{"id":6255,"date":"2026-09-25T21:11:12","date_gmt":"2026-09-25T18:11:12","guid":{"rendered":"https:\/\/www.defencemetal.com\/index.php\/2026\/09\/25\/aisi-420b-aisi-420c-difference\/"},"modified":"2026-09-30T10:43:49","modified_gmt":"2026-09-30T07:43:49","slug":"aisi-420b-aisi-420c-difference","status":"publish","type":"post","link":"https:\/\/www.defencemetal.com\/index.php\/2026\/09\/25\/aisi-420b-aisi-420c-difference\/","title":{"rendered":"What Is the Difference Between AISI 420B and AISI 420C?"},"content":{"rendered":"

AISI 420B<\/strong> and AISI 420C<\/strong> are two members of the same family: both are 13 % chromium martensitic stainless steels and both are hardened by quenching. The one deliberate difference is carbon content<\/strong> — and that difference sets the achievable hardness.<\/p>\n

Carbon equals hardness<\/h3>\n

In martensitic stainless steels the hardness obtained after quenching rises with the dissolved carbon. The 420 family is built on exactly that logic: different carbon steps at the same chromium level.<\/p>\n

Speaking in material numbers: 1.4028 has 0.26–0.35 % carbon<\/strong> and 1.4034 has 0.43–0.50 %<\/strong>. As carbon rises, so does the hardness after quenching; for 1.4034 Notz Metall, Deutsche Edelstahlwerke and Carpenter\/Latrobe report a band of about 52–55 HRC. The price is lower toughness and formability.<\/p>\n

Compared in figures<\/h3>\n

The values are EN 10088-3 cast analysis limits.<\/p>\n

\n\n\n\n\n\n\n\n\n\n\n\n\n
PROPERTY<\/th>\nAISI 420B (1.4028)<\/th>\nAISI 420C (1.4034)<\/th>\n<\/tr>\n<\/thead>\n
EN name<\/td>\nX30Cr13<\/td>\nX46Cr13<\/td>\n<\/tr>\n
Carbon (C)<\/strong><\/td>\n0.26 – 0.35 %<\/strong><\/td>\n0.43 – 0.50 %<\/strong><\/td>\n<\/tr>\n
Chromium (Cr)<\/td>\n12.00 – 14.00 %<\/td>\n12.50 – 14.50 %<\/td>\n<\/tr>\n
Manganese (Mn)<\/td>\n1.50 % max<\/td>\n1.00 % max<\/td>\n<\/tr>\n
Hardening temperature<\/td>\napprox. 980 – 1050 \u00b0C<\/td>\napprox. 980 – 1050 \u00b0C<\/td>\n<\/tr>\n
Tempering for maximum hardness<\/td>\n150 – 350 \u00b0C<\/td>\n150 – 250 \u00b0C<\/td>\n<\/tr>\n
Achievable hardness<\/td>\nlower<\/td>\nhigher<\/td>\n<\/tr>\n
Toughness<\/td>\nbetter<\/td>\nlower<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n

Heat treatment<\/h3>\n

Both grades are hardened from roughly 980 to 1050 \u00b0C<\/strong> in oil or air (the exact range varies by mill). If maximum hardness is wanted, tempering is kept low: Notz Metall gives 200–350 \u00b0C for 1.4028 and 150–250 \u00b0C for 1.4034; Carpenter\/Latrobe typically uses 149 \u00b0C.<\/p>\n

In this family corrosion resistance is best in the hardened and polished<\/strong> condition, not annealed. Neither grade is a chloride-service steel.<\/p>\n

What to watch when ordering — read this part<\/h3>\n
\n

“420A \/ 420B \/ 420C” is not defined in any standard.<\/p>\n

These letter suffixes do not appear in EN 10088-3 (which uses the names X20Cr13, X30Cr13, X39Cr13 and X46Cr13), nor in BS 970 (which used the S-number system: 420S29, 420S37), nor in ASTM\/UNS — the American system has a single Type 420 \/ UNS S42000<\/strong>. The letters are a trade shorthand from the cold-rolled strip and blade sector.<\/p>\n

And not everyone applies the same letter to the same material.<\/strong> The strip market uses 420C for 1.4034; Ugitech puts “420C” against 1.4031<\/strong> (X39Cr13) in its own bar catalogue. That is 0.07 % carbon apart, with a different chromium band.<\/p>\n

So put the material number on your order:<\/strong> not “420C” but 1.4034<\/strong> — or state the carbon range you need directly.<\/p>\n<\/div>\n

One more point: in ASTM Type 420, carbon has a minimum (0.15 % min) and no maximum.<\/strong> A certificate reading “420” is therefore not by itself a guarantee of hardness. Suppliers publish different upper limits — Rolled Alloys 0.15–0.30 %, Jacquet 0.15–0.40 %. If hardness is critical, write the carbon range into the contract.<\/p>\n

Where are they used?<\/h3>\n

Both grades are used for cutlery and blades, surgical and dental instruments, valve parts, moulds and dies, bearings and wear parts. If wear resistance and cutting edge are your priority, 420C<\/strong> (higher carbon, higher hardness); for parts that will take impact and need toughness, 420B<\/strong> is preferred.<\/p>\n

Designations, standards and AMS equivalents<\/h3>\n

The same steel is called different things depending on which system you are speaking in. Most ordering and certification confusion starts here, so a short summary:<\/p>\n