Steel Composition for Induction Hardening and Anneal-Free Cold Forging
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Solution Overview
Problem
Conventional steel for induction hardening requires spheroidizing annealing before cold forging and refining heat treatment before induction hardening, leading to increased component production costs, which is undesirable in the context of price competition and carbon neutrality.
Innovation Solution
A steel composition with specific ranges of C, Si, Mn, P, S, Al, Mo, Ti, B, and N, along with optional elements, allowing a microstructure of at least 80% ferritic and 40% ferritic microstructure, enabling omission of annealing before cold forging and refining heat treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional steel composition is used, then excellent induction hardening performance is achieved, but additional heat treatment (annealing and refining) is required increasing production cost
Solution Approach 1:
The patent changes the chemical composition parameters by strictly controlling C (0.36-0.55%), Mn (0.15-0.45%), Mo (0.05-0.35%), Ti (0.01-0.2%), and B (0.0005-0.01%) content, and controlling microstructure parameters (ferritic+pearlitic ≥80%, ferritic ≥40%). This parameter optimization enables the steel to achieve excellent cold forgeability and induction hardening performance without requiring additional annealing or refining heat treatment, thus reducing production cost while maintaining reliability.
2Productivity
If annealing and refining heat treatment are performed, then material properties are improved, but production time and cost increase
Solution Approach 1:
The patent performs preliminary action by optimizing the chemical composition and microstructure during the steelmaking stage. The controlled composition (C: 0.36-0.55%, Mn: 0.15-0.45%, Mo: 0.05-0.35%, Ti: 0.01-0.2%, B: 0.0005-0.01%) and microstructure (ferritic+pearlitic ≥80%, ferritic ≥40%) are established before forming, so that the steel inherently possesses excellent cold forgeability and induction hardening response. This eliminates the need for subsequent annealing and refining heat treatment, thereby improving production efficiency while maintaining material properties.
3Ease of manufacture
If cold forgeability is improved by composition control, then production cost decreases, but microstructure control becomes more critical
Solution Approach 1:
The patent addresses this contradiction by establishing specific parameter ranges: C (0.36-0.55%), Mn (0.15-0.45%), Mo (0.05-0.35%), Ti (0.01-0.2%), and B (0.0005-0.01%) are controlled to optimize cold forgeability. Simultaneously, the microstructure parameters are strictly controlled (ferritic+pearlitic ≥80%, ferritic ≥40%). This dual parameter control ensures that the steel achieves excellent cold forgeability while maintaining precise microstructure, allowing omission of additional heat treatment and reducing production cost.
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 steel achieves excellent cold forgeability and equivalent strength to conventional steels while omitting annealing and refining heat treatment, reducing production costs and environmental impact.
Implementation Method 1
the steel has excellent cold forgeability... allows omission of annealing before cold forging
Implementation Method 2
components for machine structures may be subjected to induction hardening as a final heat treatment
Data Source
AI summary
Provided is steel for induction hardening that has excellent cold forgeability and, in a process of producing an induction hardened component, allows omission of annealing before cold forging and refining heat treatment before induction hardening. The steel for induction hardening includes a chemical composition containing C: 0.36 mass % to 0.55 mass %, Si: 0.10 mass % or less, Mn: 0.15 mass % to 0.45 mass %, P: 0.050 mass % or less, S: 0.050 mass % or less, Al: 0.010 mass % to 0.090 mass %, Mo: 0.05 mass % to 10 0.35 mass %, Ti: 0.010 mass % to 0.200 mass %, B: 0.0005 mass % to 0.0100 mass %, and N: 0.0150 mass % or less, with the balance being Fe and impurity. The total fraction of ferritic microstructure and pearlitic microstructure is 80% or more, and the fraction of ferritic microstructure is 40% or more.