Engine Valve Heat Treatment for High-Temperature Neck Durability

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Solution Overview

Problem

Existing engine valves face durability issues due to insufficient high-temperature strength, fatigue life, and creep life, particularly in high-power engines, leading to material cost increases and weight additions that degrade valve system performance.

Innovation Solution

A method involving hot forging of heat-resistant steel at 1,150 to 1,250 °C, followed by aging, hollowed-out processing, nitride-heat treatment, and grinding to remove the nitride layer on the valve neck, which enhances high-temperature properties without increasing material cost or weight.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If material having excellent heat resistance is applied to improve neck durability, then high temperature strength is improved, but material cost increases

Engineering Contradiction:

Improvehigh temperature strengthVSAvoidmaterial cost

Core Design Contradiction:

StrengthVSQuantity of substance

Solution Approach 1:

The patent applies parameter changes by optimizing the hot forging temperature range (1,150 to 1,250°C) and aging treatment conditions to achieve the desired high-temperature strength properties using conventional heat resistant steel, rather than changing to more expensive materials. This resolves the contradiction by achieving improved strength through process parameter optimization instead of material substitution.

Inventive Principle:

Principle #35Parameter changes

2Duration of action of stationary object

If neck shape is reinforced to secure durability, then neck durability is improved, but weight of exhaust valve increases

Engineering Contradiction:

Improveneck durabilityVSAvoidweight of exhaust valve

Core Design Contradiction:

Duration of action of stationary objectVSWeight of moving object

Solution Approach 1:

The patent uses parameter changes in the hot forging temperature (1,150 to 1,250°C) and aging treatment to enhance the neck's durability through microstructural optimization, avoiding the need for geometric reinforcement that would increase weight. This maintains the valve's lightweight characteristics while achieving the required durability.

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If solid solution treatment is performed at 900 to 1,100°C, then manufacturing process is simplified, but high temperature properties are limited

Engineering Contradiction:

Improvemanufacturing process simplicityVSAvoidhigh temperature properties

Core Design Contradiction:

Ease of manufactureVSStrength

Solution Approach 1:

The patent changes the temperature parameter to a higher range (1,150 to 1,250°C) for hot forging, which enables sufficient solid solution treatment and develops the high-temperature properties of heat resistant steel. This parameter adjustment simultaneously achieves both adequate manufacturing feasibility and superior high-temperature performance.

Inventive Principle:

Principle #35Parameter changes

4Duration of action of moving object

If valve is exposed to high temperature for long period, then engine operation is maintained, but durability degradation occurs

Engineering Contradiction:

Improveengine operation timeVSAvoiddurability

Core Design Contradiction:

Duration of action of moving objectVSReliability

Solution Approach 1:

The patent applies preliminary action by performing hot forging at elevated temperatures (1,150 to 1,250°C) followed by aging treatment before the valve enters service. This pre-treatment creates a microstructure that is resistant to high-temperature degradation, enabling the valve to maintain reliability during prolonged engine operation.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent uses parameter changes in the thermal processing (hot forging temperature and aging conditions) to create a microstructure that resists high-temperature degradation. This enables the valve to maintain its mechanical properties and reliability even after extended exposure to high operating temperatures.

Inventive Principle:

Principle #35Parameter changes

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 an engine valve with improved strength, fatigue life, and creep life at high temperatures, reducing durability degradation and maintaining material and shape integrity, making it suitable for high-power engines.

Implementation Method 1

hot forging a heat resistant steel at about 1,150 to 1,250 °C to mold a valve

Methodology Applied

Scientific EffectHot forging:

Implementation Method 2

a solid solution treatment is progressed insufficiently which limits the high temperature properties

Methodology Applied

Scientific EffectSolid solution treatment:

Implementation Method 3

aging the molded valve

Methodology Applied

Scientific EffectAging: Annealing

Implementation Method 4

nitride-heating the hollow valve

Methodology Applied

Scientific EffectNitride-heat treatment: Nitriding

Implementation Method 5

grinding a surface of a neck of the nitride-heated valve to remove a nitride layer

Methodology Applied

Scientific EffectGrinding: Abrasion

Data Source

PatentEP3831967A1Preparing method of engine valve

Publication Date: 2021.06.09 HYUNDAI MOTOR CO LTD

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Figure 3A~3C

AI summary

A method of preparing an engine valve is provided. The method includes hot forging a heat resistant steel at 1,150 to 1,250 °C to mold a valve, aging the molded valve and hollowed-out processing the aging valve. Additionally, the method includes nitride-heating the hollow valve and grinding a surface of a neck of the nitride-heated valve to remove a nitride layer.