In mold making or mold casting, materials are meticulously chosen based on their specific service conditions. These materials can be broadly categorized into cold work mold materials, hot work mold materials, plastic mold materials, and other specialized mold materials. Each of these primary categories is further divided into several subcategories. This ensures that every unique requirement is met with precision and efficiency.
Cold Work Mold Steel Materials
Cold work mold materials are widely used in the industry due to their extensive application range and broad usage spectrum. The primary performance requirements for these materials include strength, hardness, toughness, and wear resistance. Over recent years, the use of carbon tool steel has decreased. Instead, high-alloy steel molds have become more dominant in terms of proportion.
| Type of Steel | Example Grades |
| Carbon Tool Steel | T7, T8, T10 |
| Oil Quenching Cold Work Mold Steel | 9Mn2V, CrWMn, 9CrWMn, 9SiCr, Cr2 |
| Air Quenching Cold Work Mold Steel | Cr5Mo1V, Cr6WV, 8Cr2MnWMoVS, Cr4W2MoV |
| High Carbon High Chromium Cold Work Mold Steel | Cr12MoV, Cr12, Cr12Mo1V1 |
| Matrix Steel and Low Carbon High-Speed Steel | 6W6Mo5Cr4V, 6Cr4W3Mo2VNb, 7W7Cr4MoV |
| Hard Alloy | YG6, YG8N, YG8C, YG11C, YG15, YG25 |
| Steel-Bonded Hard Alloy | GT35, TLMW50 |
Characteristics and Applications
Cold work mold steels primarily consist of high-carbon alloy steels. They all belong to the heat treatment strengthened type of steel, with a usage hardness exceeding 58HRC.
The low-alloy cold work mold steel, such as 9CrWMn, is typically used for simple molds in small batch production. It’s also used for prototype molds that endure minimal impact. On the other hand, the Cr12 type high carbon alloy steel is a universal material for most molds. This kind of steel boasts high strength and wear resistance but has lower toughness. For situations where the mold requires higher comprehensive mechanical performance, W6Mo5Cr4V2 high-speed steel is a common choice. It is known for its high quenching permeability.
Hot Work Mold Steel Material
Hot work mold steels operate under more intricate conditions compared to their cold work counterparts. This complexity primarily stems from factors like elevated temperatures and diverse cooling conditions. These conditions can include the presence or absence of cooling and the specific cooling method used. As a result, there are a few hot work mold materials that are widely used. However, the overall range of materials is not as extensive as the range for cold work mold materials.
Material Selection and Mechanical Properties
When selecting materials for hot work molds, it’s essential to strike a balance between thermal strength (heat wear resistance) and crack resistance. Given that the objects being processed are hot metals, they inherently possess lower strength. As a result, the yield strength requirements for hot work mold materials are not very high. However, the impact processing methods used during manufacturing require these materials to be tough. This need is further emphasized by the inevitable rapid heating and cooling they undergo.
| Type of Steel | Example Grades |
| Medium Carbon Tempered Steel | 45, 40Cr, 42CrMo, 40CrNiMo |
| Low Alloy Tempered Mold Steel | 5CrMnMo, 5CrNiMo |
| Medium Chromium Hot Work Mold Steel | H10, H11, H12, H13, H14, H19 |
| High Chromium Hot Work Mold Steel | H23, H25 |
| Tungsten Series Hot Work Mold Steel | H21, H22, H26 |
Plastic Mold Steel Materials
Plastic mold steels cater to a unique set of challenges. Given the diverse working conditions, manufacturing methods, precision levels, and durability requirements associated with plastic molds, the range of materials suitable for their construction is vast. Various high-quality steels find their application in this domain, leading to a wide-ranging series of plastic mold materials.
Factors Influencing Material Selection
Several factors influence the selection of mold materials for plastics. The object being processed, the manufacturing method, the required precision, and the durability demand all play a role. This has led to the development of a broad spectrum of steel compositions, each tailored to meet specific requirements.
| Type of Steel | Example Grades |
| Carbon Steel | 45, 50, 55, T8, T10 |
| Carburizing Type Plastic Mold Steel | 20Cr, 20CrMnTi, 20Cr2Ni4, 12Cr2Ni4 |
| Pre-Hardened Plastic Mold Steel | 3Cr2Mo, 3Cr2NiMnMo, 5CrMnMo, 8Cr2MnWMoVS, 5CrNiMnMoSCa |
| Corrosion-Resistant Plastic Mold Steel | 25CrNi3MoAl, 06Ni6CrMoVTiAl, 18Ni |
| Overall Hardening Type Plastic Mold Steel | CrWMn, 9CrWMn, 9Mn2V, Cr12MoV, Cr12Mo1V1, 4Cr5MnSiV1 |
Exploring Other Mold Materials
Beyond the primary categories of mold materials, there are several other materials that cater to specific needs and applications. These range from cast mold steels to non-ferrous alloy mold materials, glass mold materials, and even specialized new mold materials.
Cast Mold Steels
Precision casting techniques allow for the creation of complex mold castings. Compared to traditional mold production processes, this method can save processing time, reduce metal consumption, shorten the mold manufacturing cycle, and cut down on manufacturing costs. For instance, the ASTM-A597 standard in the U.S. includes seven grades of cast tool steels. Four are for cold work molds, two for hot work molds, and one for impact-resistant tools. In China, precision casting techniques have been adopted by several sectors, with notable applications in the automotive industry.
| Type | Examples |
| Cold Work Mold Steels | ZG7CrSiMnMoV |
| Hot Forging Mold Steels | JCD, 5CrMnMo |
| Cast Forging Mold Steels | ZDM-2 (3Cr3MoWVSi) |
Non-Ferrous Alloy Mold Materials
With the diversification of industrial products and the rise in small to medium-batch production, there’s an increasing demand for non-ferrous metal mold materials. These materials are low-cost, easy to process, have shorter manufacturing cycles, and possess unique properties. Commonly used non-ferrous materials include copper alloys, aluminum alloys, and zinc alloys.
| Material | Characteristics | Applications |
| Copper Alloys | Good anti-adhesion and thermal conductivity | Deep drawing and bending molds for stainless steel, injection molds |
| Aluminum Alloys | Used for mold guide plates, guide columns | Prototype molds for thin plate drawing, plastic molding, foam plastics |
| Zinc Alloys | Low melting point, good machinability, recyclable | Prototype molds for thin plate drawing, bending molds, aluminum extrusion molds |
Glass Mold Materials
Glass molds are essential for the production of glass products. These molds frequently come into contact with molten glass at temperatures exceeding 1100°C, undergoing oxidation, growth, and thermal fatigue. The primary requirement for these mold materials is oxidation resistance, with common choices being heat-resistant alloy steels and alloy cast irons.
Specialized New Mold Materials
In addition to the mold, as mentioned earlier materials, there’s ongoing research and development into specialized mold materials. Examples include non-magnetic CrMnN mold steels used for electronic products and high-temperature glass mold steels. The latter is used for high-temperature tableware and automotive lights, as well as ceramic molds and composite material molds.
Concluding Thoughts on Mold Materials
At Prototool, we pride ourselves on our deep knowledge and expertise in the realm of mold materials. Our commitment to excellence ensures that we stay at the forefront of industry innovations, always ready to provide our clients with the best solutions tailored to their needs. Whether you’re looking for cold work mold materials or hot work mold steels, Prototool is a trusted name in the industry. They also offer other specialized mold materials, ensuring quality and reliability. As we journey forward, we are committed to pushing the boundaries in mold making (Check our mold milling process.). This ensures that our clients always experience the highest level of craftsmanship and performance.
