Spring Material: Carbon Steel
Most Common Spring Material
Eighty percent of steel spring applications are carbon steel vs. approximately 20 percent for stainless steel. High-carbon (80 to 90 percent), high-drawn carbon steel is the most commonly used material for springs. It is the strongest of spring steels and it has an improved cost profile (as much as 50% less expensive) compared to stainless steel.
The carbon wire that MW Components purchases, generally has a phosphate coating to facilitate lubricity during coiling. After the wire is coiled or formed into a spring, it needs to be “stress relieved” by putting it through an oven which bakes the lubricant coating onto the spring. After the lubricant is burned off the spring, a decision needs to be made whether to post plate, oil, paint, etc. to reduce rust.
Grades / Attributes
There are many grades, with hard-drawn being the weakest, followed by music wire. Higher-strength grades of spring steel, include chrome silicone/high-tensile music wire. The correct choice has to do with the amount of stress the spring to which the spring will be subjected.
Carbon steel grades are used in a wide variety of applications including appliances, construction, industrial valves, medical, plastic injection molded parts, restraint systems and military/government. Examples of a low stress application are ball point pens and toilet roll holders. A high-stress application is performance suspension for race cars.
Strong, low maintenance. There are domestic mills that produce carbon steel, unlike stainless steel which is manufactured by offshore producers. Precoated or preplated carbon steel is more cost effective than stainless steel. Also, the right part geometry and proper packaging can reduce post-plating tangling and deformation.
Without a proper finish, carbon steel springs will rust. A secondary process—either plating, painting or an oil finish—is required to reduce corrosion probability.