ST Trading supplies A2 and A4 stainless steel fasteners: bolts, nuts, washers and threaded rods. The table helps you specify the right standard in your enquiry. Standards in our range Standard Description DIN 931 / DIN 933 Hexagon head bolts (partial / full thread) DIN 912 Hexagon socket head cap screws – T-head bolts DIN 934 / DIN 985 Hexagon nuts and nylon insert lock nuts DIN 125 / DIN 9021 Flat and large-diameter washers DIN 976 Threaded rods The stainless steel PDF catalogue is broader – it also covers set screws (DIN 913–916), countersunk (DIN 7991) and button head (ISO 7380) screws, self-drilling screws (DIN 7504), tapping screws, domed cap nuts (DIN 1587), flange nuts (DIN 6923) and retaining rings (DIN 471, DIN 472). Catalogue Download PDF catalogue Need a quote? Send us your list of parts (standard, size, quantity) or a drawing and we will get back to you. Request a quote When to choose stainless steel Stainless fasteners are used where the joint is exposed to moisture, weather or chemicals. The most common steel groups are A2 – for indoor use and moderate atmospheric conditions – and A4, alloyed with molybdenum, which usually copes better with chloride environments. Selection for chloride or chemical environments still requires an assessment of the actual service conditions. In bolt markings such as A2-70 or A4-80, the number is the property class: multiplied by ten it gives the minimum tensile strength in MPa (e.g. 70 – 700 MPa). Nuts and washers follow their own marking rules. When combining stainless steel with other metals, assess the risk of galvanic corrosion, especially in the presence of moisture – isolate the materials if needed. During assembly, keep the risk of thread galling in mind; suitable lubrication and even tightening help. Frequently asked questions What is the difference between A2 and A4? A4 contains molybdenum and usually copes better with chloride environments than A2. The choice still depends on the actual service conditions of the joint. What does A2-70 mean? A2 is the steel group and 70 is the bolt property class – a minimum tensile strength of 700 MPa. Nut and washer markings are defined by separate standards. Can stainless and galvanised fasteners be combined? Combining different metals requires an assessment of galvanic corrosion risk, especially where moisture is present. If needed, isolate the materials or use parts of a single material. How can thread galling be reduced? Suitable thread lubrication, moderate speed and even tightening all help. Clean, undamaged threads before assembly also matter.
