What’s the difference between 304, 304H and 304L?

Actually, according to the content of chromium and nickel, 304 stainless steel is made up of 18% chromium (Cr) and 8% nickel (Ni), but the main difference is the carbon content.

Chemicals (%) of 304, 304L and 304H

Grade C Mn Si P S Cr Mo Ni N
304 min.
max.

0.08

2.0

0.75

0.045

0.030
18.0
20.0
8.0
10.5

0.10
304L min.
max.

0.030

2.0

0.75

0.045

0.030
18.0
20.0
8.0
12.0

0.10
304H min.
max.
0.04
0.10

2.0

0.75
-0.045
0.030
18.0
20.0
8.0
10.5

What’s the difference between 304, 304H and 304L?

304L is ultra-low carbon stainless steel, the carbon content is reduced to less than 0.03%, which can avoid intergranular corrosion, and theoretically the effect of stress corrosion resistance is stronger than 304, but the effect is not obvious in practical applications. The purpose of reducing carbon and adding titanium is the same, but the 321 smelting cost of adding titanium is higher, the steel is thicker, and the price is more expensive.
H in 304H refers to high temperature, high carbon content is the guarantee of high temperature strength. GB150 requires austenitic steel to be used at 525 ° C or more, carbon content is not less than 0.04%, carbide is strengthening phase, especially high temperature strength. Better than pure austenite.
Among the three, the highest carbon content is 304H, and the lowest carbon content is 304L, while the 304 stainless steel has a carbon content between the two. The higher the carbon content, the worse the corrosion resistance of stainless steel and the easier it is to rust. The difference in carbon content also causes the price to vary, or the different requirements for that sentence.

The two main variants of grade 304 are the low carbon form 304L and the high carbon form 304H.
304L has a maximum of 0.30% carbon. This reduces the tendency for carbide precipitation when welding. Carbide precipitation can result in intergranular corrosion.
304H has between 0.04 and 0.1% carbon. This gives it greater strength at high temperature but does make it more vulnerable to carbide precipitation when welding.
Since 304 has as having a maximum of 0.08% carbon, there are potential overlaps in the specifications which means that it is not uncommon to find dual specification. 
304L clearly has less than 0.08% carbon and can, therefore, be described as 304/304L.
304 may have up to 0.08% carbon so if its carbon content is between 0.04 and 0.08% carbon it can be described as 304/304H.
Mechanical properties of 304, 304L, 304H
304304L 304H mechanical performance table - What's the difference between 304, 304H and 304L?

In addition, from these two lists can be judged, the view that 304L can be used instead of 304 is wrong, can be used in connection with the use of the occasion, and according to the regulations, we have no right to carry out “material substitution”, only the original design department Only then can you have the right to work on “material substitution”, so please remember to remember.

Common Applications of 304, 304L and 304H Stainless Steel

  • Architectural Moldings & Trim
  • Kitchen Equipment (sinks, saucepans)
  • Plumbing Materials
  • Textile, Paper, Pharmaceutical & Chemical Industry Processing Equipment
  • Back Splashes

Common stainless steel grades and performance

  1. 304 stainless steel. It is one of the austenitic stainless steels with a large application volume and the widest range of applications. It is suitable for the manufacture of deep-drawn parts and acid pipelines, containers, structural parts, various instrument bodies, etc. It can also manufacture non-magnetic and cryogenic equipment and component.
  2. 304L stainless steel. In order to solve the ultra-low carbon austenitic stainless steel developed by the precipitation of Cr23C6 which causes the 304 stainless steel to have severe intergranular corrosion under some conditions, the sensitized state has better resistance to intergranular corrosion than 304 stainless steel. In addition to the lower strength, other properties are the same as 321 stainless steel, mainly used for corrosion-resistant equipment and components that need to be solution treated after welding, and can be used to manufacture various types of instrument bodies.
  3. 304H stainless steel. The internal branch of 304 stainless steel has a carbon mass fraction of 0.04%~0.10%, and the high temperature performance is better than 304 stainless steel.
  4. 316 stainless steel. Adding molybdenum to the 10Cr18Ni12 steel makes the steel have good resistance to reducing medium and pitting resistance. Corrosion resistance is superior to 304 stainless steel in seawater and various other media, mainly used for pitting resistant materials.
  5. 316L stainless steel. Ultra-low carbon steel with good resistance to sensitized intergranular corrosion, suitable for the manufacture of welded parts and equipment of thick section size, such as corrosion resistant materials in petrochemical equipment.
  6. 316H stainless steel. The internal branch of 316 stainless steel has a carbon mass fraction of 0.04%~0.10%, and the high temperature performance is better than 316 stainless steel.
  7. 317 stainless steel. Pitting and creep resistance is superior to 316L stainless steel for the manufacture of petrochemical and organic acid resistant equipment.
  8. 321 stainless steel. Titanium-stabilized austenitic stainless steel, added titanium to improve intergranular corrosion resistance, and has good high temperature mechanical properties, can be replaced by ultra-low carbon austenitic stainless steel. Except for special occasions such as high temperature or hydrogen corrosion resistance, it is not recommended for general use.
  9. 347 stainless steel. Stabilized austenitic stainless steel, added yttrium to improve resistance to intergranular corrosion, corrosion resistance in corrosive media such as acid, alkali, salt, etc. Same as 321 stainless steel, good welding performance, can be used as corrosion resistant material and resistant Used in hot steel, mainly used in thermal power and petrochemical fields, such as making containers, pipes, heat exchangers, shafts, furnace tubes in industrial furnaces, and furnace tube thermometers.
  10. 904L stainless steel. Super complete austenitic stainless steel, a super austenitic stainless steel invented by OUTOKUMPU, Finland, with a nickel mass fraction of 24% to 26%, a carbon mass fraction of less than 0.02%, and excellent corrosion resistance. It has good corrosion resistance in non-oxidizing acids such as sulfuric acid, acetic acid, formic acid and phosphoric acid, and has good resistance to crevice corrosion and stress corrosion. It is suitable for various concentrations of sulfuric acid below 70 °C. It is resistant to corrosion in acetic acid and mixed acid of formic acid and acetic acid at any concentration and at any temperature under normal pressure. The original standard ASMESB-625 is classified as a nickel-based alloy, and the new standard classifies it as stainless steel. China only has the similar grade 015Cr19Ni26Mo5Cu2 steel. The key materials of a few European instrument manufacturers use 904L stainless steel. For example, the measuring tube of E+H mass flow meter uses 904L stainless steel, and the watch case of Rolex watch also adopts 904L stainless steel.
  11. 440C stainless steel. Martensitic stainless steel, the hardest in hardenable stainless steel and stainless steel, the hardness is HRC57. Mainly used for making nozzles, bearings, valve spools, valve seats, sleeves, valve stems, etc.
  12. 17-4PH stainless steel. Martensitic precipitation hardening stainless steel with hardness HRC44, high strength, hardness and corrosion resistance, can not be used for temperatures above 300 °C. It has good corrosion resistance to the atmosphere and diluted acid or salt. Its corrosion resistance is the same as that of 304 stainless steel and 430 stainless steel. It is used to manufacture offshore platforms, turbine blades, valve spools, seats, sleeves and valve stems.

Source: China Pipe Fittings Manufacturer – Yaang Pipe Industry Co., Limited (www.steeljrv.com)

(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)

If you want to have more information about the article or you want to share your opinion with us, contact us at sales@steeljrv.com

References:

  • https://www.yaang.com

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what s the difference between 304 304h and 304l - What's the difference between 304, 304H and 304L?
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What's the difference between 304, 304H and 304L?
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Among the three, the highest carbon content is 304H, and the lowest carbon content is 304L, while the 304 stainless steel has a carbon content between the two. The higher the carbon content, the worse the corrosion resistance of stainless steel and the easier it is to rust. The difference in carbon content also causes the price to vary, or the different requirements for that sentence.
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