Tungsten steel, commonly known as cemented carbide or hard metal, refers to a class of sintered composite materials comprising at least one metallic carbide. This family of materials is renowned for its exceptional hardness, wear resistance, and strength, even under high-temperature conditions. The most prevalent carbides used in its composition include tungsten carbide (WC), cobalt carbide (Co3C), niobium carbide (NbC), titanium carbide (TiC), and tantalum carbide (TaC). These carbide components, or phases, form the hard, refractory grains of the material, with their particle sizes typically ranging from a fine 0.2 micrometers to 10 micrometers. It is this fine, hard crystalline structure that provides the foundational hardness and abrasion resistance.

However, these extremely hard carbide grains are inherently brittle and cannot function effectively as a monolithic material on their own. To coalesce these grains into a usable solid mass, a metallic binder phase is employed. This binder acts as a cementing matrix, holding the hard carbide particles together and imparting crucial toughness and shock resistance to the composite. While cobalt (Co) is the most widely used and effective binder due to its excellent wetting properties and good balance of strength and toughness, other metals such as nickel (Ni), iron (Fe), or their alloys are utilized for specific applications, particularly where enhanced corrosion resistance or specific magnetic properties are required. The specific combination of carbide types, their grain sizes, and the nature and proportion of the binder metal is meticulously engineered and defined as a "grade" for that particular tungsten steel formulation.

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The classification of tungsten steel is systematically governed by international standards, most notably the ISO standard. This system categorizes grades based on their intended application and the material they are designed to machine. For instance, the "P" grades are primarily for machining steel, "M" grades for stainless steel, "K" grades for cast iron and non-ferrous materials, and "S, H" grades are dedicated to superalloys and hardened steels, respectively. The selection of the binder phase is a critical aspect of this grading, as it directly influences the overall strength, fracture toughness, and corrosion resistance of the final product.

Fundamentally, the microstructure of tungsten steel is a classic composite, consisting of two distinct parts. The first is the hard, wear-resistant phase—the carbide grains themselves. The second is the ductile binder metal, which is almost exclusively from the iron family, with cobalt and nickel being the prime choices. This combination gives rise to common alloy classifications such as tungsten-cobalt alloys (YG series), tungsten-nickel alloys, and more complex systems like tungsten-titanium-cobalt alloys (YT series), where titanium carbide adds enhanced red-hardness and crater resistance for steel machining.

It is important to distinguish cemented carbide from tungsten-bearing steels, such as high-speed steel (HSS) and certain hot-work tool steels. In these steels, tungsten is dissolved in the steel matrix as an alloying element, primarily to form secondary carbides that significantly improve the material's hot hardness (the ability to retain hardness at elevated temperatures) and tempering resistance. While this greatly enhances cutting efficiency and durability compared to ordinary tool steels, it comes at the cost of a noticeable decrease in toughness. In contrast, the structure of tungsten steel is a physical composite of hard carbides in a metal binder, resulting in vastly superior hardness and wear resistance than any steel, though often with lower overall impact toughness.

The primary application of global tungsten resources is, in fact, the production of cemented carbide. So critical is this material to modern manufacturing and engineering that it has earned the moniker "the teeth of modern industry." The utilization of tungsten steel products is extraordinarily widespread. Its applications span from metal cutting tools (inserts, drills, end mills) and mining tools (drill bits, road header picks) to wear parts (nozzles, seals, guides) and even high-precision dies for wire drawing and stamping. In essence, wherever extreme hardness, wear resistance, and dimensional stability are required under demanding conditions, tungsten steel is often the material of choice, forming the backbone of countless industrial processes and technological advancements. Its development represents a pivotal achievement in materials science, enabling the machining, shaping, and extraction of other hard materials with unprecedented efficiency.