WNr 1.7147 Alloy Steel Bar 1.7147 Round Bars 1.7147 Rods

Product Description

An Alloy Steel Bar is a solid cylindrical, square, or rectangular length of steel that has been alloyed with elements like chromium, manganese, nickel, molybdenum, or boron. Unlike standard carbon steel, these deliberate additions alter the chemical structure to provide enhanced hardenability, toughness, wear resistance, and fatigue strength.

Because "alloy steel bar" is a massive category, bars are generally classified by how they are heat-treated and their primary industrial function.

📋 The Main Classes of Alloy Steel Bars

Alloy steel round bars, rods, and flats are broadly split into three metallurgical categories based on their carbon content and intended application:

1. Through-Hardening Steels (Medium Carbon)

These steels feature a medium carbon content (typically $0.35\% - 0.50\%$) along with chromium, molybdenum, and nickel. They are designed to be hardened uniformly from the outer surface all the way through to the center core.

• Key Grades: AISI 4140 (42CrMo4), AISI 4340 (34CrNiMo6), AISI 1045, AISI 5140.

• Properties: High tensile strength, exceptional fatigue resistance, and uniform core toughness.

• Best Used For: High-torque drive shafts, crankshafts, structural aerospace brackets, and heavy-duty structural fasteners.

2. Case-Hardening / Carburizing Steels (Low Carbon)

These steels have a low carbon base (typically $0.12\% - 0.22\%$). Components are machined in a soft state and then placed in a carbon-rich furnace (carburized). This creates a glass-hard, wear-resistant outer "case" while preserving a highly ductile, shock-absorbing core.

• Key Grades: 20MnCr5 (1.7147), 16MnCr5 (1.7131), AISI 8620, AISI 5120, GOST 15KH.

• Properties: Extreme surface wear resistance, high resistance to scuffing, and exceptional impact-shock absorption.

• Best Used For: Transmission gears, steering worms, piston pins, universal joint spiders, and splined shafts.

3. Boron-Alloyed Steels (Low-to-Medium Carbon)

By adding microscopic amounts of Boron ($0.0008\% - 0.0050\%$), mills can drastically increase the hardenability of carbon-manganese steel without adding expensive quantities of nickel or molybdenum.

• Key Grades: 27MnCrB5-2 (1.7182), 30MnB5, 51B30.

• Properties: Cost-effective, highly responsive to quenching, excellent wear-resistance.

• Best Used For: Agricultural wear plates, plowshares, rotary tiller blades, and high-strength fasteners (Grade 10.9/12.9).

📐 Delivery Conditions & Surface Finishes

When procuring alloy steel bars, the manufacturing method and finish dictate how easily the material can be machined:

⚙️ Key Thermal Suffixes to Watch For

When reviewing a material certificate or buying bill for an alloy bar, look closely at the thermal treatment suffix:

• +AR (As Rolled): The bar is unheated after forming. Hardness can be inconsistent.

• +A (Soft Annealed): Microstructure is optimized for lowest possible hardness. Pick this if you have a lot of deep drilling or complex milling to do before your final heat treat.

• +FP (Ferrite-Pearlite Treatment): Specifically treated to a consistent hardness band designed to prevent tool "gumminess" and ensure perfect chip breaking during gear hobbing or high-speed turning.

• +QT (Quenched & Tempered): Fully pre-hardened at the mill to its final working strength. It is tougher to machine, but eliminates the risk of part distortion or cracking during post-machining heat treatment.