Titanium Engine Valve Texture Boundary for Creep Resistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing engine valves formed from titanium alloy face challenges such as increased inertial mass, reduced strength at stress-intensive neck portions, and variations in strength due to manufacturing methods, which hinder high-temperature creep resistance and fatigue strength.
Innovation Solution
The engine valve is designed with a stem section formed mainly of equiaxed crystallographic texture and a bevel section formed mainly of needle-like texture, with the boundary between the two textures positioned at the sliding movement area to avoid intense stress, and hot-forging is used to form the bevel section at a temperature not exceeding the β transformation point, followed by high-frequency heating to set the boundary accurately.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the boundary between needle-like texture and equiaxed texture is positioned at the neck portion to maximize strength distribution, then the high-temperature creep resistance is improved, but the strength at the neck portion is reduced due to intensive stress application
Solution Approach 1:
The patent applies local quality by positioning the boundary between needle-like and equiaxed textures at a specific location (within 5mm from the end of the stem section) rather than uniformly distributing textures. This localized texture arrangement optimizes high-temperature creep resistance at the bevel section while managing stress distribution at the neck portion, resolving the contradiction between temperature resistance and local strength.
2Strength
If the diameter of the neck portion is enlarged to increase strength at the stress-intensive boundary, then the strength is improved, but the weight of the engine valve increases
Solution Approach 1:
Instead of uniformly enlarging the neck portion diameter, the patent uses local quality by strategically positioning the texture boundary within 5mm from the end of the stem section. This localized approach enhances strength at the critical neck portion through optimized texture distribution without increasing the overall valve weight, resolving the contradiction between local strength and global weight.
3Productivity
If hot-forging is performed immediately after forming the enlarged diameter section with needle-like texture, then the manufacturing productivity is improved, but forging defects such as shrinkage and cracking occur
Solution Approach 1:
The patent applies preliminary action by performing intermediate annealing between the upset forging that creates the needle-like texture and the subsequent hot-forging of the bevel section. This intermediate heat treatment prepares the material in advance, relieving internal stresses and preventing defects during the final forging operation, thus resolving the contradiction between productivity and reliability.
4Ease of manufacture
If the boundary position between needle-like texture and equiaxed texture varies due to manufacturing tolerances, then the manufacturing ease is improved, but the variation in strength of the manufactured engine valve increases
Solution Approach 1:
The patent uses parameter changes by defining a specific range (within 5mm from the end of the stem section) for the boundary position rather than requiring an exact location. This parameter specification accommodates manufacturing tolerances while ensuring the boundary falls within the optimal zone for both strength and creep resistance, resolving the contradiction between manufacturing ease and strength consistency.
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
This design enhances manufacturing reliability, productivity, and high-temperature creep resistance and fatigue strength while maintaining a lightweight and inexpensive engine valve.
Implementation Method 1
heating a portion from the bevel section to a medial part of the stem section with a high frequency at a temperature exceeding the β transformation point
Implementation Method 2
a portion of the valve from the bevel section to a medial part of the stem section is formed mainly of a needle-like crystallographic texture
Data Source
AI summary
An engine valve, formed of a titanium alloy, enables improvement of reliability and productivity while improving creep resistance and fatigue strength at a high temperature. The engine valve, including a stem section and a bevel section provided at one end of the stem section, is integrally formed of the titanium alloy. A portion of the valve, extending from the bevel section to a medial portion of the valve stem, is formed mainly of a needle-like crystallographic texture. Another portion of the valve, extending from the medial section to the other end of the stem section, is formed of a material having a substantially equiaxed crystallographic texture. A boundary between the needle-like texture and the equiaxed texture is provided in a range of sliding movement of the valve relative to a valve guide that slidably guides the stem section within the cylinder head.