Hobson data sheet
BUMAX Stainless Grades: Definitions of BUMAX 88, 109, Duplex and More
A one-page definitions sheet from BUMAX (Swedish Engineering), distributed by Hobson. It describes each BUMAX stainless steel fastener grade in a short paragraph: what it is, its pitting resistance (PRE) value where given, its top strength class and the conditions it suits.
What this covers
- BUMAX 88 and 109
- Nitro and Super Austenite
- Duplex grades
- Ultra
- Heat grades
- Lock nut and Hard screws
Applies to Threaded Rod (Allthread), Hex Bolts & Set Screws, Machine Screw, Hex Flange Nut, Hex Nut, All-Metal Prevailing Torque Nut, Socket Head Cap Screw, Socket Countersunk Screw, Flat Washer and Mudguard / Penny Washer.
Key things to remember
The essentials from this document in plain words. Check the full document before you rely on a figure.
- BUMAX 88 is a premium A4 stainless with more molybdenum than standard A4: PRE 27 against 23. It is stronger, has fewer inclusions and lower magnetic permeability, and is used in cryogenic work down to -269°C.
- BUMAX 109 uses the same material as BUMAX 88, but a special manufacturing process makes it stronger. BUMAX calls it the strongest A4 fastener on the market.
- BUMAX Nitro: high-nitrogen austenitic stainless, PRE 35, up to strength class 12.9, suggested for marine applications. BUMAX Super Austenite (SA, EN 1.4547, 254 SMO): PRE 43, up to class 10.9, for seawater and aggressive chloride media.
- Duplex family: Lean Duplex LDX (EN 1.4162, PRE 26, up to class 12.9) for low to medium corrosive environments; Duplex DX (EN 1.4462, PRE above 34, up to 12.9); Super Duplex SDX (PRE 42, up to 12.9); Hyper Duplex HDX (EN 1.4658) for severe conditions such as hot chlorinated seawater.
- BUMAX Ultra: a precipitation hardenable stainless, PRE 25, up to strength class 16.9, described as the strongest stainless steel fastener on the market.
- Heat grades: BUMAX Heat (HE, EN 1.4980, A286) keeps high strength and oxidation resistance up to 700°C; BUMAX Heat Plus (HEP, EN 2.4952, Nimonic 80) is a nickel base alloy for up to 815°C.
- BUMAX Lock is an all-metal lock nut and BUMAX Hard a thread forming and self-tapping screw with surface hardness above HV 1200. Both are made from the same steel grade as BUMAX 88.
Who it helps: Engineers, buyers and staff choosing a stainless fastener grade for marine, chemical, cryogenic or high temperature work.
Share this document
Email it to yourself
Order the products this covers
Pick sizes and finishes on the product page, then send your list for a quote.