows gears to be forged to near-net shape, dramatically reducing scrap steel while maintaining dimensional precision through controlled forging parameters and subsequent minimal machining.
Solution Approach 2:
The invention utilizes phase transition of steel from solid to liquid and back to solid during the forging process. Steel is heated to molten state, injected into mold cavities to form gear shapes, then cooled and solidified. This phase transition enables direct formation of complex gear geometries without extensive material removal, reducing scrap while achieving precise dimensions.
2Productivity
If traditional forging methods are used for large gears with multiple tooth cavities, then gears can be produced, but high flow stresses cause die failures and increased manufacturing costs
Solution Approach 1:
By utilizing the liquid phase of steel during injection, the invention eliminates high flow stresses that occur during solid-state forging of complex geometries. The molten steel flows easily into multi-cavity molds under pressure, then solidifies to form the gear shape. This phase transition approach enables production of large gears with multiple tooth cavities without die failures, improving both productivity and reliability.
Solution Approach 2:
The invention replaces the mechanical forging system (which relies on high mechanical pressure to deform solid metal) with a thermal-fluid system (heating steel to liquid state and injecting under pressure). This substitution eliminates the high flow stresses that cause die failures in traditional mechanical forging, while enabling complex multi-cavity gear production.
3Strength
If solid steel gears are used to ensure sufficient strength, then gear strength is maintained, but vehicle weight increases and fuel efficiency decreases
Solution Approach 1:
The invention applies local quality by using steel material selectively only where strength is required (in the gear teeth and critical load-bearing areas), while using lighter materials or hollow structures in non-critical areas. This localized material distribution maintains gear strength while significantly reducing overall weight, improving fuel efficiency without compromising mechanical performance.
Solution Approach 2:
The invention employs composite material structures, combining steel with lighter materials in specific regions of the gear. This could include steel-reinforced composites or hybrid structures that provide sufficient strength in load-bearing areas while reducing overall density. The composite approach enables weight reduction of 33-50% while maintaining the strength required for gear operation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method achieves a 33-50% weight reduction in gears, leading to improved fuel efficiency and reduced manufacturing costs, with the potential for increased cargo capacity in vehicles and enhanced productivity.
Implementation Method 1
heating the cylindrical wall with high-frequency induction heating
Implementation Method 2
a first forging blow on the heated billet or on a disk-shaped rough forging forged from the heated billet with a first closed blocker die to produce a forging preform, and a second forging blow on the forging preform with a second closed blocker die to produce a netshape forging
Data Source
AI summary
A method for manufacturing a forging includes forming a bi-material billet by enclosing a core material other than steel in a steel cylinder with a cylindrical wall and steel end caps. The cylindrical wall is heated. The method includes a first forging blow on the heated billet or on a disk-shaped rough forging forged from the heated billet with a first closed blocker die to produce a forging preform, and a second forging blow on the preform with a second closed blocker die to produce a netshape forging. An evacuation hole is formed in a steel shell of the netshape forging and the core material is removed from the netshape forging via the hole. At least 85 percent of the core material is in a liquid phase during the first and second forging blows, and removal of the core material.