CalQlata's term 'special carbon' steels refers to what is generally known as 'low-alloy' steels
They comprise exactly the same alloying elements as plain carbon steel but with different ranges/quantities
The carbon steels in this group have the same physical properties as the equivalent plain carbon steel with the same last two digits, with the exception that one or more of the quantities of manganese, phosphorus and sulphur have been altered to facilitate machining and/or increase hardness⁽¹⁾
See CalQlata's Property Table below to obtain physical properties for each of steel grade
Sulphur (S) >0.05%
| AISI No |
C (%) min<max |
Mn (%) min<max |
P (%) min<max |
S (%) min<max |
|---|---|---|---|---|
| 1108 1109 1110 |
0.08<0.13 | 0.5<0.8 0.6<0.9 0.3<0.6 |
<0.04 | 0.08<0.13 |
| 1111 1112 1113 |
<0.13 | 0.6<0.9 0.7<1.0 0.7<1.0 |
0.07<0.12 | 0.08<0.15 0.16<0.23 0.24<0.33 |
| 1115 | 0.13<0.18 | 0.6<0.9 | <0.04 | 0.08<0.13 |
| 1117 1118 1119 |
0.14<0.2 | 1.0<1.3 1.3<1.6 1.0<1.3 |
<0.04 | 0.08<0.13 0.08<0.13 0.24<0.33 |
| 1120 | 0.18<0.23 | 0.7<1.0 | <0.04 | 0.08<0.13 |
| 1126 | 0.23<0.29 | 0.7<1.0 | <0.04 | 0.08<0.13 |
| 1132 | 0.27<0.34 | 1.35<1.65 | <0.04 | 0.08<0.13 |
| 1137 | 0.32<0.39 | 1.35<1.65 | <0.04 | 0.08<0.13 |
| 1138 | 0.34<0.4 | 0.7<1.0 | <0.04 | 0.08<0.13 |
| 1139 | 0.35<0.43 | 1.35<1.65 | <0.04 | 0.12<0.2 |
| 1140 1141 |
0.37<0.45 | 0.7<1.0 1.35<1.65 |
<0.04 | 0.08<0.13 |
| 1144 | 0.4<0.48 | 1.35<1.65 | <0.04 | 0.24<0.33 |
| 1145 1146 |
0.42<0.49 | 0.7<1.0 | <0.04 | 0.04<0.07 0.08<0.13 |
| 1151 | 0.48<0.55 | 0.7<1.0 | <0.04 | 0.08<0.13 |
Note: Whilst SAE grades 1111, 1112 & 1113 still officially exist, they have been superseded by SAE grades 1211, 1212 & 1213 and therefore no longer belong in the bove table
Sulphur (S) >0.05% and Phosphorus (P) >0.04%
| AISI No |
C (%) min<max |
Mn (%) min<max |
P (%) min<max |
S (%) min<max |
|---|---|---|---|---|
| 1211 1212 1213 |
<0.13 | 0.6<0.9 0.7<1.0 0.7<1.0 |
0.07<0.12 | 0.08<0.15 0.16<0.23 0.24<0.33 |
| 12L14 | <0.15 | 0.8<1.2 | 0.04<0.09 | 0.28<0.35 |
| 1215 | <0.09 | 0.7<1.0 | 0.04<0.09 | 0.26<0.35 |
Manganese (Mn) >1.65%
| AISI No |
C (%) min<max |
Mn (%) min<max |
P (%) min<max |
S (%) min<max |
|---|---|---|---|---|
| 1320 | 0.17<0.24 | 1.4<1.8 | <0.04 | <0.05 |
| 1321 | 0.4<1.0 | 1.88 | <0.04 | <0.05 |
| 1330 | 0.28<0.33 | 1.6<1.9 | <0.04 | <0.05 |
| 1335 | 0.33<0.38 | 1.6<1.9 | <0.04 | <0.05 |
| 1340 | 0.38<0.43 | 1.6<1.9 | <0.04 | <0.05 |
| 1345 | 0.43<0.48 | 1.6<1.9 | <0.04 | <0.05 |
Manganese (Mn) >1.0%
| AISI No |
C (%) min<max |
Mn (%) min<max |
P (%) min<max |
S (%) min<max |
|---|---|---|---|---|
| 1513 | 0.1<0.16 | 1.1<1.4 | <0.04 | <0.05 |
| 1518 | 0.15<0.21 | 1.1<1.4 | <0.04 | <0.05 |
| 1522 | 0.18<0.24 | 1.1<1.4 | <0.04 | <0.05 |
| 1524 | 0.19<0.25 | 1.35<1.65 | <0.04 | <0.05 |
| 1525 | 0.23<0.29 | 0.8<1.1 | <0.04 | <0.05 |
| 1526 | 0.22<0.29 | 1.1<1.4 | <0.04 | <0.05 |
| 1527 | 0.22<0.29 | 1.2<1.5 | <0.04 | <0.05 |
| 1536 | 0.3<0.37 | 1.2<1.5 | <0.04 | <0.05 |
| 1541 | 0.36<0.44 | 1.35<1.65 | <0.04 | <0.05 |
| 1547 | 0.43<0.51 | 1.35<1.65 | <0.04 | <0.05 |
| 1548 | 0.44<0.52 | 1.1<1.4 | <0.04 | <0.05 |
| 1551 | 0.45<0.56 | 0.85<1.15 | <0.04 | <0.05 |
| 1552 | 0.47<0.55 | 1.2<1.5 | <0.04 | <0.05 |
| 1561 | 0.55<0.65 | 0.75<1.05 | <0.04 | <0.05 |
| 1566 | 0.6<0.71 | 0.85<1.15 | <0.04 | <0.05 |
| 1572 | 0.65<0.76 | 1.0<1.3 | <0.04 | <0.05 |
'Special' carbon steels are simply plain carbon steels with the quantities of the four alloying elements; carbon, manganese, phosphorus and sulphur, modified in order to improve certain characteristics such as hardness and machining. No other alloying elements are added to these steels⁽¹⁾.
Whilst the above Tables contain only chemical composition, because their carbon content defines the physical properties (strength, hardness and elongation) of all carbon steels, you can use this information to obtain the properties of all of the above steel grades as follows:
1) extract the carbon content of your steel grade from the appropriate Table above
2) select the physical properties for the plain carbon steel with similar carbon content
3) apply the formulas and/or characteristics specified for manganese and phosphorus below
or
4) use CalQlata's carbon steel calculator to predict its mechanical properties
Manganese increases hardenability in carbon steels but also embrittlement up to about 2%, at which point it becomes extremely brittle. This extreme brittleness will remain a characteristic of the steel as you continue to add manganese until you have exceeded 5% when a transformation begins...
If manganese is added above 5% it starts to acquire ductility (after hot working) along with its hardness. Optimum ductility and hardness occurs with about 12% manganese.
Up to 2% (total) you should expect the Brinell hardness number of the materials in the plain carbon steel Table to increase by about '4' for each additional 0.1% manganese. Between 2% and 5% little change in hardness can be expected and after 5% it will begin to fall.
The beneficial effects of small quantities of phosphor are that it increases the strength of low-carbon steel by about 8ksi (at ≈0.15%) and improves hardenability (through heat treatment), machinability, deep drawability (cold drawing and wire production) and oxygen corrosion resistance.
Phosphorus should be kept below 0.16% in carbon steels, otherwise hardness will become embrittlement.
Yield and tensile stress modification formula: σ = σ + δP% x 73 (ksi)
Sulphur reacts with manganese in carbon steels to produce manganese sulphide, which assists chip breaking during machining hard steels but does not otherwise change the mechanical properties of the steel.
If sulphur was added to iron with no manganese it would react with the iron creating iron sulphide, which, having a lower melting point than manganese sulphide would impair hot working.
It is advisable to keep the sulphur content below 15% of the manganese as any free sulphur will combine with the iron adversely affecting hot working.
You will find further reading on this subject, incl. heat treatment, in our carbon steels web page