BS 4360 Grade 50B

These steels fill the gap between the lower strength (43A) structural steels and the ultra-high yield structural steels, eg. Macsteel VRN T690.  These steels are supplied in the normalised condition (50B < 12.5 mm as-rolled) and are silicon killed in order to improve the steel cleanliness, and to ensure fine grain structures.  Test certificates are supplied with each consignment.

As with lower grade of mild steel, procedure is dependent on the Carbon content as reflected on each Test Certificate.  For more comprehensive information in this respect B.S. 5135 should be referred to.

Cold Forming
These steels can be formed at room temperature provided adequate power is available and the correct process is employed.  A working 20% uprating on mild steel requirements is recommended making use of the following inside radius forming tolerances.
2 2 - 1 for right angle forming
3 - 1 for forming in parallel
A trial run may be necessary in order to determine the springback allowance for close tolerance work.

Punching, Drilling, Shearing and Machining
Equipment should be regulated to allow for the 20% increase in strength as opposed to that of conventional mild steels.  High-speed steel or Carbide tooling is recommended, speeds should be reduced by approximately 20% and a good lubricant/coolant will increase tool life.

When punching or shearing, a clearance of approximately 3% should be allowed for the shear angle.

Conventional Flame cutting equipment can be used without resorting to pre- or post-heating operations.

Mine fans, earth moving buckets, trailers and large road vehicles, drill rings, cranes, excavators, underground mining equipment, bridges and other high strength components requiring superior toughness.  

Typical Chemical Composition (Max) 

C. Mn. Si. S. P. Nb. V.
0.20 1.5 0.5 0.05 0.05 0.003 / 0.1 0.003 / 0.1

Typical Mechanical Properties  

Normal Thickness (mm) Tensile Strength (MPa) Min. Yield Strength (MPa) % Elong in 200 mm (Min) Impact Strength J (Min)
5 - 150 490 - 640 305 - 355 
(Depends on thickness)
18 Not specified or measured