Protective Coating for Steel in Hot Rolling Oxidation
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Solution Overview
Problem
The conventional hot-rolling process of steel results in significant oxide scale formation due to severe oxidation during reheating, leading to productivity losses and surface quality issues, despite existing protective coatings that only partially address this problem.
Innovation Solution
A protective coating comprising high melting point inorganic materials, such as zirconium silicate and silicon carbide, combined with silicates like kaolin, applied as a slurry and sintered at high temperatures to form a dense, pore-free film that prevents oxide scale formation on steel surfaces during hot working.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional hot-rolling process is used with reheating furnace, then steel can be processed and rolled, but thick oxide scale forms on the steel surface due to severe oxidation atmosphere and high temperature
Solution Approach 1:
The protective coating is applied to the steel surface before reheating to prevent oxide scale formation during the heating process. The coating acts as a barrier that blocks oxygen from reaching the steel surface, thereby preventing oxidation before it can occur during the conventional hot-rolling process.
Solution Approach 2:
The protective coating serves as an intermediary layer between the steel surface and the oxidizing atmosphere in the reheating furnace. This intermediate layer prevents direct contact between oxygen and the steel, thereby eliminating the harmful oxidation reaction while allowing the steel to be heated to the required temperature for rolling.
2Object-generated harmful factors
If protective coating is applied to prevent oxidation, then oxide scale formation is reduced, but the coating composition must withstand high temperatures and long holding times
Solution Approach 1:
The protective coating is formulated as a composite material containing multiple inorganic components including alumina, silica, magnesia, and zirconia in specific proportions. This composite composition provides high-temperature stability, oxidation resistance, and structural integrity throughout the reheating process at 1250°C for 2-6 hours, ensuring the coating remains effective and does not degrade under severe thermal conditions.
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 solution effectively reduces oxide scale formation by 80% in laboratory and pilot furnace tests, improving steel surface quality and productivity by maintaining a protective film on the steel surface for extended periods at high temperatures.
Implementation Method 1
a thick oxidation scale (potentially several mm thick) will be formed on the billet surface... a protective coating providing a temporary protection to the metals from oxidation during long heat treatment schedule
Implementation Method 2
a Chinese Patent CN102584258 (258) describes a high temperature protective coating that can protect the steel billet in a reheating furnace at a temperature of from 1250° C. to 1500° C. for from 2 hours to 6 hours
Data Source
AI summary
The present invention is drawn to a protective coating composition for a metallic substrate and a ceramic film coating layer formed thereon.