A stainless steel tool chuck was cracking during product assembly, affecting about 30% of all chuck. A failure analysis of the cracked chucks and analysis of the chuck design and manufacturing process was performed to determine the root cause of the cracking. This article discusses the findings and how the problem could have been prevented.
Product design and manufacturing often involves trade-offs to optimize product performance, reliability, and cost. One aspect of cost includes the time and effort required to perform the manufacturing steps. In the case of fabricating carbon steel components, free-machining steels are often used to improve ease of machining. However, if components made of free-machining steel must be welded together, then issues arise, and costs rise, because of the poor weldability of these steels.
The strength of metals is improved by impeding the motion of dislocations through the metals. One approach to achieving this improvement is to form a uniform distribution of closely spaced sub-micron sized particles throughout an alloy. The particles, called precipitates, impede dislocation motion through the alloy. Not every alloy can be precipitation strengthened. Alloys that can be precipitation strengthened include Al-Cu, Al-Mg-Si, Cu-Be, and 17-8 PH steel.
The metallurgical phases present in an alloy have a huge impact on the properties of a metal component. Phases are distinct materials that are comprised of the elements in the alloy. These distinct materials have distinct properties that have an impact on the overall properties of the entire alloy. Additionally, the size, shape, and location of the phases within the alloy also effect on the overall properties of an alloy. Within many common alloys it is possible to alter the phases present with heat treatment.
In metallurgy, the term phase is used to refer to a physically homogeneous state of matter, where the phase has a certain chemical composition, and a distinct type of atomic bonding and arrangement of elements. Within an alloy, two or more different phases can be present at the same time. Phase diagrams are useful to metallurgists for selection of alloys with a specific composition and design and control of heat treatment procedures that will produce specific properties.