Advances in Springmaking Materials — Part 3: Wire Drawing and Heat Treating
Technically Speaking
By C. Richard Gordon (Editor’s note: Rick Gordon’s article was developed as part of the overall theme of “Advances in Springmaking.” This is the third in the series of articles on advances in springmaking materials.)
dvances in the production of springmaking materials over A time have resulted in improvements in spring performance. Since the majority of springs are produced from carbon and
alloy steels, production methods of these materials will be described here. Production improvements have occurred in the areas of steelmaking, continuous casting, rod rolling, wire drawing and wire processing (heat treatment). Improvements in springmaking machine technology were discussed previously1. Improvements in the areas of steelmaking and continuous casting2 and rod rolling3 were also discussed previously. This article will focus on improvements in wire drawing and the patenting and oil tempering heat-treating processes. Materials Design Philosophy
In the Fall 2019 issue of Springs4, I discussed the engineering concept known as the materials design philosophy, which can be used as a tool to better understand composition-property relationships. Briefly, the materials design philosophy shows the relationship between the composition of the material and the final product properties (Figure 1). A material with a specific composition is processed in a given operation. The combination of the material and the processing results in a particular structure (metallurgical microstructure). The microstructure in turn results in the specific material properties. In reality, the process of design occurs from right to left. Engineers are interested in specific material properties, which in turn are dependent on the structure, which is a function of designed processing of a material with a specific composition. Material properties such as tensile strength and ductility are determined through mechanical testing, which have been discussed in past Springs articles5,6,7,8,9,10. Composition
Processing Wire Drawing Change Wire Size/Diameter &/or Shape D1
Composition
Processing
Structure
Properties
Figure 1. Materials Design Philosophy
For the purpose of this article, the following figures are expanded to include our current processes of interest: Figure 2 — wire drawing and Figure 3 — patenting and oil tempering heat treatments. From a materials perspective, a goal of any process improvement is to improve the uniformity of the product as well as enhance product properties. From an operations perspective, a goal is to improve productivity with the attendant reduction in cost. Thus, the challenge is to obtain both the materials goal and the productivity goal; how to achieve the balance is a subject beyond the scope of this article. For students who are interested in more detailed information on wire drawing and heat treating of wire in general, there are three excellent references: “Ferrous Wire Handbook11,” “Steel Wire Technology12” and “Wire Technology13” that I recommend for your bookshelf. C. Richard (Rick) Gordon is the technical director for SMI. He is available to help SMI members and non-members with metallurgical challenges such as fatigue life, corrosion, material and process-related problems He is also available to help manage and oversee processes related to failure analysis. This includes sourcing reputable testing labs throughout North America, forwarding member requests to the appropriate lab and reporting results and recommendations. He can be reached at c.richard.gordon@gmail.com or 574-514-9367.
Structure Cold drawn structure
Properties Change Wire Properties: Tensile Strength, Ductility, etc.
D2
D1 Figure 2. Materials Design Philosophy – Expanded for Wire Drawing
SPRINGS | Winter 2022 | 21
