---
title: "Stainless steel round bar: specification parameters"
source: "https://www.laxconsteels.com/choosing-the-right-stainless-steel-round-bar-a-guidebook-for-buyers-in-india/"
description: "Stainless steel round bar in India: the seven parameters that specify a purchase, from grade to packing, with the weight per metre for every size."
---
# Stainless Steel Round Bar: The Seven Specification Parameters

Send an enquiry

11 min read

A stainless steel [round bar](https://www.laxconsteels.com/products/hot-rolled-round-bars/) purchase in India is specified by seven parameters: grade and governing standard, diameter, tolerance class, finish or heat treatment condition, length, quantity, and test requirements. An enquiry that states only a grade, a diameter and a tonnage, such as "SS 304, 40 mm, 5 tonnes", leaves the remaining parameters open, and the possible interpretations differ from one another in price by a factor of several times. This article sets out each parameter, the published supply conditions attached to it, and the size, weight and vocabulary data used to complete it.

## Diameter and product selection

The diameter determines which product a bar belongs to, because different diameter bands are produced on different lines. Four round bar products cover the range from 5 mm to 550 mm.

| Diameter | Product | Length | Surface as delivered |
| --- | --- | --- | --- |
| 5 mm to 115 mm | [Bright bar](https://www.laxconsteels.com/products/bright-bars/) | up to 6.5 m | Cold finished, Ra 0.2 micron maximum |
| 8 mm to 81 mm | [Precision shaft quality bar](https://www.laxconsteels.com/products/precision-shaft-quality-psq-bars/) | up to 6.4 m | Cold finished, straightness 0.015 inch TIR per 10 feet |
| 16 mm to 125 mm | [Hot rolled round bar](https://www.laxconsteels.com/products/hot-rolled-round-bars/) | up to 8 m | Black, spot ground or fully ground |
| 120 mm to 550 mm | [Proof machined bar](https://www.laxconsteels.com/products/forged-proof-machined-bars/) | up to 6 m | Rough turned below the skin, inspected |

The bands overlap. Between 16 and 115 mm the same diameter is available in three products at three prices. Below 16 mm no hot rolled option exists; above 125 mm the only route is proof machined bar; and above 115 mm no cold finished route exists.

Mill length varies with the product: hot rolled bar runs to 8 metres and cold finished bar to 6.5. A cutting plan written for 6 metre stock produces offcuts when 8 metre bars are delivered, so the length belongs on the enquiry.

## Finish route

The finish route is the largest price determinant after grade. Five routes are supplied.

- **Black.** Hot rolled, with mill scale on, at an open tolerance. Suitable where the part will be fully machined and only the metal, not the surface, is being purchased. On Laxcon hot rolled round bar, 100 percent ultrasonic testing is a published supply condition.
- **Spot ground or fully ground.** Hot rolled with the surface cleaned so that defects are visible and removed.
- **Cold drawn.** A bright surface at a close tolerance, and the lowest cost cold finished route. Drawing work hardens the bar, so it arrives stronger and less ductile than the annealed grade unless it is annealed afterwards.
- **Peeled and polished.** The skin is machined away, removing the decarburised layer and any rolling defect with it. This route is preferred on larger diameters.
- **Centreless ground.** The closest tolerances and the best surface, at the highest cost.

Cost is minimised by specifying the coarsest finish the downstream process tolerates; a ground surface that will be turned away in machining is paid for twice.

## Tolerance class

A tolerance is specified by its class, with a letter and a number, rather than by terms such as "bright" or "precision". The published classes are h7 through h11, k12 and k13 and ASTM A484 on bright bar; h7, h8, h9, j6, f7 and f8 on precision shaft quality bar; and ASTM A484 and EN 10060 on hot rolled and proof machined bar. The letter places the tolerance band relative to the nominal size, and the number sets the band width. An h class bar is at or under nominal size; a k class bar at grade 12 and above is at or over it. Full tables appear in [the bright bars guide](https://www.laxconsteels.com/bright-bars-everything-you-need-to-know/) and [the PSQ guide](https://www.laxconsteels.com/everything-about-psq-bars-types-uses-and-selecting-the-right-manufacturer/).

The classes differ materially at the same nominal size: a 40 mm bar at h9 runs from 40.000 down to 39.938 mm, while at k12 it runs from 40.000 up to 40.250 mm, a difference of nearly a third of a millimetre on the same nominal order.

## Grade and governing standard

Two documents are involved, and an order names both. AISI 304 and DIN 1.4301 are grade designations, which fix the composition; the product specification, such as ASTM A276 for bars and shapes or ASTM A479 for pressure vessel service, is the separate document that fixes how the bar itself is made, tested and certified. A grade designation is specified against a single named system, because composition windows differ between systems. In the Laxcon [grade register](https://www.laxconsteels.com/grades/), AISI 304 requires chromium of 18.0 to 20.0 percent while DIN 1.4301 requires 17.0 to 19.5 percent, so a heat at 17.2 percent chromium complies with one and not the other. "304 or equivalent" is therefore not a specification. The comparison is developed in [the 304 guide](https://www.laxconsteels.com/304-stainless-steel-quality-guide-why-its-industry-standard/), and cross-standard pairings are listed in the [equivalents tables](https://www.laxconsteels.com/grades/equivalents/).

Grade selection follows the service environment first and the machining requirement second.

| If the duty is | Ask for | Because |
| --- | --- | --- |
| Indoor, dry, general fabrication | [304](https://www.laxconsteels.com/grades/aisi-304/) | PREN band 18.0 to 21.6, lowest cost austenitic |
| Welded and then exposed | [304 L](https://www.laxconsteels.com/grades/aisi-304l/) or [316 L](https://www.laxconsteels.com/grades/aisi-316l/) | Carbon held to 0.03 percent maximum, so the heat-affected zone does not sensitise |
| Coastal, marine, chlorides | [316](https://www.laxconsteels.com/grades/aisi-316/) | Molybdenum 2.0 to 3.0 percent, PREN band 22.6 to 29.5 |
| Machined in volume, dry duty | [303](https://www.laxconsteels.com/grades/aisi-303/) | Sulphur raised to 0.15 percent breaks the chip. Do not use it wet or weld it |
| Hardness and wear | [431](https://www.laxconsteels.com/grades/aisi-431/), [420](https://www.laxconsteels.com/grades/aisi-420/) | Martensitic, hardenable by quench and temper |
| Seawater, or load with corrosion | [2205](https://www.laxconsteels.com/grades/duplex-2205/) duplex | Roughly double the proof stress with a PREN band of 34.1 to 37.8 |

## Test requirements

A test that is not stated on the purchase order does not appear on the certificate and cannot be added afterwards. The published testing conditions are as follows.

- **Ultrasonic testing** is a published supply condition on hot rolled round bar and proof machined bar. On cold finished bar it is not.
- **Eddy current testing** is available to customer requirement on bright bar and precision shaft quality bar. There is no default.
- **Positive material identification** by handheld spectrometer is published supply information across the range.
- **Freedom from radioactive elements, mercury and lead** is a published declaration, supported by screening of incoming scrap with a Rad Eye meter before the furnace.
- **Other tests,** including intergranular corrosion testing, impact testing at temperature, and ferrite count on duplex grades, must be named individually.

The steel is delivered with a test certificate recording the results of the tests ordered.

## Weight per metre

Stainless long products are specified by dimension and priced by weight, so a conversion is required between the drawing and the invoice. The weight per metre of a round bar is the diameter in millimetres squared, multiplied by 0.006205, at a density of 7.90 g/cm3. Tables for every profile are published on the [weight charts](https://www.laxconsteels.com/weight-charts/).

| Diameter | Weight (kg/m) | Per 6 m bar | Diameter | Weight (kg/m) | Per 6 m bar |
| --- | --- | --- | --- | --- | --- |
| 8 mm | 0.40 | 2.4 kg | 45 mm | 12.56 | 75.4 kg |
| 10 mm | 0.62 | 3.7 kg | 50 mm | 15.51 | 93.1 kg |
| 12 mm | 0.89 | 5.4 kg | 55 mm | 18.77 | 112.6 kg |
| 16 mm | 1.59 | 9.5 kg | 60 mm | 22.34 | 134.0 kg |
| 20 mm | 2.48 | 14.9 kg | 65 mm | 26.21 | 157.3 kg |
| 25 mm | 3.88 | 23.3 kg | 70 mm | 30.40 | 182.4 kg |
| 30 mm | 5.58 | 33.5 kg | 80 mm | 39.71 | 238.3 kg |
| 35 mm | 7.60 | 45.6 kg | 90 mm | 50.26 | 301.5 kg |
| 40 mm | 9.93 | 59.6 kg | 100 mm | 62.05 | 372.3 kg |

Two corrections apply. Density varies by grade: 304 sits near 7.93 g/cm3 and 316 near 7.98, so those grades run roughly 0.4 and 1.0 percent above the table. The figures are calculated rather than weighed, so a contractual quantity is settled from the mill certificate.

## Trade vocabulary

Indian trade language and standard language describe the same steel without overlapping cleanly, and both appear on Laxcon's order book. The following table maps the common trade terms to the products they name.

| Trade term | What it means | Where to look |
| --- | --- | --- |
| Gol or round | Round bar | [Hot rolled round bar](https://www.laxconsteels.com/products/hot-rolled-round-bars/), 16 to 125 mm |
| Patti | Flat bar, quoted as width by thickness, often in inches | [HRAP flat bars](https://www.laxconsteels.com/products/hrap-flat-bars/), 20 to 150 mm wide |
| T patti | T section | [T profile](https://www.laxconsteels.com/products/t-profile/), 50 x 50 x 5 mm |
| Angle or L angle | Equal or unequal angle | [Equal angles](https://www.laxconsteels.com/products/hrap-equal-angles/), 20 x 20 to 125 x 125 mm |
| Chowkoni or square | Square bar, drawn or black | [Square bright bars](https://www.laxconsteels.com/products/square-bright-bars/), 12.70 to 55 mm |
| Mother hollow | The thick-walled tube a seamless pipe is drawn from | [Seamless pipe and mother hollow](https://www.laxconsteels.com/products/seamless-pipe-mother-hollow/), 54, 65 and 76 mm outside diameter |
| RCS | Round cornered square, the input stock for drop forging | [RCS bars](https://www.laxconsteels.com/products/hot-rolled-round-cornered-squares-rcs-bars/), 45 to 100 RCS |
| Black bar | Hot rolled, scale still on | Hot rolled round bar |
| Bright bar | Cold finished | [Bright bars](https://www.laxconsteels.com/products/bright-bars/), 5 to 115 mm |

Sizes quoted in inches are common in the Indian trade and correspond to real stock rather than roundings of metric sizes. A 101.6 x 50.8 mm channel and a 4 by 2 inch channel are the same rolled section described in two unit systems.

## Contents of a complete enquiry

A complete round bar enquiry states seven items.

1. **Grade and governing standard.** AISI, EN, DIN, JIS or UNS, named once.
2. **Diameter and tolerance class.** With the letter and the number.
3. **Finish or heat treatment condition.** Black, drawn, ground, peeled; annealed, solution annealed, quenched and tempered.
4. **Length,** and whether cut lengths are wanted.
5. **Quantity,** in tonnes or in pieces, converted with the weight table above.
6. **Test or inspection requirement.**
7. **Delivery destination,** which decides the packing. Bundles run 500 to 1,000 kg in HDPE or LDPE with two lifting slings; export destinations that require it take ISPM 15 wooden boxes or fibre tubes.

## Frequently asked questions

### What is the difference between a black bar and a bright bar?

A black bar is hot rolled with mill scale still on it, at an open tolerance, in sizes 16 to 125 mm. A bright bar has been cold finished at room temperature, giving a clean surface and a close tolerance, in sizes 5 to 115 mm. The steel is the same; the process and the price differ.

### How do I calculate the weight of a stainless round bar?

The weight of a stainless round bar in kilograms per metre is the diameter in millimetres squared, multiplied by 0.006205, at a density of 7.90 g/cm3. For a 40 mm bar this is 1,600 times 0.006205, or 9.93 kg/m, so a 6 metre bar weighs 59.6 kg.

### What sizes of stainless round bar are available in India?

Laxcon's range covers stainless round bar from 5 mm to 550 mm across four products: bright bar from 5 to 115 mm, precision shaft quality bar from 8 to 81 mm, hot rolled round bar from 16 to 125 mm and proof machined bar from 120 to 550 mm.

### Which grade should I ask for?

The grade is determined by the service environment first and the machining requirement second: 304 for indoor and dry duty, 316 near chlorides or the coast, an L variant where the part is welded and then exposed, a martensitic grade where hardness is required, and duplex where load and seawater combine.

### Do you supply cut lengths?

Round bars are supplied in cut lengths, stated with the quantity on the enquiry. Published mill lengths are up to 8 metres for hot rolled bar, 6.5 metres for bright bar and 6.4 metres for precision shaft quality bar.

### What does the bundle marking show?

The bundle marking carries the heat number, grade, size, and net and gross weight. The heat number is the only link between the physical steel and its test certificate, so the tag is worth photographing before the strapping is cut.

## Sources

Size ranges, lengths, finishes, tolerance classes, testing, declarations and packing are the published supply conditions on the [product pages](https://www.laxconsteels.com/products/). Weight per metre and the section coefficients are on the [weight charts](https://www.laxconsteels.com/weight-charts/), calculated at 7.90 g/cm3. Composition windows are in the [grade reference](https://www.laxconsteels.com/grades/), cross-standard pairings in the [equivalents tables](https://www.laxconsteels.com/grades/equivalents/), and PREN bands in the [PREN reference](https://www.laxconsteels.com/pren-stainless-steel-what-your-grade-guarantees/). The trade terms in the vocabulary table are matched to the products they name; the products, sizes and standards are published, and the trade names are common Indian usage.

![Stainless steel hot rolled round bars produced by Laxcon Steels](https://www.laxconsteels.com/images/products/stainless-steel-hot-rolled-round-bars.webp)

Enquire about **Hot Rolled Round Bars**

First name Last name Email Phone Company Location

Product

- Bright Bars
- Precision Shaft Quality (PSQ) Bars
- Pipes and Tubes
- Hexagonal Bright Bars
- Square Bright Bars
- Cold-Drawn Flat Bars
- Forged & Proof Machined Bars
- HRAP Flat Bars
- HRAP Equal Angles
- HRAP Unequal Angles
- Threaded Bars
- Hot Rolled Round Cornered Squares (RCS) Bars
- Hot Rolled Round Bars
- Continuous Cast Billets / Blooms
- Channels
- Forging Quality Ingots
- Precipitation Hardening Steels
- Duplex Steel
- T-Profile
- Others

Message

\* Required

## From the Mill

- [![Stainless steel hot rolled round bars produced by Laxcon Steels](https://www.laxconsteels.com/images/products/stainless-steel-hot-rolled-round-bars.webp) Hot Rolled Round Bars 16 mm to 125 mm](https://www.laxconsteels.com/products/hot-rolled-round-bars/)
- [![Stainless steel bright bars produced by Laxcon Steels](https://www.laxconsteels.com/images/products/stainless-steel-bright-bars.webp) Bright Bars 5 mm to 115 mm](https://www.laxconsteels.com/products/bright-bars/)
- [![Optical emission spectrometer used to certify grade composition](https://www.laxconsteels.com/images/quality/laxcon-steels-optical-emission-spectrometer.webp) Grade reference](https://www.laxconsteels.com/grades/)