Grade 304 Stainless SteelIt is not astounding that grade 304 stainless steel is one of the most popular grades. There are two (or maybe three) obvious reasons for this. Grade 304 was one of the first stainless steel grades developed, it rapidly became the workhorse for the stainless steel industry and consumers, and it retains this pre-eminent position to this day. However it is clearly not just because grade 304 was one of the first grades developed that it continues to dominate the market today. There has been considerable progress over the years, and we now have in addition to a wide range of austenitic grades of which 304 is just one - a wide range of ferritic grades, 200 series grades, Duplex, Superduplex, and Lean Duplex grades. Each of these has specific properties and has been developed for specific applications, or even in an attempt to avoid using expensive alloying elements.
For instance, you can achieve higher strength (thereby reducing weight) and even greater corrosion resistance by opting for a duplex grade. You can opt for a CrNiMo grade (for example grade 316) to achieve greater corrosion resistance where it is necessary – such as in a marine environment, or where a lot of salt is used for de-icing, or where specific chemical processes require a specific type of corrosion resistance to a specific chemical, or acid.
You can also opt for a ferritic grade, or a 200 series (CrMn) grade to reduce the cost of alloying elements, and thereby achieve a much cheaper product, or even decide to move away from stainless steel altogether, and specify galvanized steel, for example. What often becomes apparent quite quickly when adopting this approach, however, is that things can soon start rusting if they are not painted regularly, and very soon may have to be replaced completely. What seemed like a cheap option at first sight, can turn out to be very expensive indeed, or even highly dangerous.
All these “newer” grades serve their purpose, and contribute to making stainless steel a material of choice. But with such a range of grades, one might have anticipated that they would quickly supplant grade 304. Why stick with a grade developed over 100 years ago when there are today so many alternatives available which have been specifically tailored to perform well under specific conditions? One could almost say that today there is a grade for every application.
Nor does grade 304 retain its popularity because it is, generally, a ‘cheap’ option. It contains quite a bit of nickel which, as we all know, can become a very expensive ingredient indeed, especially when a period of restocking follows a period of destocking, when prices therefore start to rise. So, if it is not for historical reasons that grade 304 is so popular, and not because it doesn’t contain “expensive” alloying elements such as nickel, because it does, why does it remain the workhorse of the industry?
The appropriate response is maybe initially that grade 304 contains a very decent amount of chrome (around 18%), and it is, of course, the chrome that makes it so corrosion resistant. Why then add nickel, which just adds to the cost? Because nickel stabilises the austenitic structure, which means that the steel is both tough and ductile. How much nickel should be added? Obviously, the minimum needed to stabilise the austenitic structure – so about 8%. And there we have it – grade 18/8 (18% Cr, 8% Ni) or yes, grade 304. The result is a grade that is highly corrosion resistant in a wide range of applications, has good formability, and good weldability, but doesn’t contain so much nickel as to make it prohibitively expensive, when that amount of nickel is not needed for the particular application.
It is the combination of these properties which clarifies why grade 304 remains one of the most widely used grades. The particular combination of properties means that it is suitable, at a very reasonable cost, for use in the most varied of applications ranging from industry (chemical, pharmaceutical, foodstuffs, beverage, brewing, fermentation), to construction, distribution (counters etc), down to your very own kitchen and cutlery.
The versatility and performance of grade 304 has been proven over many years of use, but it would be wrong to say that it is a “safe bet”, or “I am sure 304 will be fine”. You could say it is a bit like buying a car. You don’t buy an Audi R8, as nice as it sounds, and as fast as it goes, if what you need is a Renault Clio that gets you to the corner shop just as quickly, and at significantly lower cost. But nor do you buy a cheap runabout, which is more than likely to break down halfway to the airport, if you have a plane to catch.
This is why you should always talk to the experts who will suggest the grade you need for your particular application, at the most reasonable cost, and help you avoid making what could be a very costly mistake in the longer term.
With that caveat, stainless grade 304 is the workhorse of the stainless steel industry. It has been so since it was first developed, and looks set to continue being so for the foreseeable future. At K. Seng Seng Industries Sdn Bhd, we always have plenty of grade 304 products in the warehouse which can be slit at short notice into the precise width of strip needed and with the required processing and finish.
BY: Joanne McIntyre
CREDIT: KCI Publishing
ORIGINAL FROM: http://www.stainless-steel-world.net/blogs/308/grade-304-the-workhorse-of-the-stainless-steel-industry.html
Published : 21-Mar-2019