ASTM A193 Grade B7 AISI 4140 Quenched and Tempered Precision Ground Steel Round Bar 31.75 mm h7

This 31.75 mm (1-1/4 inch) bar is supplied in AISI 4140 (42CrMo4 / SCM440 / 1.7225) chromium-molybdenum alloy steel, quenched and tempered to meet ASTM A193 Grade B7 mechanical requirements, then precision ground to +0 / −0.025 mm (h7). It is the standard feedstock for B7 stud bolts, cap screws and high tensile threaded rod, supplied pre-ground so fastener producers can thread or roll directly without a peeling step.

Why this bar suits B7 fastener production

• Meets A193 B7 mechanicals in the bar - tensile 860 MPa min, yield 725 MPa min, elongation 16% min, hardness 28-34 HRC typical (321 HB / 35 HRC max), verified per heat before shipment.
• Ground to h7, +0 / −0.025 mm - consistent 31.75 mm diameter holds thread rolling and centreless grinding setup, reducing scrap on high speed rolling machines.
• Clean, straight, decarb free - ground surface removes decarburised layer and mill scale, giving full hardness at the surface for rolled threads and better die life.
• Through-hardening 4140 base - good core toughness after Q&T, suitable for studs, tie rods and anchor bolts used in pressure vessels, valves and structural steelwork.
• Full traceability - heat number stencilled on every bundle, EN 10204 3.1 mill certificate, optional SGS / BV third party inspection and Charpy impact testing.

Specification

Chemical composition (AISI 4140, wt. %)

Chemistry is controlled within the ASTM A193 Grade B7 limits for 4140, with residual elements kept low to protect impact toughness and thread rolling performance.

Mechanical properties (ASTM A193 Grade B7)

Applications

• B7 stud bolts, threaded rod and anchor bolts for flanges and pressure vessels
• High tensile cap screws, tie rods and clamp bolts
• Hydraulic cylinder rods, piston rods and shafts requiring a ground finish
• Gears, spindles, mandrels and machine tool components
• Oil and gas wellhead studs, valve bonnet bolting

Processing notes

Thread rolling gives the best fatigue performance on B7 studs; because the bar arrives ground and decarb free, roll dies run cooler and thread flank hardness is retained. For cut threading, use coated carbide inserts and keep surface speed moderate. If higher toughness is required for low temperature service, specify impact tested material or the B7M / L7M chemistry route.

Packing and loading

Bars are oiled, wrapped in PE film and packed in export wooden cases or crates with moisture barrier; 20-25 tons per 20 ft container. Stock diameters ship within 7-10 days, cut-to-length and mill-run orders within 15-25 working days.

Supply capability

• Source mill with peeling, cold drawing, centreless grinding and continuous Q&T lines
• Diameter range 12-120 mm in ground condition, other sizes quoted on request
• Spectrometer chemistry, hardness mapping and tensile testing on every heat
• Export packing and documentation experience for EU, North America and Middle East fastener makers

Tell us the diameter, tolerance class and tonnage you need - we will confirm price, certificate and delivery date within one working day.