Crankshaft Casting with Gradient Microstructure
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Solution Overview
Problem
Current methods for producing crankshafts in internal combustion engines face challenges such as high weight and cost due to the use of forging steels, and lower load capacity of cast crankshafts, which are exacerbated by uneven cooling rates during the casting process leading to varying material characteristics.
Innovation Solution
A complex cast component with regions having specific cooling rates and cavities of varying volumes, achieved through the use of cores in the casting mold, allowing for optimized material thickness and characteristics along the longitudinal axis, and potentially uniform cooling rates across the component.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If forged steels are used for crankshaft production, then load capacity and strength are improved, but weight and cost increase
Solution Approach 1:
The patent applies local quality by creating regions with different material properties within the crankshaft. Specifically, it produces a gradient microstructure where the surface layer has higher strength characteristics while the interior has lower strength, optimizing the distribution of material properties to match the actual stress distribution in the crankshaft during operation.
Solution Approach 2:
The patent changes the microstructural parameters of the casting material through controlled cooling rates. By adjusting the cooling rate during solidification, the material transforms from a standard cast microstructure to an optimized gradient microstructure with refined grain size and improved mechanical properties, achieving forged-like strength from cast material.
2Weight of moving object
If cast iron with spheroidal graphite is used, then weight is reduced, but load capacity decreases
Solution Approach 1:
The patent changes the microstructural parameters by controlling the cooling rate during casting. This transforms the cast iron microstructure from a coarse, non-uniform structure to a fine, gradient microstructure with optimized grain size distribution, significantly improving mechanical properties while maintaining the weight advantages of cast material.
Solution Approach 2:
The patent creates a composite-like gradient microstructure within the homogeneous cast iron material. The gradient structure consists of different microstructural zones (fine-grained surface layer, intermediate layer, and coarser interior) that work together to provide both strength and weight efficiency.
3Ease of manufacture
If conventional casting methods are used, then manufacturing cost is reduced, but material characteristics become non-uniform due to uneven cooling rates
Solution Approach 1:
The patent applies local quality by intentionally creating different cooling conditions in different regions of the mold. The mold design incorporates features that produce faster cooling at the surface and slower cooling in the interior, resulting in a gradient microstructure where each region has optimized properties for its specific functional requirements.
Solution Approach 2:
The patent applies preliminary action by pre-designing the mold structure to control the cooling rate distribution before casting occurs. The mold geometry and material selection are optimized in advance to ensure the desired gradient solidification pattern, eliminating the need for post-casting adjustments.
4Weight of moving object
If hollow bearings are cast for weight reduction, then weight is reduced, but structural complexity increases
Solution Approach 1:
The patent applies local quality by creating cavities only in specific regions where material accumulation occurs and where weight reduction is most beneficial. This selective cavity placement optimizes the weight-to-strength ratio without requiring complex hollow structures throughout the entire crankshaft.
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 results in a crankshaft with optimized material characteristics, reduced weight, and cost advantages, while maintaining or improving load capacity, and enabling precise control over material properties.
Implementation Method 1
each region of the multiplicity of regions has a specific cooling rate during a solidification process during the course of a casting process
Implementation Method 2
a first cavity which is arranged in a first region of the multiplicity of regions and which has a volume dependent on a first cooling rate of the first region
Data Source
AI summary
A complex cast component of an internal combustion engine, in particular a crankshaft or a camshaft, has a longitudinal axis, a plurality of regions, along the longitudinal axis, and a first cavity. Each of the plurality of regions has a certain cool-down rate during a solidification process of a casting process. The first cavity is arranged in a first region of the plurality of regions and has a volume that depends on a first cool-down rate of the first region. In this way, a material thickness in the first region likewise depends on the first cool-down rate.