AISI 420F Stainless Steel Plate | UNS S42020 | Free Machining 420

As a professional China steel mill-Direct Supply and stainless steel plate supplier, SHH STEEL is pleased to present AISI 420F Stainless Steel Plate.

AISI 420F is widely known and searched under many different names and designations, including AISI 420F, UNS S42020, 420F stainless steel, 420F stainless steel plate, free machining 420, SUS420F and sulfur-bearing 420. All these names refer to the free-machining martensitic variant of Type 420.

AISI 420F keeps the high-carbon 12–14% chromium martensitic base of AISI 420 / UNS S42000, but sulfur is raised (typically 0.15% minimum) 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 420FSe (UNS S42023).

Because sulfur improves machinability, AISI 420F has lower corrosion resistance, weldability and toughness than standard 420. It is most common as bar and screw-machine parts; plate and sheet can be supplied when the drawing specifies UNS S42020 in flat form.

Do not confuse AISI 420F / S42020 with A240 UNS S42035, which is a low-carbon welded-plate grade, or with standard A240 410.

SHH STEEL supplies AISI 420F 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 420F is frequently compared with A240 410, A240 410S, A240 430, A240 429, A240 409 and a240 304. SHH STEEL provides technical support to help customers choose the most appropriate grade.

SHH STEEL can supply AISI 420F dual-certified to the required ASTM / JIS designation when specified by the project.

Typical Chemical Composition of AISI 420F (UNS S42020):

The defining features of AISI 420F are carbon of at least 0.15% plus high sulfur in a 420-type martensitic base. Carbon provides high hardness after heat treatment. Sulfur forms manganese sulfides that improve machinability. SHH STEEL carefully controls both elements so the grade machines well and can still be hardened.

Annealed Condition (typical values)

After quench and temper, AISI 420F can reach high hardness similar to Type 420, but toughness is 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 7.75 g/cm³. Melting range is approximately 1450–1510°C. The grade is magnetic in all common heat-treated conditions.

AISI 420F is selected when the part must be machined at high speed and then hardened to 420-level hardness. For blades and instruments that will be ground rather than screw-machined, standard AISI 420 is preferred. For welded plate, SHH STEEL recommends A240 410S.

AISI 420F has useful resistance to mild atmospheres and many household or food-contact environments after heat treatment, similar in principle to Type 420. Sulfide inclusions reduce resistance to pitting and crevice corrosion.

Best corrosion performance is obtained after hardening and polishing. For better corrosion resistance, SHH STEEL recommends standard 420 or a240 304.

AISI 420F has poor weldability. High carbon plus sulfur create a hard, crack-sensitive heat-affected zone. Welding is generally avoided.

If the part must be both machined and joined, SHH STEEL often recommends machining from 420F bar and using A240 410 or A240 410S for welded sections.

AISI 420F is normally supplied in the annealed condition by SHH STEEL and can be hardened by quench and temper.

Typical hardening is performed from about 980–1050°C, followed by oil or air cooling and tempering to the required hardness. Sulfide inclusions reduce toughness at a given hardness compared with standard 420. SHH STEEL can supply annealed material or discuss hardened-and-tempered supply when the drawing requires it.

SHH STEEL supplies AISI 420F in the finish required by the machining or fabrication drawing.

Dimensional tolerances for AISI 420F 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 1500–2000 mm, and length up to 6000 mm or cut-to-length. SHH STEEL can support tighter machining allowances when required.

Related grades for comparison include A240 410, A240 410S, A240 430, A240 429, A240 409 and a240 304.

AISI 420F is selected when high machining speed and later high hardness are both required. Typical applications of AISI 420F include:

SHH STEEL supplies AISI 420F 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.

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 420F 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 420F material optimized for high-speed machining and high hardness
• Flexible dimensions and finishes (including AISI 420F No.1 and AISI 420F 2B)
• Technical support for selection among AISI 420, 420F, 416 and 410
• 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.

AISI 420F Stainless Steel Plate is the free-machining sulfur-bearing variant of Type 420. It is chosen for high-speed turning and screw-machine work when the finished part must also be hardened to cutlery or wear hardness. For blades, instruments and polished tools, standard AISI 420 remains the better choice.

As a professional China steel mill-Direct Supply, SHH STEEL provides high-quality AISI 420F / UNS S42020 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 420F No.1 and AISI 420F 2B), or a competitive quotation.

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