The 4 Types of Stainless Steel

Well known for its versatility and sustainability, stainless steel is a commonly used material, easily recognized and present in many homes and industries. The name “stainless steel” is a broad term, applying to any metal with a minimum of 10.5% chromium content. There are many types of stainless steel, each given a numerical grade and organized under one of four general groups. These grades are based on the steel’s composition, properties, and uses. Familiarity with grade numbers and groups give quick insight into the steel’s makeup and applications.

The four general groups of stainless steel are austenitic, ferritic, duplex, and martensitic.

Austenitic

As the most frequently used type, austenitic stainless steels possess high chromium and nickel content. Their weldability, strength, and corrosion resistance make them a metal used both for household kitchen cutlery and structural components in the aerospace industry. Unlike ferritic types, austenitic stainless steels are not magnetic.

Types of austenitic stainless steel: 316LVM, 330, Biodur108, Nitronic 60.

Ferritic

An often magnetic, low nickel material with good corrosion resistance, ferritic stainless steels are a popular material for indoor applications. They are commonly chosen for their resistance to stress corrosion and cracking, particularly in situations that require contact with other corrosive materials. These uses include cookware and car components. Ferritic stainless steel’s cost effectiveness and decreased malleability differentiate them from austenitic types.

Types of ferritic stainless steel: 430, 430FR.

Duplex

Named for its nearly 50/50 composition of austenitic and ferritic, this hybrid is stronger than either of its alloys of origin. This strength gives duplex stainless steels improved corrosion and cracking resistance. Additionally, due to its high ferritic content, it is magnetic. Duplex stainless steels are relatively weldable and well suited for saltwater corrosive conditions, making them useful for the underwater oil industry.

Types of duplex stainless steel: S31803, S32205.

Martensitic

With a structure similar to ferritic, martensitic stainless steels stand apart with their higher carbon content (1%) and greater hardening capabilities. With their high strength and average resistance to corrosion, martensitic stainless steels have a wide range of uses, ranging from surgical instruments to turbine parts.

Types of martensitic stainless steel: 15-5PH, 17-4PH, 416, 420F, 420 MOD, 455, 465.

Stainless steel is well known and frequently used due to its strength, versatility, and recyclability. The four general categories assist in beginning to outline the many compositions and uses for the material.

Interested in stainless steel? Request a Quote.

For a full list of stainless steel supplied by Vincent Metals, click here.

The Value of Implant Grade Alloys

More body jewelers have seen the value of using implant grade metals, like ASTM F138 316 LVM Stainless Steel, for products that will be worn in or on the body. These alloys are certified to an ASTM "F" specification, which when applied to metals, signifies that the quality of the alloy is acceptable to be used in a medical application. Some of these "F specs" indicate implant grade, while others indicate surgical instrumentation grade. It is important to make sure that the material used is to the implant grade. These grades go through an additional process called "vacuum melting" (the "VM" in 316L-VM) which not only removes impurities, but in the case of stainless steel, allows for a better surface layer on the material. This layer prevents the leeching of elements, like nickel, into the body. Very important for people with nickel allergies.

Is Inconel® 625 the same as Nickel 625?

The answer, not surprisingly, is yes and no. The chemistry, mechanical properties, and range of uses are within the same standards of quality, but Inconel® is a trademark that can only be used by one mill-Special Metals Corporation.

There's still some confusion among buyers, engineers, and machinists when it comes to superalloy grades. Why does the print say Inconel® 600 and the mill test reports refer to it as Nickel 600 or "ATI"® 600? Can one be substituted for the other? The answer to this is a definite yes. ASTM and AMS specifications guide the manufacturing of these high performance alloys. Reputable mills make absolute sure that the material they produce meets these strict standards. What's important in the name is not what comes before the alloy number, but the alloy number itself.

What is the DFARS Specialty Metals Clause?

The Defense Federal Acquisition Regulation Supplement, better known as "DFARS", is an enormous and far-reaching document. As part of the even larger 'Federal Acquisition Regulations' it covers things like how a Department of Defense purchasing contract is written, negotiated, awarded, and paid for. It's an important set of guidelines designed to protect the political interests of the United States. DFARS is aimed at keeping money and quality control in the hands of our friends, and away from threats to US interests.

430FR is the choice metal for solenoids

430FR "Solenoid Quality" stainless steel rod is specifically formulated and treated to be used as the inner shaft of a linear solenoid.

Solenoids are, at heart, simple machines. You can make one yourself using copper wire, a drinking straw, a battery, and any magnetic metal. You can even use an ordinary nail for the shaft (or armature, as it is known). Coil up the wire around the straw, put the nail inside and attach the two loose ends of the wire to a battery. That's it. Watch the nail move in and out of the straw as the electrified wire creates a magnetic field that attracts or repels the shaft.