Alloy Steel B7 Round Bar
➡️ B7 | UNS G41400 | EN 1.7225
➡️ ASTM, EN, JIS & International Standards
➡️ Supply Conditions
➡️ Multiple Diameters & Supply Lengths
➡️ Global Export & International Delivery
Country of Origin:
Europe, Japan, USA
Material Type:
Alloy Steel
UNS Number:
G41400
Wr. No.:
1.7225
MTC Available:
EN 10204 3.1
Product Description for Alloy Steel B7 Round Bar
B7 is the ASTM A193 grade designation for quenched and tempered chromium-molybdenum bolting steel, based on the 4140 type composition and carried under UNS G41400. Bar is supplied to ASTM A193 / A193M with dimensions to ASTM A29 / A29M.
It is by a wide margin the most used bolting material in process plant. The composition is roughly 1% chromium and 0.2% molybdenum with carbon at 0.37-0.49%, quenched and tempered at 593 C minimum to develop strength through tempered martensite rather than through alloying.
The property that matters is the strength level, and it falls as diameter increases. Up to 64 mm the requirement is 860 MPa tensile minimum alongside 725 MPa minimum proof strength. From 64 to 100 mm it drops to 795 and 655 MPa, and from 100 to 180 mm to 690 and 515 MPa. This is a hardenability limit, not a quality issue: larger sections cannot be quenched fast enough at the core.
Service temperature is limited to roughly 400-425 C. Above that the material tempers further in service and relaxes, and B16 becomes the correct choice.
B7M is the related grade for sour service, tempered softer to a 235 HBW maximum for NACE MR0175 compliance. It is not the same material as B7 and cannot be substituted.
The grade is not intended for welding. Carbon at this level makes it strongly air hardening, and welding heat destroys the quenched and tempered condition, so bolts are machined and threaded from bar.
Available from 6 mm to 180 mm, in random or cut lengths. Typical work is flange stud bolts, anchor bolts, pressure-vessel fasteners and general high-strength bolting.
Common Applications of Alloy Steel B7 Round Bar
➡️ Machined shafts, spindles, valve stems, pump sleeves and pins for food, beverage, dairy and pharmaceutical equipment, where the passive chromium oxide film resists both product acids and caustic clean-in-place chemicals.
➡️ Fasteners, studs, bolts, threaded rod and anchor components produced from bar stock, chosen for corrosion resistance combined with the ductility needed for cold heading and thread rolling.
➡️ Chemical, water treatment and general process plant parts such as agitator shafts, flange blanks, nozzles and support components handling water, steam and mildly corrosive media free of significant chlorides.
➡️ Architectural and structural hardware including handrail stanchions, balustrade fittings, tension rods and bollards, where a bright ground or polished bar finish provides both appearance and low maintenance.
International Equivalent Grade for Alloy Steel B7 Round Bar
Standard
Country / Region
Grade
ASTM A193 / A193M
USA
Grade B7 (UNS G41400)
SAE J404 / AISI
USA
4140
EN 10083-3
Europe / EU
42CrMo4 (1.7225)
BS EN 10083-3
United Kingdom
42CrMo4 (1.7225)
JIS G4105
Japan
SCM 440
GB/T 3077
China
42CrMo
ISO 683-2
International
42CrMo4
Technical Specification for Alloy Steel B7 Round Bar
Specification
Value
Unit
Material
Alloy steel
-
Grade
B7 / UNS G41400 / 4140 / 1.7225
-
Product Form
Round bar / rod for bolting
-
Standard
ASTM A193 / A193M Grade B7
-
Diameter
6 - 180 (typical supply range)
mm
Length
3 - 6 (random), or cut to length
m
Manufacturing Process
Hot rolled or forged, quenched and tempered
-
Production Route
EAF or BOF with ladle refining, continuous cast or ingot
-
Surface Finish
Hot-rolled, rough-turned, peeled, smooth-turned, centreless ground
-
Heat Treatment / Delivery Condition
Quenched and tempered at 593 C minimum
-
Tolerance Standard
ASTM A29 / A29M
-
Density
7.85 (typical)
g/cm3
Melting Range
1425 - 1510 (typical)
C
Thermal Conductivity at 100 C
42.6 (typical)
W/m.K
Coefficient of Thermal Expansion (20-100 C)
12.3 (typical)
um/m.C
Specific Heat (0-100 C)
473 (typical)
J/kg.K
Electrical Resistivity at 20 C
0.22 (typical)
uOhm.m
Modulus of Elasticity at 20 C
205 (typical)
GPa
Magnetic Properties
Ferromagnetic in all conditions
-
Maximum Service Temperature
400 - 425 (typical practical limit, above which B16 is preferred)
C
Testing / Inspection Standard
ASTM A370 for mechanical testing, ASTM A193 for hardness verification
-
Certification / Inspection Documents
EN 10204 3.1 or 3.2 mill test certificate
-
Technical Specifications
Get the key technical specifications for Alloy Steel B7 Round Bar
Order to ASTM A193 / A193M as Grade B7, the standard covering alloy steel and stainless bolting for high-temperature or high-pressure service. Dimensional tolerance, straightness and surface condition follow ASTM A29 / A29M.
The delivery condition is quenched and tempered, with tempering at 593 C minimum. Unlike the A182 forging grades, strength here comes from tempered martensite rather than from creep-resistant carbides, which is why B7 is a strength material rather than a creep material.
Diameter matters more than for almost any other grade in this range, because the specified strength reduces in three steps as section size increases. A bar that meets the 860 MPa requirement at 50 mm will not meet it at 120 mm, and the standard reflects that by lowering the requirement rather than by rejecting the material. Design calculations must use the figures for the actual bolt diameter.
Above roughly 400-425 C the material continues to temper in service, losing preload through stress relaxation, so B16 should be specified instead for hotter joints.
For sour service, B7M is the related grade, tempered to a lower strength with hardness capped at 235 HBW to satisfy NACE MR0175 / ISO 15156. B7 and B7M are separate grades and one cannot be supplied against an order for the other.
Chemical Composition for Alloy Steel B7 Round Bar
Element
Symbol
Min
Max
Unit
Carbon
C
0.37
0.49
%
Manganese
Mn
0.65
1.10
%
Silicon
Si
0.15
0.35
%
Phosphorus
P
-
0.035
%
Sulfur
S
-
0.040
%
Chromium
Cr
0.75
1.20
%
Molybdenum
Mo
0.15
0.25
%
Iron
Fe
Balance
-
%
Chemical Composition
View the chemical composition and applicable material limits for Alloy Steel B7 Round Bar
Carbon at 0.37-0.49% is the primary strengthening element and it is far higher than in any of the A182 chromium-molybdenum grades. On quenching it produces hard martensite, and tempering then brings that back to a tough, high-strength condition. This carbon level is also why B7 is not readily weldable and why bolts are machined and threaded rather than fabricated.
Chromium at 0.75-1.20% and molybdenum at 0.15-0.25% are present mainly for hardenability, meaning the depth to which martensite forms on quenching. Without them, a 100 mm bar would transform only at the surface and be soft at the core. Molybdenum also reduces susceptibility to temper embrittlement, which matters for a material tempered at 593 C and used near that range.
Manganese at 0.65-1.10% adds further hardenability and deoxidises the melt.
Silicon at 0.15-0.35% deoxidises and contributes modest solid-solution strengthening.
Phosphorus at 0.035% and sulphur at 0.040% are residual limits. Sulphur is permitted relatively high here because bolting is machined, and a little sulphur assists machinability, though it does reduce transverse ductility.
Mechanical Properties for Alloy Steel B7 Round Bar
Mechanical Property
Value
Unit
Tensile Strength, diameter up to 64 mm
860
MPa (minimum)
Yield Strength 0.2% Proof, diameter up to 64 mm
725
MPa (minimum)
Tensile Strength, diameter over 64 to 100 mm
795
MPa (minimum)
Yield Strength 0.2% Proof, diameter over 64 to 100 mm
655
MPa (minimum)
Tensile Strength, diameter over 100 to 180 mm
690
MPa (minimum)
Yield Strength 0.2% Proof, diameter over 100 to 180 mm
515
MPa (minimum)
Elongation in 50 mm
16
% (minimum, up to 100 mm diameter)
Reduction of Area
50
% (minimum)
Hardness
321
HBW (maximum)
Modulus of Elasticity
205
GPa (typical)
Mechanical Properties
Check the key mechanical properties and performance requirements of Alloy Steel B7 Round Bar
ASTM A193 / A193M sets these for Grade B7, tested to ASTM A370. All strength figures are minima and hardness is a maximum. The critical point is that strength requirements are banded by diameter, so any quoted figure is meaningless without the size it applies to.
Up to 64 mm the requirement is 860 MPa tensile minimum alongside 725 MPa minimum proof strength. Over 64 to 100 mm it falls to 795 and 655 MPa. Over 100 to 180 mm it falls again to 690 and 515 MPa, with elongation rising to 18% in the largest band.
This banding is a hardenability consequence. During quenching, the core of a large bar cools too slowly to transform fully to martensite, so it ends up softer regardless of how carefully the treatment is carried out. The standard acknowledges the physics rather than demanding the impossible.
The practical effect is that bolt design has to use the values for the actual diameter. Assuming 860 MPa across all sizes will overestimate the capacity of large-diameter studs, and that error has caused joint failures.
Hardness capped at 321 HBW confirms tempering was adequate. Where sour service applies, the far tighter 235 HBW limit of B7M governs instead.
Dimension / Sizes for Alloy Steel B7 Round Bar
Dimension / Size
Value
Unit
Diameter
6 - 180
mm
Standard Length
3 - 6 (random / mill lengths)
m
Custom Length
Cut to length available on request
-
Diameter Tolerance
Per ASTM A29 / A29M, varies with size and finish
-
Length Tolerance
Per ASTM A29 / A29M or as agreed at order
-
Straightness Tolerance
Per ASTM A29 / A29M or as agreed at order
-
End Condition
Square cut, chamfered, or as ordered
-
Surface Finish
Hot-rolled, rough-turned, peeled, smooth-turned, centreless ground
-
Available Size Range
6 - 180, larger diameters subject to enquiry
mm
Cut-to-Length Availability
Available
-
Dimensional Standard
ASTM A29 / A29M
-
Dimensions & Sizes
Explore available diameters, lengths, and dimensional requirements for Alloy Steel B7 Round Bar
Pricing for Alloy Steel B7 Round Bar
Round Bar Prices are generally quoted per kilograms or meters tonnes and can fluctuate with the global raw material and market prices. The final price will depend on a variety of factors, including the grade size, diameter, length, surface finish, the quantity and whether the bars are cut to length or in standard lengths.
For smaller quantities, we can also quote per metre or per piece basis once the required dimensions have been confirmed. Container-loads or orders that are larger in size are typically priced per tonne, based upon the specifications required and the supply conditions.
Please provide your desired dimensions, grades, length number, and end for a current quote including the lead time applicable and details for certification.
Pricing
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Why Choose Us
Euro Steel Bars is an international distributor, stockist and exporter of stainless round steel bars that cover carbon, stainless alloy, special grades. We stock a variety of sizes and grades. We guarantee every order with mill test certificates as well as full quality-assurance documentation. Our name speaks to our roots: European-sourced materials that is backed by the certificates and rigor that buyers from Asia as well as the Gulf and Africa are looking for.
Each bar we deliver is accompanied by EN 10204 3.1 mill test certificates as well as complete documentation of quality, so what you receive corresponds to what’s written in the documents. We carry a selection of sizes and grades ready for transport, and cut length upon the request of customers, which results in quicker lead times, whether you’re ordering just a one-off spec or a complete project tonnage.
We operate an actual wholesale business that is that is supported with an internationally-operated supply chain therefore we are able to serve fabricators sourcing one grade the same way in the same way as an EPC contractor who is placing a large order. Our clients include manufacturers, fabricators EPC construction companies, engineers oil and gas projects as well as construction companies. we design our inventory as well as documentation to show what buyers need to bring projects forward.
Our customers trust us across Qatar, Oman, Bahrain, Kuwait, Jordan, Malaysia, Singapore, Thailand, Taiwan, Turkey, Italy and South Africa. If you’re looking to source an Gulf energy project, or a construction project within Southeast Asia, you get the same quality of certified material, the exact documentation, and the exact delivery procedure.
Frequently Asked Questions
What is Alloy Steel B7 Round Bar?
Why do B7 strength requirements change with diameter?
What is the difference between B7 and B7M?
What is the difference between B7 and B16?
What standard does Alloy Steel B7 Round Bar comply with?
What are the key mechanical properties of Alloy Steel B7 Round Bar?
Can Alloy Steel B7 Round Bar be welded?
What sizes and lengths are available?
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