Stainless Steel Fasteners

Different Grades of Stainless Steel Fasteners Explained

For improved corrosion characteristics, stainless steel is an alloy of low carbon steel and chromium. Stainless steel is for the price, highly corrosion resistant. As the anti-corrosive properties of the metal are intrinsic, if scratched during installation or use, it will not lose this resistance.

That stainless steel is stronger than standard steel is a common misconception. Many stainless steel alloys cannot be hardened by heat treatment due to their low carbon content. Therefore the stainless alloys used in bolts are marginally stronger than un-hardened steel relative to ordinary steel but considerably weaker than hardened steel fasteners. Stainless fasteners are prone to seizing up during installation, a condition known as galling unless great care is taken. While some grades are slightly magnetic, most stainless steel fasteners are much less magnetic than standard steel fasteners.

What are the different grades of Stainless Steel Fasteners?

 18-8 Stainless Steel Fastener

304-grade stainless steel, which is the most commonly used and versatile austenitic type of stainless steel, is 18/8 stainless steel. The 18/8 numbers reflect the 18 percent chromium and 8 percent nickel composition of this steel, making it very resistant to corrosion and oxidation. 18/8 stainless steel is also very durable and can easily be made. It is quick to clean the metal and it is available in several appearances and finishes.

Stainless Steel 316 Fastener

The 316 grade is a molybdenum-bearing austenitic stainless steel that contains 8% nickel, 18% chromium, and 2-3% molybdenum. The higher nickel and molybdenum content enables this grade to display better overall corrosion resistant properties which are particularly true in chloride environments in pitting and crevice corrosion. Moreover, Alloy 316 offers outstanding strengths of high temperature tensile and stress rupture, as well as outstanding weldability. Like 316 stainless steel screws, 316 stainless steel washers, and 316 stainless steel nuts, Fastener Solutions offers this alloy grade.

 Stainless Steel 410 Fastener

SS 410 Fasteners are used where the ideal stiffness, air or furnace cooling is tempered. Furthermore, the tempering of our Alloy 410 Fasteners in the 750 Degree F-1050 Degree F range results in reduced impact strength and slightly decreased corrosion resistance. For petroleum fractionating systems, bolts, screws, bushings and nuts, shafts, pumps and valves, gas turbines, mine ladder rungs, and so on, these Grade 410 fasteners are also used.

In both the annealed and hardened settings, our Type 410 Fasteners are magnetic and are typically used for applications involving mild corrosion, high strength, and heat resistance. Slow regulated cooling from 1500 degrees F / 1600 degrees F for solution annealing and heat to 1700 degrees F / 1850 degrees F for hardening of AISI 410 fasteners, after quenching in air or oil. By all standard methods, the 410 Stainless Steel Fasteners are readily welded, where post-weld annealing is recommended to ensure optimum ductility.

Seamless Tube

What is ASTM A312 Stainless Steel?

Overview

ASTM A312 is an American Standard specification which covers seamless, straight-seam welded, and heavily cold worked welded austenitic stainless steel pipe intended for high-temperature and general corrosive service. The most common grades are 304/304L Stainless Steel and 316/316L Stainless Steel .In this article, we illustrate the chemical and mechanical properties of the A312 specifications.

ASTM A312 STAINLESS STEEL PIPE 

Stainless steel pipes are used for high-temperature applications where corrosion is a key issue.

Stainless steel has been developed to cope with the increasing demand, across many industries, for more durable steels that could withstand demanding service conditions. Stainless steel was conceived as an evolution of standard carbon steel and obtained by adding alloying elements to the base iron like Nickel and Chromium. The addition of such alloying elements enhances the resistance of the steel to corrosion in harsh applications.

Before learning about the different grades, let’s review the types of stainless steel available on the market and their classification.

We are Leading Manufacturers, Suppliers & Exporters of ASTM A312 Stainless Steel Pipes in India.

STAINLESS STEEL TYPES

As a general rule, any steel alloy that has at least 10.5 percent of chromium may be considered stainless steel. However, a multitude of grades is available depending on the mix of the alloying elements (Nickel. Chromium, Moly, Titanium, Copper, Nitrogen, etc.) Each alloy has a specific structure and chemical and mechanical properties.

The general attribute of stainless steels is that they show resistance to corrosion thanks to an outer chromium oxide layer. Such oxide acts like a microscopic protection layer that reacts with oxygen and blocks corrosion. Further, stainless steel alloys feature better toughness in cryogenic applications than carbon steel, better strength and hardness, improved ductility and low maintenance costs.

Stainless steels may be grouped into a few families, designated as “series”. Let’s take a closer look.

Austenitic Stainless Steel (Series 300)

These are the most common grades of stainless steel. The microstructure of austenitic stainless steels is obtained with the addition of nickel, manganese, and nitrogen that give weldability and formability properties to the alloy. The resistance to corrosion can be further improved by augmenting the percentage of chrome, moly, and nitrogen to the base alloy.

Nevertheless, the basic austenitic grades are vulnerable to stress corrosion cracking (higher percentages of nickel are necessary to enhance the stress corrosion cracking). Austenitic stainless steel cannot be hardened by heat treatment but have can work-hardened to high strength levels while retaining a reasonable level of strength and ductility.

Even if austenitic steels are generally non-magnetic, they can show some magnetic property based on the actual alloy composition and the work hardening given during production. Austenitic stainless steels are divided into the series 200 (chromium-manganese-nickel alloys) and 300 (chromium-nickel alloys like 304, 309, 316, 321, 347, etc). Stainless Steel 304 Pipes is the most common austenitic stainless steel that suits most corrosive applications. Any other grade in the 300 series enhances the basic features of SS304.

Martensitic Stainless Steel (Series 400)

Martensitic stainless steels are similar to ferritic steels as they both have remarkable chromium content, however, martensitic steels have higher carbon content up to 1 percent. The high carbon content allows martensitic steels to be hardened and tempered as standard carbon and chrome alloy steels (but show generally low weldability and ductility). This type of stainless steel is specified in case of high strength and moderate corrosion resistance requirements. Different from standard austenitic stainless steels, martensitic grades are magnetic. Common martensitic grades are 410, 420 and 440C.

Ferritic Stainless Steel (SS430)

Ferritic stainless steels have significant chrome content but low additions on carbon (generally below 0.1 percent). The name of this family of stainless steels comes from the fact that their microstructure is quite similar to carbon and low alloy steels.

These steels have a wide range of application, except for thin surfaces as they have a low resistance to welding or applications requiring formability (ferritic steels show low formability and ductility). Ferritic stainless steels cannot be hardened by heat treatment. By adding moly to a ferritic grade, the steel can be used in highly aggressive applications like desalination plants and seawater. These steel show also remarkable resistance to stress corrosion cracking. Likewise martensitic steels, ferritic SS is magnetic. The most common ferritic grades are the 430 (17 percent chromium), and the 409 (11 percent chromium), largely used in the automotive sector.

Precipitation hardening (PH 17-4)

PH steels can feature remarkable strength due to the addition, in the alloy, of elements as copper, niobium, and aluminum. These steels can be machined to very specific shapes with high tolerances requirements before the final aging treatment. This is different from conventional hardening and tempering of martensitic steels that are subject to distortion during the treatment.

The resistance to corrosion of precipitation hardening steels is comparable to standard austenitic steels like SS304. The most common precipitation hardening stainless steel is the 17-4PH, which features 17 percent chromium and 4 percent nickel.

ASTM A312 PIPE DIMENSIONS

The standard stainless steel pipes dimensions are set by the ANSI ASME B36.19 specification. Seamless SS pipes are available in the size range 1/8″ thru 24″, welded stainless pipes are manufactured in the range 2″ thru 36″ (ASTM A312 Pipes i.e. electric-fusion-welded austenitic chromium-nickel stainless steel pipe, or as rolled).