T: +86-0731-85185770
E: enquiry@qilumetal.com
E: enquiry@qilumetal.com
No. 18 Xiangfu Middle Road,Yuhua District, Changsha City
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440C
Qilu
ASTM 440C stainless steel bar is the highest-carbon grade of the AISI 400 martensitic series, specified as UNS S44004 in ASTM A276 and A479, 1.4125 X105CrMo17 in EN 10088-3, SUS440C in JIS G4303 and 102Cr17Mo (the older 9Cr18Mo) in GB/T 1220. Qilu Steel supplies this grade as cold drawn bar Φ3-Φ80 mm, hot rolled bar Φ16-Φ310 mm and hot forged bar Φ100-Φ1200 mm, normally in the annealed condition with EN 10204 3.1 certification, and hardened and tempered to order against a drawing.
The alloy design buys the highest hardness available in a standard stainless steel: 0.95-1.20% carbon meets 16.00-18.00% chromium, quenching to 60-63 HRC and tempering at 150-180 °C back to 58-62 HRC. A large volume of M7C3 carbides carries the wear load, and the chromium left in the matrix holds mild atmospheric and food-grade corrosion at bay. That is why bearing balls, valve balls and seats, industrial knives and pump shafts dominate the order book. The trade is set early in the design stage: toughness is low, and with a carbon equivalent near 4.7 the grade is not a welding material.
Country | USA | EN | China | Japan | Russia |
Standard | ASTM A276/276M | EN10088-3 | GB/T1220 | JIS G4303 | GOST 5632-72 |
Grade | 440C | X105CrMo17/ 1.4125 | 9Cr18Mo | SUS440C | 95X18 |
Grade | C | Si | Mn | P | S | Cr | Mo | Ni |
440C | 0.95-1.20 | 1.00Max | 1.00Max | 0.040Max | 0.030Max | 16.00-18.00 | / | / |
X105CrMo17/ 1.4125 | 0.95-1.20 | 1.00Max | 1.00Max | 0.040Max | 0.030Max | 16.00-18.00 | 0.40-0.80 | / |
9Cr18Mo | 0.95-1.10 | 0.80Max | 0.80Max | 0.040Max | 0.030Max | 16.00-18.00 | 0.40-0.70 | 0.60Max |
| SUS440C | 0.95-1.20 | 1.00Max | 1.00Max | 0.040Max | 0.030Max | 16.00-18.00 | 0.75Max | 0.60Max |
440C steel bar is normally accepted by hardness after a hardening and tempering cycle rather than by tensile test in the delivery condition.
| Size range | Condition | Hardness | Tensile strength | Alongation |
| d≤50 | hardened + tempered 150-180 °C | 58-62 HRC | 1850-2150Mpa | 2-5% |
| 50＜d≤150 | hardened + tempered 150-180 °C | 57-61 HRC | 1800-2050Mpa | 2-5% |
| 150＜d≤300 | hardened + tempered, surface | 56-60 HRC | 1750-2000Mpa | 2-4% |
| 300＜d≤1200 | supplied annealed | 56-60 HRC | agreed on drawing | agreed on drawing |
Heat slowly. Thermal conductivity is low for a stainless steel, around 25 W/m·K, so charge cold bars into a furnace at 700-750 °C and soak before moving up to 1050-1150 °C. Finish forging above 950 °C. From ingot to bar the reduction ratio should reach at least 4:1 on heavy sections, because ingot solidification leaves a coarse primary carbide network that only heavy hot work breaks up. Cool slowly in sand or the furnace and move the charge straight into annealing; leaving a 440C forging to cool in still air is how surface cracks start.
Ultrasonic testing runs after annealing to EN 10228-3. On Φ300 mm and larger forged sections the carbide banding that gives this grade its wear resistance also attenuates the UT beam, so the class (class 2 or class 3, reference flat-bottom hole 2 or 3 mm) and the reference notch should be settled with the mill on the same heat before the PO is placed, and the acceptance distance-amplitude curve recorded.
| Condition | Temperature | Cooling | Hardness |
| Annealing | 850-880 °C | furnace cool | ≤255 HB |
| Hardening | 1010-1070 °C, preheat 800-850 °C | oil or air | 60-63 HRC |
| Tempering | 150-180 °C, double temper | air | 58-62 HRC |
Product type | Size range | Length |
Hot rolled bar | Φ10-Φ130mm | 5000-7000mm |
Hot forged bar | Φ140-Φ600mm | 2000-5800mm |
Hot rolled plate/sheet | T:2-60mm; W:310-810mm | 6000-12000mm |
Hot forged plate | T:70-250mm; W:310-810mm | 2000-5800mm |
Hot Forged block | T: 260-500mm; W: 300-1000mm | 2000-5800mm |
Surface Finish | Turned | Milled | Grinding(Best) | Polished(Best) | Peeled(Best) | Black Forged | Black Rolled |
Tolerance | +0/+3mm | +0/+3mm | +0/+0.05mm | +0/+0.05mm | +0/+0.1mm | +0/+5mm | +0/+1mm |
Straighness | 1mm/1000mm max. | 3mm/1000mm max. | |||||
We stock 440C annealed bar from Φ20 to Φ150 mm, and buyers who harden in-house typically order 1–2 mm of grinding allowance on top.
Balls, rollers, races and cages for pumps and electric motors running wet or mildly corrosive.
Ball valve balls and seats, stems, check valve internals and control valve trim in chemical and water service.
Industrial knives, food processing blades, surgical instruments, scissors and shear edges that hold a hard edge.
Shafts, plungers, bushings and wear rings handling chemical media.
Mold cores, cavities and wear inserts for corrosive resins such as PVC, where 1.2311 rusts and 1.2083 alternatives get expensive at high hardness.
Gauge pins, nozzle tips, guide bushings and metering pump parts that need dimensional stability at high hardness.
A1: 1.4125 / X105CrMo17 under EN 10088-3, SUS440C under JIS G4303 and 102Cr17Mo (old 9Cr18Mo) under GB/T 1220. The windows are close but not identical: ASTM and JIS accept molybdenum from zero up to 0.75 percent, EN requires 0.40-0.80, and the Chinese window caps carbon at 1.10. Name the governing standard on the order.
A2: It depends on the part. 440B runs 1-3 HRC softer after the same temper, with slightly better toughness. On bearing balls, valve seats and knife edges, where the 55 HRC minimum is written into the specification, the substitution misses the band and shortens service life. Buy 440B only when the drawing allows it.
A3: No. In the fully hardened state, roughly a third of the chromium sits in M7C3 carbides and the matrix carries around 11 percent, so 440C handles atmosphere, oil, and mild food acids but pits in chloride media where 316 or 2205 survive. It is the most wear-resistant stainless in the series and the least corrosion-resistant one to specify for seawater.
A4: That window holds 58-62 HRC and keeps enough chromium in solution for corrosion resistance. Temper at 400-500 °C and hardness falls to 45-52 HRC while carbide precipitation strips the matrix chromium, leaving a part that is neither tough nor corrosion resistant. If the application needs real toughness, the correct answer is a different grade such as 431 or 17-4PH.
Contact Qilu Steel for quotation, current lead time, sample or custom specification.
