Friday, May 22, 2015

Stainless Steel Applications

Stainless steel is used primarily for long lasting applications, due to its corrosion-resistant nature and durability. At Albany County Fasteners we stock fasteners in various grades of stainless steel to provide an appropriate solution for any fastener application. 
 

Making the Grades:


18-8 Stainless Steel - (18% Chrome, 8% Nickel, .08% Maximum Carbon) - This is the standard grade for stainless steel fasteners. They are corrosion-resistant and durable. They are often used in marine applications in freshwater environments, but will not work as effectively in a salt water environment.


304 Stainless Steel – (17%-19% Chrome, 8%-12% Nickel, .08% Maximum Carbon) - This is a superior grade of 18-8 stainless steel. 304 Stainless steel is often used to make Machine Screws, Cap Screws, Sheet Metal Screws, Hex Cap Screws and all cold headed or hot forged fasteners. It is often used in food service and dye applications because of its ability to resist the corrosive properties of organic acids.

305 Stainless Steel – (17%-19% Chrome, 8%-10% Nickel, .12% Maximum Carbon) - This grade has been developed specifically to improve the cold heading qualities of 18-8. This grade does not work hardened products are actually made from this grade even though they are referred to as being made from type 304 Corrosion resistance and physical qualities are equal to Type 304. 305 stainless steel is used to make deck screws, which are used (shockingly) to fasten wood or composite boards to the main beams of a deck.
Square Drive Deck Screw-305 Stainless Steel

316 Stainless Steel – (16%-18% Chrome, 10%-14% Nickel, .08% Maximum Carbon, 2.00% Maximum Molybdenum) – This grade of stainless steel is used and recommended for applications in severe or harsh environments. Its corrosion resistance is greater than 18-8 stainless, which is why we recommend using 316 stainless steel fasteners for salt water environments. It is important to remember that even the salt in the air near a body of salt water can do damage to dry applications, so 316 is the material of choice. Common applications of 316 stainless steel fasteners include boats, docks and piers.   
 
410 Stainless Steel – (11.5%-13.5% Chrome, .15% Maximum Carbon) – Due to the fact that this grade of stainless steel can be hardened up to approximately 40 Rockwell C, it is durable in most environments. It is commonly used to make roofing screws and siding screws and self tapping (or self drilling) screws, because it is a harder material than the metal being fastened in these types of applications.

Wednesday, May 13, 2015

What Do the Numbers Mean?

Stainless steel fasteners are defined by the grade of the material. Now what exactly does this mean? See the list below for information on common grades of stainless steel fasteners including material and common applications. 



  • Type 304: 17%-19% Chrome, 8%-12% Nickel, .08% Maximum Carbon. This is a superior grade of 18-8 stainless steel and is used for Machine Screws, Cap Screws, Sheet Metal Screws, Hex Cap Screws and all cold headed or hot forged fasteners. It is an equivalent to 18-8 Stainless Steel.

  • Type 305: 17%-19% Chrome, 8%-10% Nickel, .12% Maximum Carbon. This grade has been developed specifically to improve the cold heading qualities of 18-8. This grade does not work hardened products are actually made from this grade even though they are referred to as being made from type 304 Corrosion resistance and physical qualities are equal to Type 304.

  • Type 316: 16%-18% Chrome, 10%-14% Nickel, .08% Maximum Carbon, 2.00% Maximum Molybdenum. This grade is greater corrosion resistance when used with certain acids as compared to general range of 18-8 stainless steel. 316 Stainless Steel is used in saltwater application such as boats and docks.

  • Type 18-8: 18% Chrome, 8% Nickel, .08% Maximum Carbon. Used in most fasteners and is the standard.It is an equivalent to 304 Stainless Steel.

  • Type 410: 11.5%-13.5% Chrome, .15% Maximum Carbon. This grade can be bright and hardened up to approximately 40 Rockwell C. This is used in roofing screws and finishing washers.

Tuesday, May 12, 2015

Galling

Stainless Steel Fasteners locking up? It’s not the quality of the parts but the common problem of using stainless steel fasteners. 

The beneficial nature of using stainless steel is that it is corrosion resistant. This property is due to the fact that stainless steel, among other alloys, generate a protective oxide surface film. Though this may be beneficial, it can sometimes lead to problems with installation.

Thread Galling occurs during fastener tightening and installation. When pressure builds between the contacting surfaces of the male and female threads, the protective oxides or coatings begin to shear, causing high points, or imperfections in the raw material of the two pieces to become locked together. The increase in friction causes the two parts to seize or “lock-up”. In serious cases, this difficultly understood problem is even referred to as “cold welding”, which illustrates the severity of the issue. Often, galling can cause damage to the thread of the fastener, but it can still be removed. In severe cases, the two materials completely weld together preventing loosening of the parts, and adding the difficult step of a forced removal and new parts to the process. The frustrating aspect of this is that both the nut and bolt can clear inspection individually, but fail to function effectively as a mechanical unit. 

Though this problem may be frustrating, it is avoidable. The main issue to address is to decrease the friction between the adjoining parts. This can be done in several ways including a slower installation process (RPMs). The idea behind this method is to reduce the friction (and thus heat), between the parts preventing the “welding” process. Our recommended method, due to its ease of implementation, is lubrication. Common methods include specially designed lubricants and waxes, however due to its safety and ease of availability, we recommend dipping the bolt in Maalox. 

Yes, that’s right, Maalox.  

Though this product may be designed to relieve upset stomachs, this liquid antacid has excellent lubricating qualities when it comes to installing fasteners, as well as qualities which help to protect the surface film of the fastener. As an added bonus, it is a product designed for human consumption, meaning that it is completely safe to use on food service and processing equipment, where stainless steel has become the standard. 

Other precautionary measures include using coarse threaded fasteners, using different grades of stainless steel for adjoining parts (take the corrosion resistance differences into consideration), and understanding the proper use of lock nuts. Because they are designed to add resistance to the existing threads of the bolt, it is best practice to make sure that a minimal amount of threads extend beyond the nut.

Reducing friction is the preemptive strike against this problem. That is why we recommend lubrication, and Maalox specifically, due to many of its properties beneficial to both sore stomachs and stainless steel. Galling can be a frustrating problem, but it can be prevented.