Ask three buyers what “billet” they need and you may hear three different answers: MS billets, carbon steel billets or alloy steel billets. The terms overlap, and that confusion leads to wrong orders, failed test certificates and bars that crack in forging.
This guide clears it up. You’ll learn what each billet type actually is, how their chemistry and grades differ, where each one is used, and how to choose the right billet for your rolling mill or forge. For a broader overview, see our guide to steel billets manufacturer in India.
The Short Answer: How They Relate
Before comparing, it helps to know that these three are not completely separate families:
- Carbon steel billets are billets whose properties come mainly from carbon, with only small amounts of manganese and silicon. They are grouped into low, medium and high carbon.
- MS (mild steel) billets are simply low-carbon steel billets. Every MS billet is a carbon steel billet, but not every carbon steel billet is MS.
- Alloy steel billets have deliberate additions of elements like chromium, molybdenum, nickel or vanadium to reach strength, hardness or toughness that carbon alone can’t give.
So the real choice is: low carbon (MS), then higher carbon, then alloyed, moving up in strength and hardenability, and usually in price. Read more about the types of steel billets.
MS Billets (Mild Steel Billets)
What They Are
MS billets are low-carbon steel billets, typically with about 0.12–0.25% (LOW CARBON IS MAXIMUM UPTO 16-18) carbon, plus manganese to add strength. They are soft, ductile and easy to weld, which makes them the workhorse of India’s construction steel industry.
Most MS billets ( MS BILLET IS 18-22 CARBON) in India are continuous-cast from induction furnace or electric arc furnace steel and supplied to re-rolling mills. Carbon steel cast billets for re-rolling are covered by IS 2830 (Bureau of Indian Standards).
Key Properties
- Excellent weldability and ductility
- Easy to roll at lower furnace temperatures
- Moderate strength, which is boosted in the finished bar by TMT quenching
- Lowest cost of the three billet types
Where MS Billets Are Used
- TMT rebars (Fe 415, Fe 500, Fe 500D, Fe 550D to IS 1786, high strength deformed steel bars)
- Structural sections: angles, channels, flats and beams
- Wire rods, binding wire and general fabrication steel
Tip: For higher TMT grades like Fe 550D or Fe 600, mills often use micro-alloyed MS billets with small additions of vanadium or niobium. This raises strength without hurting weldability.
Carbon Steel Billets
What They Are
Carbon steel billets cover the full range of plain carbon steels. The carbon level decides almost everything about the billet:
| Carbon Category | Approx. Carbon % | Behaviour |
| Low carbon (MS) | Up to ~0.16% | Soft, ductile, very weldable |
| Medium carbon | ~0.16–0.25% | Stronger, harder, can be heat treated |
| High carbon | ~0.25–45-50%+ | Very hard and wear-resistant, less ductile |
Ranges are indicative; exact limits depend on the standard and grade.
Common Medium and High Carbon Grades
- EN8 / C45 (IS 1570: 45C8 equivalent): medium carbon, used for shafts, axles, bolts and general engineering parts
- EN9 / C55: higher strength, used for gears, sprockets and machine parts
- High-carbon wire-rod grades (about 0.60–0.85% C): for spring wire, high-tensile wire, PC strand and wire ropes
Where Carbon Steel Billets Are Used
- Bright bars and machined shafts
- Forged components that need moderate strength
- Rails, springs, high-tensile and spring wire
- Agricultural tools and wear parts
Medium and high carbon billets need slower, more careful heating and cooling. Otherwise they can crack or harden unevenly.(ANY BILLET IT IS IT NEEDS TO BE LET COOL NATURALLY OTHER IT WILL GET HARDEND IF WE PUT EXTERNAL FORCE TO COOL IT SAY AIR OR WATER
Alloy Steel Billets
What They Are
Alloy steel billets contain intentional amounts of alloying elements, usually chromium (Cr), molybdenum (Mo), nickel (Ni), manganese (Mn) or vanadium (V). These elements improve hardenability, toughness, fatigue strength and wear resistance, especially after heat treatment.
Common Alloy Steel Billet Grades
| Grade (common names) | Main Alloying Elements | Typical Uses |
| EN19 / 42CrMo4 / SAE 4140 | Cr, Mo | Crankshafts, axles, high-strength bolts, oil and gas parts |
| EN24 / 817M40 / SAE 4340 | Ni, Cr, Mo | Heavy-duty shafts, gears, aircraft and defence parts |
| 20MnCr5 / 16MnCr5 | Mn, Cr | Case-hardened gears, pinions, camshafts |
| SAE 8620 | Ni, Cr, Mo | Carburized gears and transmission parts |
| EN31 / SAE 52100 | High C, Cr | Bearings and bearing races |
Grade equivalents are approximate. Always specify the exact standard (IS, EN, DIN or SAE) in your order.
Where Alloy Steel Billets Are Used
- Automotive forgings: crankshafts, connecting rods, gears, axles
- Bearings, fasteners and heavy engineering parts
- Oil and gas, mining and defence components
Alloy steel billets are usually made with secondary refining (LRF, sometimes vacuum degassing) to control inclusions and gas content. That is part of why they cost more.
MS vs Carbon vs Alloy Steel Billets: Side-by-Side Comparison
| Factor | MS Billets | Carbon Steel Billets (Med/High) | Alloy Steel Billets |
| Carbon content | ~0.08–0.16% | ~0.18–50% | Varies (0.15–1.0%) + alloys |
| Alloying elements | None (Mn only) | None (Mn, Si only) | Cr, Mo, Ni, V, etc. |
| Strength | Moderate | Medium to high | High to very high |
| Weldability | Excellent | Fair to poor | Needs controlled procedure |
| Heat treatment | Rarely needed | Often (hardening/tempering) | Almost always |
| Typical end products | TMT bars, sections, wire rods | Shafts, springs, wire, rails | Gears, crankshafts, bearings |
| Relative cost | Lowest | Medium | Highest |
| Main buyers | Re-rolling mills | Bright bar, wire and forging units | Auto and engineering forges |
How to Choose the Right Billet
Work through these questions before you place an order:
- What is the finished product? Rebar and sections usually need MS billets. Shafts, wire and springs need carbon steel billets. Gears, crankshafts and bearings need alloy steel billets.
- What strength grade must it meet? Check the finished-product standard (IS 1786, IS 2062, IS 1570 or the customer’s drawing) and work back to the billet chemistry.
- Will it be welded or heat treated? Heavy welding favours MS. Hardening and tempering favours carbon or alloy grades.
- How tight are the chemistry limits? Specify C, Mn, S and P ranges, plus any alloy ranges, and ask for a heat-wise mill test certificate.
- What size fits your mill? Match billet size and length to your first rolling stand and furnace.
Related reading: steel billet sizes and grades and how to identify poor-quality steel billets.
FAQ
Are MS billets and carbon steel billets the same?
Not exactly. MS billets are low-carbon steel billets, so they are one type of carbon steel billet. “Carbon steel billets” also includes medium and high carbon grades, which are stronger and harder than MS.
Which billet is used for TMT bars?
Most TMT bars are rolled from MS billets. Higher grades such as Fe 550D and Fe 600 often use micro-alloyed MS billets with small additions of vanadium or niobium.
What are alloy steel billets used for?
Alloy steel billets are used for high-strength, heat-treated parts such as crankshafts, gears, axles, bearings, high-tensile bolts and oil and gas components.
Is EN8 a carbon steel or alloy steel billet?
EN8 (about C45) is a medium carbon steel, not an alloy steel. It is commonly used for shafts, bolts and general engineering parts.
Why are alloy steel billets more expensive?
They contain costly alloying elements like chromium, molybdenum and nickel. They also need tighter chemistry control, secondary refining and more testing.
Conclusion
MS billets are low-carbon, weldable and economical, the right choice for TMT bars and structural steel. Carbon steel billets with more carbon deliver higher strength for shafts, wire and springs. Alloy steel billets add chromium, molybdenum or nickel for the toughest heat-treated parts. Pick the billet by working back from your finished product, its standard and its processing route.
Need billets for your rolling mill? RP Multimetals supplies quality-tested steel billets with controlled chemistry and full test certificates. Explore our MS and alloy steel billets or request a billet quote with your grade, size and quantity.