説明

304 / 304L / 304H Stainless Steel Pipe

Stainless steel pipes are widely used in various industries, among which 304/304L/304H stainless steel pipes are the three most common types. They have similar chemical compositions, but their respective characteristics are slightly different. 304/304L/304H stainless steel pipes have been widely used in industries such as petroleum, chemical, and construction due to their excellent corrosion resistance and mechanical properties.304 stainless steel is a common material in stainless steel, with a density of 7.93 g/cm3. As a widely used steel, it has good corrosion resistance, heat resistance, low-temperature strength, and mechanical properties; Good hot workability for stamping, bending, and other processes, with no heat treatment hardening phenomenon (operating temperature -196 degree to 800 degree ). Corrosion resistant in the atmosphere. If it is an industrial atmosphere or heavily polluted area, timely cleaning is necessary to avoid corrosion. Suitable for food processing, storage, and transportation. Has good processing performance and weldability. Plate heat exchangers, corrugated pipes, household items (Category 1 and 2 tableware, cabinets, indoor pipelines, water heaters, boilers, bathtubs), automotive accessories (windshield wipers, silencers, molded products), medical equipment, building materials, chemicals, food industry, agriculture, ship components, mobile phones, etc. 304 stainless steel is a nationally recognized food grade stainless steel.

1, Chemical composition and physical properties

The chemical composition of 304, 304L, and 304H stainless steel pipes is mainly austenitic stainless steel, containing 18% chromium and 8% nickel. However, the carbon content of 304L stainless steel pipe is lower, while the carbon content of 304H stainless steel pipe is higher. This difference gives them different corrosion resistance and strength in specific environments. 304 stainless steel pipes have good comprehensive performance and are suitable for most environments; The low-carbon characteristics of 304L stainless steel pipes reduce the precipitation of carbides during welding, thereby reducing sensitization phenomena; 304H stainless steel pipes have better creep resistance in high-temperature environments due to their high carbon content.

2, Application field

304/304L/304H stainless steel pipes have been widely used in many industries. For example, in the petroleum and chemical industries, they are used to manufacture equipment such as pipelines and towers; In the construction industry, they are used as structural components, curtain walls, and decorative materials for high-rise buildings; In the food industry, they are used to manufacture food processing equipment and pipelines. According to statistics, 304 stainless steel pipes account for approximately 60% of the global market share in the stainless steel pipe market. This data indicates that 304/304L/304H stainless steel pipes dominate the stainless steel pipe market.

3,Advantages and disadvantages

304/304L/304H stainless steel pipes have excellent corrosion resistance and mechanical properties, but they also have their limitations. For example, in a chloride ion environment, they may experience pitting corrosion. In addition, although 304H stainless steel pipes have good creep resistance in high temperature environments, their toughness is relatively poor in low temperature environments. The selection of appropriate stainless steel pipes should be based on the specific application environment and requirements. In some cases, other types of stainless steel pipes may have advantages over 304/304L/304H stainless steel pipes.

Some product standards for 304, 304L, and 304H stainless steel:

1. ASTM A276 (Standard Specification for Stainless Steel Bars, Bars, and Shapes)

304 C Mn P S Si Cr Ni

Requirement,% {{0}}.08 2.00 0.045 0.030 1.00 18.0-20.0 8.0-11.0

2. ASTM A240 (Chromium and Chromium Nickel Stainless Steel Plate, Sheet, and Strip for Pressure Essentials and General Applications)

304 C Mn P S Si Cr Ni N

Requirement,% 0.07 2.00 0.045 0.030 0.075 17.5-19.5 8.0-10.5 0.10

3. JIS G4305 (Cold rolled stainless steel plate, sheet and strip)

SUS 304 C Mn P S Si Cr Ni

Requirement,% 0.08 2.00 0.045 0.030 1.00 18.0-20.0 8.0-10.5

4. JIS G4303 (Stainless Steel Bars)

SUS 304 C Mn P S Si Cr Ni

Requirement,% 0.08 2.00 0.045 0.030 1.00 18.0-20.0 8.0-10.5

Table 1: 304 / 304L / 304H Chemical composition% & Mechanical properties

	C		P	S		N
304	0.08	2.00	0.045	0.030	0.75	0.10
304L	0.030	2.00	0.045	0.030	0.75	0.10
304H		2.00	0.045	0.030	0.75

Table 2:Mechanical properties

			50mm elongation %


304	Greater than or equal to 515	Greater than or equal to 205	Greater than or equal to 40	Greater than or equal to 201	Greater than or equal to 92
304L	Greater than or equal to 485	Greater than or equal to 170	Greater than or equal to 40	Greater than or equal to 201	Greater than or equal to 92
304H	Greater than or equal to 515	Greater than or equal to 205	Greater than or equal to 40	Greater than or equal to 201	Greater than or equal to 92
Explanation: The yield strength is 0.2%

From Table 1, it can be seen that 304L indeed meets the requirements of 304 and is better than 304, as if it can automatically replace 304. However, from the mechanical properties in Table 2, it can be seen that the strength of 304 is higher than that of 304L. When designing according to 304, using 304L instead will result in insufficient strength; In addition, the pressure vessel standard GB150-1998 in China stipulates that when the operating temperature of austenitic stainless steel is higher than 525 degree , the carbon content in the steel should not be less than 0.04%. From Table 1, it can be seen that most departments in 304 can use it, but 304L cannot be used. Therefore, the view that 304L can replace 304 is incorrect. Whether it can be used depends on the usage situation, and according to the regulations, we do not have the right to carry out "material substitution". Only the original design department has the right to carry out "material substitution" work.

In general, 304L has better resistance to grain boundary corrosion, but both 304 and 304L are not resistant to media containing chloride ions.

The main difference between 304 and 304L is the different nickel content

304 (8 nickel)

304L (9 nickel)

The back strip "L" is called ultra-low carbon stainless steel, mainly due to different carbon content.

304 corresponds to domestic 0Cr18Ni9,

304L for domestic 00Cr19Ni10

The main difference between 304 and 304L is their carbon content. 304 is a general model, while those with L belong to low-carbon models, which have better welding performance.