AISI 440F Stainless Steel Plate | UNS S44020 | Free Machining 440
What is AISI 440F Stainless Steel ?
As a professional China steel mill-Direct Supply and stainless steel plate supplier, SHH STEEL is pleased to present AISI 440F Stainless Steel Plate.
AISI 440F is widely known and searched under many different names and designations, including AISI 440F, UNS S44020, 440F stainless steel, 440F stainless steel plate, free machining 440, SUS440F and sulfur-bearing 440C. All these names refer to the free-machining high-carbon martensitic variant of the 440 family.
AISI 440F keeps the 16–18% chromium and high-carbon chemistry of 440C / UNS S44004, but sulfur is raised to form manganese sulfides that break chips and raise machining speed. The grade remains magnetic and can still be hardened to high hardness. The selenium-bearing companion grade is AISI 440FSe (UNS S44023).
Because sulfur improves machinability, AISI 440F has lower corrosion resistance, toughness and polish quality than standard 440C. It is most common as bar and screw-machine parts; plate and sheet can be supplied when the drawing specifies UNS S44020 in flat form.
Do not confuse AISI 440F with ferritic A240 430 or with standard A240 410.
SHH STEEL supplies AISI 440F as true China steel mill-Direct Supply, sourcing directly from major Chinese stainless steel mills. This model delivers competitive mill pricing, consistent quality, complete heat traceability and reliable delivery.
AISI 440F is frequently compared with A240 410, A240 410S, A240 430, A240 429, a240 304 and a240 316l. SHH STEEL provides technical support to help customers choose the most appropriate grade.
AISI 440F Material Specification
| Specification Element | Requirement | SHH STEEL Compliance |
|---|---|---|
| Grade | AISI 440F / UNS S44020 | Confirmed |
| Related Standards | ASTM A582 related, JIS SUS440F | Available |
| Product Form | Plate, Sheet, Bar (as specified) | Available |
| Delivery Condition | Annealed (hardened + tempered on request) | Standard annealed |
| Thickness Range | 1 mm – 50 mm plate (other sizes on request) | Custom sizes supported |
| Width | Up to 1500 mm | Available |
| Length | Up to 6000 mm or cut-to-length | Available |
| Surface Finish | No.1, 2B, peeled / machined as specified | Available |
| Certification | EN 10204 3.1 / Mill Test Certificate | Available |
SHH STEEL can supply AISI 440F dual-certified to the required designation when specified by the project.
Chemical Composition
Typical Chemical Composition of AISI 440F (UNS S44020):
| Element | Content (%) |
|---|---|
| Carbon (C) | 0.95 – 1.20 |
| Silicon (Si) | ≤ 1.00 |
| Manganese (Mn) | ≤ 1.25 |
| Phosphorus (P) | ≤ 0.040 |
| Sulfur (S) | ≥ 0.15 |
| Chromium (Cr) | 16.00 – 18.00 |
| Molybdenum (Mo) | ≤ 0.75 |
| Iron (Fe) | Balance |
The defining features of AISI 440F are 440C-level carbon plus high sulfur. Carbon and chromium provide high hardness after heat treatment. Sulfur forms manganese sulfides that improve machinability. SHH STEEL carefully controls both so the grade machines well and can still be hardened.
Mechanical Properties
Annealed Condition (typical values)
| Property | Value |
|---|---|
| Hardness | Soft annealed for machining |
| Formability | Limited |
| Magnetism | Magnetic |
After quench and temper, AISI 440F can reach high hardness similar to 440C, but toughness and polish quality are lower because of sulfide inclusions. SHH STEEL normally supplies material in the annealed condition unless a hardened-and-tempered condition is specified.
Physical Properties
Density is approximately 7.70–7.75 g/cm³. Melting range is approximately 1370–1480°C. The grade is magnetic in all common heat-treated conditions.
Material Comparison
| Grade | UNS | Free Machining | Carbon (%) | Hardenable | Typical Preference |
|---|---|---|---|---|---|
| AISI 440C | S44004 | No | 0.95–1.20 | Yes | Bearings, maximum wear / polish |
| AISI 440F | S44020 | Yes (sulfur) | 0.95–1.20 | Yes | Machined + hardened 440 parts |
| AISI 440FSe | S44023 | Yes (selenium) | 0.95–1.20 | Yes | Screw-machine high-hardness parts |
| AISI 440A | S44002 | No | 0.60–0.75 | Yes | Tougher 440 cutlery |
| AISI 416 | S41600 | Yes | ≤ 0.15 | Yes | Free-machining 410 family |
| AISI 420F | S42020 | Yes | ≥ 0.15 | Yes | Free-machining 420 family |
AISI 440F is selected when the part must be machined at high speed and then hardened to 440-level hardness. For bearings and polished cutlery, standard 440C is preferred. For welded plate, SHH STEEL recommends A240 410S or A240 430.
Corrosion Resistance
AISI 440F has useful resistance to mild atmospheres after heat treatment, similar in principle to 440C. Sulfide inclusions reduce pitting resistance and polish quality.
Best corrosion performance is obtained after hardening and polishing. For better corrosion resistance, SHH STEEL recommends standard 440C or a240 304.
Weldability
Heat Treatment
AISI 440F is normally supplied in the annealed condition by SHH STEEL and can be hardened by quench and temper.
Typical hardening is performed from about 1010–1065°C, followed by oil or air cooling and tempering to the required hardness. Sulfide inclusions reduce toughness at a given hardness compared with 440C. SHH STEEL can supply annealed material or discuss hardened-and-tempered supply when the drawing requires it.
Surface Finishes
| Finish | Description | Typical Use / Keywords |
|---|---|---|
| No.1 | Hot-rolled, annealed and pickled | AISI 440F No.1 – industrial plate |
| 2B | Cold-rolled, annealed, pickled, skin-passed | AISI 440F 2B – thin plate / sheet |
| Peeled / Turned | Machined bar surface | AISI 440F bar for screw-machine work |
| Special | Ground or custom finishes | AISI 440F Special – on request |
SHH STEEL supplies AISI 440F in the finish required by the machining or fabrication drawing.
Tolerances
Dimensional tolerances for AISI 440F plate supplied by SHH STEEL generally conform to ASTM A480 practices. Bar products follow the applicable bar standard.
Typical plate size range is thickness 1 mm – 50 mm, width up to 1500 mm, and length up to 6000 mm or cut-to-length. SHH STEEL can support tighter machining allowances when required.
Equivalent Material Grades
| Grade / Designation | Standard / Region | Notes |
|---|---|---|
| AISI 440F | AISI | Main commercial keyword |
| UNS S44020 | Unified Numbering System | Primary UNS designation |
| SUS440F | JIS (Japan) | Japanese related grade |
| Related free-machining 440 | EN / GB | Closest national grades |
| Related 440C / 440FSe | Multiple | Standard / Se-bearing variants |
Related grades for comparison include A240 410, A240 410S, A240 430, A240 429, a240 304 and a240 316l.
AISI 440F Applications
AISI 440F is selected when high machining speed and later 440-level hardness are both required. Typical applications of AISI 440F include:
| Industry / Sector | Typical Components / Equipment (with keywords) |
|---|---|
| Screw-Machine Parts | AISI 440F fittings, pins, bushings and turned wear parts |
| Cutlery & Tools | AISI 440F blanks that will be machined then hardened |
| Valves & Pumps | AISI 440F machined seats, sleeves and small hardened parts |
| Fasteners & Hardware | AISI 440F screws and machined fasteners |
| General Machining | UNS S44020 bar and plate for high-speed machining |
| Industrial Equipment | AISI 440F No.1 plate cut for subsequent machining and hardening |
SHH STEEL supplies AISI 440F for these machining-intensive applications with consistent quality. For related industry solutions, see our equipment manufacturing and machinery industry pages. Supporting services include cnc steel machining services, steel cutting services and worldwide shipping service.
Why Choose SHH STEEL
SHH STEEL is a China steel mill-Direct Supply specializing in stainless steel plate, sheet and machining grades. By working directly with major Chinese stainless steel mills, SHH STEEL supplies AISI 440F with the following advantages:
- Genuine China steel mill-Direct Supply pricing
- Consistent quality and complete heat traceability
- Full Mill Test Certificates (EN 10204 3.1)
- Sulfur-controlled AISI 440F material optimized for high-speed machining and high hardness
- Flexible dimensions and finishes (including AISI 440F No.1 and AISI 440F 2B)
- Technical support for selection among AISI 440C, 440F, 440A and 420F
- Value-added services including cnc steel machining services, steel cutting services and worldwide shipping service
For more information about our company and full product range, please visit China steel Mill Agent-SHH STEEL.
FAQ
- What are the other common names for AISI 440F?AISI 440F is also known as UNS S44020, free machining 440 and SUS440F. SHH STEEL can certify the required designation.
- What is the difference between AISI 440F and AISI 440C?AISI 440F contains added sulfur for much better machinability. Standard 440C has better corrosion resistance, toughness and polish quality. SHH STEEL recommends 440F only when machining is the main requirement.
- Can AISI 440F be hardened?Yes. It remains a high-carbon martensitic grade and can be quenched and tempered to high hardness. SHH STEEL normally supplies annealed material unless a hardened condition is specified.
- Is AISI 440F magnetic?Yes. It is magnetic in both the annealed and hardened conditions.
- What is the density of AISI 440F?Approximately 7.70–7.75 g/cm³. SHH STEEL provides mill certificates confirming chemistry and mechanical properties.
- Can AISI 440F be welded easily?No. High carbon plus sulfur make welding very difficult. SHH STEEL recommends 410S or 304 when welding is required.
- Does SHH STEEL supply dual-certified AISI 440F / UNS S44020 material?Yes, SHH STEEL commonly supplies dual-certified material upon request.
Conclusion
AISI 440F Stainless Steel Plate is the free-machining sulfur-bearing variant of the 440 high-carbon family. It is chosen for high-speed turning and screw-machine work when the finished part must also be hardened to 440-level hardness. For bearings, polished cutlery and maximum wear quality, standard AISI 440C remains the better choice.
As a professional China steel mill-Direct Supply, SHH STEEL provides high-quality AISI 440F / UNS S44020 material with competitive pricing, full certification and complete technical support.
Contact SHH STEEL today for stock availability, plate or bar sizes, surface finish options (including AISI 440F No.1 and AISI 440F 2B), or a competitive quotation.
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