Martensitic stainless steels are not as widely consumed as the likes of ferritic and austenitic grades, yet this has more to do with the far-reaching commerciality of the latter types as opposed to some limitation in the former. In fact, martensitic steels like QT800 stainless are among the most useful engineering materials on the planet.
In this blog post, Masteel explores the properties, characteristics, and applications of QT800 stainless steel in greater depth.
History of QT800 and Martensitic Steels
Early development of in-oxidizable steel alloys found that the anti-corrosive properties of many stainless grades were impacted by heat treatment. Martensitic steels were subsequently developed to provide a group of alloys that could be hardened by heat-treatment without limiting the metal’s corrosion resistant properties. The unique body-centered cubic structure of martensite was first observed in the early 20th Century and was first approved for U.S. patents as a material for corrosion-resistant gun barrels.
The main alloying composition of martensitic stainless grades is chromium (Cr), with negligible volumes of nickel (Ni) and varying levels of carbon (C). QT800 contains as much as 17% chromium by weight and as little as 2% nickel, which is generally introduced as a stabilizing element with little impact on the end product’s mechanical properties. This explains the excellent corrosion-resistant properties of the alloy, but the strengthening and hardening capabilities are largely a result of QT800’s carbon content.
QT800 is available in low- to high-carbon steel formats, which are offered in the quenched and tempered condition to promote high hardness and tensile strength. This results in a mix of excellent wear- and corrosion-resistant properties, at the expense of toughness and weldability. Other martensitic steels aim to improve these characteristics via the introduction of additional nickel, but this reduces the characteristic strength and hardness of QT800.
When to Use QT800?
QT800 has one of the best intersections of strength, hardness, and corrosion-resistant behavior. It is inherently resistant to oxidizing agents and acids and boasts an ultimate tensile strength (UTS) upwards of 800MPa. This makes it one of the most broadly applicable martensitic stainless steel grades on the market. It is uniquely suited for manufacturing engineering parts such as pumps and valves, piston rods, fittings, nuts and bolts, gears, actuators and more. With exceptional suitability for a broad range of applications, QT800 is increasingly applied in areas as varied as:
- Shipbuilding;
- Marine infrastructure and fascia;
- Medical devices and tools;
- Commercial goods;
- Aviation and aerospace.
QT800 Stainless from Masteel
Masteel is one of the UK’s leading suppliers of stainless steels like QT800, with a secure global supply chain stemming from the highest quality steel mills in Europe. If you would like to learn more about stainless steel subfamilies, read our previous blog post: What is Martensitic Stainless Steel? Otherwise, contact us directly with any questions.