Forged Steel Strength via Low Nitrogen and Temperature Control
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Solution Overview
Problem
The production of forged products with high strength and fatigue strength is challenging due to the high cost of Vanadium resources and the need for heat treatments, which can lead to embrittlement and pearlite grain enlargement, increasing production costs.
Innovation Solution
A forging process is conducted in a temperature range of 350-600 °C on steel with less than 0.0030 mass% N, avoiding austenite precipitation and the blue shortness region, to achieve ferrite and pearlite textures, thereby enhancing strength without the need for heat treatments and reducing production costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If V is added to improve strength, then yield strength and fatigue strength are improved, but production cost increases due to resource depletion and addition cost
Solution Approach 1:
The invention extracts and removes Vanadium (V) from the steel composition entirely, replacing it with a controlled combination of other alloying elements (C, Si, Mn, P, S, Cu, Ni, Cr) to achieve the desired strength properties without relying on V addition
Solution Approach 2:
The invention changes the chemical composition parameters by strictly controlling the content ranges of multiple alloying elements, particularly maintaining C at 0.20-0.60%, Si at 0.05-1.50%, and N at less than 0.0030%, to achieve strength enhancement through compositional optimization rather than V addition
2Strength
If forging process is conducted in blue shortness region to improve strength, then strength is improved, but heat treatment for embrittlement recovery is necessary, increasing production cost
Solution Approach 1:
The invention changes the temperature parameter of the forging process to be conducted at 350-600°C, which is above the blue shortness region temperature range, thereby achieving strength improvement without inducing embrittlement that would require additional heat treatment
Solution Approach 2:
The invention performs the strength enhancement action during the forging process itself at the optimized temperature range, rather than requiring a separate subsequent heat treatment step for embrittlement recovery, thus eliminating additional production costs
3Ease of manufacture
If forging process is conducted at temperature not lower than 600°C to avoid blue shortness, then embrittlement is avoided, but austenite precipitation and pearlite grain enlargement occur, reducing strength
Solution Approach 1:
The invention optimizes the temperature parameter to a specific range of 350-600°C, which is below the threshold for austenite precipitation and pearlite grain enlargement, while still being sufficient to avoid blue shortness embrittlement, thereby achieving both embrittlement avoidance and strength maintenance
Solution Approach 2:
The invention dynamically controls the forging temperature within the 350-600°C range to balance multiple competing requirements: avoiding blue shortness embrittlement while preventing austenite precipitation and pearlite grain enlargement, thus maintaining optimal strength properties
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 process effectively improves yield and fatigue strength while suppressing pearlite grain enlargement and hydrogen embrittlement, resulting in a cost-effective production method for forged products with targeted strength properties.
Implementation Method 1
an intermediate forged product having a ferrite and pearlite texture obtained by conducting a hot forging
Implementation Method 2
the enlargement of the pearlite grains is suppressed
Implementation Method 3
hydrogen embrittlement of the forged product is suppressed
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A forging process is conducted in a temperature range of 350-600 °C on at least a portion that is required to have a fatigue strength in an intermediate forged product having a ferrite and pearlite texture obtained by conducting a hot forging on a steel in which N is not greater than an amount at which N is unavoidably dissolved as a solid, thereby improving strength of the portion that is required to have a fatigue strength. With this, there is provided a forged product having a good strength and a low price.