Cemented Carbide Powder Mixture Pressing Agent
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High pressing pressures required for fine-grained cemented carbides lead to increased risks of defects, tool wear, and safety concerns, while achieving precise dimensional control is challenging due to high internal friction and resistance to compaction.
Innovation Solution
Incorporating 1-3 wt-% of long chain C≥20 fatty acids, their esters, and salts, preferably erucic acid and behenic acid, along with PEG, into cemented carbide powder mixtures to reduce compaction pressure and achieve desired sintering shrinkage without compromising green density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If higher pressing pressure is applied to achieve necessary shrinkage for fine-grained cemented carbides, then the green density and sintering shrinkage are improved, but the risk of pressing defects, tool wear, and safety concerns increases
Solution Approach 1:
The patent introduces PEG (polyethylene glycol) as an intermediary substance between the fine-grained carbide powders and the pressing tool. This intermediary reduces internal friction during compaction, allowing adequate green density to be achieved at lower pressing pressures, thereby reducing pressing defects and tool wear while maintaining sintering shrinkage control.
Solution Approach 2:
The patent changes the physical-chemical parameters of the powder mixture by adding PEG, which modifies the friction characteristics and compaction behavior. This parameter change enables the use of lower pressing pressures to achieve the same green density, resolving the contradiction between precision and harmful factors.
2Stability of the object's composition
If higher pressing pressure is applied to achieve necessary shrinkage for fine-grained cemented carbides, then the green density is improved, but the pressing tool wear and failure risk increase
Solution Approach 1:
PEG acts as a lubricating intermediary that reduces the direct mechanical interaction between fine carbide particles and the pressing tool. This intermediary layer allows adequate green density to be achieved with lower pressing pressures, significantly reducing tool wear and failure risk while maintaining composition stability.
Solution Approach 2:
The patent uses a small amount of PEG (1-5 wt%) as a consumable additive that protects the expensive pressing tools. The PEG is sacrificed during the pressing process to reduce friction, thereby preserving tool reliability and extending tool life.
3Productivity
If higher pressing pressure is applied to achieve necessary shrinkage for fine-grained cemented carbides, then the compaction resistance is overcome, but the risk of cracks and pores in pressed bodies increases
Solution Approach 1:
PEG serves as a lubricating intermediary that reduces internal friction within the fine-grained powder mixture during compaction. This allows adequate green density to be achieved at lower pressing pressures, preventing the formation of cracks and pores that would otherwise occur at high pressures, thus maintaining pressed body integrity.
Solution Approach 2:
The addition of PEG changes the friction and flow parameters of the powder mixture, enabling more uniform compaction at lower pressures. This parameter change prevents localized stress concentrations that lead to cracks and pores, maintaining productivity while improving integrity.
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
The method allows for a significant reduction in pressing pressure, minimizing defects and tool wear, while maintaining precise dimensional control and achieving the desired 18% sintering shrinkage, as demonstrated by the examples showing up to 42% reduction in pressing pressure for submicron cemented carbide powders.
Implementation Method 1
Fatty acids and their salts and esters are long known in industry for their lubricant properties
Implementation Method 2
drying the slurry generally by spray drying
Implementation Method 3
drying the slurry generally by spray drying
Implementation Method 4
finally sintering. During sintering the bodies shrink about 16-20 % linearly
Data Source
AI summary
The present invention relates to a method of making cemented carbide at which powders forming hard constituents and powders forming binder phase are wet milled together with a pressing agent. The slurry is dried, preferably by spray drying, compacted into bodies of desired shape and sintered. A cemented carbide powder with a reduced compacting pressure at a predetermined weighing in of 18 % shrinkage can be obtained by using 1-3 wt-% of a pressing agent with the following composition: <=90 wt-% PEG and >=10 wt-% of long chain C≥20 fatty acids, their esters and salts, in particular, erucic acid and/or behenic acid. The invention also relates to a cemented carbide powder with low compaction pressure.