Alternatives to standard 316 stainless steel fasteners

So you need an alternative to standard stainless steel fasteners.  You have choices of many exotics and semi exotic materials.  Of course if money wasn't an issue you can go with a very exotic material and have most of your problems solved, but the question is alway "What do I need to get the job done?" and "Will this product fullfill my specifications or is it overkill?"

Below, I give you a few choices and of course will point out BUMAX as the in between a supper alloy and standard 316.  www.bumax.us 

Note: this is a limited list and yes I could mention 20 other materials,but pricing will not be satisfactory on the exotics.  So I list a few and hopefully this will assist you with the start of finding something other than standard 316 stainless steel fasteners.

Grade	Why it might be chosen instead of  standard 316?
Bumax A4-316L	2x Tensile strength 150ksi, 2x corrosion resistance, up to 60% less expensive than exotics
316Ti	Better resistance to temperatures of around 600-900°C is needed.
316N	Higher strength than standard 316.
317L	Higher resistance to chlorides than 316L, but with similar resistance to stress corrosion cracking.
904L	Much higher resistance to chlorides at elevated temperatures, with good formability
2205	Much higher resistance to chlorides at elevated temperatures, and higher strength than 316

 If you need assitance, my staff will be happy to assist you.  Contact me at chris.portelli@bufab.com  We are manufactures of all types of fasteners and are happy to point you in the right direction.

What is austenitic stainless steel and what type of fastener applicaiton are they used in

Lets start with the Chemical Formular
Fe, <0.03% C, 16-18.5% Cr, 10-14% Ni, 2-3% Mo, <2% Mn, <1% Si, <0.045% P, <0.03% S

Background

Grade 316 is the standard molybdenum-bearing grade, second in importance to 304 amongst the austenitic stainless steels. The molybdenum gives 316 better overall corrosion resistant properties than Grade 304, particularly higher resistance to pitting and crevice corrosion in chloride environments. It has excellent forming and welding characteristics. It is readily brake or roll formed into a variety of parts for applications in the industrial, architectural, and transportation fields. Grade 316 also has outstanding welding characteristics. Post-weld annealing is not required when welding thin sections. Grade 316L, the low carbon version of 316 and is immune from sensitisation (grain boundary carbide precipitation). Thus it is extensively used in heavy gauge welded components (over about 6mm). Grade 316H, with its higher carbon content has application at elevated temperatures, as does stabilised grade 316Ti. The austenitic structure also gives these grades excellent toughness, even down to cryogenic temperatures. Key Properties These properties are specified for flat rolled product (plate, sheet and coil) in ASTM A240/A240M. Similar but not necessarily identical properties are specified for other products such as pipe and bar in their respective specifications.

Possible Alternative Grades

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Grade	Why it might be chosen instead of 316?
Bumax A4-316L	2x Tesnile strength 150ksi, 2x corrosion resistance, up to 60% less expensive than exotics
316Ti	Better resistance to temperatures of around 600-900°C is needed.
316N	Higher strength than standard 316.
317L	Higher resistance to chlorides than 316L, but with similar resistance to stress corrosion cracking.
904L	Much higher resistance to chlorides at elevated temperatures, with good formability
2205	Much higher resistance to chlorides at elevated temperatures, and higher strength than 316

Corrosion Resistance

Excellent in a range of atmospheric environments and many corrosive media - generally more resistant than 304. Subject to pitting and crevice corrosion in warm chloride environments, and to stress corrosion cracking above about 60°C. Considered resistant to potable water with up to about 1000mg/L chlorides at ambient temperatures, reducing to about 500mg/L at 60°C.

316 is usually regarded as the standard “marine grade stainless steel”, but it is not resistant to warm sea water. In many marine environments 316 does exhibit surface corrosion, usually visible as brown staining. This is particularly associated with crevices and rough surface finish.

Heat Resistance

Good oxidation resistance in intermittent service to 870°C and in continuous service to 925°C. Continuous use of 316 in the 425-860°C range is not recommended if subsequent aqueous corrosion resistance is important. Grade 316L is more resistant to carbide precipitation and can be used in the above temperature range. Grade 316H has higher strength at elevated temperatures and is sometimes used for structural and pressure-containing applications at temperatures above about 500°C.

Heat Treatment

Solution Treatment (Annealing) - Heat to 1010-1120°C and cool rapidly. These grades cannot be hardened by thermal treatment.

Welding

Excellent weldability by all standard fusion methods, both with and without filler metals. AS 1554.6 pre-qualifies welding of 316 with Grade 316 and 316L with Grade 316L rods or electrodes (or their high silicon equivalents). Heavy welded sections in Grade 316 require post-weld annealing for maximum corrosion resistance. This is not required for 316L. Grade 316Ti may also be used as an alternative to 316 for heavy section welding.

Machining

A “Ugima” improved machinability version of grade 316 is available in round and hollow bar products. This machines significantly better than standard 316 or 316L, giving higher machining rates and lower tool wear in many operations.

Dual Certification

It is common for 316 and 316L to be stocked in "Dual Certified" form - mainly in plate and pipe. These items have chemical and mechanical properties complying with both 316 and 316L specifications. Such dual certified product does not meet 316H specification and may be unacceptable for high temperature applications.

Applications

Typical applications include:

•         Food preparation equipment particularly in chloride environments.

•         Laboratory benches & equipment.

•         Coastal architectural panelling, railings & trim.

•         Boat fittings.

•         Chemical containers, including for transport.

•         Heat Exchangers.

•         Woven or welded screens for mining, quarrying & water filtration.

•         Threaded fasteners.

•         Springs.

Thank you to Atlas Steels Australia for some of this information.

Overview of Fasteners in Pump and Valve Systems including BUMAX 88 316 fastener

Why stainless steel grades in pump and valve systems ?

      Corrosion resistance in Process Industries

o   (Oil & Gas, Chemicals, Waste and Salt water, etc.);

      Pressure and Temperature resistance;

      Hygienic requirements in Food & Beverage Industries

o   (Chocolate, Drinking water, Wine, Milk, etc.);

      Life cycle cost

o   (Low maintenance costs).

Which stainless steel grades in pump and valve systems ?

Standard grades :

      FERRITIC STEELS (1.4016 –1.4105 – 1.4106 –1.4114) :

o   Magnetic

o   Low strain hardening coefficient

o   Good tensile strength at high temperature

      MARTENSITIC STEELS (1.4006  > 1.4034 – 1.4005 >1.4035 – 1.4057 – 1.4418) :

o   Magnetic

o   High mechanical properties

      AUSTENITIC STEELS (1.4307/1.4301 – 1.4541 – 1.4404/1.4401 – 1.4571) :

o   Not or slightly magnetic

o   Good impact test even at low temperature

BUMAX

      Bulten Stainless BUMAX 88 and BUMAX 109 (1.4404)

o   Slightly magnetic

o   Extremely high tensile strength compared to 316

o   Good impact test even at low temperature

o   Corrosive resistance 3x standard grades

Special grades :

      DUPLEX STEELS (1.4362 – 1.4462 – 1.4507) :

o   Excellent corrosion resistance

o   High mechanical properties

      SUPER AUSTENITIC STEELS (1.4539 – 1.4529 – 1.4980) :

o   Very high stress corrosion resistance

      HEAT RESISTING STEELS (1.4841 – 1.4845) :

o   Austenitic steel with a good oxidation resistance

      PRECIPITATION HARDENING STEELS (1.4542 – 1.4545 – 1.4568) :

o   Very high mechanical properties

o   Good corrosion resistance

Pumps with a wide range of requirements

      Irrigation Pumps

o   Use – Pump water from ground wells

o   Requirements – Corrosion resistance in water

o   Reason to use BUMAX – Corrosion resistance 3x longer and strength

      Centrifugal Pumps

o   Use – Pump for low viscosity materials (water, oil, etc)

o   Requirements – Corrosion resistance in wastewater, Chemicals ect

o   Reason to use BUMAX – Corrosion resistance and lower cost than special grades

      Progressing Cavity Pumps

o   Use – Pump for very viscous materials

o   Requirements – corrosion resistance in process industries

o   Reason to use BUMAX – Corrosion resistance and lower cost than special grades

      Butterfly Valves

o   Use – Large flow at low pressure

o   Requirements – Corrosion resistance in process industries

o   Reason to use BUMAX – Corrosion resistance and lower cost than special grades

      Ball Valves

o   Use - Gases or liquids with suspended solids

o   Requirements – Corrosion resistance in process industries

o   Reason to use BUMAX – Corrosion resistance and lower cost than special grades

      Solenoid Valves

o   Use – Liquid, gases, oil

o   Requirements – Corrosion resistance

o   Reason to use BUMAX – Corrosion resistance and lower cost than special grades

What is PED and BUMAX fasteners

The PED Directive  arises from the European Community's Programme for the elimination of technical barriers to trade and is formulated under the "New Approach to Technical Harmonisation and Standards". Its purpose is to harmonise national laws of Member States regarding the design, manufacture, testing and conformity assessment of pressure equipment and assemblies of pressure equipment. It therefore aims to ensure the free placing on the market and putting into service of the equipment within the European Union and the European Economic Area. Formulated under the New Approach the directive provides for a flexible regulatory environment that does not impose any detailed technical solution. This approach allows European industry to develop new techniques thereby increasing international competitiveness. The pressure equipment directive is one of a series of technical harmonisation directives for machinery, electrical equipment, medical devices, simple pressure vessels, gas appliances etc.

The Directive concerns items such as vessels, pressurised storage containers, heat exchangers, steam generators, boilers, industrial piping, safety devices and pressure accessories. Such pressure equipment is widely used in the process industries (oil & gas, chemical, pharmaceutical, plastics and rubber and the food and beverage industry), high temperature process industry (glass, paper and board), energy production and in the supply of utilities, heating, air conditioning and gas storage and transportation.

Under the Community regime of the Directive, pressure equipment and assemblies above specified pressure and/or volume thresholds must:

• be safe;
• meet essential safety requirements covering design, manufacture and testing;
• satisfy appropriate conformity assessment procedures; and
• carry the CE marking and other information.

Pressure equipment and assemblies below the specified pressure / volume thresholds must:

• be safe;
• be designed and manufactured in accordance with the sound engineering practice of a Member State; and
• bear specified markings (but not the CE marking).

 

Bumax 88 for pressure vessels

The new pressure equipment directive, PED, 97/23/EC, came into force within the EU on 29 May 2002, concerning pressure-bearing equipment with a working pressure > 0.5 Bar. Bumax 88 is currently the only high-strength fasteners with approval for pressure vessels in Europe. Bumax 88 has been approved by TÜV in a special Particular Material Appraisal in compliance with PED 97/23/EC and TÜV documents Nos. 011P01421H and 0121P003310-1 and in accordance with AD 2000 W2 issued December 2002.

Why use Stainless Steel Fasteners

I thought I would keep it simple this morning and just chat about why we use Stainless Steel Fasteners.  Lets look at the main reasons below

 

Strength

The majority of stainless steels are at least 30% stronger than ordinary carbon steel. This not only helps the strength of whatever it is you build, but also extends the lifetime of the fixings.

Corrosion resistance

Stainless Steel is resistant to corrosive elements such as water, alkaline solutions and most chlorine bearing environments, which would rust ordinary steel fixings. This allows the stainless steel fixings to be used for both interior and exterior work and allow for a much higher quality finish with a longer lifetime. It also makes stainless steel fixings ideal for marine use. 

Heat resistance
Stainless Steel retains its high strength within high temperature situations. This broadens the use of your stainless steel fixings and allows you to use them for a variety of different jobs.

Hygiene

Stainless Steel is easy to clean in comparison to other metals. This makes it ideal for use in homes and in particular areas such as Kitchens and Bathrooms. 

Aesthetic appearance

The bright, easily maintained surface of stainless steel provides a modern and attractive appearance so is perfect for use around the home.

Ease of fabrication

Despite Stainless Steels enhanced strength, modern steel-making techniques mean that stainless steel can be cut, welded, formed, machined, and fabricated as readily as traditional steels.

Long term value

When the total life cycle costs are considered, stainless steel is often the least expensive material option due to its longer lifetime expectancy. This ensures that your fixings stay stronger for longer, and ultimately, are less likely to break or need replacing over time.

What is Grade 8.8 stainless steel fasteners

A grade 8.8 fastener can be manufactured from any material whose mechanical properties meet or exceed the requirements set forth in the relevant harmonised standards.
The two-digit nomenclature is not used to describe individual steel grades and only applies to metric fasteners defined under ISO 965 (as well as derived standards)
The designation system is based on two numbers e.g 8.8 . The first number is the tensile strength of the bolt material (N/mm² )/100. The second number is = 1/100.(the ratio of the Proof (or Yield ) stress and the Tensile strength expressed as a percentage = 100.[Yield (Proof stress) /Tensile strength] /100
meaning that a grade 8.8 bolt has a nominal ultimate tensile strength (UTS) of 800N/mm² (or Mpa) and a nominal yield strength of 640N/mm² (or Mpa).
These values are not expressed in Kg/mm² or PSI as the first is an expression of mass by surface-area, the second is an expression of weight by surface-area and neither are true units under the SI system.
Lastly, the actual steel grade used by manufacturers may vary but in most cases, a grade 8.8 fastener (self-colour, black-oxide or zinc plated) will be manufactured from a medium-alloy medium carbon steel, typically with 0.30 - 0.50 % Carbon and alloyed with other elements such as Molybdenum, Vanadium, Manganese and sometimes Boron or Cobalt in small quantities. These alloying elements provide the required mechanical properties to reach the minimum strength set forth by the harmonised standards.

Bare in mind that people sometimes refer to "high-tensile bolts" which are typically grade 8.8 or superior under the metric fastener system. Grade 8.8 and superior bolts should always have their grade permanently marked on the head to differentiate them from "low-tensile bolts" as inadvertantly replacing the former with the latter could have disastrous effects.
Grade 4.6 bolts are typically refered to as "low tensile" and are often used in the construction industry as these bolts offer higher ductility and resilience compared to "high-tensile" bolts.
Hope this helps.

Compare this to BUMAX 88 series by contacting your local BUMAX stainless steel fastener engineer at www.bufabusa.com  BUMAX is product line of BUFAB Bulten Stainless.

Understanding Common Abbreviations Your Fastener Distributor Uses

Your fastener distributor will offer advice and direction during the design, prototype and manufacturing stages. But you’re bound to come across an array of abbreviations during that communication, dealing with everything from the materials to fastener size, design and a range of other specifications.  Of course you can always contact the technical staff at BUFAB USA to help with all stainless steel fastener needs including our BUMAX products.  We at BUFAB are happy to help anyone with the simple to complex request for 316 stainless steel fasteners.  sales@bufabusa.com or www.bufabusa.com

Understanding these abbreviations is helpful for OEM staff.

General Abbreviations

ASTM – This designation indicates that the fastener follows a standard developed by the American Society for Testing and Materials.

DIN – This designation indicates that the fastener follows a metric standard developed by the Deutsches Instit fur Normung. These German standards are often used in the automotive industry.

Galv or Galvi – This abbreviation states that the fastener has been galvanized for greater strength.

BR – Stating that the fastener is made of brass.

CR – Stating that the fastener is made of chrome.

S/S – Stating that the fastener is made of stainless steel.

SBR – Stating that the fastener is made of silicon bronze.

Z – Stating that the fastener is made from zinc.

CL – Used for metric fasteners, this abbreviation states the class that the fastener falls under, which specifies the material and strength.

G – Used for US fasteners, this abbreviation states the grade that the fastener falls under.

NC – Used to indicate that the fastener is made with a National Coarse Thread.

NF – Used to indicate that the fastener is made with a National Fine Thread.

Types of Fasteners in Abbreviated Form

BT indicates a Bolt, and is often seen on drawings.

NT or &NT indicates that the fastener must include a Nut.

HHMB indicates a Hex Head Machine Bolt.

HX indicates a Hex fastener.

JMNT is used to indicate Jam Nuts.

LB is used to indicate Lag Bolts and is often followed by a weight measured in pounds.

MB is used to indicate Machine Bolts.

MS is used to indicate Machine Screws, while MSNT is used to indicate Machine Screw Nuts.

SMS indicates a Sheet Metal Screw.

SS indicates a Set Screw, although it may also be used to indicate stainless steel.

WS is used to indicate Wood Screw.

You’ll find common fastener abbreviations on drawings, in specifications and on purchase orders and invoices. Your fastener distributor will translate any terminology that seems confusing, but with knowledge of these abbreviations you should be well on the way to understanding.