Materials & Properties

Mild Steel

Black mild steel is steel direct from a hot rolling forming process, which still has a scale coating on its surface, is not precise in its dimensions, nor straightness or flatness. It is used for general non-critical work, especially where welding is performed. Black Mild steel has a dark blue oily surface and is not as accurate as bright mild steel because bright steel undergoes additional processes to produce higher quality material. Mild steel is reasonably soft and ductile. It is easily cut and machined and is a good material to practice welding on. The reason for this is its carbon content, which varies between 0.15% and 0.3%. Some of the uses of Mild Steel are Ship Hulls, Garden Gates, Girders, General Structural Steel, etc. 

Bright Steel

The term Mild Steel applies to all low carbon steel that does not contain any alloying elements in its makeup and has a carbon content that does not exceed 0.25%. Bright mild steel bar is usually a carbon steel alloy which has had the surface condition improved by drawing, peeling or grinding over the hot rolled finish supplied by the steel mill. Mild Steel is used in mechanical engineering applications for parts that will not be subject to high stress. Compared to normal Mild Steel, bright Mild Steel provides tighter sectional tolerances, increased straightness, and a much cleaner surface. The main advantage of cold drawn Steel is that Steel can be brought closer to the finished machine size, providing reduce machining costs. Another benefit of bright Steel bars is a marked increase in physical strength over hot rolled bars of the same section. 

Stainless Steel

Stainless Steels is also classed as an Alloy Steel. The main alloying elements are Nickel and Chromium. It has a very high resistance to corrosion and as a result is ideal for areas where clenliness is important. Resistance to corrosion and staining, low maintenance, and familiar luster make stainless steel an ideal material for many applications where both the strength of steel and corrosion resistance are required. Moreover, stainless steel can be rolled into sheets, plates, bars, wire, and tubing. These can be used in cookware, cutlery, surgical instruments, major appliances, vehicles, construction material in large buildings, industrial equipment (e.g., in paper mills, chemical plants, water treatment), and storage tanks and tankers for chemicals and food products. 

Tool Steel

The different carbon content levels give tool steel different properties compared to regular mild steel. Tool steel is harder and stronger than carbon steel but is more expensive and difficult to work with. With a carbon content between 0.7% and 1.5%, tool steels are manufactured under carefully controlled conditions to produce the required quality. The manganese content is often kept low to minimize the possibility of cracking during water quenching. Tool steel is used to make other products, for cutting, stamping, punching and machining other metals, plastics and wood. They are usually supplied in a soft annealed condition, machined into the tools required, then heat-treated to improve their hardness.

Galvanised Steel

Galvanized iron is the same as standard iron, the only difference is that it features a layer of zinc. The added layer of zinc helps to protect the iron from rust and corrosion. Without it, the iron will be exposed to moisture and oxygen from its surrounding environment. If left unchecked, this will trigger a chemical reaction with the iron known as oxidation. Oxidation will cause the iron to rust and corrode.

Galvanised construction steel is the most common use for galvanised metal, and hundreds of thousands of tons of steel products are galvanised annually worldwide. In developed countries most larger cities have several galvanising factories, and many items of steel manufacture are galvanised for protection. Typically these include: street furniture, building frameworks, balconies, verandahs, staircases, ladders, walkways, and more. Hot dip galvanised steel is also used for making steel frames as a basic construction material for steel frame buildings.

Cast Iron

Cast iron is made from pig iron, which is the product of melting iron ore in a blast furnace. Cast iron can be made directly from the molten pig iron or by re-melting pig iron, often along with substantial quantities of iron, steel, limestone, carbon (coke) and taking various steps to remove undesirable contaminants. Cast iron is a class of iron–carbon alloys with a carbon content more than 2%. 

Cast iron tends to be brittle, except for malleable cast irons. With its relatively low melting point, good fluidity, castability, excellent machinability, resistance to deformation and wear resistance, cast irons have become an engineering material with a wide range of applications and are used in pipes, machines and automotive industry parts, such as cylinder heads, cylinder blocks and gearbox cases. It is resistant to damage by oxidation but is notoriously difficult to weld.

Aluminium

Aluminium is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one-third that of steel. Aluminium is a natural element and can be found on the periodic table. This metal is commonly mixed with copper and zinc to create other alloy materials. Aluminium is a lightweight material used to manufacture cans for food products and building products such as window frames. 

Tinplate

Tinplate consists of sheets of steel, coated with a thin layer of tin. Before the advent of cheap milled steel the backing metal was iron. While once more widely used, the primary use of tinplate now is the manufacture of tin cans. Tinplate is made by rolling the steel (or formerly iron) in a rolling mill, removing any mill scale by pickling it in acid and then coating it with a thin layer of tin. Plates were once produced individually (or in small groups) in what became known as a pack mill. In the late 1920s pack mills began to be replaced by strip mills which produced larger quantities more economically. Formerly, tinplate was used for cheap pots, pans and other holloware. This kind of holloware was also known as tinware and the people who made it were tinplate workers.

For many purposes, tinplate has been replaced by galvanised (zinc-coated) vessels, though not for cooking as zinc is poisonous. The zinc layer prevents the iron from rusting through sacrificial protection with the zinc oxidising instead of the iron, whereas tin will only protect the iron if the tin-surface remains unbroken.

Titanium

Titanium is a chemical element with the symbol Ti and atomic number 22. Titanium can be alloyed with iron, aluminium, vanadium, and molybdenum, among other elements, to produce strong, lightweight alloys for aerospace (jet engines, missiles, and spacecraft), military, industrial processes (chemicals and petrochemicals, desalination plants, pulp, and paper), automotive, agriculture (farming), medical prostheses, orthopedic implants, dental and endodontic instruments and files, dental implants, sporting goods, jewellery, mobile phones, and other applications.

As a metal, titanium is recognised for its high strength-to-weight ratio. It is a strong metal with low density that is quite ductile (especially in an oxygen-free environment), lustrous, and metallic-white in colour. The relatively high melting point (1,668 °C ) makes it useful as a refractory metal. It is paramagnetic and has fairly low electrical and thermal conductivity compared to other metals. Titanium is superconducting when cooled below its critical temperature of -272°C. However, titanium loses strength when heated above 430 °C.

Titanium is not as hard as some grades of heat-treated steel; it is non-magnetic and a poor conductor of heat and electricity. Machining requires precautions, because the material can gall unless sharp tools and proper cooling methods are used.

Tungsten

Tungsten (also called wolfram) is a chemical element with the symbol W and atomic number 74. The free element is remarkable for its robustness, especially the fact that it has the highest tensile strength and highest melting point of all known elements, melting at 3,422 °C . It also has the highest boiling point, at 5,930 °C.

In its raw form, tungsten is a hard steel-grey metal that is often brittle and hard to work. Purified, monocrystalline tungsten retains its hardness (which exceeds that of many steels), and becomes malleable enough that it can be worked easily. It is worked by forging, drawing, or extruding but it is more commonly formed by sintering.

Tungsten carbide (WC) is used to make wear-resistant abrasives, and "carbide" cutting tools such as knives, drills, circular saws, dies, milling and turning tools used by the metalworking, woodworking, mining, petroleum and construction industries. Carbide tooling is actually a ceramic/metal composite, where metallic cobalt acts as a binding (matrix) material to hold the WC particles in place. This type of industrial use accounts for about 60% of current tungsten consumption

What does RHS, SHS and CHS stand for?

In the world of engineering and construction, the acronyms RHS, SHS and CHS are often used.  This is most common in Australia and associated countries, including the UK and New Zealand. 

The term RHS stands for Rectangular Hollow Section. RHS is the most prevalent term and is generally accepted for describing square hollow section as well, which is technically incorrect. The correct term for square tube is SHS which stands for Square Hollow Section. Less known is the term CHS, which stands for Circular Hollow Section. 

These terms are widely used to describe mild steel; however, they can also be translated for stainless steel and aluminium engineering and construction by engineers who are familiar with the terminology.