# Effect of Induction Heating Temperature on the Uniformity of Mechanical Properties of Bulb Flat Steel Sections in the Quenched State

## TL;DR

This study shows how adjusting induction heating temperature improves mechanical property uniformity in bulb flat steel sections after quenching.

## Contribution

The paper reveals how temperature-dependent strengthening mechanisms affect mechanical property uniformity in bulb flat steel.

## Key findings

- Increasing induction heating temperature reduces yield strength disparity between bulb and flat sections by 93%.
- Prior austenite grain size coarsens with higher heating temperatures.
- Dislocation strengthening dominates at lower temperatures, while grain boundary strengthening prevails at higher temperatures.

## Abstract

Induction quenching is critical for high-strength bulb flat steel, yet the influence of the heating temperature on mechanical property uniformity across sections remains underexplored. This study systematically investigates the effect of the induction heating temperature on mechanical property uniformity, prior austenite grain size, and microstructural evolution in bulb flat steel. Experimental results reveal that increasing the induction heating temperature from 845 °C to 1045 °C induces distinct mechanical responses: the yield strength disparity between the bulb and flat sections decreases by 93% (from 94 MPa), significantly improving sectional uniformity. Microstructural analysis indicates that prior austenite grain size coarsens with higher induction heating temperatures. The quenched microstructure comprises martensite and bainite in the bulb core, while the flat section is entirely martensitic. The yield strength differential between the bulb and flat sections is governed by temperature-dependent strengthening mechanisms: dislocation strengthening dominates at 845 °C~985 °C, with the bulb region exhibiting higher strength due to increased dislocation density, while grain boundary strengthening prevails at 1045 °C, where the flat region benefits from finer grains.