The industries that use 39CrMoV13 9 steel grade include automotive, aerospace, oil and gas, construction, power generation, and heavy machinery. This steel grade is known for its high strength, excellent toughness, and good wear resistance, making it suitable for applications that require high load-bearing capacity, impact resistance, and durability. It is commonly used in components such as gears, shafts, turbine blades, cutting tools, and structural parts in these industries.