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
20 · 45 · 40Kh · S 10–75 · GOST 2879
Hexagonal steel bar
Hexagonal bar 10–75 mm across flats in steels 20, 45 and 40Kh to GOST 2879; equivalents 20#, 45#, 40Cr
GOST 2879-2006GOST 8560-78GOST 1050-2013GOST 4543-2016GB/T 702-2017GB/T 699-2015GB/T 3077-2015204540Kh20#45#40Cr
Parameters
| Parameters | |
|---|---|
| Across flats | 10–75 mm |
| Length | fixed and random length, 6 m — to specification |
| Rolling accuracy | B1, B2, V1–V3 per GOST 2879; calibrated — per GOST 8560 |
| Steel grade | 20, 45, 40Kh |
| Delivery condition | hot-rolled; annealed — to specification |
| Surface | untreated; calibrated — to specification |
Description
Hexagonal bar is a hot-rolled bar with the cross-section of a regular hexagon; the size is defined by the distance between parallel flats, that is the diameter of the inscribed circle. Dimensions and tolerances are specified by GOST 2879-2006, rolling accuracy classes are raised B1, B2 and ordinary V1–V3. Cold-finished hexagonal bar with tighter tolerances and a bright surface is supplied to GOST 8560-78 and is agreed separately.
Hexagonal bar is used where the part needs spanner flats straight from the stock without milling: nuts, hexagon-head bolts, unions, adapters, shafts with a spanner grip. Grades are quality carbon steels 20 and 45 to GOST 1050 and alloy steel 40Kh to GOST 4543; equivalents at mills in China are 20#, 45# and 40Cr. Steel 20 goes into fasteners and pipeline fittings, steels 45 and 40Kh into parts for subsequent hardening.
During inspection at the mill the bureau measures the across-flats distance with a micrometer on all three pairs of flats and compares the spread with the tolerance of the chosen accuracy class, checks twist of the bar about its axis and straightness, and the condition of flats and corners — free of laps, cracks and rounded-off corners. The heat number on the tag is checked against the mill test certificate (MTC) and the chemical composition in the specification; for steels 45 and 40Kh the as-delivered hardness is read. Marking on the ends and strapping of bundles are recorded in the inspection report with photographs before shipment.
The theoretical weight per metre of hexagonal bar is calculated from the cross-sectional area and the density of 7.85 g/cm³: 0.0068·S² in kilograms per metre with the across-flats distance S in millimetres. The specification is drawn up on this formula; shipment and acceptance go by actual weight from weighing.
Applications
- nuts, bolts and studs with spanner flats
- unions, adapters and plugs for pipeline fittings
- shafts and axles with a spanner grip
- stock for automatic lathes
- repair and tool shops of enterprises
Packing and shipment
Bundles strapped with steel band or wire rod, mill tag with grade, heat, across-flats 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 · 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#
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.
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