Martensitic Stainless Steel Strip Quenching Temperature Gradient
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Solution Overview
Problem
Martensitic stainless steel strips with thicknesses of 1 mm or less are prone to shape defects such as excessive medium elongation, edge waves, and waviness due to sudden temperature changes during the quenching process in existing production methods, which compromise their quality without addressing productivity.
Innovation Solution
A method involving a quenching process with a temperature raising unit and a holding unit in a non-oxidizing gas atmosphere, where the temperature raising unit sets a heating temperature higher on the exit side than the entry side, and the holding unit maintains the quenching temperature, along with a temperature lowering unit to control heating and prevent rapid temperature changes, ensuring the steel strip spends equal to or more time in the temperature raising unit than the holding unit, thereby preventing shape defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the steel strip is rapidly heated in a quenching furnace to improve heat treatment capacity and productivity, then productivity is improved, but shape defects such as excessive medium elongation, edge waves, and waviness occur due to sudden temperature changes
Solution Approach 1:
The quenching furnace is divided into multiple heating zones (first heating zone, second heating zone, third heating zone) along the strip travel direction. Each zone has different heating characteristics, allowing gradual temperature increase rather than sudden heating. This segmentation enables both high productivity and prevention of shape defects by controlling the heating rate through zoned temperature distribution.
2Adaptability or versatility
If the steel strip is thinned to 1 mm or less to meet various application requirements, then adaptability is improved, but shape defects are more likely to occur due to the thinning
Solution Approach 1:
Different heating temperatures are applied to different regions of the steel strip through the zoned heating system. The heating temperature varies along the strip width and length, with higher temperatures in certain zones and lower temperatures in others. This local quality approach prevents uniform overheating that causes shape defects in thin strips while still achieving the desired martensitic transformation.
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 method effectively prevents shape defects in martensitic stainless steel strips without reducing productivity, ensuring a favorable shape and desired characteristics while maintaining high production efficiency.
Implementation Method 1
a set heating temperature on an exit side of the steel strip is higher than a set heating temperature on an entry side of the steel strip when the steel strip passes through the temperature raising unit
Implementation Method 2
the holding unit is set to a quenching temperature T (° C.)
Implementation Method 3
a quenching process in which the steel strip is passed through a quenching furnace in a non-oxidizing gas atmosphere and heated and then cooled
Implementation Method 4
a tempering process in which the quenched steel strip is passed through a tempering furnace in a non-oxidizing gas atmosphere and tempered
Data Source
AI summary
In the method of producing a martensitic stainless steel strip, a quenching furnace of a quenching process includes at least a temperature raising unit and a holding unit. When a predetermined quenching temperature is set as T (° C.), the temperature raising unit is set to be within a temperature range of 0.7T (° C.) or higher and lower than T (° C.), and a set heating temperature on an exit side of the steel strip is set to be higher than a set heating temperature on an entry side of the steel strip when the steel strip passes through the temperature raising unit. The holding unit is set to the quenching temperature T (° C.). A time spent in the furnace by the steel strip in the temperature raising unit is equal to or longer than a time spent in the furnace by the steel strip in the holding unit.