Types Of Steel And Their Properties: A Working Guide

Most guides stop at four types and skip weathering steel entirely. It’s a smaller category, but if you’re specifying anything exposed to weather without ongoing maintenance, it’s worth knowing about.

Carbon Steel

Iron and carbon, with carbon content usually between 0.2% and 2.1%, is what defines its hardness and strength. Low carbon (under 0.3%) is malleable, good for car bodies and structural components. Medium carbon (0.3-0.6%) steps up strength for machinery parts. High carbon (0.6-1.4%) is hard and wear-resistant, the grade behind cutting tools, blades and springs. It’s the cheapest and most versatile option here, but it corrodes without protection, so expect coatings or alloying on anything exposed.

Stainless Steel

Add a minimum 10.5% chromium and you get a passive oxide layer that resists corrosion, which is why stainless shows up everywhere from kitchen benches to marine hardware. Common grades include 304 (general-purpose, most widely used), 316 (better corrosion resistance, the one you want near saltwater), 409 and 430 (ferritic grades, magnetic, used in automotive trim and household appliances). Austenitic grades like 304 and 316 are non-magnetic and handle food-processing and marine environments well; ferritic grades trade some corrosion resistance for cost.

Alloy Steel

Carbon steel plus deliberately added elements, chromium, manganese, nickel, molybdenum, to push specific properties higher: hardness, tensile strength, wear resistance, or performance at temperature. Grades like 4130, 4140, 4340 and 8620 balance strength, toughness and machinability differently depending on what they’re alloyed with, which is why aerospace and heavy machinery manufacturers specify by grade number rather than just “alloy steel.”

Tool Steel

A type of alloy steel loaded with carbon (up to 2%) plus tungsten, molybdenum or vanadium, built to hold a sharp edge and resist deformation under the heat and stress of cutting, drilling and forming operations. If a component needs to stay hard and dimensionally stable while doing damage to something else, it’s probably tool steel.

Weathering Steel (Or Corten Steel)

Small amounts of copper, chromium, nickel and phosphorus let this steel form a stable, rust-coloured protective layer on exposure to weather, instead of corroding through. No painting, no coating, and the maintenance bill drops accordingly. That’s why you see it on bridges, building facades and outdoor sculpture, it’s not just an aesthetic choice, the rust layer is doing structural protection work.

Each type earns its place for a reason, not as a generic upgrade over the last one. If you’re not sure which grade your project actually needs, that’s exactly the kind of question worth asking before you order rather than after. Browse our range of products or get in touch and we’ll help you land on the right specification, including where a structural beam grade differs from a decorative or corrosion-critical one.

The diverse types of steel boast unique properties and applications, each contributing to the foundation of modern infrastructure and technology. At Australian Steel Traders, we can supply you with all types of steel for any application – whether it be for construction or beyond. Get in touch with us today, or browse our range of products online.