CalQlata's term 'alloy carbon' steels refers to what is generally known as 'high-alloy' steels
They comprise the same alloying elements as special carbon steel along with additional alloying elements⁽¹⁾
Moreover, these steels have the same alloying elements as the equivalent plain carbon steel with the same last two digits, but perhaps in different quantities, along with additional alloying elements to facilitate work hardening and heat treatment.
See Physical Properties below to obtain physical properties for each of steel grade
All the alloy steels on this page contain the following:
Sulphur (S) <0.04%⁽²⁾, Phosphorus (P) <0.035%, Silicon (Si) 0.02%<0.035%
| AISI No |
C (%) min<max |
Mn (%) min<max |
Ni (%) min<max |
|---|---|---|---|
| 2330 | 0.3 | 0.8 | 3.6 |
| 25XX | ??<?? | ??<?? | 5 |
| AISI No |
C (%) min<max |
Mn (%) min<max |
Cr (%) min<max |
Ni (%) min<max |
|---|---|---|---|---|
| 3140 | 0.4<0.5 | 0.5<0.8 | 0.45<0.75 | 1<1.5 |
| 32XX | ??<?? | ??<?? | 1.07 | 1.75 |
| 33XX | ??<?? | ??<?? | 1.5<1.57 | 3.5 |
| 34XX | ??<?? | ??<?? | 0.77 | 3 |
| AISI No |
C (%) min<max |
Mn (%) min<max |
Mo (%) min<max |
Cr (%) min<max |
Ni (%) min<max |
|---|---|---|---|---|---|
| 4012 4023 4024⁽²ᴬ⁾ 4027 4028⁽²ᴬ⁾ 4037 4047 |
0.09<0.14 0.2<0.25 0.2<0.25 0.25<0.3 0.25<0.3 0.35<0.4 0.45<0.5 |
0.75<0.1 0.7<0.9 0.7<0.9 0.7<0.9 0.7<0.9 0.7<0.9 0.7<0.9 |
0.15<0.25 0.2<0.3 0.2<0.3 0.2<0.3 0.2<0.3 0.2<0.3 0.2<0.3 |
||
| 4118 4130 4137 4140 4142 4145 4147 4150 4161 |
0.18<0.23 0.28<0.33 0.35<0.4 0.38<0.43 0.4<0.45 0.43<0.48 0.45<0.5 0.48<0.53 0.56<0.64 |
0.7<0.9 0.4<0.6 0.7<0.9 0.75<1.0 0.75<1.0 0.75<1.0 0.75<1.0 0.75<1.0 0.75<1.0 |
0.08<0.15 0.15<0.25 0.15<0.25 0.15<0.25 0.15<0.25 0.15<0.25 0.15<0.25 0.15<0.25 0.25<0.35 |
0.4<0.6 0.8<1.1 0.8<1.1 0.8<1.1 0.8<1.1 0.8<1.1 0.8<1.1 0.8<1.1 0.7<0.9 |
|
| 4320 4340 E4340⁽²ᴮ ⁴⁾ |
0.17<0.22 0.38<0.43 0.38<0.43 |
0.45<0.65 0.6<0.8 0.65<0.85 |
0.2<0.3 | 0.4<0.6 0.7<0.9 0.7<0.9 |
1.65<2.0 |
| 4419 | 0.18<0.23 | 0.45<0.65 | 0.45<0.6 | ||
| 4615 4620 4621 4626 |
0.13<0.18 0.17<0.22 0.18<0.23 0.24<0.29 |
0.45<0.65 0.45<0.65 0.7<0.9 0.45<0.65 |
0.2<0.3 0.2<0.3 0.2<0.3 0.15<0.25 |
1.65<2.0 1.65<2.0 1.65<2.0 0.7<1.0 |
|
| 4718 4720 |
0.16<0.21 0.17<0.22 |
0.7<0.9 0.5<0.7 |
0.3<0.4 0.15<0.25 |
0.35<0.55 | 0.09<0.12 |
| 4815 4817 4820 |
0.13<0.18 0.15<0.2 0.18<0.23 |
0.4<0.6 0.4<0.6 0.5<0.7 |
0.2<0.3 | 3.25<3.75 |
| AISI No |
C (%) min<max |
Mn (%) min<max |
Cr (%) min<max |
|---|---|---|---|
| 5015 50B44 50B46 50B50 50B60 |
0.12<0.17 0.43<0.48 0.44<0.49 0.48<0.53 0.56<0.64 |
0.3<0.5 0.75<1.0 0.75<1.0 0.75<1.0 0.75<1.0 |
0.3<0.5 0.4<0.6 0.2<0.35 0.4<0.6 0.4<0.6 |
| 5117 5120 5130 5132 5135 5140 5145 5147 5150 5155 5160 51B60 E51100⁽²ᴮ ⁴⁾ E52100⁽²ᴮ ⁴⁾ |
0.15<0.2 0.17<0.22 0.28<0.33 0.3<0.35 0.33<0.38 0.38<0.43 0.43<0.48 0.46<0.51 0.48<0.53 0.51<0.59 0.56<0.64 0.56<0.64 0.98<1.1 0.98<1.1 |
0.7<0.9 0.7<0.9 0.7<0.9 0.6<0.8 0.6<0.8 0.7<0.9 0.7<0.9 0.7<0.95 0.7<0.9 0.7<0.9 0.75<1.0 0.75<1.0 0.25<0.45 0.25<0.45 |
0.7<0.9 0.7<0.9 0.8<1.1 0.75<1.0 0.8<1.05 0.7<0.9 0.85<1.15 0.7<0.9 0.7<0.9 0.7<0.9 0.7<0.9 0.9<1.15 1.3<1.6 1.3<1.6 |
| AISI No |
C (%) min<max |
Mn (%) min<max |
Cr (%) min<max |
V (%) min<max |
|---|---|---|---|---|
| 6118 6150 |
0.16<0.21 0.48<0.53 |
0.5<0.7 0.7<0.9 |
0.5<0.7 0.8<1.1 |
0.1<0.15 0.15 |
| AISI No |
C (%) min<max |
Mn (%) min<max |
Cr (%) min<max |
W (%) min<max |
|---|---|---|---|---|
| 72XX | ??<?? | ??<?? | 0.75 | 1.75 |
| AISI No |
C (%) min<max |
Mn (%) min<max |
Mo (%) min<max |
Cr (%) min<max |
Ni (%) min<max |
|---|---|---|---|---|---|
| 81B45 | 0.43<0.48 | 0.75<1.0 | 0.08<0.15 | 0.35<0.55 | 0.2<0.4 |
| 8615 8617 8620 8622 8625 8627 8630 8637 8640 8642 8645 8655 |
0.13<0.18 0.15<0.2 0.18<0.23 0.2<0.25 0.23<0.28 0.25<0.3 0.28<0.33 0.35<0.4 0.38<0.43 0.4<0.45 0.43<0.48 0.51<0.59 |
0.7<0.9 0.7<0.9 0.7<0.9 0.7<0.9 0.7<0.9 0.7<0.9 0.7<0.9 0.75<1.0 0.75<1.0 0.75<1.0 0.75<1.0 0.75<1.0 |
0.15<0.25 | 0.4<0.6 | 0.4<0.7 |
| 8720 8740 |
0.18<0.23 0.38<0.43 |
0.7<0.9 0.75<1.0 |
0.2<0.3 | 0.4<0.6 | 0.4<0.7 |
| 8822 | 0.2<0.25 | 0.75<1.0 | 0.3<0.4 | 0.4<0.6 | 0.4<0.7 |
| AISI No |
C (%) min<max |
Mn (%) min<max |
Mo (%) min<max |
Cr (%) min<max |
Ni (%) min<max |
|---|---|---|---|---|---|
| 9255⁽³⁾ 9260⁽³⁾ |
0.51<0.59 0.56<0.64 |
0.7<0.95 0.75<1.0 |
|||
| 94B17⁽⁵⁾ 94B30⁽⁵⁾ |
0.15<0.2 0.28<0.33 |
0.75<1.0 | 0.08<0.15 | 0.3<0.5 | 0.3<0.6 |
These are not ''stainless' steels. The term; 'Alloy Carbon Steel' refers to carbon steels 'alloyed' with elements that can be used to significantly improve their physical properties by:
a) increasing mechanical strength and hardness prior to heat treatment
and
b) responding better to heat treatment and/or work hardening processes
and
c) retaining their mechanical properties at much higher temperatures than it otherwise would
Therefore, whilst carbon is still the dominant alloying element in these steels with regard to their mechanical properties, and chromium, vanadium, nickel and tungsten all increase the hardness and strength of carbon steels prior to heat treatment, the principal benefits of these alloying elements is that alloy steels will retain these properties at much higher temperatures than plain or special carbon steels and that they will (mostly) exist right through the material thickness.
For example: AISI 4130 grade steel, with 0.28% to 0.33% carbon, equates to the plain carbon steel AISI 1030, the respective mechanical properties of which are as follows:
| AISI No | SMYS (ksi) | UTS (ksi) | Elongation(%) |
|---|---|---|---|
| 1030 | 45<75 | 55<85 | 16.8<29.4 |
| 4130 | 95 | 148 | 17.7 |
The AISI 4130 is stronger because of the chromium, but it is made considerably tougher (less susceptible to brittle fracture) due to the molybdenum.
Whilst the above Tables contain only chemical composition, 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) modify hardness and strength according to the alloying elements present
4) apply the effects of heat treatment (hardening & tempering, annealing or normalising)
or
5) use CalQlata's carbon steel calculator to predict its mechanical properties
Note: Item 4 is necessary because it is unlikely that any of these alloy steels will be employed without heat treatment of some kind
See special carbon steels for the attributes of manganese, phosphorus and sulphur.
About 0.3% Molybdenum reduces temper-brittleness in hard alloy carbon steels such as chromium and/or nickel making them much more resilient to impact.
Chromium is a carbide stabiliser in that it forms the very hard Cr₇C₃ & Cr₂₃C₆ carbides with the carbon atoms in the steel preventing their movement under deformation with the effect of significantly increasing its hardness but if chromium is kept to less than about 1% (as is the case with virtually all alloy carbon steels) its strength will remain largely unaffected. However, chromium promotes grain growth, so continued use at relatively high temperatures can lead to a reduction in strength.
The Brinell hardness number of carbon steel increases by ≈8 for each additional 0.1% chromium
Chromium also improves corrosion resistance.
In addition to increasing tensile strength and toughness of carbon steels nickel has a grain refining effect. However, used on its own in carbon steels nickel will destabilise relatively unstable carbides into graphite making this alloying element more suitable for low carbon steels.
The Brinell hardness number of carbon steel increases by ≈3 for each additional 0.1% nickel
Nickel is therefore excellent for case hardening low carbon steels and is normally used with other elements that form very stable carbides (e.g. chromium) in high carbon steels.
Tungsten combines with carbon to form the very stable WC & Fe₄W₂C carbides and in doing so inhibits grain growth and raises the temperature at which carbon steels loose their strength and hardness making them very suitable for high-speed tool steels; e.g. drills, taps, reamers, dies, formers, etc.
Vanadium, which is rarely used in carbon steel without another alloying element, combines with carbon to form the carbide V₄C₃, stabilises martensite and improves hardenability. Chrome-vanadium steels are similar to nickel-chrome steels but they are easier to form and machine into smaller sections.
The Brinell hardness number of carbon steel increases by ≈9 for each additional 0.1% vanadium
Silicon generates fluidity in steel improving material flow during forming and is especially useful in steels intended for casting. Silicon also improves corrosion resistance.
Its quantity must be kept below 0.3% as silicon destabilises cementite, which may decompose into graphite and ferrite
You will find further reading on this subject, incl. heat treatment, in our carbon steels web page