Rustiness colors are a unique phenomenon that occurs on the surface of stainless steel after it has been heated or oxidized. This is not just an aesthetic effect, but an important indicator that reflects the temperature regime and the quality of heat treatment of the alloy. Let us consider in more detail how the colors of rustiness appear, their effect on steel properties and control methods.
What are the colors of victory?
Fluid colors are interference shades formed on metal due to the reflection of light from thin layers of oxide films. These films are formed when the metal is heated, and their thickness and density depend on temperature, heating time and alloy composition. Different colors indicate different processing temperatures:
- Light yellow — this color usually appears at relatively low steel heating temperatures (about 200—250°C). It occurs due to the formation of very thin oxide layers that reflect light poorly.
- orange — when the temperature rises to about 250—300°C, thicker oxide films begin to form on the steel surface, which leads to an orange tint. This color is due to an increase in the thickness of the oxide layer and a change in its optical properties.
- Red-brown — a further increase in temperature to 300—400°C causes the formation of even thicker oxide layers. The reddish-brown hue is due to an increase in the intensity of light reflection from these layers.
- Purple — at a temperature of about 400—500°C, the oxide layers become even thicker, which leads to the appearance of a purple tint on the surface of the material. This is due to changes in the optical properties of oxide layers and their ability to reflect light of certain wavelengths.
- Blue — The thickest and densest oxide layers form at temperatures above 500°C. The maximum reflection of light from such layers creates a deep blue shade of strength.
Resistance colors are used to estimate the heating temperature of stainless steel and quality control heat treatment of metal products.
How are the colors of vanity formed?
The main reason for the appearance of rustiness colors is the oxidation of the stainless steel surface. When heated, the metal reacts with oxygen, resulting in the formation of oxide films. Their thickness directly depends on the temperature and time of exposure, as well as on environmental conditions. The thicker the film, the more intense its ability to reflect light and produce bright colors.
At high temperatures, oxidation increases. Therefore, in order to avoid unnecessary changes in the properties of steel, it is important to carefully monitor the heat treatment process.
How does temperature affect the properties of an alloy?
The colors of strength are not only a visual indicator, but also an important factor affecting the performance characteristics of steel. For corrosion-resistant steels, resistance may indicate damage to the protective layer — places prone to corrosion. However, a decrease in weather resistance is not all the consequences of failure:
- Decrease in strength and reliability. Stainless steel products that have undergone significant changes due to rustiness colors may lose their strength and become less reliable. This is especially important for structures operating under load.
- Change of appearance. The appearance of rubbish colors affects the appearance of the product, which may be undesirable in some cases. For example, for decorative elements, this may be categorically unacceptable.
- Deterioration of functional characteristics. Changes in steel properties may impair the functional characteristics of products. For example, a decrease in thermal conductivity has a negative effect on the operation of heat exchangers.
At low temperatures, oxide films are thin and almost transparent, and do not lead to a noticeable change in the color of the metal surface. This allows us to determine that the properties of the alloy have hardly changed after heat treatment. However, as the temperature rises, the oxide films become thicker and denser, reflecting more light and creating bright bright colors, which indicates significant changes in the performance characteristics of the material. Therefore, it is important to control the process of heating and cooling steel in order to minimize undesirable changes in its properties.
How do you control and prevent the appearance of flowers?
To avoid the undesirable appearance of rustiness colors, it is important to follow the basic rules for processing stainless steel:
- Controlled heating and cooling. It is necessary to strictly control the process of heating and cooling steel to avoid excessive oxidation and the formation of rustiness colors. This can be done by precisely controlling the temperature and heating time.
- Use of protective coatings. The application of protective coatings to the steel surface prevents its oxidation and the appearance of rustiness colors. Various materials, such as varnishes or enamels, can be used as such coatings.
- Compliance with technological processes. When manufacturing and operating stainless steel products, strict adherence to technological processes helps to minimize the risk of rustiness and preserve the properties of steel.
However, it is necessary not only to follow the rules of heat treatment stainless steel, but also throughout the entire heating and cooling process, control the appearance of rustiness colors on the product:
- Visual inspection. Regular inspection of the surface of stainless steel products reveals the appearance of rustiness colors in the early stages. This is the simplest and most affordable method of control that does not require special equipment.
- Using spectrophotometers. These devices make it possible to accurately measure the color characteristics of the surface and determine the presence of coating colors, which is useful for controlling surface quality during production.
- Temperature control. The use of thermometers and pyrometers helps control the heating temperature of steel, which helps prevent excessive oxidation and the formation of rust colors.
These methods not only prevent undesirable changes, but also ensure the high quality of the finished products.
Where to buy high-quality stainless steels?
You can buy at the PZPS cold rolled strip:
Our company also sells precision alloys with various characteristics: with specified elastic properties and a thermal coefficient of linear expansion, hard and magnetically soft materials, steels with high electrical resistance, and much more. The PZPS also provides a number of production services — from accurately determining the chemical composition of the customer's materials to developing our own alloys and steels. Contact usto get advice and place an order.
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