Unitary Combustion Engine Valve with Localized Surface Quenching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional materials for producing inlet valves for diesel engines, such as carbon steels and chromium-silicon steels, lack sufficient resistance to corrosion and mechanical stress, and austenitic steels, while offering better corrosion resistance, are costly and have thermal conductivity disadvantages, making them unsuitable for industrial production.
Innovation Solution
A method for producing a unitary valve using a steel composition with specific weight percentages of elements like chromium, silicon, and nitrogen, thermomechanically transformed and subjected to localized surface quenching to achieve high hardness and resistance to corrosion without excessive material costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If austenitic steels are used to produce inlet valves, then corrosion resistance is improved, but material cost increases significantly
Solution Approach 1:
The invention changes the chemical composition parameters of the steel by adding specific amounts of chromium (12-18%), silicon (1-2.5%), and nitrogen (0.05-0.15%) to a martensitic steel base. This parameter modification transforms the steel's properties to achieve corrosion resistance comparable to austenitic steels while maintaining the lower cost advantage of martensitic steels.
2Reliability
If austenitic steels are used to produce inlet valves, then corrosion resistance is improved, but thermal conductivity deteriorates
Solution Approach 1:
The invention modifies the steel composition by adding chromium, silicon, and nitrogen to martensitic steel, creating a new material that maintains the high thermal conductivity characteristic of martensitic structures while achieving the corrosion resistance typically associated with austenitic steels.
3Ease of manufacture
If conventional carbon steels and chromium-silicon steels are used to produce inlet valves, then production cost is reduced, but resistance to corrosion and mechanical stress deteriorates
Solution Approach 1:
The invention enhances conventional martensitic steel by adding specific amounts of chromium (12-18%), silicon (1-2.5%), and nitrogen (0.05-0.15%). This compositional modification significantly improves corrosion and mechanical stress resistance while maintaining production costs much lower than austenitic steel alternatives.
4Device complexity
If valves are produced as single solid component from martensitic steel, then device complexity is reduced, but surface hardness and abrasion resistance deteriorate
Solution Approach 1:
The invention applies localized surface quenching to specific portions of the valve (such as the valve seat contacting surface and stem end) after forming the complete valve from martensitic steel. This creates a hard, abrasion-resistant surface layer on critical areas while maintaining the ductility and toughness of the martensitic base material throughout the rest of the valve structure.
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 results in valves with improved mechanical properties and corrosion resistance comparable to austenitic steels but at a lower production cost, using a single solid component and reducing thermal conductivity issues.
Implementation Method 1
it is thermomechanically transformed in the hot state, for example, by means of rolling and/or forging between 1000 and 1200° C.
Implementation Method 2
a softening annealing operation is optionally carried out between 650 and 900° C. for from 2 to 8 hours followed by cooling in air or in the oven
Implementation Method 3
ending the production with a localised surface quenching operation, such as an HF quenching operation, plasma quenching or laser shock
Data Source
AI summary
The invention concerns a method for making a unitary spark ignition valve, characterized in that it consists in preparing and casting a steel made up in wt. % of: 0.45%≦C 0.55%; 12%≦Cr≦18%; 1%≦Si≦2.5%; traces≦Mn≦2%; 0.2%≦V≦0.5%; traces≦Mo≦0.5%; 0.05%≦N≦0.15%, with 0.55%≦C+N≦0.70%; traces≦Ni≦1%; traces≦Cu≦0.25%, or Cu≦0.5 Ni if Cu>0.25%; traces≦Co≦1%; traces≦W≦0.2%; traces≦Nb≦0.15%; traces≦AI≦0.025%; traces≦Ti≦0.010%; traces≦S≦0.030%; traces≦P≦0.040%; traces≦B≦0.0050%; the balance being iron and impurities resulting from the preparation; in transforming by hot thermomechanical process, for example, by rolling and/or forging between 1000 and 1200° C.; optionally soft annealing, between 650 and 900° C. for 2 to 8 hours followed by air or furnace cooling; and performing the final thermal or thermomechanical treatments which will impart to the valve its shape and its final properties, including hot-shaping by forging or extrusion, and in a final manufacturing step a localized surface quenching, such as a high-frequency quenching, a plasma or a laser shock quenching, performed on certain parts of the valve. The invention also concerns a unitary spark ignition engine valve obtained by said method.