Short answer: SAE 8620, EN353 and 20MnCr5 are all low-carbon (about 0.2% C) case-hardening steels: carburised and hardened, each gives a hard, wear-resistant surface of about 58–62 HRC over a tougher core. The difference is the alloying behind the core. SAE 8620 is a lean nickel-chromium-molybdenum steel and the most widely used general-purpose grade. EN353 has about twice the nickel, so it gives a stronger, tougher core in bigger sections. 20MnCr5 has no nickel or molybdenum and relies on manganese and chromium instead.
In this guide: At a glance · Chemistry · Case and core · Which to use · Substituting · FAQ
At a glance
| SAE 8620 | EN353 | 20MnCr5 | |
|---|---|---|---|
| Alloy type | Ni-Cr-Mo, lean | Ni-Cr-Mo, more nickel | Mn-Cr, no nickel |
| Equivalents | 20NiCrMo2-2 (1.6523), 805M20, SNCM220 | 815M17 (nearest), 17NiCrMo6-4, IS 15Ni5Cr4Mo1 | 1.7147, IS 20MnCr5, nearest AISI 5120 |
| Case hardness after carburising | 58–63 HRC | 58–62 HRC | about 58–62 HRC |
| Core toughness | Good | Very good | Good, lower in thick sections |
| Typical use | General gears, pins, cams, bushes | Heavy-duty gears, pinions, transmission shafts | Gears and shafts on European drawings |
| Stocked by Sai International | Yes, as-rolled, Ø14–315 mm | Yes, as-rolled, Ø16–205 mm | No |
Chemical composition compared
| Element, % | SAE 8620 (SAE J404) | EN353 (Indian mill range) | 20MnCr5 (EN 10084) |
|---|---|---|---|
| Carbon (C) | 0.18–0.23 | max 0.20 | 0.17–0.22 |
| Silicon (Si) | 0.15–0.35 | max 0.35 | max 0.40 |
| Manganese (Mn) | 0.70–0.90 | 0.50–1.00 | 1.10–1.40 |
| Nickel (Ni) | 0.40–0.70 | 1.00–1.50 | — |
| Chromium (Cr) | 0.40–0.60 | 0.75–1.25 | 1.00–1.30 |
| Molybdenum (Mo) | 0.15–0.25 | 0.08–0.15 | — |
EN353 is shown as Indian mills certify it, which follows the original BS 970 En353 range rather than the later 815M17 (which asks for 1.20–1.70% nickel). Our mill's SAE 8620 range allows up to 0.045% phosphorus and sulphur against SAE J404's 0.030% and 0.040%. Always check the mill test certificate against the standard on your drawing; our mill test certificate guide shows how.
Case and core: what the alloying changes
All three are carburised the same way: the machined part is heated in a carbon-rich atmosphere so the surface picks up carbon, then hardened and tempered at a low temperature. The surface ends up at roughly the same hardness in each grade, because that depends mainly on the carbon added during carburising. What the alloying decides is the core: how strong and tough the inside of the part is, and how deep into a thick section it still hardens.
- SAE 8620: core typically 30–45 HRC, core tensile about 650–950 MPa. Enough for most gears and pins in small and medium sections.
- EN353: core typically 30–42 HRC, core tensile about 800–1100 MPa. The extra nickel keeps the core tough and strong in larger sections and under shock.
- 20MnCr5: manganese and chromium give good hardenability without nickel, which keeps cost down. Its core is less tough than the nickel grades, which matters most in big sections and impact-loaded parts.
See our hardness guide for case and core values of all our grades in HRC.
Which one to use
- General gears, gudgeon pins, cams, bushes and sprockets: SAE 8620. The economical default, and the widest size range we stock.
- Heavy-duty gears, crown wheels, pinions and transmission shafts, especially in larger sections or with shock loads: EN353.
- The most demanding gears and highly stressed parts: step up to EN36C (3% nickel). See EN36A vs EN36B vs EN36C.
- A drawing that specifies 20MnCr5: follow the drawing where you can source it; if you cannot, see below.
Substituting one for another
Because the case hardness is similar, these grades are often substituted, but the core is not the same, so any change should be approved by whoever owns the design:
- EN353 in place of SAE 8620 is a step up: a stronger, tougher core. It is the safer direction, though the carburising cycle may need adjusting.
- SAE 8620 in place of EN353 is a step down in core strength, so check the part's section size and loading first.
- SAE 8620 or EN353 in place of 20MnCr5 changes the alloy system entirely (nickel-molybdenum instead of manganese-chromium). The carburising cycle and the expected core properties should be confirmed with your heat treater.
If you are unsure, send us the drawing or the grade and size and we will tell you what we have in stock and how it compares.
SAE 8620 and EN353 from Sai International
We keep both grades in ready stock at Darukhana, Mumbai, as as-rolled round bar: SAE 8620 Ø14–315 mm (forged bar from Ø160 mm) and EN353 Ø16–205 mm. Every dispatch comes with the mill test certificate for its heat. Minimum order is 100 kg; datasheets are on each product page.
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SAE 8620, EN353 and 20MnCr5: frequently asked questions
What is the difference between SAE 8620 and EN353?
Both are nickel-chromium-molybdenum case-hardening steels. EN353 carries more nickel (about 1.0–1.5% against 0.4–0.7%) and more chromium, so after carburising it gives a stronger, tougher core, especially in larger sections. SAE 8620 is leaner and more economical, and is the most widely used general-purpose carburising grade.
Is 20MnCr5 equivalent to SAE 8620?
Not exactly. Both are carburising steels with about 0.2% carbon, but 20MnCr5 has no nickel or molybdenum; it relies on manganese (1.10–1.40%) and chromium (1.00–1.30%) for hardenability. It often reaches a similar case hardness, but core toughness and response in large sections differ, so a substitution should be approved by the designer.
Which is better for gears: SAE 8620, EN353 or 20MnCr5?
For general automotive and machine gears, SAE 8620 or 20MnCr5 are the usual choices. For heavier-duty gears and pinions in larger sections or with shock loads, EN353 is preferred because its higher nickel gives a tougher core. For the most demanding gears, EN36C (3% nickel) is the next step up.
What is the case hardness of SAE 8620 and EN353 after carburising?
Both typically reach 58–62 HRC at the surface after carburising, hardening and low-temperature tempering. Core hardness is typically about 30–45 HRC for SAE 8620 and 30–42 HRC for EN353, depending on section size.
In what condition do you supply SAE 8620 and EN353?
We stock both as as-rolled round bar: SAE 8620 from Ø14 to Ø315 mm (forged from Ø160 mm) and EN353 from Ø16 to Ø205 mm, every dispatch with its mill test certificate.
Values are typical figures for guidance and are not a guarantee; actual properties depend on the heat, section size and heat treatment. Please confirm suitability for your application.