General Information for Stainless Steel 440A
| Material Group |
M - Stainless Steel |
| Sub-Group |
Martensitic Stainless Steel |
| Hardness |
42.5 HRC |
| Tensile Strength |
1000-1800 [N/mm^2] |
| Machinability Range |
48% |
MACHINABILITY OF 440A STAINLESS STEEL
Stainless Steel 440A is a martensitic (magnetic) stainless steel alloy with 17% chromium, 0.1% carbon and a machinability rating of 48%.
The amounts of carbon (Range 0.1-1.2%) and chromium (10-15%) are the main factors that affect the machinability of martensitic stainless materials.
More carbon ==> More strength, but lower machinability and less corrosion resistance
More chromium ==> More corrosion resistance, but lower machinabilty
Due to its low carbon content stainless steel 440A has high toughness, and therefore it is very malleable. The main challenge to machining it (relative to other martensitic stainless alloys) is breaking the chips. Therefore, it is recommended to select a sharp cutting edge with a tight chip breaker. For this reason, inserts that are designed for arsenic stainless alloys (Such as 304 and 316) will work well also on stainless steel 440A.
SUMMARY:
For general turning of Stainless Steel 440A at stable conditions use a grade with a semi hard substrate and thin CVD coating.
In case you are running at a cutting speed that is lower than 390 SFM (120 m/min), it is better to use a grade with a semi hard substrate and PVD coating.
For general milling, use the grade with a semi-hard substrate and thin PVD coating.
For detailed carbide grades recommendations,check the table below.
Recommended cutting speed range for turning at stable conditions is 590 - 790 [SFM] / 180 - 240 [m/min].
Recommended cutting speed range for milling with stable clamping and short over hang is 360 - 490 [SFM] / 110 - 150 [m/min]
For detailed cutting speed recommendations, check the table below.
Equivalent International Designations for Stainless Steel 440A
| Standard |
Name |
| SAE |
440A |
| WNR |
1.4109 |
| DIN |
X70CrMo15 |
| UNS |
UNS S44002 |
Chemical Composition for Stainless Steel 440A
| Element |
Amount |
| Iron (Fe) |
81% |
| Chromium (Cr) |
17% |
| Silicon (Si) |
1% |
| Manganese (Mn) |
1% |
| Molybdenum (Mo) |
0.75% |
| Nickel (Ni) |
0.5% |
| Phosphorus (P) |
0.04% |
| Carbon (C) |
0.07% |
| Sulfur (S) |
0.003% |
Cutting Speeds Recomendations for Stainless Steel 440A
| Application |
Vc (m/min) |
Vc (SFM) |
| Turning |
180-240 |
590-790 |
| Milling |
110-150 |
360-490 |
| Parting |
70-95 |
230-310 |
| Grooving |
105-145 |
340-480 |
| Drilling |
50-70 |
160-230 |
Important! The speed estimation is given for an ideal situation:
- Most suitable carbide grade
- Stable tool clamping
- Stable workpiece clamping
- Good quality raw material
- A short overhang of the cutting tool.
- Nominal hardness of the material.
- etc.
Recommended Carbide Grades for Stainless Steel 440A
Grade for Milling (Indexable)
Recommended Insert Cutting Edge Geometry for Stainless Steel 440A
| Honing Size |
0.03-0.05 mm / 0.001-0.002" |
| Rake Angle |
9°-11° |
| Land Angle |
Positive |
| Land Width |
0.20-0.30 mm / 0.008-0.012" |
