UNS · United States · 3 designations

K12121

K12121 is a designation in UNS for the material held under material number 1.5421, also listed as 20MnMo3-5. It is a material in the category Heat-resistant structural steels. We list 3 designations recorded for this grade, in the standards DIN / EN and UNS.

Material no. 1.5421
Category Heat-resistant structural steels · 62 grades
Designations 3

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If you came for one of these

The most-used names for this grade.

About Heat-resistant structural steels

Heat-resistant structural steels are structural steels designed to retain useful strength and dimensional stability at elevated temperatures. They are used for load-bearing components in hot-service equipment where mechanical performance must be maintained during heating.

This describes the material class as a whole. Always confirm the individual grade against the standard before ordering.

Also known as

3 designations · 2 standards · nothing hidden

This grade’s own namerecorded in our sources as this grade’s own designation under that standard.

Indicativetaken from a published cross-reference table; a close match, not a guarantee of interchangeability. Verify against the mill certificate before ordering.

Withdrawndesignation no longer current — a separate column from the two above, so a name can be same grade and withdrawn at once.

DIN / ENEurope · 1

20MnMo3-5This grade’s own name

UNSUnited States · 2

K12121This grade’s own name
K12822This grade’s own name

Every designation on file is listed — no truncation, no “+ n more”. Each one is itself a route that leads back here.

Chemical composition

6 elements on file · weight %

What this alloy is

Iron — the balance, never listed by a standard — 98.2 %Mn — 0.9 %Mo — 0.5 %C — 0.2 %Traces & impurities · 0.2 %

Logarithmic scale, 0.01 % to 100 % — every value here compares directly, decade by decade.

Element	% by weight
	0.15–0.25
	0.15–0.25
	0.7–1
	0.025
	0.025
	0.4–0.6

0.01 %0.1 %1 %10 %100 %

The scale is logarithmic, not the element’s raw share of the alloy — the only honest way to fit 0.01 % and 100 % in one picture, and it means every value here can be compared with every other.

Element	As publishedsource text, verbatim	Min% by weight	Max% by weight	Bound
C	0,15-0,25	0.150	0.250	Range
Si	0,15-0,25	0.150	0.250	Range
P	0,025	0.025	0.025	Exact
S	0,025	0.025	0.025	Exact
Mn	0,70-1,00	0.700	1.000	Range
Mo	0,40-0,60	0.400	0.600	Range

The published column is the source string byte-for-byte, decimal comma and all; Min and Max are the parsed bounds. Elements not listed have no value on file — they are omitted, never inferred.

Predicted transformation temperatures

Not enough recorded composition to predict a transformation temperature for this grade — missing: Ni, Cr.

Physical & mechanical properties

Density7,85g/cm³Exact

An absent property means we hold no value for it — it is left out rather than estimated, interpolated from a neighbouring grade, or filled from a handbook. It does not mean the property is undefined for the material.

Similar grades — and why

Selection rule, stated so you can disagree with it: same number class 1.5, a shared category, and a published range for Mn / Mo that overlaps this grade’s. These are neighbours in composition space — they are not equivalents, and none is claimed to be interchangeable with this grade.

G20Mo51.5419

Mn 0,50-1,00 · Mo 0,40-0,60