Buy 4140 Alloy Round Online at Metals Depot - America's Small Quantity Store. Huge selection of steel round, stainless round, and aluminum round. Any Quantity, Any Size, Delivered Anywhere! 4140 Alloy Steel Round, is an cold drawn annealed steel of relatively high hardenability with its chromium content provides good hardness penetration, and the molybdenum imparts uniformity of hardness and