Pros And Cons Of Different Stainless Steel Types

Industrial & Manufacturing Blog

Introduction

  • The different types of stainless steels are delineated by their predominant structural components. Structural component refers to the physical way atoms are arranged with respect to one another. This arrangement specifies the phase present.
  • In this article, the advantages and disadvantages of each type of stainless steel are described. When relevant, the types are compared to each other.
  • Ferritic, austenitic, and duplex stainless steels will be described in detail.
  • Martensitic and precipitation hardening stainless steels will be described in less depth.

Ferritic

  • They are composed mostly of the ferrite phase. These stainless steels have high strengths and moderate corrosion resistance. They typically contain 12.5 or 17% chromium, a few percent molybdenum, and low to no nickel content.
  • The high strength is a consequence of the ferrite phase. An advantage of this type of stainless steel compared to others is high resistance to stress corrosion cracking (SCC) caused by chlorides. 
  • They are particularly susceptible to intergranular corrosion cracking (IGC), and all of these steels become brittle at low temperatures. These steels generally have low toughness, which restricts their use to thin components such as sheet or tubular products.

Austenitic

  • Most widely used stainless steels, they are composed mostly of the austenite phase. These steels offer moderate strength but high corrosion resistance. Chromium contents range from 16% to 26%, the most common grades containing around 18%. Nickel added to these steels, at a minimum of about 8%, improves corrosion resistance and stabilizes the austenite phase.
  • Compared to the ferrite phase, austenite improves toughness, and removes low temperature brittleness.  Molybdenum is also often added to improve pitting and crevice corrosion resistance.
  • These steels are slightly weaker, and more immune to chloride-induced SCC than ferritic.

Duplex

  • A hybrid of ferritic and austenitic stainless steels, they've recently came into greater usage. Typical compositions are 22-25% Cr, 5% Ni and in many cases a few percent of molybdenum.
  • The high strength of ferrite and high corrosion resistance of austenite are combined to resist against the harshest environments in these types.
  • Hydrogen-induced SCC and susceptibility to IGC in the higher alloyed grades are cons of this type.  Duplex alloys are slightly more expensive than austenitic, however, cost savings can be achieved in pressure vessels or tubing because the added strength allows less material to be required for them.

Martensitic

  • This type of steel has very high strength but low corrosion resistance. The strongest phase of steel, martensite, confers the strength to this type. 
  • Lower corrosion resistance than the preceding three types.

Precipitation hardening

  • Similar to martensitic steels, precipitation hardening steels are used for their high strength. They are processed in a way to induce precipitate phases to form.
  • Strength can be tuned from around that of martensitic steels to above them, depending on processing conditions. Similarly depending on processing, these steels can have either low corrosion resistance or high corrosion resistance approaching that of austenite.
  • More expense must be incurred to impart higher strength and corrosion resistance. (For more information, you can contact C & R Pipe Steel)

Share

30 April 2015

Planning a Construction Project Without all the Stress

Planning a large construction project can be stressful as the project leader. As a consultant for large construction companies, I see project planners buckle under pressure all the time – usually because the right support systems and resources are not put into place. It takes more than a good plan to pull together an effective and stress-free construction project. Finding the right service providers, laborers, and plan developers is just as important. This blog was designed to provide those in the construction world with tips and tricks for getting a job done in a straight forward and profitable manner. From project supply ideas to support service options, hopefully you can find some answers to your pressing questions here.