tool steel(n = noun.substance) - alloy steel that is suitable for making tools; is hard and tough and can retain a cutting edge;
is a kind of alloy steel
has particulars: high-speed steel, hot-work steel

   Hard steel, usually crucible steel, capable of being tempered so as to be suitable for tools. [Webster 1913 Suppl.]

alloy steel, austenitic manganese steel, austenitic steel, basic steel, bessemer steel, bronze steel, carbon steel, case-hardened steel, cast steel, cement steel, chisel steel, chrome steel, chrome-nickel steel, chrome-tungsten steel, chromium steel, crucible steel, cutting tool, damascus steel, damask steel, drill steel, edge tool, entrenching tool, eutectoid steel, garden tool, graving tool, hand tool, hard steel, high steel, high-speed steel, hot-work steel, hyper-eutectoid steel, hypo-eutectoid steel, india steel, ingot steel, lawn tool, low steel, low-carbon steel, machine tool, manganese steel, medium steel, mild steel, molybdenum steel, native steel, natural steel, nickel steel, oil-hardened steel, open-hearth steel, phosphorus steel, power tool, quenched steel, shaping tool, shear steel, siemens-martin steel, soft steel, soft-cast steel, spring steel, stainless steel, steel, steel arch bridge, steel band, steel blue, steel company, steel drum, steel engraving, steel factory, steel gray, steel grey, steel guitar, steel industry, steel mill, steel oneself against, steel onself for, steel plant, steel plate, steel production, steel trap, steel wool, structural steel, tire tool, tool, tool around, tool bag, tool cabinet, tool case, tool chest, tool kit, tungsten steel, vanadium steel, weld steel, wolfram steel