Bought for parts that, once hardened, must cut, hold a cutting edge and resist wear while still offering corrosion resistance in mild environments: knife and cutting edges, surgical and dental instruments, valve parts, shafts, pins, bearings, die and gauge parts, agricultural blades.<\/div>\n<\/div>\n
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Forms<\/div>\n
Round bar, flat bar, plate, sheet, pipe, forging. All forms are supplied to order.<\/div>\n<\/div>\n
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Standards<\/div>\n
ASTM: A276 \/ SA-276 (bars and shapes; Condition A only, with a hardness ceiling) \u00b7 A314 \/ SA-314 (billets and bars for forging) \u00b7 A484 \/ SA-484 (general requirements) \u00b7 A580 \/ SA-580 (wire) \u00b7 A473 (forgings) \u00b7 A493 (cold heading wire) \u00b7 F899 (surgical instruments, 420A). EN: 1.4021 \u00b7 10088-2 (flat products, +A \/ +QT650 \/ +QT750) \u00b7 10088-3 (bars, +A \/ +QT700 \/ +QT800) \u00b7 10250-4 (open die forgings) \u00b7 EN ISO 7153-1 (surgical instruments). AMS: 5506 (sheet, strip, plate) \u00b7 5621 (bars, wire, forgings) \u00b7 5620 (bars, wire, forgings). THE CARBON BAND OF THOSE THREE AMS NUMBERS IS 0.30-0.40%; see the specification note. Welding wire: AWS A5.9 \/ SFA-5.9 ER420.
THE AMS TRAP – THIS IS THE MOST IMPORTANT NOTE ON THIS CARD. Verified from SAE title records: AMS 5506 ‘Sheet, Strip, and Plate, 13Cr (0.30 – 0.40C) (420), Annealed’ \u00b7 AMS 5621 ‘Bars, Wire, and Forgings, 13Cr (0.30-0.40C) (51420), Annealed’ \u00b7 AMS 5620 ‘Bars,\u2026<\/span><\/div>\n<\/div>\n\n
Advantage<\/div>\n
For the same heat treatment cycle it delivers a clearly higher hardness than 410, and in numbers: in one and the same table Jacquet measures 43 HRC for 410 tempered at 204 \u00b0C (400 \u00b0F) and 48 HRC for 420 under the same condition – a 5 HRC difference on an identical cycle whose only variable is\u2026<\/div>\n<\/div>\n
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Welding<\/div>\n
420 is NOT a material chosen for welding; if it is welded, the full cycle is applied. PREHEAT: Carpenter 149-204 \u00b0C (300-400 \u00b0F) \u00b7 AZoM and The World Material at least 200 \u00b0C (390 \u00b0F) \u00b7 Hobart 204-316 \u00b0C (400-600 \u00b0F) for martensitic stainless steels.<\/div>\n<\/div>\n
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Limits<\/div>\n
1) FORBIDDEN TEMPERING BAND: 425-600 \u00b0C. AZoM and Atlas prohibit this band explicitly for 420. Carpenter states it as a ceiling: for maximum corrosion resistance 420 should NOT be tempered over 427 \u00b0C (800 \u00b0F). Latrobe states for 420 HC that the 427-552 \u00b0C band decreases both the corrosion resistance and the toughness.<\/div>\n<\/div>\n