Friction Welded Piston Hardening via Heat-Affected Zone
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Solution Overview
Problem
Modern internal combustion engine pistons face increased thermal and mechanical stress, leading to inadequate oil supply and higher tribological loads, resulting in increased wear and reduced service life, with existing hardening methods like nitriding and laser treatment being costly and effort-intensive.
Innovation Solution
A method involving friction welding of heat-treated or precipitation-hardening steel piston components, where the components are tempered or precipitation-hardened before welding, creating a heat-affected zone that hardens the friction weld seam area, eliminating the need for additional hardening processes like nitriding or laser treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional hardening methods like nitriding or laser treatment are applied to harden the lower groove flank, then wear resistance is improved, but manufacturing cost and process complexity increase
Solution Approach 1:
The patent converts the harmful heat-affected zone created during friction welding into a beneficial hardened surface layer. The friction welding process generates localized heat that hardens the lower groove flank area, transforming what would normally be a detrimental thermal effect into a useful hardening mechanism that eliminates the need for additional hardening processes.
Solution Approach 2:
The patent merges the joining process (friction welding) with the surface treatment process (hardening) into a single operational step. By positioning the lower groove flank within the heat-affected zone of the friction weld, the joining operation simultaneously creates the hardened surface layer, combining two previously separate manufacturing steps into one.
2Productivity
If friction welding is used to connect piston components, then manufacturing efficiency is improved, but unintended hardening of the friction weld seam occurs which may affect material properties
Solution Approach 1:
The patent applies local quality by creating a localized hardened zone specifically at the lower groove flank area through controlled friction welding. The heat-affected zone is precisely positioned to harden only the wear-critical surface layer while leaving the bulk material properties of the piston components unchanged, achieving localized property modification without affecting overall material characteristics.
3Ease of manufacture
If the lower groove flank is positioned within the heat-affected zone of the friction weld, then hardening is achieved without additional processes, but the position of the friction weld seam must be precisely controlled
Solution Approach 1:
The patent applies preliminary action by pre-positioning the lower groove flank within the anticipated heat-affected zone before friction welding occurs. The component geometry is designed such that the groove location is predetermined to fall within the hardened zone, allowing the welding process to automatically create the desired hardening effect without requiring real-time adjustment or additional positioning steps.
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 effectively hardens the heat-affected zone around the friction weld seam, increasing hardness by up to 400 HV, reducing wear on high-wear areas such as the lower groove flank, and maintaining hardness after stress-relief annealing, thus extending piston service life without additional costly treatments.
Implementation Method 1
connecting the blank of the first piston component to the blank of the second piston component via their joining surfaces by means of friction welding to form a piston blank, forming at least one friction weld seam and a heat-affected zone in the area of the at least one friction weld seam
Implementation Method 2
friction welding causes hardening in the immediate vicinity of the friction weld seam
Implementation Method 3
quenching or precipitation hardening of the blanks; tempering or stress relieving the piston blank while maintaining the heat affected zone
Implementation Method 4
The hardness increases in this area by up to 400 HV (Vickers). This hardened area is referred to as the 'heat-affected zone'
Implementation Method 5
tempering or stress relieving the piston blank while maintaining the heat affected zone
Data Source
Figure 1a
Figure 1b~2b
Figure 2a
AI summary
The invention relates to a method for producing a piston (10, 110, 210) for an internal combustion engine from a first piston component (11, 111, 211) and a second piston component (12, 112, 212), characterized by the following method steps: (a) providing a blank (211') of the first piston component (11, 111, 211) made of a heat-treatable steel or a precipitation-hardening steel and having at least one joining surface (29, 31), (b) providing a blank (212') of the second piston component (12, 112, 212) made of a heat-treatable steel or a precipitation-hardening steel and having at least one joining surface (32, 33), (c) heat-treating the blanks (211', 212'), (d) connecting the blank (211') of the first piston component (11, 111, 211) to the blank (212') of the second piston component (12, 112, 212) by means of the joining surfaces (29, 31, 32, 33) thereof using friction welding in order to form a piston blank (210'), at least one friction weld (25, 26, 125, 226) and a heat-affected zone (30, 30') in the region of the at least one friction weld (25, 26, 125, 226) being formed in the process, (e) tempering or stress-relief annealing the piston blank (210) while preserving the heat-affected zone(s) (30, 30'), and (f) post-processing and/or finishing the piston blank (210') to form a piston (10, 110, 210). The invention further relates to such a piston (10, 110, 210).