Quick Answer
Quick Answer
GOST 380 covers common-quality carbon structural steel supplied as rolled products (plates, shapes, bars, strip). It defines eight base grades — St0 through St6 — each available in up to three deoxidation classes: sp (fully killed), ps (semi-killed), and kp (rimming). St3sp is the dominant grade and is broadly equivalent to ASTM A36, EN S235JR, and Chinese Q235B.
GOST 380 (Межгосударственный стандарт — Interstate Standard) is the foundational carbon structural steel standard within the CIS bloc. Adopted originally as a Soviet standard and maintained by the CIS Interstate Council for Standardization (МГСН), it applies uniformly in Russia, Kazakhstan, Belarus, Ukraine, and other former Soviet states. The standard covers hot-rolled flat products, sections, and bars for general structural use — bridges, industrial buildings, farm equipment, and light machinery.
The designation prefix St (Сталь — steel) distinguishes GOST 380 grades from the alloy-steel grades defined under GOST 4543 and the low-alloy grades under GOST 19281.
Scope and Applicability
GOST 380 applies to:
- Hot-rolled plates, sheets, and strips
- Structural sections (I-beams, channels, angles, T-sections)
- Round, square, and hexagonal bars
- General structural fabrications not subject to elevated or cryogenic service conditions
The standard does not cover:
- Pressure vessel steel (governed by GOST 5520 and GOST 19281)
- Low-temperature structural steel (see GOST 19281 grade 09G2S)
- Heat-treatable alloy steels (GOST 4543)
- Seamless pipe material (GOST 8731/8733)
Grade Designation System
GOST 380 grades follow a structured naming convention:
St [Grade number] [Deoxidation suffix] [Category letter (optional)]
Grade number (0–6): Increasing number indicates increasing carbon content and, generally, increasing strength. St0 has no guaranteed composition; St6 has the highest carbon.
Deoxidation suffixes (appended directly to the number, no separator):
| Suffix | Russian term | Meaning | Western analogue |
|---|---|---|---|
| sp | спокойная (spokoinaya) | Fully killed — deoxidized with Al/Si/Mn. No gas evolution during solidification. | Killed steel |
| ps | полуспокойная (poluspokoinaya) | Semi-killed — partial deoxidation. Intermediate segregation behaviour. | Semi-killed steel |
| kp | кипящая (kipyashchaya) | Rimming — minimal deoxidation. Significant carbon monoxide evolution during casting. Not suitable for cold-forming or welding in structural applications. | Rimming steel |
If no suffix appears on a certificate, the grade is typically sp (killed). The kp suffix is prohibited for grades St5 and St6.
Category letters (sometimes appended as A, B, C after the suffix) indicate the level of guaranteed test requirements:
- No letter or B: composition + mechanical properties guaranteed
- A: mechanical properties only guaranteed (no composition requirement)
- C: composition only guaranteed (no mechanical requirement)
Grade Coverage
| Grade | Deoxidation classes available | Typical carbon range (wt%) | Primary application |
|---|---|---|---|
| St0 | sp, ps, kp | No limit specified | Non-structural filler, packaging |
| St1 | sp, ps, kp | 0.06–0.12 | Light-duty cold-formed sections |
| St2 | sp, ps, kp | 0.09–0.15 | Sheet metal, stampings |
| St3 | sp, ps, kp | 0.14–0.22 | General structures, welded fabrications |
| St4 | sp, ps, kp | 0.18–0.27 | Heavier sections, bolts, studs |
| St5 | sp, ps | 0.28–0.37 | High-load structural parts, shafts |
| St6 | sp, ps | 0.38–0.49 | Rails, springs, agricultural implements |
St3 is by far the highest-volume grade in CIS construction and infrastructure. Within St3, St3sp dominates for structural welded work; St3ps is acceptable for many structural applications; St3kp is limited to non-welded, non-cold-formed uses.
Chemical Composition Requirements
All values are wt%. Ladle analysis (плавочный анализ) governs; product analysis tolerances are defined in the standard.
St0
| Element | Limit |
|---|---|
| C | Not normalized |
| Mn | Not normalized |
| P | ≤ 0.07 |
| S | ≤ 0.06 |
St1
| Sub-grade | C | Mn | Si | P max | S max |
|---|---|---|---|---|---|
| St1sp | 0.06–0.12 | 0.25–0.50 | 0.05–0.17 | 0.040 | 0.050 |
| St1ps | 0.06–0.12 | 0.25–0.50 | 0.05–0.17 | 0.040 | 0.050 |
| St1kp | 0.06–0.12 | 0.25–0.50 | ≤ 0.05 | 0.040 | 0.050 |
St2
| Sub-grade | C | Mn | Si | P max | S max |
|---|---|---|---|---|---|
| St2sp | 0.09–0.15 | 0.25–0.50 | 0.05–0.17 | 0.040 | 0.050 |
| St2ps | 0.09–0.15 | 0.25–0.50 | 0.05–0.17 | 0.040 | 0.050 |
| St2kp | 0.09–0.15 | 0.25–0.50 | ≤ 0.05 | 0.040 | 0.050 |
St3
| Sub-grade | C | Mn | Si | P max | S max |
|---|---|---|---|---|---|
| St3sp | 0.14–0.22 | 0.40–0.65 | 0.12–0.30 | 0.040 | 0.050 |
| St3ps | 0.14–0.22 | 0.40–0.65 | 0.05–0.17 | 0.040 | 0.050 |
| St3kp | 0.14–0.22 | 0.40–0.65 | ≤ 0.05 | 0.040 | 0.050 |
Note: Si ≥ 0.12 in St3sp confirms full killed status; the higher silicon distinguishes sp from ps/kp.
St4
| Sub-grade | C | Mn | Si | P max | S max |
|---|---|---|---|---|---|
| St4sp | 0.18–0.27 | 0.40–0.70 | 0.12–0.30 | 0.040 | 0.050 |
| St4ps | 0.18–0.27 | 0.40–0.70 | 0.05–0.17 | 0.040 | 0.050 |
| St4kp | 0.18–0.27 | 0.40–0.70 | ≤ 0.05 | 0.040 | 0.050 |
St5
| Sub-grade | C | Mn | Si | P max | S max |
|---|---|---|---|---|---|
| St5sp | 0.28–0.37 | 0.50–0.80 | 0.15–0.35 | 0.040 | 0.050 |
| St5ps | 0.28–0.37 | 0.50–0.80 | 0.05–0.17 | 0.040 | 0.050 |
kp not permitted for St5.
St6
| Sub-grade | C | Mn | Si | P max | S max |
|---|---|---|---|---|---|
| St6sp | 0.38–0.49 | 0.50–0.80 | 0.15–0.35 | 0.040 | 0.050 |
| St6ps | 0.38–0.49 | 0.50–0.80 | 0.05–0.17 | 0.040 | 0.050 |
kp not permitted for St6.
Mechanical Properties
Yield strength (предел текучести) in GOST 380 varies by section thickness, unlike many Western standards that use a single minimum value. Tensile strength (предел прочности при растяжении) and elongation (относительное удлинение) are less thickness-dependent.
Yield Strength (MPa) by Section Thickness
| Grade | ≤ 20 mm | 20–40 mm | 40–100 mm | > 100 mm |
|---|---|---|---|---|
| St0 | — | — | — | — |
| St1sp/ps | 225 | 215 | 205 | 195 |
| St1kp | 225 | 215 | 205 | 195 |
| St2sp/ps | 235 | 225 | 215 | 205 |
| St2kp | 225 | 215 | 205 | — |
| St3sp/ps | 245 | 235 | 225 | 215 |
| St3kp | 235 | 225 | 215 | — |
| St4sp/ps | 265 | 255 | 245 | 235 |
| St4kp | 255 | 245 | 235 | — |
| St5sp/ps | 285 | 275 | 265 | 255 |
| St6sp/ps | 315 | 305 | — | — |
Tensile Strength, Elongation, and Bend Test
| Grade | UTS (MPa) | Elongation δ₅ min % (t ≤ 20 mm) | Elongation δ₅ min % (20–40 mm) | Cold bend test (180°, d = mandrel) |
|---|---|---|---|---|
| St0 | ≥ 310 | — | — | — |
| St1 | 310–410 | 34 | 32 | d = 0 (sp/ps); d = 0.5t (kp) |
| St2 | 340–440 | 33 | 31 | d = 0.5t |
| St3 | 370–480 | 26 | 24 | d = 0.5t (sp); d = t (ps); d = 1.5t (kp) |
| St4 | 420–540 | 24 | 22 | d = t (sp); d = 1.5t (ps/kp) |
| St5 | 500–640 | 20 | 18 | d = 2t |
| St6 | 590–730 | 15 | 13 | Not required by default |
δ₅ = elongation measured on gauge length L₀ = 5.65√S₀. For flat specimens this is typically 50 mm gauge length on standard test pieces.
Additional Tests
GOST 380 defines three test categories; the applicable category is stated on the purchase order or product standard:
- Category 1: Chemical composition and dimensional tolerance only.
- Category 2: Composition + mechanical properties (standard for most structural supply).
- Category 3: Composition + mechanical properties + impact (notch toughness) testing. KCU impact energy tested at +20 °C on ISO-V or U-notch specimens per GOST 9454.
- Category 4: Category 3 requirements plus impact at −20 °C or −40 °C (grade and specification dependent).
- Category 5: Full Category 4 requirements plus additional aging test.
Weldability note: St3sp and St3ps have carbon equivalents (CE = C + Mn/6 ≈ 0.32–0.37) within the generally weldable range without preheat for most thicknesses up to 25 mm.
GOST Certificate Requirements
A valid ГОСТ сертификат качества (quality certificate) for GOST 380 material must state:
| Field (Russian) | Field (English) | Required content |
|---|---|---|
| ГОСТ 380 | Standard reference | Edition year recommended |
| Марка стали | Steel grade | Full designation with deoxidation suffix, e.g. St3sp |
| Плавка № | Heat number | Unique ladle identifier |
| Химический состав | Chemical composition | C, Mn, Si, P, S values from ladle analysis |
| Механические свойства | Mechanical properties | YS, UTS, δ₅ for representative lot |
| Категория | Test category | 1 through 5 |
| Масса плавки (кг) | Heat weight | Traceability to physical material |
| Штамп и подпись | Stamp and signature | Mill's quality inspector; official seal |
Cross-Standard Equivalents
St3sp is the grade most frequently matched to Western specifications. Equivalences are approximate — they reflect overlapping composition and mechanical ranges, not certified dual compliance.
| GOST 380 Grade | ASTM | EN (Eurocode) | Chinese GB | Indian IS | Notes |
|---|---|---|---|---|---|
| St3sp | A36 | S235JR | Q235B | E250 (Fe 410-W)A | Closest match; YS min 235–245 MPa, UTS 370–480 MPa |
| St3ps | A36 | S235J0 | Q235A | E250A | Semi-killed; slightly lower notch toughness than sp |
| St3kp | — | — | Q235 | — | Rimming; no direct structural equivalent |
| St4sp | A572 Gr. 42 | S275JR | Q275 | E300 | Approximate only |
| St5sp | A572 Gr. 50 (partial) | S355JR (partial) | — | — | UTS range overlaps; YS lower than S355 |
Do not specify St3kp as a substitute for A36 or S235JR. The rimming process produces uneven segregation and unpredictable impact properties at sub-zero temperatures.
MTC Verification Checklist
When receiving GOST 380 material against a purchase specification, verify:
- Grade designation includes deoxidation suffix (sp/ps/kp) — unmarked certificates should default to sp but must be confirmed
- C, Mn, Si values are within the limits for the stated sub-grade
- P ≤ 0.040 and S ≤ 0.050 (wt%)
- Yield strength value matches the thickness band of the delivered product
- Test category meets the project minimum (Category 2 for standard structural; Category 3 or 4 for dynamic or low-temperature service)
- Heat number on certificate matches markings on material (spray paint, stamping, or tag)
- Mill stamp (Штамп) and authorized signature present
Frequently Asked Questions
What does 'sp' mean in St3sp?
Sp stands for спокойная (spokoinaya), meaning "calm" or fully killed steel. The steel has been deoxidized with additions of aluminium, silicon, and manganese before casting, eliminating gas evolution during solidification. This produces a more uniform, inclusion-controlled structure with better impact and weld properties compared to the semi-killed (ps) and rimming (kp) variants.
Is St3sp the same as ASTM A36?
They are broadly equivalent for most structural applications: both have a minimum yield strength around 235–250 MPa and an overlapping UTS range of 370–490 MPa. However, they are not certified dual-compliance unless the mill explicitly tests and certifies against both standards. For import documentation or ASME/AWS applications, request dual-certified material or accept a cross-reference equivalency letter from the mill.
Can St3kp be used for structural welding?
Generally no. The rimming (kp) process produces a steel with higher segregation of carbon and sulfur in the ingot core. This leads to unpredictable HAZ (heat-affected zone) properties during welding and poor notch toughness at low temperatures. Most structural codes and project specifications prohibit kp steel for welded structural connections. Use St3sp or St3ps for welded fabrications.
How does GOST 380 handle section-thickness variation in yield strength?
Unlike ASTM A36, which specifies a single minimum yield of 250 MPa regardless of thickness, GOST 380 reduces the guaranteed minimum yield in steps as section thickness increases. For St3sp this ranges from 245 MPa at ≤ 20 mm down to 215 MPa for sections over 100 mm. When specifying structural sections, always verify the yield strength against the delivered thickness band, not just the nominal grade.
What is the difference between GOST 380 and GOST 19281?
GOST 380 covers common-quality plain carbon structural steel (St grades). GOST 19281 covers high-strength low-alloy (HSLA) structural steel with guaranteed elevated strength through alloying additions (Mn, Si, Cr, Ni, Cu, V, N). The GOST 19281 grades — such as 09G2S — are used where higher strength, better low-temperature toughness, or pressure-vessel service is required. GOST 380 is the workhorse general structural standard; GOST 19281 is the step up for demanding applications.
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