S235JR vs S355JR steel sheet (ST37 vs ST52): differences and typical uses

Buyers of hot-rolled sheet from Iran will meet two trade names, ST37 and ST52, alongside the European grades S235JR and S355JR on current drawings. This guide compares the two grades using producers' published data: strength, chemistry, weldability, toughness class and weight, and where each is normally specified.

Are ST37 and ST52 the same as S235JR and S355JR?

ST37 and ST52 are legacy trade names from the former German standard DIN 17100. Today these steels are designated under EN 10025-2: "S" stands for structural steel, the number is the minimum yield strength in MPa for thin sections, and the letters "JR" give the toughness class.

In the Ahan Asa catalog, S235JR sheet is sold under the market name ST37 and S355JR under ST52. One nuance: in Arvedi's equivalents table, S235JR corresponds to DIN 17100 St 37-2, but no DIN 17100 equivalent is listed for S355JR, and St 52-3 maps to S355J0 and S355J2. So "ST52" is a trade label; confirm the exact grade on the quotation and the mill test certificate.

Mechanical properties

The figures below come from Arvedi's EN 10025-2 product page; Ovako's data sheet gives the same values for S355JR.

In short, S355JR's minimum yield strength is about 51% higher up to 16 mm, while S235JR elongates slightly more before fracture. For heavier plate, Ovako lists 345 MPa for 16–40 mm and 335 MPa for 40–63 mm for S355JR.

Chemistry and weldability

S355JR has higher maximum carbon and manganese limits. Maximum values from Arvedi's table:

Carbon equivalent indicates how sensitive a steel is to welding; the higher it is, the more the welding procedure matters. The procedure for S355JR should be qualified for that grade. IDEA StatiCa notes that the new draft of Eurocode 3 Part 1-8 sets a larger minimum fillet weld size for S355 than for S235.

JR, J0 and J2

The suffix gives the Charpy test temperature. Per Arvedi's table all of them must absorb at least 27 J: JR at 20 °C, J0 at 0 °C and J2 at −20 °C. Both grades in our sheet and plate range are JR. If a design calls for J0 or J2 (cold climates, impact loading), do not substitute a JR grade without the designer's approval.

Weight and sizes: identical for both grades

Nominal weight depends on thickness and size, not on grade; in the Ahan Asa catalog it is the same for both grades at each thickness. Sizes listed in the Ahan Asa catalog for both grades:

• S235JR hot-rolled sheet and S355JR hot-rolled sheet: 2–6 mm, in 1000×2000, 1250×2500 and 1500×6000 mm, tolerances to EN 10051.
• S235JR plate and S355JR plate: 8–60 mm, in 1500×6000 and 2000×6000 mm, tolerances to EN 10029.

Sheet is sold by actual weight; these figures are for estimating. The full range is in the sheet and plate category.

Which grade to choose

The grade is the structural engineer's decision, but the logic helps when buying:

• S235JR (ST37) is enough where strength does not govern the size of the part; a higher grade adds no stiffness, so it brings no benefit there.
• S355JR (ST52) is chosen where strength governs and the designer wants the same resistance with a smaller section or thinner plate.

IDEA StatiCa points out that cost and energy per kilogram are almost the same for S235 and S355, and higher grades save material for the same strength. But stronger steel is not stiffer: a smaller section may deflect more or be more prone to local buckling, which the designer must check.

Buying tips

1. Take the grade from the drawings, not the trade name; the quotation should state S235JR or S355JR with thickness and size.
2. Ask for the mill test certificate (MTC) showing grade, chemistry and tensile results.
3. Keep the two grades apart on site and mark them on delivery; they look identical.
4. Substitute only with the structural engineer's approval.

Summary

S235JR (ST37) and S355JR (ST52) sheet weigh the same and come in the same sizes; the difference is strength, with a minimum yield of 235 versus 355 MPa up to 16 mm. S355JR has higher carbon and carbon equivalent and needs a suitable welding procedure; S235JR has slightly higher elongation. The drawings set the grade and the MTC confirms it. To request a quotation for the thickness and grade you need, use our contact page.