When using cold heading, material selection for a cold-formed part is very important. High quality material is purchased per cold heading raw material specifications with strict requirements placed on vendors for material chemistry and surface defects. Initial cost for raw material may be greater, but the added expense up front is worth eliminating quality problems later on.
Failure to use high quality wire results in any of the following conditions:
• Head cracking
• Seams
• Problems rolling threads
• Inability to form certain shapes
Cold heading material is specially processed (annealed) to withstand the heavy upset and extrusion that takes place during the cold heading process. All wire is annealed to specific properties to make this easier.
Bar stock is used for screw machining, which is distinctively processed for its good machining characteristics. It has additives such as lead and sulfur to make it easier to machine, but these elements are detrimental to cold forming. A material change is necessary to convert a screw machine part to a cold-headed part. If bar stock is used, cracking will occur.
At Bossard, an Applications Specialist works with the customer’s engineering department to select an acceptable replacement material for cold heading.
Popular materials used for cold heading:
• Low carbon steel (1010 – 1022)
• Medium carbon steel (1030 – 1045)
• Alloys (i.e. 4037, 4140, 8620)
• Copper, brass, bronze
• Aluminum (2024, 6061)
• Stainless steel (302, 410, 430, 316L, 17-4)
• High tech alloys (A286, Inconel)
• Tool Steels (52100, M2)
The level of difficulty in forming parts increases from the top of the list to the bottom. Most cold heading companies have skilled tool designers and have developed unique capabilities to successfully cold form these materials.
The cost of the raw material increases as well, but from bottom to top. Since cold heading moves metal by extrusion and/or upset, Bossard can greatly reduce the raw material content and cost, especially when compared to screw machining.
Typically, the greatest savings are seen in working with more expensive materials, but savings can still be seen in the cheaper grades. Remember, in addition to raw material savings, cold heading still provides all the advantages and benefits previously discussed.
Significant cost savings can be realized by heading parts to net or near net shape. Even if secondary machining is required, the material cost saved by cold heading can sometimes be substantial.
Selection of cold heading materials is vital to cost savings and a quality end product.
To learn more about Cold Heading Materials, contact us at ProvenProductivity@bossard.com.
Cold Heading Materials by Bossard
