Hardness-Gradient Chisel Structure to Prevent Breakage
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Solution Overview
Problem
Chisels used for chiseling mineral rock, particularly in heavily reinforced concrete, suffer from a high risk of breakage, significantly reducing their actual service life compared to the theoretically maximum possible service life.
Innovation Solution
A chisel design with varying hardness levels, featuring a softer interior (structural core areas) compared to the exterior, and incorporating tempering martensite in the core regions, achieved through specific heat treatment processes, including induction heating and shock treatment, to enhance toughness and reduce breakage risk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If the chisel is made uniformly hard throughout to increase wear resistance and extend service life, then the working section maintains hardness for longer, but the risk of breakage increases significantly
Solution Approach 1:
The chisel is designed with non-uniform hardness distribution: the working section (cutting edge) has high hardness (58-64 HRC) for wear resistance, while the shank section has lower hardness (48-54 HRC) for toughness and breakage resistance. This local differentiation allows each region to have properties optimized for its specific function.
Solution Approach 2:
The chisel employs a composite microstructure with different phases distributed throughout: martensite (hard, wear-resistant) in the working section and tempered martensite (tougher, more ductile) in the shank section. This creates a material composite that combines wear resistance with fracture resistance.
2Strength
If the chisel working section is made very hard to resist wear from reinforced concrete, then cutting edge durability improves, but the chisel becomes brittle and prone to breaking
Solution Approach 1:
The working section is selectively hardened to 58-64 HRC through controlled heat treatment, providing maximum wear resistance where needed. The shank section is intentionally kept softer at 48-54 HRC to maintain toughness and absorb impact energy without fracturing.
Solution Approach 2:
The patent applies different heat treatment parameters to different sections: the working section undergoes austempering or martempering to achieve high hardness, while the shank section receives milder treatment or is cooled more slowly to achieve lower hardness and higher ductility.
3Strength
If the entire chisel is heat-treated uniformly to increase overall hardness, then both working section and shank become harder, but the shank becomes too brittle and the chisel breaks more easily
Solution Approach 1:
The heat treatment process is segmented into zone-specific treatments: the working section receives intensive heat treatment for maximum hardness, while the shank section receives reduced or modified heat treatment to preserve toughness. This may involve selective heating, different cooling rates, or interrupted treatment cycles.
Solution Approach 2:
The heat treatment process is made dynamic with varying temperature profiles and cooling rates applied at different locations and times. The working section is heated to higher temperatures and cooled more rapidly, while the shank is heated to lower temperatures or cooled more slowly to achieve the desired hardness gradient.
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 chisel design significantly reduces the risk of breakage, extending the service life to several times that of conventional chisels, with some achieving up to 500,000 cycles without failure in rigorous tests.
Implementation Method 1
an induction heat treatment of the working section, wherein both the first outer area and the first core area are hardened
Implementation Method 2
an induction heat shock treatment of the working section, such that the first outer area has a significantly greater hardness than the first core area
Data Source
Figure 1
Figure 2~3
Figure 4a~4b
AI summary
The invention relates to a chisel (10) comprising a working section (12), a shank section (14), a striking surface (16), and a longitudinal axis (L) extending through the working section (12), the shank section (14), and the striking surface (16). It is characterized in that, in a cross-section of the working section (12) extending transversely to the longitudinal axis (L), a first structural core area (KB1) has a first core hardness (HK1) that is significantly lower than a first outer hardness (HA1) in a first outer area (AB1) outside the first structural core area (KB1) of the same cross-section. Furthermore, a method (1000) for manufacturing such a chisel (10) is presented. The chisel (10) is characterized by a particularly long service life.