St3 · 20 · 45 · a 10–200 · GOST 2591
Hot-rolled square bar
Square bar with a side of 10–200 mm in St3, 20 and 45 to GOST 2591; equivalents Q235B, 20#, 45#
St3 · 09G2S · 20×4–200×40 · GOST 103
Hot-rolled flat bar
Flat bar of rectangular cross-section 20×4–200×40 mm in St3 and 09G2S to GOST 103; equivalents Q235B and Q355B
GOST 103-2006GOST 535-2005GOST 19281-2014GB/T 702-2017GB/T 700-2006GB/T 1591-2018St3spSt3ps09G2SQ235BQ355B
Parameters
| Parameters | |
|---|---|
| Width | 20–200 mm |
| Thickness | 4–40 mm |
| Length | fixed and random length, 6 m — to specification |
| Rolling accuracy | thickness BT1–BT3 or VT1–VT3, width BSh1–BSh3 or VSh1–VSh3 per GOST 103 |
| Steel grade | St3sp, St3ps, 09G2S |
| Surface | untreated, with mill scale; galvanized — to specification |
Sizes and weight
| Size, mm | Weight, kg/m |
|---|---|
| 20×4 | 0.628 |
| 25×4 | 0.785 |
| 30×4 | 0.942 |
| 40×4 | 1.26 |
| 40×5 | 1.57 |
| 50×5 | 1.96 |
| 60×6 | 2.83 |
| 80×8 | 5.02 |
| 100×10 | 7.85 |
| 120×10 | 9.42 |
| 150×12 | 14.1 |
| 200×20 | 31.4 |
Theoretical weight at steel density 7.85 g/cm³. Actual batch weight is by scale and mill certificate.
Description
Flat bar is a hot-rolled product of rectangular cross-section defined by width and thickness. Dimensions and tolerances are specified by GOST 103-2006: width from 20 to 200 mm, thickness from 4 to 40 mm within the bureau's supply range; mills in China roll flat bar to GB/T 702-2017. Rolling accuracy under GOST 103 is set separately for thickness — BT1–BT3 raised, VT1–VT3 ordinary — and for width — BSh1–BSh3 and VSh1–VSh3; camber and squareness of edges are specified by the standard separately.
The main grade is St3sp and St3ps to GOST 535: flat bar for welded structures, cover plates, clamps, earthing and forging, equivalent Q235B. For loaded joints and service at low temperatures 09G2S to GOST 19281 is taken — a low-alloy steel with a specified impact toughness at minus 40 °C, nearest equivalent Q355B. Flat bar is rolled on bar mills from billet; it differs from slit strip in that the edges are produced by rolling rather than by slitting a coil.
During inspection at the mill the bureau measures the thickness with a micrometer and the width with a calliper at several points along the bar, checks camber on a surface plate and the squareness of edges. The heat number on the tag is checked against the mill test certificate (MTC) and the chemical composition in the specification; for 09G2S the impact test results are checked. Surface — free of scabs, laps and edge tears; marking on the bundle ends and strapping are recorded in the inspection report with photographs before shipment.
Applications
- cover plates, clamps and gusset plates of welded steel structures
- earthing and lightning protection circuits
- stock for forging and bending of fencing
- frames, brackets and equipment supports
- blades, keys and strips in repair shops
Packing and shipment
Bundles strapped with steel band at several points, mill tag with grade, heat, size and weight.
Grade equivalents
| GOST | GB (China) | ASTM | EN | Note |
|---|---|---|---|---|
| St3sp | Q235B | A36 | S235JR | Nearest equivalents: carbon, manganese and impact toughness limits differ between the standards. The specification fixes the GOST grade and the control values. |
| Steel 20 | 20# | 1020 | C22E | Quality carbon steel; the equivalents match in carbon content, impurity limits are checked against the certificate. |
| Steel 45 | 45# | 1045 | C45E | Steel for heat treatment; hardness and delivery condition are checked — hot-rolled, normalised or annealed. |
| 40Kh | 40Cr | 5140 | 41Cr4 | Chromium alloy steel; the equivalents are close in composition, chromium content is confirmed by the heat certificate. |
| 09G2S | Q355B | A572 Gr. 50 | S355JR | Nearest equivalents by strength; 09G2S specifies impact toughness at minus 40 °C, the equivalents use other test temperatures. |
| St1kp | Q195 | 1008 | — | Wire rod for drawing and tying wire; the nearest equivalent by carbon content, there is no single EN grade for this class. |
| 08Kh18N10 | 06Cr19Ni10 | 304 | 1.4301 | Austenitic chromium-nickel steel; nearest equivalents: chromium and nickel ranges differ between the standards, composition is confirmed by the heat certificate. |
| 12Kh18N10T | 06Cr18Ni11Ti | 321 | 1.4541 | Titanium-stabilised; nearest equivalents: the upper carbon limit is 0.12 % for 12Kh18N10T and 0.08 % for 321 and 1.4541; titanium content is checked against the certificate. |
| 03Kh17N14M3 | 022Cr17Ni12Mo2 | 316L | 1.4404 | Molybdenum-bearing, low-carbon; nearest equivalents: the lower nickel limit of 03Kh17N14M3 is higher than that of 316L, composition is confirmed by the heat certificate. |
Equivalents are the closest match, not identical: chemistry and tolerances differ between standards. The exact grade and standard are written into the contract.
Related items
St3 · 20 · 45 · 40Kh · Ø10–300 · GOST 2590
Hot-rolled round bar
Round bar Ø10–300 mm in St3, 20, 45 and 40Kh to GOST 2590; equivalents Q235B, 20#, 45#, 40Cr
Buyer questions
How to read a mill test certificate (MTC) for long products
In the certificate the mill states the heat number, grade and standard, the chemical composition of the heat, the mechanical properties from test results, the size and weight of the batch. The heat number must match the tag on the bundle or coil — this is the first thing the bureau's inspector checks. If the mill rolled to GB, the bureau attaches to the certificate a table of GOST-to-GB grade correspondence and the control values from the specification.
How St3 differs from steels 20, 45 and 40Kh
St3 is an ordinary-quality steel to GOST 535: strength is specified, impurities are allowed within wider limits; it goes into structures and non-critical parts. Steels 20 and 45 are quality carbon steels to GOST 1050: impurities are limited more tightly, properties are set by carbon content, steel 45 is used for hardening and quench-and-temper treatment. 40Kh is a chromium alloy steel to GOST 4543 for shafts, axles and gears after heat treatment. The grade is chosen from the part drawing, not from what is in stock.
How the tonnage of long products is calculated
The theoretical weight per metre is calculated from the cross-sectional area and the steel density of 7.85 g/cm³: round bar 0.006165·d², square bar 0.00785·a², flat bar 0.00785·b·t in kilograms per metre with dimensions in millimetres. The specification and the contract with the mill are drawn up on theoretical weight. Shipment and acceptance at the warehouse go by actual weight from weighing; the difference from theory lies within the dimensional tolerances of the standard.
What the bureau checks when inspecting a batch at the mill
Cross-section — with a micrometer and a calliper in two perpendicular directions on bars from different bundles, checked against the GOST tolerances for the rolling accuracy class. Documents — the heat number on the tag against the certificate, the chemical composition against the specification, for stainless grades a rapid composition check with a portable spectrometer. Appearance — surface free of cracks, laps and scabs, straightness, twist of square and hexagonal bar. Packing — strapping of bundles, a legible tag, grade marking on the bar ends. Everything is recorded in an inspection report with photographs.
How a batch is sized and what to send for a quotation
The batch is sized to your volume — send your specification: steel grade to GOST, product type and cross-section size, rolling accuracy class, bar length or coil weight, volume in tonnes for each size, certificate and packing requirements. On the specification the bureau selects a mill, agrees terms with it and returns to you a draft contract describing inspection and acceptance.
Price request
Send your specification and we will quote your batch
Steel pricing depends on grade, size, tonnage and delivery terms on the day of contract. A number on the page would be wrong by the time you read it.
Request received