Grades And Types Of Stainless Steel For Piping

Stainless steel is a cost effective, low-maintenance metal used in civil and mechanical engineering projects Australia wide. Stainless steel is particularly popular for pipe fittings because it is resistant to oxidation and has no effect on other metals. Stainless steel has applications everywhere from shipping, oil and gas, water treatment facilities, energy industries, to the textile machinery.

Stainless steel is an umbrella term for a family of corrosion resistant alloy steels containing 10.5% or more chromium. Stainless steel has a chromium-rich oxide film on the surface, which makes it resistant to corrosive attack, and although stainless steel is relatively thin and lightweight, it is highly protective and strong, with a tensile strength ranging from about 621 MPa to 1300 MPa.

As a result, stainless steel is the material of choice for durable long-life span pipes and pipe fittings. There are five basic grades of stainless steel that you will frequently come across.

Grades and Basic Types

Stainless steel can include other elements besides chromium, such as nickel, molybdenum, titanium and niobium, giving rise to a wide range of different steel types and grades. The grade of stainless steel refers to its quality, durability and temperature resistance. The most common grades are 304 and 316, characterised by their different levels of corrosion resistance in saline and chloride exposed environments, as well as differing levels of heat tolerance. Stainless steel can be further divided into five basic categories:

Austenitic

18% chromium content and 8% nickel. Excellent corrosion resistance, excellent weldability, excellent in high and low temperatures, hardened by cold.

Ferritic

Varying chromium content between 12 and 18% and a low carbon content. Moderate to good corrosion resistance, hardened by heat. Poor weldability.

Duplex

High chromium (18 to 28%), moderate nickel (between 4.5 and 8%) and in many cases molybdenum (2.5 to 4%). High resistance to stress and corrosion, increased resistance to chloride iron, high tensile and yield strength, good weldability.

Martensitic

Relatively high carbon of 0.1 to 1.2% and chromium of 12 to 18%. Moderate corrosion resistance can be hardened for high strength. Poor weldability.

Precipitation Hardening

Formulated so they can be supplied in a solution treated condition. Characterised by corrosion resistant properties, high strength and weldability.

Pipes and Fittings

Following the above, selecting stainless steel piping and fittings by grade and category is the next step. Pipes and fittings are chosen through the careful review of their purpose and environment, including any chemicals they may come into contact with.

Stainless Steel Tubing for Resistance to Corrosion

Austenitic and martensitic stainless steels are frequently employed when corrosion is the biggest hurdle. Austenitic steel, with its high quotient of chromium and nickel, is especially resilient.

Pressure Pipes

High pressure pipes require alloy-elements to resist stress and high temperatures. Piping made from solid chromium or chromium and nickel alloys is common, particularly in seamless, welded and electric fusion combinations.. Use of press fitting connections has revolutionised stainless steel installation, saving time, specialised labour, welding gas, hot work permits etc.

Hydraulic Line Tubing

Used for fuel lines and hydraulic systems, hydraulic line tubing is typically smaller in diameter than other tube types. Austenitic steel types are ideal for their strength and corrosion resistance.

Stainless Steel Sanitary Tubing

As the name suggests, sanitary tubing is designed to maintain sanitary standards. Depending on your requirements, sanitary tubing can be austenitic or ferritic, and is defined by being non-porous and easy to clean, suitable for pharmaceuticals, food and beverage, and drinking water applications.

Mechanical Tubing

Mechanical tubing is typically martensitic, composed of high carbon and chromium ratios that can be hardened for strength.

Speak to the Experts

Union Steel Industry supplies a comprehensive range of stainless steel pipes and fittings. We have 35 years of experience across a wide variety of technical industries across China. We promise fast, dependable, cost-effective solutions to suit your specifications. Browse online our stainless steel piping and fittings or contact us today for assistance.