Meaning
Material evaluation determines the optimal alloy for a manufacturing application by balancing the requirements for hardness and toughness against the expected environmental conditions and production volume. This tool steel selection governs the durability of the mold or die and determines the total cost of ownership for the manufacturing equipment. It defines the criteria for choosing between different grades of steel based on their chemical composition and heat treatment response.
The process stops when the final material specification is locked into the design for the production run. Making the correct choice is necessary to prevent premature tool failure and maintain consistent part quality.
Alloy Tradeoff
Engineers must choose between materials that offer high wear resistance and those that provide the toughness needed to resist cracking under impact. While tool steel selection is underway, the team considers whether the tool will face abrasive wear from glass filled resins or thermal shock from molten metal. High alloy steels like h13 provide excellent hot hardness but are more expensive and harder to machine than simpler grades like p20.
If the steel is too hard, it may become brittle and fail catastrophically during the first few production cycles. Conversely, a steel that is too soft will deform or wear out quickly, leading to dimensional inaccuracies in the parts. Finding the right balance is a technical challenge that requires a deep understanding of both material science and the specific production process.
Fatigue Resistance
Cyclic loading and thermal changes create internal stresses that can eventually lead to the failure of the tool through cracking. When tool steel selection is performed for high volume projects, the focus shifts to the fatigue strength of the material and its ability to withstand millions of cycles. Steels with a very clean microstructure and fewer impurities are less likely to develop the small cracks that lead to major failures.
Some grades are specifically designed to resist the heat checking that occurs when the tool surface is repeatedly heated and cooled. Proper heat treatment is also required to maximize the fatigue resistance of the chosen steel. If the tool is expected to run for several years, the extra cost of a high performance alloy is often justified by the reduction in maintenance and repair costs.
Cost Lifecycle
Initial material prices are only a small part of the total expense involved in creating and maintaining a production tool. Because tool steel selection affects the speed of machining and the need for heat treatment, it has a direct impact on the lead time for the project. A cheaper steel that is difficult to machine may end up costing more in labor and tool wear than a more expensive but easily cut grade.
The cost of a production stoppage due to a tool failure is often much higher than the price of the steel itself. By choosing a grade that is easier to repair through welding, manufacturers can extend the life of the tool and avoid the cost of building a replacement. A complete analysis looks at the initial cost, the machining time, the expected maintenance and the total number of parts the tool will produce.
