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Characterized by their durability, hardness, price, and ability to withstand shock without deforming, tool steels are used to cut, press, extrude, or stamp other metals. After being worked, they may be hardened to increase wear resistance and strength. Grades are specified by the American Iron and Steel Institute (AISI), the Society of Automotive Engineers (SAE), or the American Society for Testing and Materials (ASTM). For more information, see Tool Steel Comparison on page 105.

Design Considerations

HEAT TREATING DURABILITY COMPARATIVE COST

W1 O1 A2

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After machining, steel is heat resistance to deformation at low cost Water-hardening tool treated and quenched, depending elevated temperatures steel is used more often than oil- on the type of steel used, to (also known as red-hardness) or air-hardening tool steels increase toughness and strength

Tool Steel Grades

Tool steels are defined by their dimensional stability, wear resistance, toughness, hot hardness, and machinability. Severe conditions – high temperatures, heavy loads, or corrosive environments – require higher alloy and carbon contents.

Cold Work Steels Hot Work Steels than other steels. Best suited for small parts Frequently used for making cold working Feature high hot yield strength, toughness, and working conditions up to 150ºC (302ºF). tools for applications under 200ºC (392ºF). high red-hardness, wear resistance, erosion Higher amounts of chromium reduce resistance, and resistance to softening in High-Speed Steels (HSS) distortion during heat treatment. Feature temperatures up to 675°C (1,247ºF). Designed for high speed metal cutting high hardenability, high toughness, and and machining operations. Features H1-H19 high abrasion, impact, and wear resistances. hardenability to HRC 60-70, high heat Medium carbon content with 5% chromium. resistance for red-hardness up to 500ºC A2-A10, Air-Hardening Can be through hardened to HRC 40-55 (932ºF) enables sharpening without Medium alloy composition with 1% – 6% with little distortion. Requires oil quenching. damaging material, and reasonable carbon and up to 5% chromium. Has the toughness. H20-H26 least tendency to crack during hardening. M1-M47 Considered a mid-range grade between oil- Low carbon content with 9% – 18% hardening and shock resistant grades. Do tungsten and 3% – 4% chromium. Extra Contain molybdenum as a primary alloying not quench in oil or water. resistant to softening, more prone to element that increases resistance to brittleness, working hardness to HRC 45-55. softening at elevated temperatures. O1-O7, Oil-Hardening To minimize scaling, quench in oil or salt. A low alloy/high carbon (0.85% – 1.55%) Shock-Resistant Steels H41-H43 steel with manganese, chromium, and S1-S7 Low carbon content with 8% molybdenum molybdenum. Quenched in oil to produce Contain medium carbon content from along with chromium, tungsten, and high wear resistance and hardness between 0.40 – 0.55%, 1% – 2% silicon, or up to vanadium. HRC 56-62. 3% nickel. As their name suggests, they have good wear/abrasion resistance and D2-D7, High Carbon, High Chromium Water-Hardening Steels resist shock at low to medium temperatures, Contain 1.4% – 2.3% carbon and 12% – W1-W3 with high strength and toughness. Can 14% chromium along with molybdenum, Most common. These general purpose, low- achieve HRC 58-60. cobalt, and vanadium. Often thought of cost, medium to high carbon (0.60% – 1.3%) as stainless or semi-stainless, but corrosion steels are easily machined, or formed. They resistance is limited due to high chromium can be case hardened by heat treating up to and carbon. Wear resistant, but not as HRC 68. Overall, they are more brittle and tough as low alloy steels. more susceptible to cracking or warping

Prices, materials, dimensions, tolerances, designs, and grades subject to change without notice. © 2016 G.L. Huyett 98 *Limited warranty for surface finish: 30 days from date of shipment. See page 12 for details. HUYETT.COM • 785-392-3017

TOOL STEEL TYPES

Ground Stock Drill Rod Definitions

Ground stock is rectangular or square steel Drill rod is round unhardened tool Hardness that has been ground to close tolerances steel which is precision ground to tight The measure of how resistant for use in a wide range of industries. Once tolerances. After machining, it may be steel is to various kinds of shaped, ground stock may be heat treated hardened by heat treating, then drawn permanent deformation when a to harden. back to the desired hardness. force is applied. strength A measure of steel's elastic range, where it will return to its original shape when gradual force is removed. Toughness The maximum amount of energy or impact force that can be absorbed before fracturing.

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QUICK REFERENCE GUIDE

Common Applicable Fabrication How to Common Comments Names Standards Identify Uses

Tool Steel; AISI/SAE A2; Cold drawn, Tight tolerances Depending Ground stock Ground Flat AISI/SAE D2; annealed bar stock and ground surface on grade, is free from Stock; Flat Bar AISI/SAE O2; that is subsequently finish. Durable ground stock decarburization. Stock; Flat AISI/SAE W2 ground to remove and resistant to can be used as Stock; Gauge all traces of abrasion. dies, punches,

Stock Plate decarburization and templates, and

Ground Ground achieve precision stripper plates. height and width.

Drill Rod AISI/SAE A2; Cold drawn, Tight tolerances Drill rod, Drill rod is AISI/SAE D2; annealed round stock and ground surface depending on free from AISI/SAE O2; that is ground and finish. Durable grade, is used to decarburization. AISI/SAE H13; polished to achieve and resistant to make tools like AISI/SAE W2 exacting size with no abrasion. drill bits, taps, Rod Drill decarburization left dowel pins, and on the bars. hammers.

mild steel vs. hardened steel

Hardened steel is much more difficult to work or machine. Mild steel can generally be machined using high-speed steel (HSS) or cobalt tools. Both mild steel and hardened steel can be called “ground” as this refers to a method used to shape steel, not the material or the tempering process.

Have a piece of steel and are unsure if it has been Mild steel can be filed A file will tend to skid hardened or not? Here's an easy way to find out: fairly easily and leaves along the surface of a visible relief hardened steel

Prices, materials, dimensions, tolerances, designs, and grades subject to change without notice. © 2016 G.L. Huyett *Limited warranty for surface finish: 30 days from date of shipment. See page 12 for details. 99