The American system is not this one in different numbers
Switch the tool to ASTM and it is not a conversion. The two systems put different information in the name, and that is the whole difficulty of working across them.
EN puts the property in the name. S355 is 355 N/mm2 of yield, and the suffix that follows is toughness at a test temperature.
ASTM puts a document number in the name. A992 means specification A992 and tells you nothing about strength until you open it. A36 looks like an exception because it happens to be named after its yield, and that coincidence is what catches people: they read A572 the same way. A572 holds grades 42, 50, 55, 60 and 65 inside one number, so A572 on its own is an incomplete specification. A500 holds grades A, B and C, and the yield differs again depending on whether the tube is round or shaped.
A British reader looks for the J2 and there is nothing there
This is the mirror of the fact this page was built around. In EN, the suffix is the toughness. In ASTM, toughness is not in the designation at all. Charpy testing is a supplementary requirement somebody has to ask for by name, or you move to A709, the bridge specification, where it is built into the grade: HPS 50W carries 25 ft-lb at 10 degrees F and HPS 70W carries 30 ft-lb at minus 10.
So the error runs both ways. A British fabricator assumes the toughness came with the grade, because at home it does. An American engineer reading S355J2 assumes the J2 is a strength variant, because at home the letters after a number usually are.
A992 has a ceiling, because too strong is a hazard
Almost nothing in structural steel specifies a maximum strength. A992 does: 50 to 65 ksi, with the yield to tensile ratio capped at 0.85.
The reason is in the numbers behind the change. Moving from A36 to A992 raised the minimum yield by over 38 percent while the minimum tensile rose by only 12. That narrows the gap between the point where steel yields and the point where it breaks, and a narrow gap means less warning. Steel that is stronger than the designer assumed is not a free upgrade: it can move the failure away from the ductile mode the design was relying on.
It is the same class of thinking as the British suffix, arrived at from the other end. Both are specifications protecting a property that is not strength.
Why some rows here have no tensile figure
The ASTM specifications sit behind a paywall and this site does not buy data. So a figure appears on this page only where it was read from an open document: AISC's Engineering Journal for A992, the FHWA High Performance Steel guide for the A709 grades. Where the yield is stated in the designation, as with A36, it is given.
Everywhere else the page says to read the mill certificate. That is not a gap being excused: a reference table that prints a yield strength nobody checked is worse than one that admits what it does not know, and the certificate is what governs the steel on your floor in any case.
S355JR and S355J2 are the same strength
Identical. Both 355 N/mm² minimum yield in the thinnest range. There is no strength difference between them at all.
What differs is the temperature the steel was impact tested at, and the energy it had to absorb doing it:
- JR: 27 joules at +20°C
- J0: 27 joules at 0°C
- J2: 27 joules at −20°C
- K2: 40 joules at −20°C
That is the whole difference. Pick a grade in the tool and it lists every same-strength alternative beside it, all reading 355, with only the temperature moving. The belief that J2 is "stronger steel" has nowhere to hide once they are in a column together.
Why this matters, and it is not pedantry
The property J2 is bought for is resistance to brittle fracture: a failure with no warning and no deformation, in a material that would pass every tensile test you gave it.
It gets specified when four things stack up: thick material, low temperature, high restraint, and a notch. A heavy welded connection, in an unheated building, in February, with a stress raiser at the weld toe. Every one of those pushes the same direction.
Which is why a substitution to JR "because it is the same strength and it is in stock" is one of the more consequential shortcuts in fabrication. It is the same strength. It is not the same steel, and the person who wrote J2 on the drawing was not worried about strength.
If a substitution is genuinely needed, and sometimes it genuinely is, it goes back to whoever specified it. That is a two-minute phone call, not a stock decision.
355 is only 355 if it is thin
The second thing people get wrong, and it is quieter.
Minimum yield falls as thickness increases, because thicker sections cool more slowly and end up with a coarser grain structure. For S355:
- up to 16mm: 355
- 16 to 40mm: 345
- 40 to 63mm: 335
- 63 to 80mm: 325
- 80 to 100mm: 315
- 100 to 150mm: 295
That last one is 17 per cent below the headline number. A drawing that says S355 without a thickness is quoting the thin figure, and on heavy plate the material does not deliver it.
Move the thickness slider in the tool and watch it come down.
+N and +M are conditions, not strengths
+N is normalised, or normalised rolled. +M is thermomechanically rolled, which usually gives better weldability at the same strength because it gets there with less carbon.
One trap with +M worth knowing: it must not be hot formed afterwards. The properties come from the controlled rolling process itself, and heating it to bend it undoes them. Nobody tells you that when they sell it to you.
The old designations
Plenty of drawings still say grade 43 and grade 50. Broadly, 43 became S275 and 50 became S355, and the letter suffixes changed as well: old grade 50B is not exactly S355JR, it is near enough that people treat it as such and far enough that a drawing worth questioning is worth questioning.
If a drawing is old enough to say grade 50, it is old enough that the loadings behind it are worth a look too.
It will not choose a grade for you
It will not tell you which grade to use. That depends on thickness, service temperature, restraint and the consequence of failure, and it is a design decision belonging to whoever signs the job.
What it is for is reading a drawing and questioning a substitution. Knowing that the suffix is toughness rather than strength is enough to make you ask the right question, and asking it is the whole point.
Next to it: metal weights for the same material, and section properties when it lands.
Common questions
What is the difference between A36 and A992?
A36 has a minimum yield of 36 ksi. A992 has a yield of 50 to 65 ksi and a minimum tensile of 65, and it is what a wide flange beam actually arrives as. So designing a W shape on 36 ksi understates the material by about a third. The other difference is the one people miss: A992 has a MAXIMUM yield as well as a minimum, and caps the yield to tensile ratio at 0.85. Moving from A36 to A992 raised minimum yield by over 38 percent while minimum tensile rose only 12, which narrows the gap between yielding and fracture, and the cap exists to keep the failure ductile.
Does the ASTM number tell me the strength?
No, and that is the trap. An ASTM designation names a specification document, not a property. A36 happens to be named after its yield and that is a coincidence rather than a pattern: A572 contains grades 42, 50, 55, 60 and 65 inside one number, and A500 contains grades A, B and C with different yields again depending on whether the tube is round or shaped. So "A572" on a drawing is an incomplete specification. Compare EN, where S355 states the yield in the name.
What is the ASTM equivalent of S355J2?
There is no direct equivalent, and the reason is worth understanding. S355 is close to A572 Grade 50 or A992 on strength, since 355 N/mm2 is about 51 ksi. But the J2 part has no ASTM counterpart in a building specification at all: Charpy toughness is not part of an ASTM structural designation. It is a supplementary requirement that has to be asked for by name, or you move to A709, the bridge specification, where CVN is built into the grade. A fabricator assuming the toughness came with the grade has assumed something the designation never said.
Why does this page show tensile strength for some grades and not others?
Because the ASTM specifications are paywalled and this site does not buy data. A figure appears only where it was read from a document that is open: AISC Engineering Journal for A992, the FHWA High Performance Steel guide for the A709 HPS grades. Where a yield is stated in the designation itself, as with A36 and the A572 grade numbers, it is given. Everywhere else the page tells you to read the mill certificate, which is honest and is also the right habit: the certificate governs the steel in front of you and no reference table does.
What is the difference between S355JR and S355J2?
Not strength. They have identical minimum yield: 355 N/mm² in the thinnest range, both of them. The difference is the temperature the steel was impact tested at: JR at +20°C, J2 at −20°C, both to 27 joules. J2 is tougher when cold, which is a completely different property from being stronger.
So can I substitute JR for J2 to save money?
Not without asking whoever specified it. J2 gets called up because of brittle fracture risk: thick material, low service temperature, high restraint, a notch or a weld detail that concentrates stress. Swapping in JR does not buy an equivalent material at a better price; it removes the exact property the grade was chosen for.
What does the K in S355K2 mean?
Same test temperature as J2, −20°C, but a higher energy requirement: 40 joules instead of 27. It is the toughest of the commonly available grades. The letter changes because the energy band changes, not because the temperature does.
What do +N and +M mean?
Delivery conditions, not strengths. +N is normalised or normalised rolled. +M is thermomechanically rolled, which generally gives better weldability at the same strength, but +M material must not be hot formed afterwards, because that undoes the rolling process that gave it its properties.
Does S355 always mean 355?
Only in the thinnest range. Minimum yield falls as thickness goes up: 355 up to 16mm, 345 to 40mm, 335 to 63mm, and 295 by the time you are at 150mm. That is a 17 per cent reduction on the headline figure, and a drawing that just says S355 is quoting the thin number.
Will this tell me which grade to use?
No. That depends on thickness, service temperature, restraint and what happens if the thing fails, and it is a design decision belonging to whoever signs the job. This page tells you what a designation means so you can read a drawing and question a substitution.