Low-Silicon Bronze C65100
The silicon bronze for cold-headed screws and bolts — 70 to 100 ksi in small sizes under F468, with the corrosion resistance and warm colour of bronze.
What C65100 Silicon Bronze is.
C65100 contains about 1.5 percent silicon and small amounts of manganese and iron. Silicon strengthens copper without hurting its corrosion resistance, and the low-silicon grade is ductile enough to cold head, so it is the alloy behind most silicon bronze wood screws, machine screws and small bolts. It resists seawater, brine, mild acids and the atmosphere, and weathers to a dark bronze.
ASTM F468 lists C65100 as Cu 651 (marking F468K), with 70 to 100 ksi full-size tensile in sizes to ¾ inch. We supply C65100 hardware cold headed or machined from certified B98 rod.
Chemical composition.
| Element | Symbol | Min % | Max % |
|---|---|---|---|
| Copper | Cu | balance | — |
| Silicon | Si | 0.8 | 2.0 |
| Manganese | Mn | — | 0.7 |
| Iron | Fe | — | 0.8 |
| Zinc | Zn | — | 1.5 |
| Lead | Pb | — | 0.05 |
Values per ASTM B98/B98M-13(2019) Table 1 (verified against the specification). Confirm the edition called out on your purchase order with our estimating team.
Mechanical properties.
| Nominal diameter (in.) | Hardness | Full-size tensile (ksi) | Full-size yield, min (ksi) | Machined tensile, min (ksi) | Machined yield, min (ksi) | Elongation in 4D, min (%) |
|---|---|---|---|---|---|---|
| 0.250 to 0.750 | 75–95 HRB | 70–100 | 55 | 70 | 53 | 8 |
| 0.875 to 1.500 | 70–95 HRB | 55–90 | 40 | 54 | 38 | 8 |
Values per ASTM F468-23 Table 2 (verified against the specification). Confirm the edition called out on your purchase order with our estimating team. Full-size tensile range and yield; machined-specimen minimums in the last three columns.
| Nut style | Hardness, min | Proof stress, min (ksi) |
|---|---|---|
| Hex and hex flange | 75 HRB | 70 |
| Heavy hex, large hex flange and thick | 75 HRB | 76 |
Values per ASTM F467-24 Table 2 (verified against the specification). Confirm the edition called out on your purchase order with our estimating team.
| Temper and size (in.) | Tensile strength, min (ksi) | Yield strength at 0.5 % extension, min (ksi) | Elongation, min (%) |
|---|---|---|---|
| O60 soft anneal — all sizes | 40 | 12 | 30 |
| H02 half-hard — to ½ | 55 | 20 | 11 |
| H02 half-hard — over ½ to 2 | 55 | 20 | 12 |
| H04 hard — to ½ | 65 | 35 | 8 |
| H04 hard — over ½ to 2 | 65 | 35 | 10 |
| H06 extra-hard — to ½ | 85 | 55 | 6 |
Values per ASTM B98/B98M-13(2019) Table 2 (verified against the specification). Confirm the edition called out on your purchase order with our estimating team.
Specifications that apply.
How C65100 Silicon Bronze ships from Houston.
- Cold-headed hex bolts, cap screws and machine screws to F468
- Hex and heavy hex nuts to F467
- Studs and threaded rod
- Machined bronze hardware
- Certified B98 rod
C65100 Silicon Bronze fasteners we make.
Every item is manufactured to your drawing or standard in C65100 Silicon Bronze, imperial or metric, with an EN 10204 3.1 certificate.
What is low-silicon bronze?
The silicon bronzes were developed as a corrosion-resistant, weldable alternative to tin bronze. C65100, with about 1.5 percent silicon, is the more ductile of the two wrought grades and work-hardens to high strength, which suits it to cold heading. Corrosion resistance matches the other bronzes in seawater, mild acids and alkalis, and the alloy is non-magnetic and non-sparking.
As a fastener
ASTM F468 gives C65100 bolts (F468K) 70 to 100 ksi tensile and 55 ksi yield in sizes to ¾ inch, dropping to 55 to 90 ksi and 40 ksi yield from ⅞ to 1½ inch. Nuts to F467 (F467K) carry a 70 ksi proof stress. For larger diameters or higher strength, C65500 or nickel-aluminum bronze are the usual steps up.
Testing, certification and marking
- Tensile and hardness tested per lot on the finished product
- Grade or alloy marking F468K on bolts and F467K on nuts and manufacturer's identification on every piece
- EN 10204 3.1 material test report with heat number and chemistry; 3.2 witness available
- Alloy identified by UNS number on the certificate
High-Silicon Bronze C65500
The strongest common silicon bronze in bar form, 90 ksi in hard temper and 100 ksi extra-hard in small rod — for machined marine fasteners, valve stems and pump parts.
ASTM F468 / F467 fasteners · ASTM B150 rod and barNickel-Aluminum Bronze C63000
Steel-like strength in a bronze — 100 to 130 ksi as a fastener — with seawater, cavitation and wear resistance for propellers, pumps, valve seats and subsea hardware.
ASTM F468 / F467 fasteners · ASTM B21 rod and barNaval Brass C46400
The marine brass — 1 percent tin for seawater resistance — and the ASTM F468 structural brass fastener alloy (F468D).