303 vs 304 Stainless Steel, What is The Difference

As its name suggests, Stainless steel has a considerable ability to resist stain. It has many types; this article introduces the “Stainless steel 304 and 303” types; they are the most used forms of stainless steel, used for bushings, screws, nuts, etc.

These two types come under the ferritic series of metals. Ferritic stainless steel is ordinarily containing a high level of nickel, chromium, and non-magnetic. What makes them distinguished is their resistance to corrosion and formability, unlike the other metals and series.

They made Both 303 and 304 of iron. 303 and 304 formulation is almost the same. But how do 303 and 304differ from each other? How to decide which one to choose? In this post, you will find answers for whatever you are thinking about, related to Stainless steel 304 and 303, of course.

Table of Contents

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What is Stainless Steel 303?

The type of 303 represents the best performance in machinability, compared with the other austenitic stainless-steel types. It is mainly used when manufacturing contains huge machining in the machines of the automatic screw. Machinability Rate (compared to B1212) is about 78%.

303 has the availability as a ‘Ugima” Enhanced Machinability level. With higher machinability than standard 303.

What lower 303 corrosion resistance than 304 is the addition of sulfur. It is accountable for the enhanced galling and machining features of grade 303. About other austenitic levels, what gives 303 superb toughness is the structure, despite in 303, the sulfur lessens its toughness somewhat.

Level 303Se (UNS S30323) does not have sulfur addition but selenium, increasing the cold and hot creation features more than 303 and delivering a milder machined surface terminate. The rate of machinability is gently decreased. Level 303Se is not easily accessible in Australia.

What is Stainless Steel 304?

Level 304 is a model “18\8” stainless. It’s the most commonly used and most flexible stainless steel exists, although the availability of a considerable number of substitutes; and has excellent welding and forming features.

The even-handed austenite form of level 304 allows it to be strictly deep pulled without medium annealing. This implies that this steel level predominates in creating drawn stainless components such as saucepans, hollow-ware, and sinks. It’s usual to use particular “304DDQ” variants for these applications.

Level 304 can be easily crushed or roll-formed into a diversity of elements for applications in the architectural, transportation, and industrial fields. It also has excellent welding features. When welding thin parts, it does not require post-weld annealing.

Level 304L, the 304 low carbon version, does not need pre-weld annealing and is hence widely used in large gauge components (more than 6mm). With its more extensive carbon content, Level 304H has used applications at high temperatures. Also, the austenitic form provides outstanding toughness to these levels. The austenitic structure also gives these grades excellent toughness, even down to cryogenic temperatures, even in very down to cryonic temperatures.

303 vs 304 Stainless Steel, What Are The Differences?

303 is always used for cases that mainly need smooth cutting and extreme surface finish. It contains selenium, making it easy to cut; on the other hand, 304 is flexible stainless steel, that it does not include selenium. It is commonly used for producing well extensive performance (Moldability and corrosion resistance) material and machine parts.

Let speak in detail about the difference between 303 and 304, from 4 points: alloy composition, mechanical properties, typical applications, and cost.

Alloy Comparison

Typical compositional ranges for grade 303 and 304 stainless sheets of steel are given in this table:

Element	Stainless Steel 303	Stainless Steel 304
Carbon (C), %	Max 0.15	Max 0.08
Chromium (Cr), %	17.0~19.0	18.0~20.0
Selenium, %	/	Min 17.0
Manganese (Mn), %	Max 2.0	Max 2.0
Silicon (Si), %	Max 1.0	Max 0.75
Phosphorus (P), %	Max 0.2	Max 0.045
Sulphur (S), %	Min 0.15	Max 0.03
Nickel (Ni), %	8.0~10.0	8.0~10.5
Nitrogen (N), %	Min 0.1	Max 0.1
Iron (Fe), %	Balance	Balance

Mechanical Properties

There are some light differences between the two types of stainless steel 303 Vs 304, these mechanical properties are represented in: MACHINABILITY, WELDABILITY, DURABILITY.

Machinability Comparison

The essential elements when using stainless steel in applications are weldability, heat treatment, and Machinability.

Besides the fact that it is a free-cutting material, Level 303 has the best Machinability of all the austenitic stainless steel. And the most crucial part is that 303 is unweldable.

Meanwhile, level 3o4 far away from being a free-cutting material, and it doesn’t deal with heat treatment, which makes it less ideal for machining use. Yet, type 304 stainless steel is somewhat weldable.

Weldability Comparison

Grade 304 has huge weldability by all model fusion ways. With filler metals or without. AS 1554.6 pre-qualifies soldering of 304 with level 308 and 304L with 308L electrodes or rods (and with their sever silicon tantamounts). Heavy soldered segments in class 304 may need pre-solder annealing for the most significant corrosion resistance. This is not needed for level 304L. Level 321 may be used as a substitute 304 if a massive section soldering is required, and pre-solder heat handling is impossible.

In contrast, in general, 303 is not recommended, but if inevitable and can bear lower strength, use 309 or 308L electrodes. As soldering of 303 is not pre-qualified by 1554.6. Solders have to be annealed for the most significant amount of resistance of corrosion.

Durability Comparison

In general, stainless steel naturally resistant to corrosion. Yet, type 303 has an altered composition to rise machinability. So, compared with level 304, type 303 is weakened to the resistance of corrosion.

Type 304 stainless steel possesses excellent corrosion resistance and toughness but is subject to pitting in warm chloride-based atmospheres.

Applications Comparison

Users think that 304 is a grade for food since they used most of it for equipment packaging. Others believe that 304 is used for general purposes, let’s see the real applications.

Level 303 stainless is usually used for elements that demand to be heavily machined, making it ideal for small, intricate pieces. Regular applications include:

Aircraft gears and fittings
Bushings
Electrical components
Screws, bolts, and nuts
Shafts

Level 304 stainless steel, because of its aesthetic and superior corrosion resistance, is usually found in applications such as:

Components of aerospace
Components of architecture
Piping
Packaging
Food processing
Automotive parts
Chemical containers
Heat exchangers
Construction materials
Liquid or food processing equipment
Kitchen appliances, utensils, and surfaces

Cost Composition

Costs can creep up rapidly, based on project requirements and the form of properties you’re seeking. Buying 303 stainless will conventionally cost you a bit more than type 304; however, costs keep changing based on the market, regularly.

The best way to handle these changes is to deal with an OEM trader who can help you decide whether your particular project needs a more expensive alloy.

F.A.Q

Here, you will find the most common questions, that may come to your mind, when thinking about the differences between the two grades of stainless steel, 303 and 304. Follow up.

303 vs 304, Which is easier to machine?

After a journey of researching, it came up with the answer; there is no significant difference between the two grades, but 304 may have higher rust resistance. 303 has extra sulfur to make it easy to machine. So, 304 is less machinable than 303, while 303 has higher corrosion resistance, and weldable. That’s because of the reduction of corrosion resistance because of the sulfur in 303.

303 vs 304, which is cheaper?

As mentioned above, in the 'COST COMPOSITIN' point, 304 is a little cheaper than 303. The increased machinability will be the reason for the increased cost, you can decide which one to choose when dealing with an OEM, who can help you to decide if your project demands the 303 or 304, then you will save your money and your business too.

303 vs 304, which is harder?

Surface shine and finish aren't the same things in turned surfaces, and 304 produces an excellent finish; that's not the reason behind its shiny look, but because its tough to cut; besides, the shine is more because of the burnishing of the surface. Here, we come to the answer that 304 is harder than 303.

303 vs 304. Which has better corrosion resistance?

303 has a lower corrosion resistance than the 304. Like all austenitic steels, in nature, 304 is non-magnetic, and it also offers low electrical and heating conductivity. It also is distinguished by its higher resistance of corrosion than other stainless-steel grades.

303 vs 304. Which one is better?

Here we come, to answer the question you have been waiting for, all the time, '' Which alloy I have to choose?'' To the answer directly, to be honest, there is nothing called this is better than that; the real answer depends on the requirements of your project. Both 303 and 304 have their applications. 303 grade is better for manufacturing bolts, nuts, bushings, etc., while 304 grade is better for applications where cleanliness and aesthetics are essential.

Summary

Through this article, I believe you have a certain understanding of the difference between 303 and 304, if this article useful to you, please share to more people, that is my honor, thanks!

Besides, DEK offers premium quality CNC machining services for both stainless steel 303 and 304, our pricing is favorable, and lead time as short as 1-3 days. If you need to machining any parts, do not hesitate to contact us today.