Hot-Rolled Duplex Stainless Steel Without Solution Heat Treatment
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Solution Overview
Problem
The existing production processes for hot rolled duplex stainless steel materials and clad steel plates require solution heat treatment, which degrades toughness and corrosion resistance, and are energy-intensive, making them costly and environmentally inefficient.
Innovation Solution
Adjusting the chemical composition and hot working conditions to control chromium nitride precipitation, eliminating the need for solution heat treatment, while maintaining strength and corrosion resistance by optimizing the chromium nitride precipitation temperature range during hot rolling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solution heat treatment is carried out to solid-solubilize precipitates, then corrosion resistance is improved, but energy consumption increases and production cost increases
Solution Approach 1:
The invention performs preliminary action by controlling the chemical composition and hot working conditions during the hot rolling process itself to prevent chromium nitride precipitation. By adding specific alloying elements (Ti, Nb, V) and controlling the hot rolling temperature to be below the chromium nitride precipitation temperature, the material achieves the desired microstructure without requiring subsequent solution heat treatment, thereby eliminating the energy-consuming post-processing step while maintaining corrosion resistance.
Solution Approach 2:
The invention applies parameter changes by modifying the chemical composition parameters (adding Ti, Nb, V elements) and hot working parameters (controlling temperature and deformation conditions) to shift the chromium nitride precipitation temperature above the hot rolling temperature range. This parameter optimization allows the material to avoid precipitation during processing, eliminating the need for solution heat treatment and reducing energy consumption.
2Reliability
If solution heat treatment is carried out to solid-solubilize precipitates, then corrosion resistance is improved, but toughness degrades
Solution Approach 1:
The invention performs preliminary action by controlling the chemical composition and hot working conditions during the hot rolling process itself to prevent chromium nitride precipitation. By adding specific alloying elements (Ti, Nb, V) and controlling the hot rolling temperature to be below the chromium nitride precipitation temperature, the material achieves the desired microstructure without requiring subsequent solution heat treatment, thereby eliminating the energy-consuming post-processing step while maintaining corrosion resistance.
Solution Approach 2:
The invention converts the potentially harmful effect of chromium nitride precipitation into a beneficial outcome by using the precipitation mechanism itself to achieve the desired microstructure. By controlling hot working conditions to induce controlled precipitation of chromium nitrides while preventing excessive or harmful precipitation, the material achieves both corrosion resistance and toughness without requiring aggressive solution heat treatment that would degrade toughness.
3Strength
If chromium nitrides are precipitated to strengthen the material, then strength is improved, but corrosion resistance degrades due to chromium-depleted layer
Solution Approach 1:
The invention applies parameter changes by modifying the chemical composition parameters (adding Ti, Nb, V elements) and hot working parameters (controlling temperature and deformation conditions) to shift the chromium nitride precipitation temperature above the hot rolling temperature range. This parameter optimization allows the material to avoid precipitation during processing, eliminating the need for solution heat treatment and reducing energy consumption.
Solution Approach 2:
The invention uses intermediary elements (Ti, Nb, V) that act as mediators to control the precipitation behavior of chromium nitrides. These elements form their own nitrides or carbides preferentially, or modify the precipitation kinetics of chromium nitrides, thereby preventing excessive chromium depletion in the matrix while still achieving the desired strengthening effect. This intermediary action allows the material to maintain both strength and corrosion resistance.
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 alloying element-saving hot rolled duplex stainless steel materials and clad steel plates achieve higher strength, improved toughness, and excellent corrosion resistance without solution heat treatment, reducing energy consumption and production costs.
Implementation Method 1
chromium nitrides are precipitates generated by the combination of Cr and N, and, in the duplex stainless steel, cubic CrN or hexagonal Cr 2 N is frequently precipitated in ferrite grains or ferrite grain boundaries
Implementation Method 2
a solution heat treatment was carried out at a temperature of 1000°C or higher so as to solid-solubilize the precipitates
Data Source
AI summary
The present invention relates to an alloying element-saving hot rolled duplex stainless steel material containing, by mass%: C: 0.03% or less; Si: 0.05% to 1.0%; Mn: 0.5% to 7.0%; P: 0.05% or less; S: 0.010% or less; Ni: 0.1% to 5.0%; Cr: 18.0% to 25.0%; N: 0.05% to 0.30%; and Al: 0.001% to 0.05%, and further comprising one or more selected from: V: 0.05% to 0.5%; Nb: 0.01% to 0.20%; and Ti: 0.003% to 0.05%, with a remainder being Fe and inevitable impurities, wherein the alloying element-saving hot rolled duplex stainless steel material is produced by hot rolling, a chromium nitride precipitation temperature TN2, which is a second index regarding precipitation of chromium nitrides during the hot rolling, is in a range of 960°C or lower, a yield strength is 50 MPa or more higher than that of a hot rolled steel material which is subjected to a solution heat treatment, and the alloying element-saving hot rolled duplex stainless steel material is as hot rolled state, and is not subjected to a solution heat treatment.