Ferrous metals

Bright and Black Steel Materials

What is the difference between black steel bars and bright steel bars?
To the end user, the difference is precision. Bright steel bars are produced by passing black bars through dies in a cold process or by turning the bars in a peeler. Thus, a greater degree of profile precision, straightness and finish is achieved. Typically bright bars are used where specific tolerances are required. The majority of steel nuts manufactured by us are made from bright steel. These bars also have a 'bright' finish - hence the name.

Conversely, black steel bars have a darker finish and are not produced to such tight profile tolerances.

Trojan Special Fasteners has strong links with European Steel Mills that produce steels in the following grades to our exacting standards. We can provide 3.1 Material certificates accompanying our internally threaded fasteners.

Table comparing Black Steel Bars with Bright Steel Bars.

Feature Bright Bar Black Bar
Production Hot Rolling Cold Drawing
Finish Dark matte Bright shiny
Precision High Precision - smaller tolerance range Low Precision - larger tolerance range
Cost More expensive than Black Bar Steel due to a more complex manufacturing process Less expensive than Bright Bar Steel due to a simpler manufacturing process.
Properties Excellent tensile strength Strength and Durability
Common use Manufacturing of nuts, bolts, gears, shafts and other precision parts Construction and other industrial applications
Production Process Produced by passing black steel bars through dies in a cold condition (cold forming) or by turning the bars in a peeling machine. Usually these bars are annealed (heat treated) before cold finishing. Produced by heating billets of raw material to around 1200 degrees C and then passing them through a rolling mill to achieve the required shape and size. The 1200 degrees C (or around 2100 degrees F) temperature is important because this exceeds the recrystallisation temperature of the material.
Hexagon and Round Steel Bars

Hexagon and Round Steel Bars

The table shows the range for each heat treatment condition for steels. Note that there is overlap between some heat treatment grades.

Hardness Grade Ranges for Steel

Heat Treated Condition Q R S T U V W X Z
Tensile Strength (N/mm2) 625-775 700-850 775-925 850-1000 925-1075 1000-1150 1075-1225 1150-1300 1550
Hardness Brinell 179-229 201-225 223-277 248-302 269-331 293-352 311-375 345-401 444

Chemical Limits for Ferrous Metals

The following table shows the typical chemical minima and maxima for each of the material grades listed.

C Si Mn P S Cr Mo Ni
BS970:91 BS970:55 min max min max min max max min max min max min max min max
045A10 EN2A 0.08 0.13 0.10 0.40 0.30 0.60 0.05 0.05
045M10 EN32A 0.07 0.13 0.10 0.40 0.30 0.60 0.05 0.05
070M20 EN3B 0.16 0.24 0.10 0.40 0.50 0.90 0.05 0.05
070M55 EN9 0.50 0.60 0.10 0.40 0.50 0.90 0.05 0.05
080A15 EN3B 0.13 0.18 0.10 0.40 0.70 0.90 0.05 0.05
080A30 EN5B 0.26 0.34 0.10 0.40 0.70 0.90 0.05 0.05
080A42 EN8D 0.40 0.45 0.10 0.40 0.70 0.90 0.05 0.05
080A47 EN43B 0.45 0.50 0.10 0.40 0.70 0.90 0.05 0.05
080M15 EN32C 0.12 0.18 0.10 0.40 0.60 1.00 0.05 0.05
080M30 EN6 0.26 0.34 0.10 0.40 0.60 1.00 0.05 0.05
080M40 EN8 0.36 0.44 0.10 0.40 0.60 1.00 0.05 0.05
080M50 EN43A 0.45 0.55 0.10 0.40 0.60 1.00 0.05 0.05
150M19 EN14A 0.15 0.23 0.10 0.40 1.30 1.70 0.05 0.05
150M36 EN15 0.32 0.40 0.10 0.40 1.30 1.70 0.05 0.05
210M15 EN32M 0.12 0.18 0.10 0.40 0.90 1.30 0.05 0.10 0.18
212A42 EN8DM 0.40 0.45 0.25 1.00 1.30 0.06 0.12 0.20
216M36 EN15AM 0.32 0.40 0.25 1.30 1.70 0.06 0.12 0.20
226M44 EN8M 0.40 0.48 0.25 1.30 1.70 0.06 0.22 0.30
230M07 EN1A 0.15 0.05 0.90 1.30 0.09 0.25 0.35
530M40 EN18 0.36 0.44 0.10 0.40 0.60 0.90 0.035 0.04 0.90 1.20
605M36 EN16 0.32 0.40 0.10 0.40 1.30 1.70 0.035 0.04 0.22 0.32
606M36 EN16M 0.35 0.40 0.10 0.40 1.30 1.70 0.035 0.15 0.25 0.22 0.32
635M15 EN351 0.12 0.18 0.10 0.40 0.60 0.90 0.04 0.05 0.40 0.80 0.70 1.10
637M17 EN352 0.14 0.20 0.10 0.40 0.60 0.90 0.04 0.05 0.60 1.00 0.85 1.25
655M13 EN36 0.10 0.16 0.10 0.40 0.35 0.60 0.04 0.05 0.70 1.00 3.00 3.75
665M17 EN34 0.14 0.20 0.10 0.40 0.35 0.75 0.04 0.05 0.20 0.30 1.50 2.00
708M40 EN19 0.36 0.44 0.10 0.40 0.70 1.00 0.035 0.04 0.90 1.20 0.15 0.25
709M40 EN19 0.36 0.44 0.10 0.40 0.70 1.00 0.035 0.04 0.90 1.20 0.25 0.35
722M24 EN40B 0.20 0.28 0.10 0.40 0.45 0.70 0.035 0.04 3.00 3.50 0.45 0.65
805M17 EN361 0.14 0.20 0.10 0.40 0.60 0.95 0.04 0.05 0.35 0.65 0.15 0.25 0.35 0.75
805M20 EN362 0.17 0.23 0.10 0.40 0.60 0.95 0.04 0.05 0.35 0.65 0.15 0.25 0.35 0.75
815M17 EN353 0.14 0.20 0.10 0.40 0.60 0.90 0.04 0.05 0.80 1.20 0.10 0.20 1.20 1.70
817M40 EN24 0.36 0.44 0.10 0.40 0.45 0.70 0.035 0.04 1.00 1.40 0.20 0.35 1.30 1.70
820M17 EN354 0.14 0.20 0.10 0.40 0.60 0.90 0.04 0.05 0.80 1.20 0.10 0.20 1.50 2.00
822M17 EN355 0.14 0.20 0.10 0.40 0.40 0.70 0.04 0.05 1.30 1.70 0.15 0.25 1.75 2.25
826M31 EN25 0.27 0.35 0.10 0.40 0.45 0.70 0.035 0.04 0.50 0.80 0.45 0.65 2.30 2.80
826M40 EN26 0.36 0.44 0.10 0.40 0.45 0.70 0.035 0.04 0.50 0.80 0.45 0.65 2.30 2.80
835M15 EN39B 0.12 0.18 0.10 0.40 0.25 0.50 0.04 0.05 1.00 1.40 0.15 0.30 3.90 4.30
945M38 EN100 0.34 0.42 0.10 0.40 1.20 1.60 0.035 0.04 0.40 0.60 0.15 0.25 0.60 0.90