Stainless steel comes in many different grades. Each grade brings its own unique chemical composition, tensile strength, and other characteristics. Let’s take a look at two of the most popular grades of stainless steel — 430 and 304.
What is stainless steel?
Like other forms of steel, stainless steel is an alloy of iron and carbon. What distinguishes stainless steel is the addition of chromium. To be considered stainless steel, the alloy must contain at least 10% chromium by weight. The chromium gives stainless steel its non-corrosive characteristics, which help lengthen the metal’s lifespan.
Stainless Steel Spec Sheet
Carbon steel typically gets used for infrastructure, automobiles, and weapons. Stainless steel, by contrast, generally forms medical tools and food or beverage equipment. It tends to be brighter and more attractive than carbon steel.
What do the different grades of steel signify?
The steel industry classifies metals by grades in order to ensure the consistency and quality that precise steel processing requires. A steel’s grade is determined by all the factors that make that steel unique.
| Item | 304 | 430 |
| Corrosion resistance | Excellent, although other alloys may be used ifresistance is needed for very salty conditions | Excellent, although other alloys may be usedin very acidic or very salty conditions |
| Magnetic | NO | Yes |
| Weldable | High weldability | Limited weldability |
| Hardens during cold-working | Yes | NO |
| Formability / Ductility | Very formable | Less formable |
| Machinable (when annealed) | Fairly machinable | Very machinable |
| High temperature resistance | High | High |
| Maximum intermittent service temp | 850°C | 850°C |
Steel standards organizations determine how to classify each grade of steel. Because there are several standards organizations around the world, the same grade of steel may be classified differently across national boundaries. Grades 304 and 430 are American Iron and Steel Institute (AISI) standards.
What is 430 stainless steel?
Type 430 stainless steel is a mild, corrosion-resistant metal that can be easily bent, stretched, or drawn.
It features the following chemical composition:
- Iron = Balance
- Carbon < 0.12%
- Chromium = 16-18%
- Nickel < 0.75%
- Manganese < 1.0%
- Silicon < 1.0%
- Phosphorus < 0.040%
- Sulfur < 0.30%
Its relatively high carbon content and lack of stabilizing elements make this grade difficult to weld.
Type 430 stainless steel has a minimum yield strength of 30 ksi and a minimum tensile strength of 65 ksi. Most commonly, type 430 stainless steel is used in cosmetic applications that require more aesthetic appeal than strength.
What is 304 stainless steel?
Type 304 stainless steel is the most widely used of all stainless steel grades. It generally appears in kitchen equipment and industrial applications.
This grade of stainless steel features the following chemical composition:
- Iron = Balance
- Carbon = 0.0 – 0.07%
- Chromium = 17.50 – 19.50%
- Manganese = 0.0 – 2.0%
- Silicon = 0.0 – 1.0%
- Phosphorous = 0.0 – 0.05%
- Sulphur = 0.0 – 0.03%
- Nickel = 8.0 – 10.5%
- Nitrogen = 0.0 – 0.11%
Type 304 can be welded to plain carbon steel using TIG or MIG welding. This grade of stainless steel has a minimum yield strength of 30 ksi and a minimum tensile strength of 75 ksi.
This stainless steel grade is routinely stocked in various formats, including: 304 stainless steel sheet, 304 stainless steel plate, 304 stainless steel tube, and 304 stainless steel bar.
What is 304 stainless steel sheet?
304 stainless steel sheet is a commonly used grade of stainless steel that belongs to the austenitic family of stainless steels. It is also known as 18/8 stainless steel because it contains approximately 18% chromium and 8% nickel by weight. The alloy composition of 304 stainless steel provides excellent corrosion resistance, high durability, and good formability.
Here are some key features and properties of 304 stainless steel sheet:
- Corrosion resistance: 304 stainless steel exhibits excellent resistance to corrosion in various environments, including atmospheric conditions and mild chemical environments. It is particularly resistant to oxidation and corrosion by most organic and inorganic acids.
- Strength and durability: While not as strong as some other stainless steel grades like 316, 304 stainless steel still offers good tensile strength and durability. It maintains its strength and integrity even at elevated temperatures.
- Formability and weldability: 304 stainless steel is highly formable, allowing it to be easily fabricated into different shapes and structures. It can be cold worked, bent, or rolled without significantly affecting its mechanical properties. It is also readily weldable using common welding techniques.
- Hygienic and food-grade suitability: Due to its corrosion resistance and easy cleaning properties, 304 stainless steel is widely used in applications where hygiene and cleanliness are important, such as in food processing equipment, kitchen appliances, and medical devices.
- Appearance and finish: 304 stainless steel has a bright, reflective surface finish, often referred to as a “brushed” or “mill” finish. It provides an attractive aesthetic appearance and can be further polished or coated for specific applications.
304 stainless steel sheet finds diverse applications in various industries, including:
- Construction: Roofing, cladding, architectural trim, and decorative applications.
- Kitchenware and appliances: Sinks, countertops, utensils, and appliances.
- Food processing: Equipment, storage tanks, and piping systems.
- Automotive: Trim, exhaust systems, and components.
- Chemical processing: Tanks, valves, and fittings.
- Medical and pharmaceutical: Surgical instruments, implants, and laboratory equipment.
It’s important to note that 304 stainless steel is not suitable for applications involving exposure to highly corrosive environments or high temperatures, where higher-grade stainless steels like 316 or 321 may be more appropriate.
Are 340 and 430 stainless steel ferritic, austenitic, or martensitic?
Stainless steel can be classified into three common categories — austenitic, ferritic, and martensitic.
Austenitic steel is the most common. It has a relatively high chromium content, making it especially corrosion-resistant and non-magnetic (although it may become magnetic after cold working).
Ferritic metals are the second most common category. These steels are less expensive than austenitic steels due to their lower nickel content. They are magnetic and can be hardened through cold working.
Martensitic stainless steel is the least common category of stainless steel. Although it is the hardest and most durable kind of stainless steel, martensitic metals are the least corrosion-resistant. Martensitic stainless steels are increasingly found in the automotive industry.
Type 430 stainless steel is ferritic while type 340 stainless steel is austenitic.
Is 430 or 304 grade stainless steel rust proof?
All grades of stainless steel resist corrosion, but grade 304 is particularly rustproof because of its high nickel content. This addition to the alloy makes grade 304 considerably more expensive than grade 430 stainless steel, however.
In general, grade 430 works best for budget-conscious buyers while grade 304 serves buyers with an eye for the long term.
Is 304 or 430 grade stainless steel magnetic?
Austenitic stainless steels are not magnetic. Since grade 304 stainless steel is austenitic, it is not magnetic.
Ferritic stainless steel grades are magnetic. Thus, grade 430 is magnetic. Most kitchen knives are made from the 400 grades of stainless steel, which is why they can be stored on a magnetic strip.
What is the hardness of 430 and 304 stainless steel?
Stainless steel’s hardness is measured by the Brinell Hardness Number (BHN). The BHN is a measure of an alloy’s ability to resist permanent indentation.
Grade 430 stainless steel’s BHN is 183, and grade 304 stainless steel’s BHN is 201. The higher the BHN, the harder the alloy.
Is grade 304 or grade 430 stainless steel better?
Each grade of stainless steel brings its own benefits and drawbacks. In general, grade 304 stainless steel offers more corrosion resistance than grade 430 because of its higher nickel content. The nickel also makes grade 304 easier to draw or press. That same element, however, also raises the price of grade 304 steel.
Put simply, grade 304 offers higher malleability and greater longevity, and grade 430 offers a less expensive steel option.
430 vs 304 stainless steel
- Corrosion Resistance
- Grade 430 stainless steel provides resistance to corrosion because it contains chromium like all other stainless steel grades.
- Grade 304 stainless steel offers exceptionally strong corrosion resistance due to the addition of nickel to the alloy.
- Popularity
- Grade 430 stainless steel is the second most widely used of all stainless steel grades.
- Grade 304 stainless steel is the most widely used of all stainless steel grades.
- Workability
- Grade 430 stainless steel can easily be bent, stretched, or drawn but is difficult to weld.
- Grade 304 stainless steel is easy to weld, press, and stretch. It offers good weldability.
- Magnetism
- Grade 430 stainless steel is magnetic.
- Grade 304 stainless steel is not magnetic.
- Food grade stainless steel
- Grade 304 stainless steel is also known as food-grade stainless steel because it is often used to create the hygienic surfaces needed in the food and beverage industry.
Grades 430 and 304 are the two most common grades of stainless steel. Both offer a durable iron alloy that can resist rust and corrosion. Typically, however, grade 304 provides more corrosion resistance and thus greater longevity than grade 430, which is a more budget-friendly option.
To find out which grade of stainless steel may be right for your project, contact Kloeckner today.
A GUIDE TO WELDING STAINLESS STEEL
The welding of stainless steel is substantially different from welding other materials. The difference begins with the unique chemical composition of stainless steel.
What is stainless steel?
Like other steels, stainless steel is an alloy of iron and carbon. What makes stainless steel different, though, is its inclusion of at least 10.5% chromium, an element that makes the resulting alloy corrosion resistant. Kloeckner Metals supplies stainless steel in various formats, including stainless steel sheet, stainless steel plate, stainless steel tube, and stainless steel bar.
Stainless steel comes in five types, but just three of these typically show up in fabrication shops — austenitic stainless steel, martensitic stainless steel, and ferritic stainless steel. The most common is austenitic. Martensitic stainless steel goes in hard-facing applications. And ferritic steel, the cheapest option, gets used most in consumer products.
Each of these types of steel is categorized based on its microstructure, which influences its ductility and strength. The microstructure of steel depends on its chemical composition. For example, austenitic steel contains 16-26% chromium (Cr) and 8-22% nickel (Ni). Martensitic steel has a Cr content in the range 11-28%. Ferritic steel runs 12-18% Cr. As a result, the material welded to each type of steel must match that steel’s composition.
Can you weld stainless steel?
In short, yes. However, welding stainless steel is more complicated than carbon steel welding.
First, stainless steel effectively retains heat causing it to warp when exposed to the high temperatures that welding creates. Stainless steel can also warp or crack during the cooling process after it has been heated by a welder. Even when a piece of stainless steel doesn’t crack or warp after a bad welding session, it will nearly always show scratches and blemishes.
Each kind of stainless steel presents a distinct challenge to welders. Austenitic steel may crack if given a high heat input or if you make a concave or flat weld. Martensitic steel can crack if not properly preheated. And with its low maximum interpass temperature of 300, ferritic steel will lose strength unless it’s heated with a low heat input.
The key to successfully welding stainless steel lies in getting the right filler material. The filler material grade needs to match the base material’s grade to get a good weld.
Materials and equipment you need to weld stainless steel
Why does stainless steel welding require specialized equipment, and what are the must-have tools and materials for welding stainless steel?
Stainless steel can be stick welded, shielded metal arc welded (MIG), or gas tungsten arc welded (TIG). The best choice depends on what you’re trying to accomplish since each process yields a different outcome.
You can weld stainless steel with a stick, but you probably shouldn’t. Other, better options are out there.
A MIG welding machine creates the most solid, reliable welds with stainless steel. It’s an especially good choice if you are welding something thick. TIG welding machines can be the right option for thinner materials and for welds that require beauty and precision. Still, TIG is a tough weld unless you have the experience and the time to do it properly. An inexperienced TIG welder can leave unfortunate marks or blemishes on stainless steel.
Although producing a less fine weld, a MIG machine is generally your best option for welding stainless steel. Choose a machine that comes with a welding gun and a sample welding wire. Most machines have a gun, but you can upgrade yours if you’re looking for something that will produce a more precise weld. You’ll also want to pick up some welding gun tips to replace yours when they wear out.
To protect your welding gun, you can purchase a liner. This is a great add-on because it allows you to switch between different types of metal wire quickly and efficiently. You don’t need a welding wire feeder unless you are a professional welder or you plan on doing a lot of welding. As for the wire itself, you must use the appropriate stainless steel welding wire, which is usually .030 inches in diameter but .035-inch to .045-inch wire could be right for thicker pieces.
Since you need to check the temperature when welding stainless steel to avoid performance problems, you’ll want to have a temperature-tracking device on hand. You can go with a traditional stick, but remember that it’s range is limited. Other options include electronic infrared thermometer and an electronic surface temperature probe.
You’ll also need a shielding gas. Inert gasses are not recommended, so you probably want a mixture of 7.5% argon, 90% helium, and 2.5% carbon dioxide. Finally, you will need to add a brush for metal scraping and cleaning. This tool can help you prepare your workspace and ultimately help you achieve a more durable weld.
Preparing to weld
What are the things to take care of when preparing to weld? How does it differ for the various types of steel?
Use your metal brush to eliminate any dust, dirt, oil, grease, or water from your workstation. You can also help prevent warping and cracking by clamping a piece of brass or copper behind your welding seam. This trick can help absorb heat and keep your stainless steel cool enough.
Keep a separate set of tools for welding stainless steel. Once your tools touch carbon steel, they will get carbon residue on them. That residue will transfer to stainless steel during a weld, and it can cause the product to rust eventually.
Other tips to take into account while welding stainless steel
How can you ensure best results when actually welding?
- If TIG welding, go with a DCEN or DC electrode negative setting and a current with a ratio of 1 amp for every 1/1000-inch thickness of the metal.
- If MIG welding, use the push technique. This approach lets you see what you are doing more clearly and produces less beading. Only use the pull technique when you need deeper penetration.
- Hold your welding gun at a 90-degree angle with a travel angle of 5 -15 degrees. For T-joints and lap joints, try a greater angle of about 45-70 degrees.
- Keep your work area clean, safe, and well ventilated.
Although welding stainless steel is a little more complicated than other welds, it can be done. You can even weld stainless steel to mild steel. Using the right equipment, managing your temperature, and getting the right filler material can produce a strong, durable weld.
Can I weld stainless steel?
It is possible to weld stainless steel with the correct tools and procedure, although it can be tricky. You need to be careful because it can get bent or cracked when it gets too hot. Even if it doesn’t crack, it can end up with scratches and marks. Keep the following in mind when welding stainless steel:
- Different types of stainless steel need different welding techniques.
- MIG and TIG welders are the best machines for welding stainless steel.
- MIG is good for thicker pieces, while TIG is better for thinner ones.
- You need a welding gun, wire, and temperature-checking device for welding.
In short, we recommend leaving welding stainless steel to the experts.
