Bumax grades

BUMAX 88 offers better corrosion resistance than standard A4 due to higher molybdenum content. Bumax 88 is a very consistent material that offers higher yield strength and lower amount of inclusion than standard A4 fasteners, that gives superior mechanical properties and fatigue resistance. Bumax 88 fasteners are used in many applications that demands very low magnetic permeability, it has lower magnetic permeability and less variation from batch to batch compared to standard A4 fasteners.

BUMAX 109 is the strongest A4 bolt on the market. Same material as Bumax 88 but higher strength due to special manufacturing process.

BUMAX Nitro, austenitic stainless steel with high nitrogen content, characterized by very high strength and fatigue resistance, in combination with good corrosion resistance. Excellent material for marine application and can be supplied in strength class 12.9 up to M42.

BUMAX Super Austenite (SA), high-alloy austenitic stainless steel for seawater and other aggressive chloride bearing medias. Excellent resistance to general, crevice, pitting and stress corrosion.

BUMAX Lean Duplex (LDX) offers economical solution for high strength fasteners in medium corrosive environments.

BUMAX Duplex (DX) are characterized by excellent strength, ductility and fatigue resistance in combination with good general, pitting, crevice and stress corrosion properties.

BUMAX Super Duplex (SDX) are characterized by excellent mechanical properties and very good corrosion resistance. Excellent resistance to general crevice, pitting and stress corrosion in chloride bearing medias.

BUMAX Hyper Duplex (HDX), a groundbreaking alloy used in the most demanding applications. Suited for use in severe corrosive environments such as hot chlorinated sea-water and for aggressive acidic chloride containing media in chemical, oil/gas, marine and petrochemical industry.

BUMAX Ultra, a unique precipitation hardenable stainless steel that can be delivered in ultra high strength levels. Offers an unique combination of ultra high strength combined with excellent ductility and good corrosion resistance in chloride environments. Strongest stainless steel fastener on the market.

BUMAX Heat (HE), high temperature resistant material for applications requiring high strength and good oxidation resistance at temperatures up to 700°C. Can be precipitation hardened.

BUMAX Heat Plus (HEP), precipitation hardenable high temperature resistant material with excellent oxidation resistance and high tensile and creep properties at temperatures up to 815°C.

Other special grades can be offered on request




Chemical composition

All values are nominal unless stated otherwise
GradesENUNSMicro structureC maxCrNiMoOtherPre¹
BUMAX 881.4432, 1.4436, 1.4435S31603Austenitic0.031711.52.727
BUMAX 1091.4432, 1.4436, 1.4435S31603Austenitic0.031711.52.727
BUMAX NitroS31675Austenitic0.03520.5102.4N 0.4, Mn 435
BUMAX SA1.4547S31254Austenitic0.0120186.2N, Cu43
BUMAX LDX²1.4462S32101Ferrite-Austenitic0.0321.51.50.3N 0.22,Mn 526
BUMAX DX1.4462S31803, S32205Ferrite-Austenitic0.03225.23.2N 0.1836
BUMAX SDX1.4410S32750Ferrite-Austenitic0.032574N 0.342
BUMAX HDX1.4658S32707Ferrite-Austenitic0.03276.54.8N 0.4, Co49
BUMAX Ultra S46910Martensitic0.021294Al, Ti, Cu25
BUMAX HE1.4980S66286Austenitic0.0815261.5Ti, V
BUMAX HEP 2.4952N07080Austenitic0.1019>65-Al, Ti, Co
Other grades can be offered on request
¹ PRE (Pitting Resistance Equivalent) number shows the pitting corrosion resistance of stainless steels. A higher PRE number indicates better corrosion resistance. The PRE is defined as, in weight-%: PRE= % Cr + 3.3 x % Mo + 16 x % N
² Standard offer for Bumax LDX is 1.4162 (PRE 26), but we have also the possibility to supply 1.4661 (PRE 33)