5 stainless fasteners - James Glen

1 stainless Steel The strengths of a product group of fasteners are expressed as: stainless steel is a broad term used for steels containing a minimum of chromium. These steels exhibit various in the imperial system as GRADES. degrees of corrosion resistance; their other properties can be in the metric system as PRODUCT CLASS. manipulated by the addition of nickel, molybdenum, titanium, niobium and other elements such as carbon and nitrogen. stainless steels' corrosion resistance is thanks largely to the The approximate tensile strength chromium oxide lm that forms naturally on the surface of the steels comparison of steel grades and classes corrosion. There are 5 basic types of stainless steel: Austenitic, Martensitic, MPa Ferritic, Duplex and Precipitation Hardening. 80% of all stainless steel fasteners are produced in Austenitic grades. Austenitic stainless Steels % Chemical Composition Material Grade Element Symbol A2 A4.

2 5 things you need to Carbon C Silicon S Manganese Mn Phosphorous P know about .. Sulphur S Chromium Cr to to stainless fastener s Molybdenum Mo - to Disclaimer Information contained in this lea et has been obtained from AS/NZS Standards, International Nickel Ni to to Standards, data provided by or published by international fastener suppliers, manufacturers and institutions, and by direct calculation and measurement by James Glen Pty Ltd. Every care Copper Cu has been taken by the sta of James Glen Pty Ltd in compilation of data contained herein and Note: Single values are maximum allowed. in veri cation of its accuracy when published, however the content of this lea et is subject to change without notice due to factors outside the control of James Glen Pty Ltd and this lea et Typical Applications: should therefor be used as information only. For example, the products referred to in this A2 (satis ed by 304) publication are continually improved through further research and development and this may lead to information contained in this lea et being altered without notice.

3 This lea et is published Architecture, Food processing equipment, Rainwater goods, and distributed on the basis that the publisher is not responsible for the results of any actions Hospital equipment, Dairy equipment, Heat exchangers, taken by users of information contained in this lea et nor for any error in or omission from this Brewing equipment, Bulk milk coolers, Refrigeration equipment, lea et. James Glen Pty Ltd does not accept any responsbility to any person, whether a reader of this lea et or not, in respect of claims, losses or damage or any other matter, either direct or Evaporators, Beer barrels, Kitchen equipment. consequential arising out of or in relation to the use and reliance, whether wholly or partially, upon any information contained or products referred to in this lea et. A4 (satis ed by 316). Exterior applications, Marine conditions, Chemical processing, NEW SOUTH WALES : Head Office Address - LIDCOMBE BUSINESS PARK, Unit F2, 3-29 Birnie Avenue, Lidcombe NSW 2141 Australia Textile manufacture, Pulp and paper equipment, Photographic Postal Address - Private bag 2002, Lidcombe NSW 1825.

4 Developing, Wine vats, Sewerage/e uent plants, Pumping Telephone (02) 9737 5252 : Facsimile (02) 9737 0028 : Email Outside Metropolitan area telephone freecall (1-800) 112 415. stations, Dyeing equipment, Sugar mills, Mining equipment. VICTORIA : 114 Boundary Road, Braeside, VIC 3195. Telephone (03) 9587 1966 : Facsimile (03) 9580 9141 Email In addition to excellent corrosion resistance stainless steels have Outside the Metropolitan area telephone (1-800) 331 739. a range of other properties that make them well suited to a wide WESTERN AUSTRALIA : 54 Wittenburg Drive, Canning Vale, WA 6155. Telephone (08) 9456 5955 : Facsimile (08) 9456 5911 : Email range of service conditions. Outside the Metropolitan area telephone (1-800) 998 415. Very low temperatures - resists brittleness QUEENSLAND : 12 Breene Place, Morningside, QLD 4170. Telephone (07) 3395 5266 : Facsimile (07) 3395 6860 : Email High temperatures - resists scaling & maintains strength Outside the Metropolitan area telephone (1-800) 112 415.

5 TASMANIA : c/- Daniels & Co. Pty. Ltd. 29 Mornington Road, Mornington TAS 7018. High strength to weight ratio Telephone (03) 6244 7455 : Facsimile (03) 6244 7317 : Email Easy cleaning for hygienic conditions NEW ZEALAND : 5 Industry Road, Penrose, Auckland 1006. Telephone (09) 571 0007 : Facsimile (09) 571 2111 : Email T H E B E S T D E S E R V E S T H E B E S T. Aesthetic appearance - no rust & no painting required Outside the Auckland area telephone (0800) 804 536. Wet abrasion resistance Visit our website at: James GLEN PTY LTD ABN 38 000 472 506 ACN 00 472 506. stainless Steel fastener Head Markings Tightening Torques Galling Torque is the measure of resistance of a thread to further What is galling? tightening measured in Newton metres (Nm). Whilst austenitic stainless steel fasteners exhibit many desirable Tightening Torque Mv Nm* properties a common problem is seizing or pick-up on assembly or Diameter Class 80 70 50 disassembly.

6 This phenomenon is M3 known as galling. It is thought to be caused by cold welding of the high M4 points of clean, oxide free metal left M5 when the oxide lm is dislodged by M6 surfaces rubbing against each other. M8 Surface hardness Surfaces treated so that they are M10 harder, hard faced or cold worked M12 surfaces, are less susceptible to M14 galling. There is a rule of thumb that a hardness di erence of 50 Brinell M16 between mating parts is required for M20 e ective prevention of galling. M24 Surface Finish M27 Highly polished or very rough surfaces tend to gall more. Cold M30 rolled surfaces are better as they tend to be smoother than A4-70 machined surfaces. Machined threads should be carefully deburred M36 before assembly. Signi cant galling problems may also arise with A = Austenitic steel (300 series) electropolished surfaces which can be very smooth. 1 = Free cutting stainless steel with lower corrosion Tightening Torque Mv Nm* Surface Stress resistance (known as 303) Reducing the surface pressure is e ective in reducing the risk of Diameter Class 80 70 50 galling.

7 This may be achieved by increasing the contact area or 2 = Cold formed steel containing chromium and nickel 1/4 UNC reducing the load, so that there is less stress on parts in contact and (known as 304). 5/16 UNC less thread wear. Over tightening the bolt will give excessive surface 4 = Cold formed stainless steel containing chromium, stresses and the only way to control this is to use the torque wrench nickel and molybdenum (known as 316) 3/8 UNC set to the appropriate torque setting. Dirty threads may cause under- 1/2 UNC tightening and fatigue failures. Indicates the strength (property class). 5/8 UNC Material Selection 50 = 1/10 of the tensile strength min 500 MPa 3/4 UNC It should be noted that while using 304 bolts with 316 nuts is often (approx 7200 psi) quoted as a cure for galling, the hardness di erence is not su cient 7/8 UNC 70 = 1/10 of the tensile strength min 700 MPa to prevent galling even when cold rolled, harder 304 is used with an (approx 101000 psi) 1 UNC annealed softer 316 nut.

8 80 = 1/10 of the tensile strength min 800 MPa If an austenitic bolt such as 304 or 316 is used, a way to minimise galling would be to use a hard nut of duplex stainless steel or a soft (approx 116000 psi) * Mv information refers to at blurr-free surfaces, lubricated (and also less corrosion resistant) nut of aluminium bronze. with good-quality lubricant and was calculated using a Common stainless Head Markings and Strengths Heat friction factor of Heat is a major factor when combatting galling. Austenitic stainless Property Tensile Yield The nominal induced load in joints tightened to these torque steel has a heat conductivity rate 40-50% lower than mild steel and Grade Class Strength Stress Elongation values is calculated as 65% of the load at the permanent has a heat expansion rate 50% greater than mild steel. These two 2 2. Rm. MPa (N/mm ) min Rp. MPa (N/mm ) min set limit but in practice, the value can be expected to vary factors combined with a relatively high coe cient of friction create A2 & A4 50 500 210 the conditions for seizing, cold welding or galling.

9 To avoid the build between 50% and 80% of the load at the permanent A2 & A4 70 700 450 up of heat, friction should be kept to a minimum by using copper set limit. free, solid type, quality lubricants, keeping application speeds low A2 & A4 80 800 600 Many factors a ect friction and even slight deviations and torque within guidelines. Nickel lled lubricants are available for Points to note from normal or test conditions can produce wide variations. stainless . Graphite lubricants may cause corrosion. Product markings are not uniform over all stainless fasteners Accordingly, when friction coe cients are used in design Lock Nuts Where A2 and A4 are used without property class, assume it calculations, factors of safety should be considered Prevailing torque locking nuts such as nylon insert lock nuts and is lowest strength grade unless speci ed with a certi cate and in critical cases, speci c tests conducted to provide Glenloch metal insert locking nuts present elevated risks of galling A2 and A4 may be replaced with 304 and 316 respectively actual coe cients for material, geometery, and/or lubricant due to tight tolerances and increased friction from the locking M used in Australia on non- stainless product to indicate combinations.

10 Mechanisms. Extra care must be taken when using these products. Appropriate lubrications should be used even in permanent metric is not consistently used on stainless . applications.