W2 Material Selection for Toolings

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Production Tool Design: Material Selection for Toolings

TAUFIKFaculty of Manufacturing Engineering

UTeMWeek 2

04/09/23 BMFR3143 Production Tool Design

Learning Objectives

The objectives of this chapter are to : Understand the behavior of metals in

terms of their mechanical properties. Describe the properties and

applications of carbon steels, alloy steels and tool steels.

Describe the properties and uses of nonmetallic tool materials.

04/09/23BMFR3143 Production Tool

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Properties of Tool Materials

Hardness Toughness Wear Resistance Machinability Brittleness Tensile Strength Shear Strength


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Tensile & Shear Strength


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Ferrous Tool Materials Carbon Steels

Carbon steel is the primary material of jig and fixture tooling.

Alloy Steels Used for tool construction of their added cost.

Tools Steels Are steels that are mad to exact standards

for specific types of services


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Alloy Steels Carbon : main hardening element Sulfur : easier machining Phosphorus : easier machining Manganese : controls sulfur effects; increases

hardness Nickel : toughness Chromium : corrosion resistance (over 15%

chromium); depth hardness (less than 15% chromium)


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Numbering System is a four-digit code that indicates

specific information about the metal. The first digit indicates the type of metal. For example, 1 indicates carbon steel; 2, nickel steel; 3, nickel-chromium steel; and so forth,


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The second digit indicates either the percentage of major alloy in the metal or a code to denote a specific alloy. The last two digits when read together express the carbon content in hundredths of a percent.


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Example of Numbering System


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Tools Steels Tool steel is specified for numerous die

components and it may be well to discuss briefly the most commonly used types. They are: Water-hardening tool steel Oil-hardening tool steel Air-hardening tool steel High carbon, high chromium tool steel High speed steel Shock-resisting tool steel Hot work die steel


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Classes of Standard Tool Steels


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Tool Steels Classifications


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Exercise 1: List and briefly explain the tool steels

characteristics with an excellent wear resistance.

Solution Type M, classification as high-speed with

Molybdenum base. Type D, classification as cold work with high carbon

and high chromium. Type F, classification as special purpose with

carbon-tungsten base


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Exercise 2: List and briefly explain the tool steels

classification with a good to excellent machinability.

Solution: Type O, classification as shock resisting with

oil hardening. Type P, classification as mold work.


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Cast Iron and Invar Cast iron is used for tool bodies and some

commercial jig and fixture components. The term cast irons refer to a family of ferrous

alloys composed of iron, carbon (ranging from 2.11% to about 4.5%), and silicon (up to about 3.5%). Cast irons are also classified by their structure: ferrite, quenched and tempered.

Invar comprises iron (64%), nickel (35%) and carbon + manganese (1%) and has a very low expansively when heated.


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Nonferrous Tools Material Aluminum Magnesium Bismuth Alloys Carbides Cermets


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Numbering System for aluminum


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Four Digit Code Aluminum


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Tool Material Comparison


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Magnesium Identification System


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Plastic Mould & Stamping Die Materials

Steel AISI Application

P20Suitable for all types and sizes of machine-cut moulds. Usually used in the prehardened condition Rockwell "C" 32 to 35.

H13Used for large and small moulds when toughness and strength is required. Good dimensional stability during hardening. Hardens up to Rockwell “C” 52 but is tougher at "C" 48.

A2For small and medium size moulds when higher hardness is required as for moulding abrasive materials.

D2For small moulds when abrasion becomes a problem. Also for moulds operating at temperatures up to 750°F.

Type 420 StainlessFor small and large moulds for moulding corrosive resins, such as PVC and Delrin. Also used when routing is problem because of "sweating" of mould surface.

SAE 4140Usually used for holders and shoes. Can be used for moulds where a high finish is not necessary. Usually used in the prehardened condition Rockwell "C" 28 to 32.

M2 High Speed SteelUse if operating temperatures are above l000°F, but not higher than 1I50°F, and the mould hardness must be higher than 60 Rc

Precipitation hardening and

maraging steels

For large moulds or moulds containing deep cuts and heavy sections; to avoid stresses and brittleness associated with quenching and tempering; also for mould components which require exceptional hardness and/or fracture toughness.


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Heat Treatment of Tools Tool designers normally do not concern

themselves with the actual mechanics of heat treating. However, a general understanding of how this process affects design is important. Occasionally failures that seem to be due to improper heat treatment are in fact caused by poor design.


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Treatment for Ferrous Materials

Normalizing To refine grain structure after forging to improve machinabilty Heat up to 100o to 200 o

F above critical range.

Spheroidizing Heating and cooling steel to make rounded or globular carbides increases toughness

and machinabilty, heat hold for one to four hours and cool in furnace Heating up to 1380 – 1400 F holding for one to four hours and cooling slowly.

Stress Relieving Relieve stress – heating up to 1200 o to 1350 o F air-cooling.

Annealing Slow heating – holding for 4 to 5 hours and cooling it in furnace – refines grain

structure.

Hardening Hardening is a rapid cooling process after heating in order to increase hardness.

Tempering Heating below critical temperature to relieve stresses. (550 – 600 o F)


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Treatment for nonFerrous Materials

Treatment for nonferrous material approximates that of steel but the temperature ranges are lower.


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Documents

W2 Material Selection for Toolings