What is Mild Steel? an in depth technical guide

26 Fe 55.845

Mild Steel

An in depth guide

metals4U are proud to stock a fully comprehensive and sensibly priced range of mild steel products. The grades we stock are; Grade A Corten, EN24T, EN8, S275JR, EN3B, rebar 500B, EN1A, A142, A193, A252 and galvanised to BS EN ISO 1461. We also stock BS4 T45 specification Carbon-manganese steel that conforms to BS5T100/S600 tube stock standards and requirements.

Mild steel is a ferrous metal made from iron and carbon. It is a low-priced material with properties that are suitable for most general engineering applications. Low carbon mild steel has good magnetic properties due to its high iron content, it is therefore defined as being ‘ferromagnetic’.

Mild steel has a carbon content of between 0.16% and 0.29 % maximum with a relatively high melting point of between 1450°C to 1520°C. Steels with a higher carbon content than mild steel, have a lower melting temperature. This high melting temperature means that mild steel is more ductile when heated, making it particularly suitable for forging, cutting, drilling, welding and is easy to fabricate.

Mild steel is not suitable for through hardening. It can be case hardened by being heated and a chemically reactive source of carbon added, the subsequent quench cycle will harden the surface layer. This outer layer, ‘the case’ will become hardened.

Mild steel, including galvanised products, is recyclable.

Mild steel does not have a high resistance to corrosion in its untreated form, however, the corrosion resistance can be greatly improved by applying an appropriate surface protection product to the exposed parts of any project. There is a wide range of red oxide primers, metal paint, metal spray paint and zinc treatments available to enhance the appearance of mild steel and to protect it from rust and corrosion.

Mild steel can be cleaned by ‘pickling’. This is a chemical surface treatment that removes stains, contaminants, rust and scale. Surface rust can also be removed by mechanical grinding and then treating with a surface protector such as red oxide primer, zinc primer and metal paints and sprays.

Mild steel is graded according to its chemical composition, how it is produced, and its properties, so you can easily choose the best product for your project.

The forms we supply

We supply mild steel in sheet and a wide range of profiles such as channel, box section, angle, channel, square, flat, round, hexagon, pipe, T section, tube, threaded bar, sheet, rebar, mesh, half round moulding, and RSJ.

Welding guide

Welding mild steel to Use filler wire type
Itself Rutile, 6013, lo hy, 7018 , 7024, sifsteel 11
Corten Lo hy, rutile, 6013, 7018, 7024, sifsteel 11
Galvanised mild steel Sifredicote 1, 6013, 7018, rutile, lo hy, 7024, sifsteel 11
Brass Sifbronze 8
Copper Sifbronze 8
Stainless steel Sifbronze 8, sifsteel 312
Bronze Sifbronze 8
Cast iron Sifbronze 2
Aluminium Pre-coat mild steel with sif silver solder 40 or 43 then weld using sifalumin 15
Weldability Value
Gas Excellent
Arc Excellent
Resistance Very good
Brazability Very good

The grades of mild steel

With so many grades of mild steel, here is a guide to each one to help you make the best choice for your project.

Grade A Corten

Corten Steel (grade A) is also known as weathering steel or atmospheric corrosion resistant steel and is specified to EN 10025-5. Corten is a cost-effective choice for structures that are exposed to extremes of weather. The surface of Corten oxidises to give it a distinctive brown/ orange colour; this does not just look great, it also protects the metal. The oxidisation develops and regenerates the surface as it is exposed to weather and air pollution. When Corten is supplied it will not have developed its distinctive brownish surface, this will slowly develop over the following months and years.

Due to the stiffness, strength and low maintenance qualities, Corten is particularly suitable for use in;

  • Bridges
  • Steel frame structures
  • Structural components
  • External design detail
  • Sculpture – just think of the impact of Gormley’s ‘Angel of the North’.

Corten is a versatile choice for many projects as it is strong, long lasting, resilient to all types of weather, recyclable and very importantly- economical.​


Physical Property Value
Density 8000
Melting Point 1370-1400°c
Modulus of Elasticity 190-210 GPa
Electrical Resistivity 0.7 µΩm
Thermal Conductivity 42.7W/m.K
Thermal Expansion 16-17 µm/m-k
Mechanical Property Value
Yield Strength 345 N/mm²
Tensile Strength 485 N/mm²
Proof Stress 0.2% -
Shear Strength -
Hardness 105 Vickers - HV
Elongation (in 200mm) 20% minimum

The chemical composition (% of weight)

Carbon Silicon Manganese Phosphorus Sulphur
0.15 max 0.25 - 0.75 0.2 - 0.5 0.07 - 0.15 0.03 max
Aluminium Copper Cromium Nickel Iron
0.015 - 0.06 0.25 - 0.55 0.5 - 1.25 0.65 max Balance


Corten is suitable for drilling and machining. You can reduce wear and damage to tools by reducing the fabrication speeds necessary on other mild steels. Drilling speeds can be reduced to 2/3 of standard mild steel speeds and to 3/7 of the speed for machining.


Corten can be cut in the same way as standard steel products by using shears or gas / flame cutting techniques.


Weathering steel is suitable for manual and mechanical welding, but, there are couple of pointers you need to remember. The weather resistance of Corten means that any welding consumables you choose need to have similar corrosion resistance and preferably be a good colour match too. On a single pass weld, mild steel electrodes can be used because the pick up from the base metal will help to get the desired colour match. If you are doing multiple pass welds, it is better to use low alloy electrodes to make sure you get a good colour and corrosion resistant match.

Back to top

 EN24T /817M40T

EN24T, also commonly referred to as 817M40T is a high strength engineering steel that has nickel, chrome, and molybdenum as its alloying elements. The addition of nickel gives the steel toughness, the chrome provides a depth of hardness and the molybdenum reduces the risk of temper brittleness that may occur during some temperature intervals.

The physical properties of EN24T makes this grade suitable for use in high strength machine parts, axles, components for use in high temperature environments such as oil refineries and power stations, manufacture of punches and dies, gears, shafts

This grade of engineering steel is supplied hardened and tempered to 'T' designation.

EN24T Chemical properties (% weight)

C Si Mn P S Mo Cr Ni Fe
0.36-0.44 0.10-0.35 0.45-0.70 0.035 max 0.04 max 0.20-0.35 1.00-1.40 1.30-1.70 Balance

EN24T Physical properties

Property Value Unit
Density 7840 Kg/m3
Melting point 1500 °C
Modulus of elasticity 207 GPa
Electrical resistance   µΩm
Thermal conductivity 41.9 W/m°k
Thermal expansion   µm/m-k
Yield strength 650 N/mm²
Proof stress 680 N/mm²
Shear modulus   GPa
Hardness Vickers 252-303 Vickers - HV
Elongation 13 %
Tensile strength 850-1000 N/mm²
Impact / Izod 54 J
Impact Charpy (KCV) 50 J


EN24 T has excellent results when machined. The use of carbide tipped HSS tools is recommended to give the best milling, grinding, and machining results to deliver high dimensional tolerances and good surface finishes.

Best results are achieved with slower speed and a higher feed at initial roughing out stage, followed by high speed and moderate feed to finish off.

Machined components that require extra resistance to wear can be case hardened to enhance performance.


As this grade is renowned for its toughness and its high strength in it heat treated and tempered condition, it is primarily used for the manufacture of machined components it is not considered relevant for use in cold working processes.


EN24T engineering steel has good ductility.


EN24T can be sawn, flame or plasma cut.


The addition of Chrome, molybdenum and nickel as alloying elements mean that EN24T is not particularly well suited to welding applications.

If welding is unavoidable, the metal will require a preheat and post-weld heat treatment. The most appropriate welding consumables for this grade is SifChrome 312 welding rod or Siftrode 7018 electrode.

  • Preheat the part to be welded to 250°C by furnace, induction coils, gas torch or resistance heating mats. Maintain this heat throughout the welding process.
  • Use consumables with high Mn content to help reduce the risk of hot cracking during the welding process.
  • Cool to 180°C before performing the post-weld heat treatment.
  • Post-weld; heat to between 6200176C and 650°C at a maximum temperature rise of 100°C per hour. Once temperature reached, soak at that heat for 2 hours.
  • Slowly control the cooling process by 100°C per hour until the metal reaches room temperature.


To anneal, slowly heat the metal through to 840°C to 860°C, soak well at a steady temperature then cool in the furnace to 580°C before removing.

To perform a stress relief cycle if necessary, after hard machining, cold working or being ground, slowly heat the worked piece to between 650°C and 670°C, hold at a steady temperature to allow the piece to soak well. Cool in the furnace or air cool.


This grade is supplied pre-hardened and tempered.

If further heat treatment is needed, the metal can be through hardened by heating slowly to between 830°C and 850°C and then quench in oil. The piece should be tempered once it cools to room temperature.

To case harden EN24T, heat through to between 850°C and 950°C until the metal is cherry red; once glowing, plunge the component into the hardening compound and allow it to cool a little. Reheat through to glowing cherry red followed by a water quench cycle. Case hardening can provide surface hardness in excess of 50 HRc.


EN24T is supplied with a 'T' designated temper, however, this grade is suitable to temper to a higher designation if required. EN24T can be held for 2 hours per 25mm (1inch) thickness at the appropriate temperature to achieve the desired temper

The mechanical properties of each EN24 temper is shown below.

Temper designation Vickers Hardness Impact strength KCV Tensile strength Elongation
EN24 T 252-303 35 J 850-100 N/mm2 13 %
EN24 U 271-342 42 J 925-1075 N/mm2 12 %
EN24 V 292-361 42 J 100-1150 N/mm2 12 %
EN24 W 311-393 35 J 1075-1225 N/mm2 11 %
EN24 X 351-406 28 J 1150-1300 N/mm2 10 %
EN24 Y 376-448 2 J 1275-1375 N/mm2 10 %
EN24 Z 458 9 J 1550 N/mm2 5 %

Tempering this grade of steel between 250°C and 375°C is not recommended as it will considerably reduce the impact strength.

Corrosion resistance

The corrosion resistance of EN24 T is designated as poor, however, machined components will have a smooth, work hardened surface which offers a slight improvement to resisting corrosion.


EN24T is suitable for forging. The steel should be carefully preheated, then the temperature raised to between 1000°C and 1150°C for forging. The worked metal should then be slowly cooled, preferably in a furnace. It is not recommended to forge at temperatures below 850°C.

Process Rating
Workability - Cold Not required
Hot Good
Machinability Excellent
Weldability – Gas Poor
Weldability – Arc Poor
Weldability – Resistance Poor
Brazability Not recommended
Solderability Not recommended

How supplied

EN24T is supplied as a round bar presentation in a range of diameters in a mill finish.

Back to top

Grade Type A Mesh

A142, A193, A252 A393 grades of reinforcing steel mesh

All our type A reinforcing mesh is supplied to the BS4483:2005 specification. Type A is the most commonly used welded fabric in the construction industry. This reinforcing square mesh is constructed with the same diameter wire used in the longitudinal and transverse directions.

This type of steel mesh is used where the same area and specification of reinforcement is needed in both directions. The mesh is supplied in sheets with full welding at all points the wires intersect. Reinforcing mesh is set into concrete to reinforce structures as it reduces warping and helps to distribute tensile loads.

  • Concrete
  • Load bearing


BS4483 reference Wire diameter Cross sectional area Pitch
A142 6mm 142mm 200mm
A193 7mm 193mm 200mm
A252 8mm 252mm 200mm
A393 10mm 393mm 200mm


Mechanical properties Value
Yield Strength 400-600 N/mm²
Tensile Strength 550 N/mm² (maximum)


Steel reinforcing mesh can be welded. Due to slight differences in the contraction and expansion rates of mild steel and concrete it is recommended to use loop end tying wires and tying tool.


Back to top

Grade 500B

500B reinforcing bars

Reinforcing bars, or rebar as they are also referred to, are manufactured from 500B grade mild steel that conforms to the BS 4449:2005 specification. Reinforcing bars are used as a tension device in reinforced concrete and masonry structures. Rebar strengthens the structure by holding the concrete in a compressed state. Concrete is strong under compression but has relatively weak tensile strength, setting rebar into the concrete significantly increases the tensile strength of the structure.

Mild steel and concrete have similar coefficient thermal expansion properties, this reduces internal stress caused by changes in temperature to strengthen the structure, maintain the integrity of the construction and reduce or limit cracking.

Under the BS4449:2005 standard there is no standard chemical composition or metallurgic quality recommended, but there is a standard yield / tensile strength standard stated.

Rebar has a distinctive surface pattern of notches, this helps the bond of the concrete to the bar. Products without this notched pattern are reinforcing wire or rod.

  • Concrete
  • Masonry
  • Sleepers

Mechanical properties of 500B rebar

Yield strength Re Mpa Tensile / yield strength ratio Rm / Re Total elongation at max force, AGT %
500 1.08 5.00

Due to the uses of reinforcing bar there is no requirement to machine, form, drill or perform any heat treatments.


Reinforcing bars can be welded, and for many tradespeople this is their preferred option. As there is not close control regarding the chemical properties of rebar this can prove problematic as the correct choice of electrode or rod will be uncertain. The slight differences in the rates of contraction and expansion of the rebar and concrete may cause cracking at the weld joint.

The preferred method for many is tying the rebar by using loop end tying wires and a rebar and reinforcing mesh tying tool. This system for joining enables the slight movement of the concrete and metal to be absorbed and enabled by the ties. The wire ties are supplied in 16 swag black annealed mild steel with a loop at both ends.

A range of supports are also available to assist in the support of the rebar while being set in situ. The supports are spacer supports, plastic floor spacers, circular mesh spacers and continuous plastic chair supports.

Back to top

 GMS Mild Steel

Galvanised Mild Steel

Galvanised mild steel products are mainly used in external applications due to the protective and maintenance free benefits the range delivers.

All our galvanised mild steel products conform to BS EN ISO 1461 which is the specification for the standard of hot dipped galvanisation. This is also often abbreviated to HDG. The standard states the minimum coating thickness in relation to the thickness of the steel, i.e. 6mm mild steel thickness will have a galvanised coating of 85µm.

Galvanised mild steel is extremely corrosion resistant so is predominantly used for applications that need to be resistant to rain, extremes of temperature and weathering. It is commonly used for:

  • Framework
  • Sheds
  • Outdoor structures
  • Trailer parts
  • Vehicle construction
  • Panels

The process of HDG is made up from a series of steps to ensure the best quality product is supplied. Firstly, the surface is checked for roughness and any rough patches are removed by gentle grinding if necessary. The mild steel is then ready to begin a five-stage surface preparation process. The mild steel is degreased, rinsed, then pickled, rinsed again, submerged in a flux solution and then dried. Once dried, the mild steel is submerged in a zinc bath (containing a minimum of 98% pure zinc plus iron) at between 435°C to 455°C, it is then cooled and inspected. If the product had not been properly cleaned prior to the process, the zinc coating will not adhere, the unclean areas will be easy to identify as they will have no distinctive silver lustre coating. Some processes leave the surface with a uniform smooth surface pattern, others leave a crystalline pattern that looks like frost- this is also known as ‘spangle’. Neither one of these surface patterns are more effective than the other, they are just different. During the galvanisation process, the zinc and iron becomes metallurgically bonded to the base mild steel and forms a series of zinc-iron alloy layers, these are shown below.


Physical Property Value
Density 7870 Kg/m³
Melting Point 1350-1530 °C
Modus of Elasticity 200 GPa
Electrical Resistance 1.59 µΩm
Thermal Conductivity 45-64.8 W/m°k
Thermal Expansion 12.06 µm/m-k
Mechanical Property Value
Yield Strength 370 N/mm²
Tensile Strength 440 N/mm²
Shear Modulus 80 GPa
Hardness Vickers 140 Vickers - HV
Elongation (in 200mm) 15 %
Levels from surface to base Composition of layer Hardness (DPN)
Eta 100% Zn 70
Zeta 94% Zn 6% Fe 179
Delta 90% Zn 10% Fe 244
Gamma 75% Zn 25% Fe 250
Base mild steel To spec of product / grade used To spec of product / grade used

The gamma, delta and zeta layers are harder than the base metal – this provides protection from abrasion. The Eta layer is quite ductile- this provides the product with extra impact resistance.

Health and safety precautions

During heating, flame cutting, welding, mechanical cutting, drilling and machining galvanised products, it is important to follow stringent hazard reduction protocols. Heating will burn off the coating which will produce zinc rich, irritant fumes. Appropriate ventilation, preferably working outside, is recommended, as is wearing respiratory PPE. If working must be performed in a confined space, fume extraction is necessary. If the fumes are inhaled there is a possibility of contracting ‘metal fume fever’ or ‘welders flu’. The symptoms are similar to viral influenza, they are usually short lived but very unpleasant and most of all, avoidable.

Prolonged direct skin contact with galvanised products or with the dust produced while working may cause localised skin irritation, or in severe cases, contact dermatitis- this can be avoided, or the risk reduced by washing your hands after contact or wearing PPE gloves while working.

Medical attention should be sought immediately for any skin or eye injury suffered while working with galvanised products.


Galvanised products can be machined and drilled, however, this would remove the galvanised coating from the part that was worked on. Any machined areas would need to be treated afterwards with an appropriate zinc surface treatment.


Can be flame or disk cut, sheet can be successfully cut with tin snips or shears.


Galvanised products are suitable for welding by all methods. As HDG products have a coated surface, more amperage is required for welding. A 150-amp AC SMAW or ARC welder will weld galvanised mild steel with A0.3 cm (3mm) 6011 rod running at about 90-110 amp- a smaller rod will run at a lower amperage, a larger at a higher amperage.

The hot dipped galvanised coating has a melting point of between 419°C and 450°C.

First, grind a weld prep; as the coating will burn away during the weld there is no need to remove the coating during the weld prep grind.

During the welding process there will be more sparks generated than with un- galvanised mild steel welding, and a slower weld speed is necessary to burn the zinc out of the way as you weld the join.

Clean the slag and zinc oxide residue off between each pass, then grind the weld smooth if required. When cool, coat the cleaned weld with zinc rich primer, this will not have the same level of corrosion resistance of the original hot dip coating but will provide an excellent level of protection.


Hot dipped galvanised coating has good adhesion and cracking resistance making these products very versatile.


Annealing, case hardening, through hardening and tempering are not appropriate processes for this product as the heat will remove the coating.

We stock galvanised mild steel box section, tube, sheet, angle, flat and weld mesh products.

Back to top

Grade S275JR

S275JR conforms to the BS EN10025 structural steel specification and is one of the most commonly used grades in general construction. It is an un-alloyed, hot rolled, low carbon mild steel. S275JR is available in a wide choice of profiles and presentations.

It is easy to cut, weld, machine and drill which makes it the perfect choice to use for;

  • Frames
  • Vehicles
  • Joist supports
  • Lintels
  • Shelves
  • Brackets
  • Construction
  • Maintenance projects


Physical Property Value
Density 7800 Kg/m³
Melting Point 1460 °C
Modus of Elasticity 210 GPa
Electrical Resistance 0.20-0.25 µΩm
Thermal Conductivity 50 W/m°k
Thermal Expansion 11 µm/m-k
Mechanical Property Value
Yield Strength 275 N/mm²
Tensile Strength 370 - 530 N/mm²
Shear Modulus 80 GPa
Hardness Vickers 115 - 154 Vickers - HV
Elongation (in 200mm) 20%

The chemical composition (% of weight)

Carbon Silicon Magnesium Potassium Sulphur Iron
0.25 max 0.05 max 1.6 0.04 0.05 Balance


This grade of steel is very easy to machine and drill.


This grade of steel has good ductility.


S275JR can be easily cut using appropriate grade cutting disks or by flame cutting methods.


There is no need to preheat the metal before welding. For best results ensure you use the most appropriate specification of welding rods and electrodes for low carbon mild steel.


To anneal, slowly heat the piece to 650°C - 700°C and then slowly cool, preferably in a furnace.


As with all low carbon mild steels, S275JR is not ideally suited to induction or through hardening.

It can be successfully case hardened by heating to between 850°C and 950°C and plunging into a hardening compound, allowed to cool slightly and then reheated to initial temperature range and quenched in water.

Alternatively, it can be gas or pack carburised by heating to 900°C (max) for the appropriate time for the required carbon content and case depth to be achieved. The metal will require core refining and tempering after carburising by allowing the part to cool, then reheating it to 880°C - 900°C and quenching in water.


Heat metal to 180°C–200°C, then quench in water for 1 hr per 25 mm of steel thickness and air cool.

Corrosion resistance

S275JR is susceptible to rusting easily. It is important to surface treat the product after fabrication by using an appropriate metal paint, metal paint spray or red oxide primer and paint.

Our RSJ’s are supplied pre-treated with red oxide primer.

If extra corrosion resistance is required, it may be worth considering using a pre-galvanised or stainless steel equivalent product.

We stock S275JR in angle, channel (c section), flat bar, bar and rod, square and rolled steel joists (also known as I beams) that conform to BS4 pt 4 BE EN 10025 S275RJ specification.

Back to top

Grade EN1A

EN1A grade is also known as free cutting or free machining mild steel. It is supplied to meet the BS970: 1991 230M07 specification. It is available in both unleaded and leaded (Pb) form. (The addition of lead to EN1A increases the machinability). EN1A is a bright, cold drawn steel that is ideal for use with automatic lathes and CNC machining centres, especially where intricate drilling and machining is necessary. EN1A does not have good transverse properties so should not be used for making hollow components that may be subject to internal pressure.

It is particularly well suited to the manufacture of;

  • Bolts
  • Studs
  • Nuts
  • Precision machined components


Physical Property Value
Density 7870 Kg/m³
Melting Point 1093 °C
Modus of Elasticity 200 GPa
Electrical Resistance 1.74 µΩm
Thermal Conductivity 51.9 W/m°K
Thermal Expansion 11.5 µm/m-k
Mechanical Property Value
Yield Strength 240 - 400 N/mm²
Tensile Strength 370 - 480 N/mm²
Shear Modulus 80 GPa
Hardness 170 Vickers - HV
Elongation 6 - 10%

The chemical composition - unleaded (% of weight)

Carbon Silicon Magnesium Potassium Sulphur Lead Iron
0.15 max 0.25 - 0.35 0.90 - 1.30 0.07 max 0.40 max 0 Balance


EN1A is designed for its very good machining properties and is easily drilled. The addition of lead (Pb) increases the machinability to excellent. This mild steel grade is designed specifically for high speed machining as the swarf forms in small chips that prevent machine blockage. Most lubricants are suitable for use with this grade, however, cutting oils may cause some surface staining.


EN1A has reasonable ductility.


Known as free cutting steel, the high sulphur content forms inclusions along the grain that enable shear cutting and grinding to be performed easily.


Due to the low carbon content, welding is not recommended for this grade. If using EN1A (Pb), welding should not be attempted due to the lead content.


EN1A can be hardened by case hardening or carburising.

To case harden; heat the metal to between 850°C - 950° C, the heat can be isolated to the specific area to be hardened if preferred. Once the metal has reached bright cherry red, remove from the brazing hearth and plunge part into hardening compound. Allow to cool slightly. Reheat to red hot and then quench in water.

To carburise; Pack or gas carburise at 900°C for a sufficient time to develop the required carbon content and case depth. This should then be followed by a core refine cycle and tempering. To core refine, slow cool the part after carburising and reheat to between 880°C - 900°C, once the temperature is uniform throughout quench in oil or water. Finally, temper the part.

EN1A is not suitable for induction or through hardening.


Heat the part to between 180°C and 210°C, soak for 1 hr per 25mm of thickness and then air cool.

Corrosion resistance

EN1A leaded and unleaded mild steel has good corrosion resistance properties. It will not rust as quickly as standard mild steel.

We stock EN1A as free cutting bright mild steel round and leaded hexagon bar. These products are supplied with an oily finish.

Back to top

Grade EN3B

EN3B is a bright, unalloyed low carbon mild steel manufactured under the BS 970: 1991 standard category. Bright steel is cold finished and drawn during production to tolerate higher levels of stress, tighter sectional tolerances, increased accuracy in dimension and shape and a smoother surface finish. Cold drawing is done at room temperature and entails the mild steel being hammered and rolled to fit through a die. The metal is not squeezed through the die but pulled through to reshape it. The process is usually repeated through several different dies to achieve the dimensions closest to the required machine size.

Bright, cold drawn steel is particularly suitable for the manufacture of high precision parts and projects involving geometric dimensioning and tolerances (GD&T) where accuracy of dimension of shape, strength and surface condition are major factors.

EN3B grade bright steel is particularly suited to the manufacture of:

  • Axles
  • Machine parts
  • Threaded bars
  • General engineering parts and components
  • Light duty gears


Physical Property Value
Density 7870 Kg/m³
Melting Point 1515 °C
Modus of Elasticity 190-210 GPa
Electrical Resistance 1.59 µΩm
Thermal Conductivity 51.9 W/m°K
Thermal Expansion 11.7 µm/m-k
Mechanical Property Value
Yield Strength 300 - 400 N/mm²
Tensile Strength 400 - 560 N/mm²
Shear Modulus 72 GPa
Hardness Vickers 124 - 241 Vickers - HV
Elongation (in 200mm) 10 - 14%

The chemical composition (% of weight)

Carbon Silicon Magnesium Potassium Sulphur Iron
0.16 - 24 0.35 max 0.50 - 0.90 0.05 max 0.05 max Balance


EN3B machines very well and can be easily drilled.


Cutting disks are the recommended option for EN3B grades of bright steel.


Pre-heating is not required in most cases; however, this can be beneficial if welding large sections. Bright mild steel is very well suited to all types of welding using low carbon electrodes.


EN3B has very good ductility.


Slowly heat to between 880°C and 910° C and furnace cool.


Due to the low carbon levels in EN3B it is not suitable for ‘through hardening’. Carburising or case hardening is the appropriate method and is done by heating the metal to between 850°C and 950°C until it is cherry red. If only a small part needs to be carburised the heat can be concentrated in that one area. Remove from brazing hearth and plunge part into hardening compound and allow to cool slightly. Reheat to cherry red, remove from brazing hearth and quench in water.


Reheat EN3B to 150° C to 200°C until the temperature is even throughout the metal then soak for 1 hour per 25mm of thickness, finally, air cool.


Heat to a maximum temperature of 1100°C to 1200°C until a consistent temperature is achieved throughout. Do not forge below 900°C. When forging is complete, the metal can be air cooled.

Corrosion resistance

Bright mild steel has a better tolerance to rust and corrosion than plain mild steel, however, it is still recommended to finish your project by using metal paint, metal spray paint or red oxide preparations to protect it.

We stock bright EN3B in angle, flat, round bar and square in a wide range of dimensions and it is supplied in an oily finish.

Back to top

Grade EN8

EN8 steel is an unalloyed medium carbon bright steel that is categorised under the BS 970-1955 standard.

EN8 is stronger and higher quality than standard bright mild steel which makes it particularly suitable for the manufacture of;

  • Shafts
  • Studs
  • Bolts
  • Connecting rods
  • Axles
  • Screws
  • Automotive parts
  • General engineering components


Physical Property Value
Density 7850 Kg/m³
Melting Point 1520 °C
Modulus of Elasticity 190 - 210 GPa
Electrical Resistivity 1.71 µΩm
Thermal Conductivity 50.7 W/m°k
Thermal Expansion 11.3 µm/m-k
Mechanical Property Value
Yield Strength 465 N/mm²
Tensile Strength 500 - 800 N/mm²
Proof Stress 0.2% 450 min N/mm²
Shear modulus 80 GPa
Hardness 199 - 258 Vickers - HV
Elongation (in 200mm) 16% minimum 12% cold drawn

The chemical composition (% of weight)

Carbon Silicon Magnesium Potassium Sulphur Iron
0.35 - 0.45 0.05 - 0.35 0.60 - 1.00 0.015 - 0.06 0.015 - 0.6 Balance


EN8 is suitable for machining and drilling.


EN8 can be easily cut with shears, flame or by using a plasma cutter.


EN8 is suitable for welding by SMA, MMA, MIG, MAG, GMA methods.

EN8 bright Mild Steel can be welded up to 18mm thick without preheating using MIG wire (SG2) or 7018 electrodes. It is recommended that you anneal afterwards to prevent breaking and cracking of the weld.

For welding pieces more than 18mm thick, preheat the metal to 180°C in resistance heating mats, induction heating coils, by gas torch or in a furnace. It is important to maintain this preheat temperature throughout the weld to prevent cracking and distortion.

Basic coated electrodes are suitable for SMA or MMA welds. Check the electrodes you use are a match for the tensile strength of the steel. You could also use an alloyed basic coated electrode to achieve a weld with the same yield strength as carbon steel.

MIG, MAG (GMA) welding or flux cored arc welding with the necessary consumables will also produce a weld of matching and correct strength.

Temper the metal after the weld has cooled back to the 180°C preheat temperature.


Slowly heat the metal to a temperature of between 680°C and 710°C then cool slowly.


Heat the metal slowly to between 820°C and 860°C until heated through then quench in oil or water.


Temper the metal after quenching while it is still slightly warm. Re-heat the metal to the most suitable temperature for your project; this will be somewhere between 550°C and 660C° and then soak for a minimum of 2 hours, allowing 1 hour per 25mm of metal thickness. Finally, air cool the EN8.

Corrosion resistance

Cold drawn bright mild steel is more resistant to rust than standard mild steel.


To forge EN8, slowly preheat the steel and raise the temperature to 1050°C for work. Do not forge below 850°C. Cool the steel slowly after forging, preferably in a furnace.

Bright EN8 round bar is supplied in an oily finish and is stronger than regular plain mild steel.

Back to top


T45 is not a grade of low carbon steel, but a steel tube that conforms to the chemical composition specification BS4 T45. T45 is a High tensile Carbon Manganese steel, supplied in a seamless tube presentation that is suitable for use in motorsport, aerospace, and associated industries. Initially designed over 60 years ago for aerospace use, it was used for the construction of WW2 Spitfire, Hurricane, and Hawker chassis and is currently widely used for the manufacture of roll cages, pilot and crew seats, roll bars, defence and aerospace applications, motorbike and bicycle frames, chassis construction, stunt vehicles, and impact protection structures.

T45 offers almost double the yield strength of other grades of cold drawn seamless (CDS) tube and 2/3 higher tensile strength; these qualities mean a thinner gauge (tube wall) can be used without any compromise on strength or frame rigidity with the additional benefit of reducing weight. The weight of a frame constructed in BS4 T45 specification tube can be as much as 10-15% lighter than with standard CDS tube profiles.

T45 is slightly higher priced than standard grade CDS tube, but the higher specification means better performance and safety, and the superior strength to weight ratio makes this the preferred tube specification chosen by high end, serious motorsport competitors.

T45 will not snap or split when used within high G force environments and applications; the cold drawing process ensures precise dimensions and a very good surface finish. All our T45 stock has been Eddy-current tested by the manufacturer so you can be confident of buying stock that has no surface and sub-surface flaws.

All our T45 tube stock is supplied with the manufacturers’ etching marks to authenticate the Chemical Composition specification of BS4 T45 and confirmation that the product conforms to BS5T100/S600; this is the specification for the procedure for inspection, testing and acceptance of seamless steel tubes and tube stock for aerospace use.


Chemical Composition of T45 (% of weight)


C Cr Mn Mo Ni P S Si Fe
0.17-0.25 0.25 max 1.3 - 1.7 0.1 max 0.4 max 0.04 max 0.04 max 0.1 – 0.35 max Balance


Mechanical properties of T45


Property Value Unit
Density 7890 Kg/m3
Melting point   °C
Modulus of elasticity 196 GPa
Electrical resistance   µΩm
Thermal conductivity   W/m°k
Thermal expansion   µm/m-k
Yield strength 620 N/mm²
Proof stress (0.2%) 620 N/mm²
Shear modulus   GPa
Hardness Vickers 199-262 Vickers - HV
Elongation (A50 mm) 15% %
Tensile strength 700-900 N/mm²


Excellent results can be achieved with most machining techniques. The most common machining process within tube fabrication projects would be preparation of the ends of tubes to be joined, this can be done most easily with a tube notcher to produce fish mouth cuts ready for positioning and welding in place.


T45 has excellent formability. Excellent results are achieved when using manual, hydraulic and mandrel tube benders. T45 will not split or crack during appropriate forming work and does not require pre or post working heat treatment.


T45 can be cut with manual files and hacksaws and is easily machine cut with all usual mechanical and flame cutting techniques including band saw, tube saw and guillotine. T45 will not require a post cutting anneal cycle.


This specification of carbon manganese steel tube is easy to weld with excellent results. It has excellent weldability and does not require a pre, or post weld heat treatment.

Some fabricators report that while welding there feels to be a slight magnetic pull as the filler can stick to the edge of the weld puddle so caution should be taken to ensure the filler is kept within the gas shield.

MIG and TIG welding is recommended for joining T45 tubes. These techniques add less metal to construction than braze welding, this maintains the lighter weight of the fabricated part.

If T45 is being used for construction of frame work for competitive events held under the governance of a regulatory body, it is the responsibility of the fabricator to check the relevant governing body regulations on standards regarding circumferentially welded joint criteria, and the acceptance of brazing and soldering for competitive events.


There is no need for pre or post working heat treatments with T45 tube.


T45 is supplied pre-hardened so requires no further hardening.

If a hardening cycle is desired the recommended temperature is 870°C -910° C followed by a fast quench in water or oil.


BS4T45 tube is supplied in a hard temper presentation and no pre or post working heat treatments are necessary. Should a further temper cycle be wished for, the recommended temperature is 675°C and a slow cool.

Corrosion Resistance

T45 has a good level of corrosion resistance and can be painted and powder coated to improve the corrosion resistance and to enhance the aesthetics of the finished product.


This specification of steel tube can be forged with a guideline temperature to not exceed 1321°C, however, with T45 tube applications this would not usually be a required procedure during the construction of a framework project.


Good results can be obtained by brazing, however, if the final weight of the workpiece is crucial to success, it is worth remembering that brazing can add weight to the finished product. Welding requires less additional joining metal to perform a sound join.

Process Rating
Workability-cold Excellent
Workability-Hot Not applicable
Machinability Very good
Weldability–Gas Tig /mig tig Excellent
Weldability–Arc Excellent
Weldability–Resistance Good
Brazability Good
Solderability Not recommended

How Supplied

Our T45 stock is supplied in a mill finish round tube in r/ls or ‘random lengths’ and a range of diameters. Random lengths are produced as the metal lengthens with each drawing, this will deviate with each cycle. Tubes are sold with guidance length or can be supplied ready cut to the required length. All stock is manufacturer stencilled/etched to confirm specification compliance.

Welding consumables for welding T45

  • Sifbronze no 101 using gas fluxer process (rod)
  • Tig / mig welding – sifsteel A32. A31
  • Tig sifsilcopper 968
  • Brazing - sifbronze1
Back to top