Identify type 304 stainless steel for reasons of rust

Introduction: Type 304 stainless steel is a versatile stainless steel that is widely used to make equipment and components that require good overall performance (corrosion resistance and formability). So how do we identify Type 304 stainless steel, and what are its causes of rust?

Type 304 stainless steel is a common material in stainless steel, with a density of 7.93 g/cm3, also known as 18/8 stainless steel in the industry. High temperature 800 degrees, with good processing performance, high toughness characteristics, widely used in industrial and furniture decoration industry and food and medical industries.

The common marking methods in the market are 06Cr19Ni10, SUS304, of which 06Cr19Ni10 generally represents the national standard production, 304 generally represents the production of the ASTM standard, and SUS 304 represents the standard production of the Japanese standard.

304 is a versatile stainless steel that is widely used to make equipment and parts that require good overall performance (corrosion resistance and formability). In order to maintain the inherent corrosion resistance of stainless steel, steel must contain more than 18% of chromium, more than 8% of the nickel content. 304 stainless steel is a grade of stainless steel produced according to American ASTM standards.

Identify 4 types of 304 stainless steel common methods:

1, identify the amount of nickel with stainless steel syrup, see the authenticity. Can only look at the amount of nickel, is a very simple way to save time and effort to save money.

2, using the EDM spectrometer to identify, this accuracy is greater than the syrup, but the required experience is relatively high.

3, radiological direct reading, this accuracy is high, but the cost of the equipment is too high, there is a long-term bulk cargo out of the proposed equipment.

4. The laboratory test of the sampling block is the most accurate, the price is high or low, but it is time-consuming and it will also destroy a little raw material.

The rusting phenomenon of Type 304 stainless steel material may be due to the following reasons:

1, chloride ion

Chloride ions are widely present, such as salt/sweat/water/sea breeze/soil. Stainless steel in the presence of chloride ions, corrosion, and even faster than ordinary low-carbon steel. Therefore, the use environment of stainless steel is required, and it needs to be wiped regularly to remove dust and keep it clean and dry. (This would give him an “improper use.”) In the United States, there is an example: An enterprise uses an oak container to hold a solution containing chloride ions. The container has been in use for nearly 100 years. It was planned to be replaced in the 1990s. Due to the lack of modern oak material, the container leaked due to corrosion after 16 days of stainless steel replacement.

2, solution treatment

Alloying elements do not dissolve into the matrix, resulting in low matrix alloy content and poor corrosion resistance.

3, intergranular corrosion

This titanium- and tantalum-free material has a tendency to intergranular corrosion. Addition of titanium and niobium, together with a stable treatment, can reduce intergranular corrosion. A high-alloy steel that resists corrosion in air or in chemically corrosive media. Stainless steel has an aesthetically pleasing surface and good corrosion resistance. It does not require surface treatment such as plating, and it exerts the inherent surface properties of stainless steel. A type of steel, usually called stainless steel. Representative performance of 13 chrome steel, 18-8 chromium nickel steel and other high alloy steel. From the metallographic point of view, since the stainless steel contains chromium and forms a thin chromium film on the surface, this film separates and invades oxygen from the steel and acts as a corrosion resistance. In order to maintain the inherent corrosion resistance of stainless steel, steel must contain more than 12% chromium. Used for welding occasions. The lower carbon content minimizes the precipitation of carbides in the heat-affected zone near the weld, and the precipitation of carbides may result in intergranular corrosion of the stainless steel in some environments (weld erosion).