4620 is a nickel molybdenum carburizing steel for gears, shafts and pins in light to medium sections. Without chromium it is less hardenable than 4320, which suits smaller cross sections where a deep hardened core is neither needed nor wanted.
It machines and carburizes predictably and is a cost effective answer for high volume geared and pinned hardware.
Stocked as bar and billet, typically annealed or normalized for machining before carburizing.
Sizes and stock
- Custom shapes and forgings: per request
Processing capabilities
- Vacuum melted (VAR / VIM-VAR) stock with full melt traceability
- Normalize, anneal, quench and temper to the ordered condition
- Saw cutting, trepanning, gun drilling and rough machining
- Magnetic particle and ultrasonic inspection to AMS 2301 / AMS 2154 on request
Specifications
Material is released to the applicable specification with mill test reports and, on request, independent lab verification.
Why engineers specify 4620
- Reliable case hardening response in light and medium sections
- Tough, ductile core
- Good machinability before carburizing
- Economical carburizing grade
Nominal chemistry
Percent by weight, nominal composition per the governing specification. The mill test report for your heat is the controlling document.
Typical applications
- Gears and pinions
- Camshafts and pins
- Bushings and sleeves
- Transmission shafting
Fabrication notes
Machining
Best machined in the annealed or normalized-and-tempered condition, then heat treated to final strength. Rough machining before hardening, with a finish pass after temper, controls distortion on long or thin sections. We can supply rough turned, trepanned or gun drilled stock so your first operation starts closer to net shape.
Welding
Weldable with low hydrogen practice, preheat appropriate to carbon equivalent and section size, and a post weld stress relief or full re-heat treat. For high strength conditions the weld and heat affected zone should be re-treated to restore properties.
Forming
Hot work in the annealed condition. Cold forming is limited at high hardness, so bend and form before hardening and follow with stress relief where the geometry is tight.
4620 compared with similar grades
4320
Adds chromium for deeper hardenability in heavier sections.
8620
Widely used general purpose carburizing grade at lower alloy content.
Designations and cross reference
- Material family
- Alloy Steels
Working from an obsolete, foreign or superseded designation? Send it over and we will cross reference it to a current grade and specification.
Quality, testing and traceability
Supplied aircraft quality with mill test reports, melt and heat traceability, and, on request, magnetic particle inspection to AMS 2301 or AMS 2300, ultrasonic inspection to AMS 2154, chemical assay, hardness and full mechanical testing.
We are AS9100D and ISO 9001:2015 registered. If our stock does not already carry the inspection your specification requires, we can quote the material with that work performed. More on our quality system
Available forms
Custom sizes converted from billet, plus saw cut, waterjet and near-net blanks. See custom conversions
4620 frequently asked questions
What is 4620?
4620 is a nickel molybdenum carburizing steel for gears, shafts and pins in light to medium sections. Without chromium it is less hardenable than 4320, which suits smaller cross sections where a deep hardened core is neither needed nor wanted.
What forms is 4620 available in?
We supply 4620 in forging. Custom sizes are converted from billet, and we can provide saw cut, waterjet or near net blanks so material arrives closer to your finished part.
What specifications can 4620 be supplied to?
Commonly ordered specifications include AMS 6294. Material is released to the specification and condition on your purchase order, with mill test reports supplied as standard.
Can you cut 4620 to size?
Yes. Saw cutting, waterjet, laser and shearing are available, along with trepanning, gun drilling, lathe turning and CNC machining, so you can order blanks or rough machined pieces rather than full lengths.
Do you provide test reports and additional testing on 4620?
Every order ships with mill test reports and heat traceability. If your print calls for ultrasonic inspection, penetrant dye, magnetic particle, chemical assay, micrography, hardness or mechanical testing and our stock does not already carry it, we can quote the material with that work performed.
Can 4620 be supplied to DFARS domestic melt requirements?
Tell us at quote stage if the order is DFARS or domestic melt restricted and we will confirm availability against that requirement before you commit.
What do you need to quote 4620?
Grade, form, dimensions, quantity, specification and condition, plus any testing or certification requirements and the date you need it. Send a drawing if you have one. Quotes are typically ready within 24 hours.
How does 4620 compare with 4320?
Adds chromium for deeper hardenability in heavier sections.