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42CrMo4 B7 Double End Stud
QS Fastener: 42CrMo4 B7 Double End Stud
Name: 42CrMo4 B7 Double End Stud
Standard: ASTM
Material: A193 B7
Size: 3/4 inch
Lenght: 100 mm
Surface: Black/ PTFE/ Zinc
Standard: ASTM
Material: A193 B7
Size: 3/4 inch
Lenght: 100 mm
Surface: Black/ PTFE/ Zinc
Quantity
42CrMo4 B7 Double End Stud is made of ASTM A193 B7 high-strength alloy steel, supplied in full black-oxide finish, with tensile strength ≥860 MPa and service temperature up to 400 °C. The 3/4 in × 100 mm double-end design keeps thread coaxiality ≤0.05 mm on both ends, giving a stable assembly torque. It is ideal for valves, pressure vessels and heavy-duty mould clamping, offers high safety redundancy and is available for immediate bulk delivery.
What coatings are used on fasteners?
Fastener coatings fall into four groups: metallic, chemical-conversion, organic and composite. All examples below refer to 42CrMo4 B7 Double End Stud so that one project can select materials consistently.
Fastener coatings fall into four groups: metallic, chemical-conversion, organic and composite. All examples below refer to 42CrMo4 B7 Double End Stud so that one project can select materials consistently.
1. Electro-plated zinc (Zn)
Features: 8–12 µm, bright white, NSS salt-spray 48–96 h.
Pros: cheap, easy to run on.
Cons: hydrogen-embrittlement risk; parts >320 HV must be baked; powdering above 120 °C.
Example: 42CrMo4 B7 Double End Stud for car interior, white zinc plus colour passivation, cost <0.01 USD.
Features: 8–12 µm, bright white, NSS salt-spray 48–96 h.
Pros: cheap, easy to run on.
Cons: hydrogen-embrittlement risk; parts >320 HV must be baked; powdering above 120 °C.
Example: 42CrMo4 B7 Double End Stud for car interior, white zinc plus colour passivation, cost <0.01 USD.
2. Hot-dip galvanising (HDG)
Features: 40–60 µm, metallurgically bonded to steel, NSS 1000 h.
Pros: 25-year outdoor life without replacement.
Cons: threads need clearance for zinc build-up, nuts must be tapped oversize; no post-machining possible.
Example: 42CrMo4 B7 Double End Stud M20×120 on HV transmission tower, 80 µm after HDG, torque coefficient drops 15 %.
Features: 40–60 µm, metallurgically bonded to steel, NSS 1000 h.
Pros: 25-year outdoor life without replacement.
Cons: threads need clearance for zinc build-up, nuts must be tapped oversize; no post-machining possible.
Example: 42CrMo4 B7 Double End Stud M20×120 on HV transmission tower, 80 µm after HDG, torque coefficient drops 15 %.
3. Zn-Ni (12–18 % Ni)
Features: 8 µm, NSS 1000 h, very low hydrogen embrittlement.
Pros: withstands 150 °C, small galvanic potential gap to aluminium, prevents bimetallic corrosion.
Cons: higher price, bath must be heated.
Example: 42CrMo4 B7 Double End Stud on Boeing 787 landing gear, no post-plate bake, weight only 17 g, 5 % lighter.
Features: 8 µm, NSS 1000 h, very low hydrogen embrittlement.
Pros: withstands 150 °C, small galvanic potential gap to aluminium, prevents bimetallic corrosion.
Cons: higher price, bath must be heated.
Example: 42CrMo4 B7 Double End Stud on Boeing 787 landing gear, no post-plate bake, weight only 17 g, 5 % lighter.
4. Dacromet (Zn-Al flake)
Features: 6–8 µm, NSS 1200 h, no hydrogen embrittlement.
Pros: stable from –55 °C to 300 °C, consistent K-factor.
Cons: poor conductivity, hexavalent-chrome version not eco-friendly.
Example: 42CrMo4 B7 Double End Stud M30×220 on wind-turbine blade, 25-year maintenance-free life.
Features: 6–8 µm, NSS 1200 h, no hydrogen embrittlement.
Pros: stable from –55 °C to 300 °C, consistent K-factor.
Cons: poor conductivity, hexavalent-chrome version not eco-friendly.
Example: 42CrMo4 B7 Double End Stud M30×220 on wind-turbine blade, 25-year maintenance-free life.
5. Phosphate (Mn-Zn)
Features: 3–5 µm, porous black-grey, NSS 24 h.
Pros: holds oil, lowers friction coefficient to ~0.1; good paint base.
Cons: no stand-alone corrosion protection.
Example: 42CrMo4 B7 Double End Stud on engine connecting rod, phosphated + oiled, assembly noise down 3 dB.
Features: 3–5 µm, porous black-grey, NSS 24 h.
Pros: holds oil, lowers friction coefficient to ~0.1; good paint base.
Cons: no stand-alone corrosion protection.
Example: 42CrMo4 B7 Double End Stud on engine connecting rod, phosphated + oiled, assembly noise down 3 dB.
6. Anodising (Al₂O₃)
Features: 5–25 µm, hard HV 500, electrically insulating.
Pros: for light alloys, colours (red, blue) can be dyed-in.
Cons: brittle, pitting in Cl⁻ media.
Example: aluminium rivet-style 42CrMo4 B7 Double End Stud on UAV, colour-anodised, 30 % weight saving.
Features: 5–25 µm, hard HV 500, electrically insulating.
Pros: for light alloys, colours (red, blue) can be dyed-in.
Cons: brittle, pitting in Cl⁻ media.
Example: aluminium rivet-style 42CrMo4 B7 Double End Stud on UAV, colour-anodised, 30 % weight saving.
7. Organic coatings (Xylan, PTFE, epoxy)
Features: 15–35 µm, friction 0.08–0.14, chemical resistant.
Pros: anti-galling, colour coding possible; salt spray 500–1500 h.
Cons: thin on edges, poor UV resistance.
Example: offshore platform 42CrMo4 B7 Double End Stud A320 L7, blue PTFE/ETFE film, 25-year no-removal life.
Features: 15–35 µm, friction 0.08–0.14, chemical resistant.
Pros: anti-galling, colour coding possible; salt spray 500–1500 h.
Cons: thin on edges, poor UV resistance.
Example: offshore platform 42CrMo4 B7 Double End Stud A320 L7, blue PTFE/ETFE film, 25-year no-removal life.
8. Composite coating (Geomet + top-coat)
Features: 8 µm Geomet base + 5 µm sealer, NSS 1500 h, chrome-free.
Pros: stable torque, environmentally friendly.
Cons: high price, narrow process window.
Example: Tesla battery pack 42CrMo4 B7 Double End Stud, total 14 µm, zero dust loss in automated assembly.
Features: 8 µm Geomet base + 5 µm sealer, NSS 1500 h, chrome-free.
Pros: stable torque, environmentally friendly.
Cons: high price, narrow process window.
Example: Tesla battery pack 42CrMo4 B7 Double End Stud, total 14 µm, zero dust loss in automated assembly.
Selection rule of thumb:
Indoor dry → bright zinc saves money;
Outdoor heavy load → hot-dip galvanising;
High temp / H₂ risk → Zn-Ni;
Long life, chrome-free → Geomet.
—equally valid for 42CrMo4 B7 Double End Stud.
Indoor dry → bright zinc saves money;
Outdoor heavy load → hot-dip galvanising;
High temp / H₂ risk → Zn-Ni;
Long life, chrome-free → Geomet.
—equally valid for 42CrMo4 B7 Double End Stud.
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