304/304L Stainless Steel

304 Stainless is a low carbon (0.08% max) version of basic 18-8 also known as 302.

ASTM A213 TP304 Stainless Steel Seamless Tube is manufactured by seamless process used in high pressure environment, stainless steel TP304 grade is the most used material due to its high strength and excellent corrosion resistance.

Type 304 has slightly lower strength than 302 due to its lower carbon content. Type 304 finds extensive use in welding applications because the low carbon permits some exposure in the carbide precipitation range of 800°F - 1500°F without the need for post-annealing operations.

However, the severity of corrosive environments may necessitate annealing after welding or the use of 304L.

Type 304L has a carbon content of 0.03% or less. This alloy can be used in the as-welded condition without becoming susceptible to intergranular corrosion.

304 stainless is a low-carbon (0.08% max) version of basic 18-8, also known as 302. Type 302 has 18% chromium and 8% nickel. Type 304 has a slightly lower strength than 302 due to its lower carbon content. Type 304 is used in welding applications, because the low carbon permits some exposure in the carbide precipitation range of 800° F - 1500° F without the need for post-annealing operations. However, the severity of the corrosive environments may necessitate annealing after welding or the use of 304L. Type 304L has a carbon content of 0.03% or less.

Specifications - Stainless Steel 304/304L

The main constituents of 304 stainless steel - other than iron - are Chromium and Nickel.

Welding Applications and Benefits

The reduced carbon content in type 304 stainless steel makes it particularly suitable for welding applications. In welding, exposure to high temperatures can lead to carbide precipitation, a process where chromium carbides form at the grain boundaries of the steel. This can compromise the material’s corrosion resistance. However, type 304’s low carbon content allows it to tolerate some exposure to the carbide precipitation range, which typically spans from 800° F to 1500° F. This tolerance reduces the need for post-annealing operations, making type 304 a practical choice for many welding tasks.

Nevertheless, the severity of the corrosive environments in which type 304 stainless steel is used may require additional measures to ensure long-term durability. In such cases, post-weld annealing might be necessary to restore the material’s corrosion resistance. Alternatively, type 304L, which has an even lower carbon content of 0.03% or less, may be used. The reduced carbon content in type 304L further minimizes the risk of carbide precipitation and enhances the material’s performance in welding applications.

304 stainless steel is a low-carbon variant of type 302, distinguished by its slightly reduced strength but superior performance in welding applications due to its lower carbon content. While type 304 is generally suitable for most applications, the choice between type 304 and type 304L should be based on specific requirements, including the corrosive nature of the environment and the need for post-weld processing. Understanding these differences helps in selecting the appropriate stainless steel grade for various industrial and construction applications.

Typical Applications

Sanitary Systems

In sanitary systems, stainless steel plays a critical role due to its non-reactive properties and ease of cleaning. These systems are designed to maintain high levels of hygiene and prevent contamination, which is essential in healthcare facilities, laboratories, and food and beverage industries. Stainless steel’s smooth surface prevents the buildup of bacteria and other pathogens, making it ideal for applications such as piping, tanks, and fixtures in environments where cleanliness is paramount. The material’s resistance to rust and staining further ensures the system’s longevity and reliability.

Dairy and Food Processing

The dairy and food processing industries require materials that can handle aggressive cleaning agents and resist corrosion from various food products. Stainless steel is the material of choice for equipment and components used in these industries, including mixing tanks, pipelines, and processing equipment. Its non-porous surface ensures that there are no places for bacteria to hide, making it easier to maintain sanitary conditions. Additionally, stainless steel’s resistance to high temperatures and chemical cleaning agents makes it ideal for use in pasteurization and other processing steps that require stringent hygiene standards.

Heat Exchangers and Evaporators

Heat exchangers and evaporators are essential components in many industrial processes, including chemical manufacturing, HVAC systems, and power generation. Stainless steel is favored in these applications due to its excellent thermal conductivity, resistance to high temperatures, and durability. Heat exchangers, which transfer heat between two or more fluids, benefit from stainless steel’s ability to withstand thermal cycling and pressure changes. Similarly, evaporators, which are used to concentrate solutions by removing water, rely on stainless steel’s resistance to corrosion and scaling, ensuring efficient and reliable operation.

Feedwater Heaters

Feedwater heaters are used in power plants and industrial facilities to preheat water before it enters the steam generation system. Stainless steel is commonly used in these heaters due to its resistance to high temperatures and pressure, as well as its ability to withstand corrosive environments. The material’s durability ensures that feedwater heaters maintain optimal performance over long periods, contributing to the overall efficiency and safety of the steam generation process.

304 contains 18 - 20% Chromium (Cr). Chromium is the essential chemical in all stainless steel and it is that which forms the thin passive layer that makes the metal "stainless"

304 also contains 8-10.5% Nickel (Ni). This is added to make the Austenitic structure more stable at normal temperatures. 

The nickel also improves high-temperature oxidation resistance makes the steel resistant to stress corrosion cracking.

Where the steel is to be stretched formed a lower percentage (8%) of nickel should be selected. If the steel is to be deep drawn a higher percentage is better (9% or more).

In addition a number of other chemicals may be present but these are expressed as maximum permited levels with the exception of the increased quantity of carbon required in 304H - i.e. a minimum of .04% and a maximum of 0.10%

*Maximum carbon content of 0.04% acceptable for drawn tubes

What’s the Difference Between Grade 304 ,304L & 304H Stainless Steel?

There are hundreds of different grades of stainless steel on the market. Each of these unique formulations of stainless steel offer some degree of corrosion resistance above and beyond that of plain steel.

The existence of these stainless steel variants can cause some confusion—especially when the names & formulations of two stainless steel alloys are almost the same. This is the case with grade 304 and 304L stainless steel.

Chemical Composition - Stainless Steel 304/304L

Element Percentage by Weight Maximum Unless Range is Specified
304 304L 304H
Carbon 0.08 0.030 0.04-0.10
Manganese 2.00 2.00 2.00
Phosphorus 0.045 0.045 0.045
Sulfur 0.030 0.030 0.030
Silicon 0.75 0.75 0.75
Chromium 18.00
20.00
18.00
20.00
18.00
20.00
Nickel 8.0
10.50
8.0
12.00
8.0
10.5
Nitrogen 0.10 0.10 0.10
304 Stainless PMI

PMI

304 Stainless PMI

PMI

304 Stainless PMI

PMI

304 Stainless PMI

PMI

304 Stainless PMI

PMI

304 Stainless PMI

PMI

These three alloys are remarkably similar—but there is one key difference. In grade 304 stainless, the maximum carbon content is set at 0.08%, whereas grade 304L stainless steel has a maximum carbon content of 0.03%. The “L” in 304L can be interpreted as meaning extra-low carbon.

This difference of 0.05% carbon content produces a slight, but marked, difference in the performances of the two alloys.

Typical Mechanical Properties-Stainless Steel 304/304L

Grade Tensile Strength Rm N/mm²
Yield Strength Rp 0.2, N/mm² Elongation (%)
304 Annealed 500-700 195 40
304L Annealed 460-680 180 40

Physical Properties

Data Metric English
Density 8 g/cc 0.289 lb/in³

Mechanical Properties

Hardness, Brinell 123 123 Converted from Rockwell B hardness.
Hardness, Knoop 138 138 Converted from Rockwell B hardness.
Hardness, Rockwell B 70 70  
Hardness, Vickers 129 129 Converted from Rockwell B hardness.
Tensile Strength, Ultimate 505 MPa 73200 psi  
Tensile Strength, Yield 215 MPa 31200 psi at 0.2% offset
Elongation at Break 70 % 70 % in 50 mm
Modulus of Elasticity 193 - 200 GPa 28000 - 29000 ksi  
Poissons Ratio 0.29 0.29  
Charpy Impact 325 J 240 ft-lb  
Shear Modulus 86 GPa 12500 ksi  

Electrical Properties

Electrical Resistivity 7.2e-005 ohm-cm 7.2e-005 ohm-cm at 20°C (68°F); 1.16E-04 at 650°C (1200°F)
Magnetic Permeability 1.008 1.008 at RT

The Mechanical Difference

Grade 304L has a slight, but noticeable, reduction in key mechanical performance characteristics compared to the “standard” grade 304 stainless steel alloy.

Typical specifications for 304 Plate and 304L Stainless Steel Plate are ASTM A-240, ASME SA -240 and A666.

304 stainless steel,also known as 18/8 stainless steel, European norm 1.4301, is the most common stainless steel. The steel contains both chromium (usually 18%) and nickel (usually 8%) metals as the main non-iron constituents. It is an austenite steel. It is not very electrically or thermally conductive, and is non-magnetic. It has a higher corrosion resistance than regular steel and is widely used because of the ease in which it is formed into various shapes.

Grade 304L is the low carbon version of 304. It does not require post-weld annealing and so is extensively used in heavy gauge components.

Thermal Properties

Design Features - Stainless Steel 304/304L

Typical Applications - Stainless Steel 304/304L

Tensile Requirements - Stainless Steel 304/304L

304 Stainless Steel Plate has very good formability and can be readily welded by all common methods.

Our precision machinery and state of the art facilities enables us to produce these 304 tube shield in superior quality and precise dimensions. All these years have enhanced our capabilities and enabled us to produce all kinds of standard tube shield as well as custom snap rings as per customer’s specifications. We have numerous combinations of sizes readily available in large number of stocks and can fabricate custom sizes according to customer’s requirement.

In common with other austenitic stainless steels, 304 grade has strong work hardening characteristics. Clearly, in some cases, this can be an advantage, but generally, it is an issue to be considered carefully.

If it is likely to be an issue, discussion with the producer can be valuable as minor variations to the precise composition and process can have benefits.

Where heavy sections have to we welded, post-weld annealing may be necessary to restore corrosion resistance.

The cross-sectional shape of boiler tube erosion shields is mostly semi-circular (180 degrees), and there are also 120-160 degrees. It is mainly used on finned tubes (water-cooled walls); boiler tubes erosion shields are divided into direct wear-resistant shields, in-curve anti-wear shields, outer-curve anti-wear shields, side-curve anti-wear shields, s-curve anti-wear shields, etc. The length of the straight anti-wear shields ranges from 20mm to 3000mm, and the general length of 1000-2000mm is commonly used. The anti-wear shields with bends generally requires a processing, drawing and the following parameters should be on the drawing: outer diameter of the pipe used, bending of the pipe radius r (to the centre of the pipe), the degree of bending angle, and the length of the straight sections on both sides of the arc segment of the wear-resistant shields.

The most basic parameter of boiler tube erosion shields is the outer diameter of the tube used (that is, the inner diameter of boiler tubes erosion shields). The main specifications of the tube are: 32, 38, 42, 44.5, 48, 51, 57, 60, 63.5 , 76, 89mm, etc .; the inner diameter of the boiler tubes erosion shields is usually 1-3mm larger than the outer diameter of the tube used, depending on the actual requirements.

Alloy 304 a T-300 series stainless steel austenitic, which has a minimum of 18% chromium and 8% nickel. Type 304 has a maximum carbon of 0.07% . It is the standard “18/8 stainless” that is commonly found in pans and cooking tools. Alloy 304 is the most versatile and widely used alloy in the stainless steel family. Ideal for a wide variety of home and commercial applications, Alloy 304 exhibits excellent corrosion resistance and has a high ease of fabrication, outstanding formability. The austenitic stainless steels are also considered to be the most weldable of the high-alloy steels and can be welded by all fusion and resistance welding processes.

Specifications: UNS S30400

Each alloy represents an excellent combination of corrosion resistance and fabricability. This combination of properties is the reason for the extensive use of these alloys which represent nearly one half of the total U.S. stainless steel production. The 18-8 stainless steels, principally Alloys 304, 304L, and 304H, are available in a wide range of product forms including sheet, strip, and plate. The alloys are covered by a variety of specifications and codes relating to, or regulating, construction or use of equipment manufactured from these alloys for specific conditions. Food and beverage, sanitary, cryogenic, and pressure-containing applications are examples.

Alloy 304 is the standard alloy since AOD technology has made lower carbon levels more easily attainable and economical. Alloy 304L is used for welded products which might be exposed to conditions which could cause intergranular corrosion in service.

Alloy 304H is a modification of Alloy 304 in which the carbon content is controlled to a range of 0.04-0.10 to provide improved high temperature strength to parts exposed to temperatures above 800°F.

For example, the ultimate tensile strength (UTS) of 304L is roughly 85 ksi (~586 MPa), less than the UTS of standard grade 304 stainless, which is 90 ksi (~620 MPa). The difference in yield strength is slightly greater, with 304 SS having a 0.2% yield strength of 42 ksi (~289 MPa) and 304L having a 0.2% yield strength of 35 ksi (~241 MPa).

This means that if you had two steel wire baskets and both baskets had the exact same design, wire thickness, and construction, the basket made from 304L would be structurally weaker than the standard 304 basket.

Why Would You Want to Use 304L, Then?

So, if 304L is weaker than standard 304 stainless steel, why would anyone want to use it?

The answer is that the 304L alloy’s lower carbon content helps minimize/eliminate carbide precipitation during the welding process. This allows 304L stainless steel to be used in the “as-welded” state, even in severe corrosive environments.

If you were to use standard 304 stainless in the same way, it would degrade much faster at the weld joints.

Basically, using 304L eliminates the need to anneal weld joints prior to using the completed metal form—saving time and effort.

In practice, both 304 and 304L can be used for many of the same applications. The differences are often minor enough that one isn’t considered massively more useful over the other. When stronger corrosion resistance is needed, other alloys, such as grade 316 stainless steel, are usually considered as an alternative.

ASTM A213 / ASME SA213

ASTM A213 / ASME SA213 is a America specification for stainless steel boiler, super heater, heat exchanger tubes, executed by most world stainless steel seamless tubes mills and factories, minimum wall thickness required in A213 seamless tube, or average wall thickness as customers requirement, tight tolerance of outside and wall thickness stated as A213 standard or A1016

Related 304/304L Stainless Steel

【H】 Ceramic lined pipe

Ceramic lined pipe is made through self-propagating high-temperature synthesis (SHS) technique.

【H】 Cast basalt lined steel pipe

Cast basalt lined steel pipe is composed by lined with cast basalt pipe, outside steel pipe and cement mortar filling between the two layers.

【H】 Ceramic Tile Lined Pipes

Ceramic tile lined pipes have very uniform coating of specially formulated ceramic material that is affixed to the inner of the pipe.

【H】 Rare earth alloy wear-resistant pipe

The material of the rare earth alloy wear-resistant pipe is ZG40CrMnMoNiSiRe, which is also the grade of rare earth alloy steel.

【H】 Tubes Erosion Shields

Tubes Erosion Shields are used to protect boiler tubing from the highly erosive effects of high temperatures and pressures thereby greatly extending tube life.

【H】 ASTM A213 T91 Alloy Tube

The ASTM A213 T91 seamless tubes are primarily used for boiler, superheater, and heat-exchanger.