Fe-based heat-resisting steel for engine valves
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current heat-resisting steels for engine valves, such as 21-4N steel and Ni-based alloys, are costly and insufficient in high temperature strength to meet the demands of enhanced combustion temperatures in modern gasoline engines, while existing cost-effective solutions require complex production processes and strict temperature management.
Innovation Solution
An Fe-based heat-resisting steel with specific chemical compositions, including controlled amounts of C, Si, Mn, P, Ni, Cr, Cu, Nb, Mo, W, and N, satisfying certain formulae to achieve high temperature strength comparable to Ni-based alloys, utilizing solid solution and precipitation strengthening mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If Ni-based heat-resisting alloys with γ′ precipitation strengthening are used, then high temperature strength is enhanced, but material cost increases significantly
Solution Approach 1:
The patent replaces expensive Ni-based alloys with a cost-effective Fe-based steel formulation. By using inexpensive Fe as the base metal and carefully controlling the composition of alloying elements (Ni: 8-15%, Cr: 16-25%, Mo: 0.03-2%, Nb: 0.03-1%, W: 0-2%, P: 0.1-0.5%, N: 0.02-0.3%), the invention achieves comparable high temperature strength without the high material cost of Ni-based superalloys
Solution Approach 2:
The patent creates a composite strengthening mechanism by combining multiple alloying elements that work synergistically. The Fe-based steel incorporates Ni, Cr, Mo, Nb, W, P, and N to achieve both solid solution strengthening and precipitation strengthening, resulting in a composite material structure that delivers high temperature strength comparable to Ni-based alloys at lower cost
2Quantity of substance
If 21-4N steel or improved steels are used, then material cost is reduced, but high temperature strength becomes insufficient for enhanced combustion temperatures
Solution Approach 1:
The patent significantly modifies the chemical composition parameters compared to conventional 21-4N steel. By increasing Cr to 16-25% (vs. typical 4-5%), Mo to 0.03-2% (vs. trace amounts), Nb to 0.03-1%, W to 0-2%, and optimizing Ni to 8-15%, the invention transforms the material properties to achieve high temperature strength suitable for modern high-compression ratio engines while maintaining cost-effectiveness
Solution Approach 2:
The patent applies local quality enhancement by strategically distributing different alloying elements to achieve specific functions: Ni and Cr provide solid solution strengthening and oxidation resistance, Mo and Nb provide precipitation strengthening through carbide and nitride formation, W enhances high temperature strength, and P and N contribute to both strengthening and grain boundary strengthening. This localized functional distribution optimizes high temperature performance
3Strength
If P, Mo, Nb, and N are added to Fe-based heat-resisting steel, then high temperature strength is improved through precipitation strengthening, but complex production processes and strict temperature management are required
Solution Approach 1:
The patent incorporates all necessary alloying elements (P, Mo, Nb, N, Ni, Cr, W) during the initial steelmaking process. The composition is designed so that precipitation strengthening occurs naturally during standard heat treatment and service exposure, eliminating the need for separate precipitation hardening steps. The alloying elements are pre-positioned to form strengthening precipitates during normal processing and high-temperature exposure
Solution Approach 2:
The Fe-based heat-resisting steel is designed to self-strengthen through precipitation during service exposure to high temperatures. The alloying elements (particularly Mo, Nb, and N) automatically form precipitates and intermetallic compounds during normal engine operation, providing continuous strengthening without requiring external intervention or complex controlled heat treatment processes. The material essentially strengthens itself during its operational life
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 Fe-based steel achieves high temperature strength and cost reduction by optimizing the composition and interaction of alloying elements, enabling application in regions with elevated combustion temperatures and reducing material costs.
Implementation Method 1
adding appropriately Mo, Nb and V besides C, N, Mn, Ni and Cr to a base of inexpensive Fe-based heat-resisting steel, and suppressing as much as possible the use of expensive raw materials such as Ni is used, which is subjected to a solution heat treatment
Implementation Method 2
utilizing solid solution and precipitation strengthening mechanisms
Data Source
AI summary
To provide an inexpensive heat-resisting steel for engine valves by causing Fe-based heat-resisting steel to exhibit high temperature strength not inferior to that of Ni-based heat-resisting steel. A heat-resisting steel for engine valves excellent in high temperature strength containing, in % by mass, C: 0.20 to 0.50%, Si: 1.0% or less, Mn: 5.0% or less, P: 0.1 to 0.5%, Ni: 8.0 to 15.0%, Cr: 16.0 to 25.0%, Mo: 2.0% or less (including 0%), Cu: 0.5% or less, Nb: 1.0% or less (including 0%), W: 2.0% or less (including 0%), N: 0.02 to 0.30%, B: 0.01% or less, and remnants of Fe and impurities, wherein the heat-resisting steel for engine valves satisfies formulae below:156.42P(%)+0.91Mo(%)+0.73W(%)−12.27Nb(%)+220.96N(%)+120.59≧170 Formula (1)13.70P(%)−6.97Mo(%)−4.32W(%)−3.29Nb(%)+119.10N(%)+27.75≧25 Formula (2).