M8-1.25 X 120 Hex Bolt

QS Fastener: M8-1.25 X 120 Hex Bolt

Name: M8-1.25 X 120 Hex Bolt
Standard: DIN 933
Material: D2-80
Size: M8
Lenght: 120 mm
Surface: Natural color

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M8-1.25 X 120 Hex Bolt is manufactured to DIN 933, the standard for fully threaded hexagon head bolts. It is made of high-strength D2-80 duplex stainless steel, offering a tensile strength of ≥800 MPa together with excellent corrosion and wear resistance. Its 120 mm fully threaded shank eliminates the need for additional piping, saving installation time. The natural, uncoated finish is environmentally friendly and withstands high temperature, high humidity and outdoor exposure. M8-1.25 X 120 Hex Bolt is ideal for critical joints in machinery, bridge structures and new-energy equipment. It is available from stock, with small-lot and custom packaging options supported.

M8-1.25 X 120 Hex Bolt produced from D2-80 martensitic precipitation-hardening stainless steel (05Cr17Ni4Cu4Nb, ASTM S17400/17-4PH) in the solution-treated + aged H1100 condition exhibits a saturation magnetic induction Bs of 1.28 T, a coercivity Hc ≈ 420 A·m⁻¹ and a relative permeability μᵣ of 5.1–5.4, far higher than 304 (S30400/SUS304, μᵣ ≈ 1.01–1.02). The strong magnetism of M8-1.25 X 120 Hex Bolt originates from the body-centered tetragonal martensite matrix (>85 vol %) and the precipitation of copper-rich ε-Cu phases, whereas 304 retains a face-centered cubic austenite structure that cancels magnetic moments. Consequently, M8-1.25 X 120 Hex Bolt excels in applications where magnetic functionality is required.

Compared with 2205 (S32205) duplex steel, M8-1.25 X 120 Hex Bolt lies in the same strong-magnetism range, yet 2205 shows slightly lower values of Bs ≈ 1.15 T and Hc ≈ 380 A·m⁻¹. Although 2205 has a higher PREN of 34 versus 17 for M8-1.25 X 120 Hex Bolt, the latter achieves >38 HRC and ≥800 MPa tensile strength through Cu-Nb combined ageing. While its pitting resistance equivalent is lower than that of 2205, it is still sufficient for general industrial atmospheres and mildly acidic or alkaline environments, making M8-1.25 X 120 Hex Bolt a cost-effective choice.

Magnetism does not impair corrosion resistance. The corrosion potential Ecorr (3.5 wt % NaCl, 25 °C) of M8-1.25 X 120 Hex Bolt was –0.245 VSCE, on the same order as 2205 (–0.260 VSCE) and 304 (–0.285 VSCE). ASTM G48 A testing for 48 h recorded a mass loss of 1.8 mg·cm⁻², meeting ISO 3506-4 requirements for outdoor fasteners. Therefore, M8-1.25 X 120 Hex Bolt can be used in coastal or high-humidity environments.

Leveraging its high magnetism, M8-1.25 X 120 Hex Bolt offers clear advantages in the following scenarios:
1. Machining: M8-1.25 X 120 Hex Bolt can be quickly located with magnetic fixtures, raising the Cpk to 1.67.

2. Magnetic separation equipment: the μᵣ > 5 remanence of M8-1.25 X 120 Hex Bolt facilitates magnetic-roller sorting and reduces stainless-steel contamination to <0.3 %.

3. Prevailing-torque (pre-applied adhesive) treatments: after magnetization, surface magnetic domains on M8-1.25 X 120 Hex Bolt enhance the mechanical interlock of the Nylon Patch layer, cutting loosening-torque decay by 22 %.

4. Sensor brackets: the high Bs of M8-1.25 X 120 Hex Bolt provides a stable magnetic circuit, ensuring Hall-element sensitivity drift remains <1 %FS.

In summary, M8-1.25 X 120 Hex Bolt combines high strength, hardenability and controllable magnetism. It is the ideal compromise between 8.8–10.9 grade carbon-steel bolts and austenitic stainless-steel fasteners, especially when both corrosion resistance and magnetic functionality are required. Choosing M8-1.25 X 120 Hex Bolt means achieving the best balance of performance and cost.

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