Hot Forging Ingot Forming With Staged Bite Ratio to Prevent Cracks
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Solution Overview
Problem
Hot forming of cast forging ingots often results in cracking in the surface region due to uneven loading and high bite ratios, which are necessary for influencing the microstructure in the core area, despite existing methods to mitigate this issue.
Innovation Solution
The method involves initial near-surface forge processing with eccentric drives to achieve a degree of deformation that prevents cracking, followed by hydraulic forge pressing with a large bite ratio, ensuring uniform forming and recrystallization near the surface, and subsequent radial forging to improve microstructure and surface quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a large bite ratio is used to achieve sufficient core forming for pore reduction, then the microstructure in the core area is improved, but uneven loading of surface regions occurs leading to cracking
Solution Approach 1:
The patent applies preliminary radial forging with a small bite ratio before the main press forging operation. This preliminary action creates a flow sheath in the surface regions that prevents cracking during subsequent high bite ratio press forging, while still allowing the core area to achieve sufficient deformation for pore reduction and microstructure improvement.
Solution Approach 2:
The patent segments the forging process into two distinct stages: (1) radial forging with small bite ratio to create protective flow sheath in surface regions, and (2) press forging with large bite ratio to achieve core area deformation. This segmentation allows different bite ratios to be applied at different stages to address both surface and core requirements.
2Object-affected harmful factors
If radial forging with high forming speed and small bite ratio is used, then surface quality is maintained, but insufficient deformation occurs in the core area for adequate pore reduction
Solution Approach 1:
Radial forging with small bite ratio is performed as a preliminary action to create the flow sheath and prevent surface cracking. This is followed by press forging with large bite ratio that provides the necessary deformation for core area pore reduction, combining the benefits of both approaches.
Solution Approach 2:
The patent changes the bite ratio parameter between two stages: small bite ratio (≤0.5) for radial forging to protect surface regions, then large bite ratio (>0.5) for press forging to achieve sufficient core deformation. This parameter change allows optimization for both surface quality and core microstructure.
3Object-affected harmful factors
If the bite ratio is reduced to avoid surface cracking, then surface quality is maintained, but the pressed saddle length decreases leading to insufficient core area influence
Solution Approach 1:
The patent segments the forging process into radial forging (small bite ratio, shorter pressed saddle) followed by press forging (large bite ratio, longer pressed saddle). This segmentation allows the pressed saddle length to be optimized for each stage: sufficient for surface protection in radial forging, and sufficient for core influence in press forging.
Solution Approach 2:
Radial forging with shorter pressed saddle is performed as a preliminary action to protect surface regions. This enables the subsequent press forging operation to use a longer pressed saddle for adequate core area influence without risking surface cracking.
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 approach effectively prevents crack formation in the surface region while achieving microstructure improvement down to the core of the forging ingot, maintaining surface quality and avoiding grain growth through controlled deformation and heat management.
Implementation Method 1
the inner die part can be driven in the sense of a press forging when the hydraulic cylinder between the two die parts is pressurized
Implementation Method 2
The outer of the two die parts is driven by an eccentric drive which, when the hydraulic cylinder between the two die parts is locked, drives the inner die part receiving a forging tool in the sense of radial forging with a comparatively high number of blows
Implementation Method 3
In order to convert the cast structure of a cast forging ingot into a largely pore-free, recrystallized structure, the forging ingot is subjected to hot forming by a press forging operation
Data Source
AI summary
A method for hot forming of a cast forging ingot uses a forging device with radially guided forging dies of which each have two die parts, which can be radially moved relative to each other and of which the inner die part bearing a forging tool is drive-connected, using a hydraulic cylinder, to the other, outer die part, which can be driven using an eccentric drive. In order to provide advantageous forging conditions, the forging ingot is formed under heat, first using the forging dies driven by the eccentric drive, in near-surface forge processing with a degree of deformation which is above the critical degree of deformation and which excludes the formation of cracks, and then, with the outer die parts stopped, with the aid of the inner die parts driven by the hydraulic cylinders, in forge pressing with a bite ratio of >0.5.