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Materials, including metals, alloys, plastics, and other composite compounds, are of prime importance to the mechanical designer, tool designer, machinist, and metalworker. The most important characteristics of materials to those who design and manufacture parts are the physical and chemical properties and the various uses to which the materials may be applied. This chapter discusses a great number of metals, alloys, plastics, and compounds, including elastomers. Included are composition, physical properties, hardness, heat-treatment temperatures, and other characteristics useful for design and metalworking practices.
In design and metalworking practices, sometimes a material defect or failure occurs for unknown reasons. With the information provided in this chapter and in other appropriate American Society for Testing and Materials (ASTM), Society of Automotive Engineers (SAE), American Iron and Steel Institute (AISI), and American Gear Manufacturers Association (AGMA) standards, you may decide to have the material analyzed at a metallurgical and chemical laboratory to check the properties and compositions, or you may have the material checked mechanically at your company to determine if it meets the requirements of the material standards listed herein.
When producing the engineering drawings or specifications for a particular part, the appropriate American standard material designation or military/federal specification always must be indicated on the drawings or specifications. For example, if you are preparing a drawing for a mechanical spring, and you wish to use music wire in its construction, you must indicate on the drawing that the material is to meet ASTM A-228 or appropriate SAE specifications. You also may request a certified material analysis data sheet from the supplier of the material, whether it comes from a mill, a foundry, a forge, or a materials processing plant. It is the responsibility of material suppliers to provide design engineers and purchasing departments with these analysis sheets when so directed, which is the usual procedure.
Chapter 7 of this Handbook lists the machining characteristics and machine tool cutting and drilling speeds for many common and popular steels, alloys, other metals, plastics, and composites. In this chapter you also will find master cross-reference tables of all current hardness scales or systems such as Rockwell, Brinell, and Vickers. With these tables, you will be able to convert the hardness numbers for all the common and currently used hardness measurement systems relative to each other.
Materials specifications and characteristics or properties tables throughout this and other chapters of this Handbook are extracted from the latest standards of the ASTM, SAE, and AGMA.
There are a tremendous number of different engineering materials for which the ASTM and SAE have listings: metallic, plastic, and composite. Steels alone account for hundreds of different alloys for wrought products, castings, and forgings. Although these alloys are listed and have specifications for composition and physical properties, they may not be readily available, except as special order “mill run” quantities. A typical example would be austenitic stainless steel sheet in light gauges, cold-rolled to three-quarters hard, spring temper. This material is listed in the various 300 series stainless steels but may only be available from stock in 301 grade, three-quarters hard, spring temper. If you require 304 grade in your design application, it may be available only in mill-run quantities of a minimum of 500 to 2000 lb per single order.
As a general rule, during the early design stages of a particular part, alternate materials must be investigated. Owing to limited availability of your chosen material, you may be forced to use another material that is stocked by the material vendors. When your anticipated material quantities are large, you then will have control of the material type as well as its physical size and special characteristics, such as finish, temper, and gauge. For example, some of the larger companies that order hundreds of tons of hot-rolled sheet steel per year may specify to the mill that they want to run light on the minus side of a particular gauge. The tolerance on hot-rolled sheet steel is such that when it is run on the minus side of the gauge limits, many thousands of pounds of steel can be saved. The same is true for wrought-copper products such as bus bars and copper sheet, where the savings may be even more advantageous.
The list of steel alloys is so large that some authorities and regulating organizations have contemplated restricting the material standards to controlled listings, wherein redundant materials are eliminated. The large listings of alloys, plastics, and composites create a stocking problem for distributors of mill products, plastics, and composite materials.
For designers, machinists, tool makers, and metalworkers employed at small to medium-sized companies, a good approach to the aforementioned materials problems is to obtain the stock materials catalogs available from the large distributors and manufacturers such as Ryerson, Vincent, Atlantic, Alcoa, Reynolds, Bethlehem Steel, U.S. Steel, Anaconda, General Electric, DuPont, Monsanto, and others. The design and fabrication data for a great number of materials are listed in this and other chapters of this Handbook, together with typical uses and applications for these materials.
This section lists carbon and alloy steels, as well as the stainless steels, in their wrought form, that is to say, in the hot-rolled, cold rolled, or cold-drawn forms. The usual shapes are sheets, plates, bars or strips, rounds, hexagons, tube, pipe, and structural configurations (beams, angles, channels, tees, square and rectangular tubes, and zees).
When carbon is added to iron in small quantities, carbon steel is produced. Besides carbon, a number of metallic elements can be added to iron to give the characteristics inherent in the various types of steels. The usual alloying elements are:
- Aluminum, which controls grain size in the steel
- Boron, which improves hardenability
- Chromium, which increases response to heat treatment as well as toughness (Chromium is used in stainless steels alone or with nickel.)
- Columbium, which is used in 18-8 stainless steels and welding electrodes
- Copper, which controls atmospheric corrosion and increases yield strengths
- Lead, which greatly improves machinability
- Manganese, which imparts strength and response to heat treatment
- Molybdenum, which increases depth of hardness and toughness
- Nickel, which increases strength and toughness but is not effective in improving hardenability
- Phosphorus, which is present in all steels and increases yield strength
- Silicon, which improves tensile strength and can improve hardenability
- Sulfur, which improves machinability but is detrimental to hot-forming properties
- Tellurium, which improves machinability in leaded steels
- Titanium, which is added to 18-8 stainless steels to prevent carbide precipitation
- Tungsten, which is used in good tool steels, making a fine-grain structure when used in small amounts (When used in amounts from 17 to 20 percent, it produces a high-speed steel that retains hardness at high temperatures.)
- Vanadium, which is used to improve the shock strength of steels and retards grain growth even after hardening from high temperatures
Glossary of steel terms
Age hardening A process of aging that increases hardness and strength. Age hardening usually follows rapid cooling or cold working.
Annealing A process involving heat and cooling, usually applied to induce softening.
Austenite A term designating a metallurgical phase of steels, i.e., austenitic stainless steel.
Carburizing To introduce carbon while the steel is molten or while it is in the solid state by heating it in contact with carbonaceous material below its melting point.
Case hardening A process of hardening a ferrous alloy so that the case, or surface layer, is much harder than the interior of the part. The typical case-hardening processes are carburizing and quenching, cyaniding, carbonitriding, nitriding, induction hardening, and flame hardening. Cases of Rockwell C 55 to 60 are readily obtained in medium- to high-carbon steels.
Ductility The property of a material that allows it to be drawn out of shape before fracturing by stress.
Elastic limit The maximum stress a material is capable of sustaining without a permanent set or deformation.
Fatigue The tendency for a metal to break after repeated or cyclic loadings that are below the ultimate tensile strength. Also known as fatigue-endurance limit.
Flame hardening A process of hardening a ferrous alloy by heating it above the transformation range by means of a flame and then cooling as required.
Hardenability The property of a ferrous alloy that determines the depth and distribution of hardness induced by quenching.
Induction hardening A process of hardening a ferrous alloy by heating it above the transformation range by means of electrical induction and then cooling as required.
Killed steel Steel that is deoxidized with silicon or aluminum in order to reduce the oxygen content so that no reaction occurs between carbon and oxygen during solidification.
Martensite An unstable constituent in quenched steel formed without diffusion only during cooling below a certain temperature. Martensite is the hardest of the transformation products of austenite.
Nitriding A process of case hardening in which a ferrous alloy, usually of special composition, is heated in an atmosphere of ammonia or in direct contact with a nitrogenous material to produce surface hardening by absorbing nitrogen without quenching.
Normalizing Heating a steel part of heavy section to a temperature 100°F above the critical range and then cooling in still air.
Picketing Chemical or electrochemical removal of surface scale and oxides.
Quench hardening Heating a steel within or above the transformation range and cooling at a rate faster than the critical rate to increase the hardness substantially. Usually involves the formation of martensite.
Solution heat treatment A process in which an alloy is heated to a suitable temperature, held at this temperature long enough for certain constituents to enter into solid solution, and then cooled rapidly to hold the constituent in solution. The metal is left in a supersaturated state that is unstable and subsequently may exhibit age hardening.
Spheroidizing Any process of heating and cooling that produces a round or globular form of carbide in steels.
Strain hardening An increase in hardness and strength caused by plastic deformation at temperatures lower than the recrystallization range.
Stress relieving A process of reducing residual stresses in a metal part by heating the part to a suitable temperature and holding this temperature for a sufficient time. This process is applied to relieve stresses induced by casting, quenching, normalizing, machining, cold working (i.e., springs), or welding.
Temper A condition produced in a metal or alloy by mechanical or thermal treatment and having characteristic structure and mechanical properties. In addition to the annealed temper, conditions produced by thermal treatment are the solution heat-treated temper and the heat-treated and artificially aged temper.
Yield strength The stress at which a material exhibits a specified limited deviation from proportionality of stress to strain. In most steels, there is a proportionality between the amount of stress that produces a certain amount of strain. This phenomenon is known as Hooke’s law. When a material passes its yield point, a lesser amount of stress produces a greater amount of strain until the ultimate strength point is reached, where the material breaks.
Carbon, alloy, stainless steel, and tool and die steels: Physical properties, compositions, heat treatment, and uses
Tables 4.1 through 4.20 contain the numbering system for identification of the various types of steels given in the SAE and Unified Numbering System (UNS) designations. Figure 4.1 shows properties and heat treatments for carbon, alloy, and stainless steel. Table 4.21 is an approximate equivalent hardness number table for Brinell hardness numbers for steel, with cross-references to other hardness designation systems. Table 4.22 is an approximate equivalent hardness number table for Rockwell C hardness numbers for steel, with cross-references to other hardness designation systems.
Typical uses for the various steels.
Following is a listing of the popular 0 11 d readily available steels that are usually stocked by suppliers and which have vast applications in industry. Tables 4.1 through 4.20 show the physical properties and heat-treatment processes for a great number of American standard steels. The following list of applications will prove useful to many designers and mechanical engineers, as well as to machinists, tool engineers, tool and die makers, and other metalworkers throughout industry. The following list is not fill-inclusive but rather is indicative of the much-used and readily available types of carbon, alloy, and stainless steels.
Carbon and alloy steels: Uses by SAE/AISI number
SAE/AISI 1006 through 1015. Low-carbon, high-formability, weldable. Used for sheet metal, strip, wire, and rod. Excellent drawing qualities. Low-strength applications. Sheet metal structures, body and fender work, deep-drawing parts of sheet steel.
SAE/AISI 1016 through 1030. Increased strength over the low-carbon group. These are known as the case-hardening or carburizing grades. The higher-manganese grades machine well. The higher-carbon types are used for thicker sections where a stronger core is desired. Type 1018 is used for a great many applications, may be easily case-hardened, and is readily available. Grades 1020 and 1025 are used for low-strength bolts. All these steels are readily welded.
SAE/AISI 1030 through 1052. These are the medium-carbon types of steels used where higher strength than the lower-carbon grades is required. All these steels are used for forgings. Axles and shafts are made from the 1038 to 1045 group. Widely used for machined parts, both heat-treated and non-heat-treated. Welding is possible with precautions taken during the cooling process.
SAE/AISI 1055 through 1095. These are the high-carbon grades of carbon steel. Used for flat stampings, spring wire, cutting tools, flat springs, and many other high-strength applications. These steels are usually heat-treated for their particular application and provide excellent wear resistance. Not recommended for welding applications.
SAE / AISI 1018. Low-carbon, medium-manganese steel. Quality bar for carburized parts: gears, shafts, bolts, pins, etc.
SAE / AISI1035. Medium-carbon, special-quality steel used for bolts, nuts, shafts, pins, etc. Can be heat-treated.
SAE / AISI1045. Medium-carbon, special-quality steel used for shafts, axles, gears, splines, etc. Can be heat-treated.
SAE / AISI 12L14. Low-carbon, resulfurized, rephosphorized, and leaded steel used for screw-machine parts such as studs, nuts, and various fasteners. Can be case-hardened.
SAE / AISI 1215. Similar to 12L14 and low-carbon steel used for studs, nuts, and fasteners. Can be case-hardened.
SAE / AISI 12L15. Leaded version of 1215 used for screw-machine parts. Can be case-hardened.
SAE / AISI 1117. Low-carbon, resulfurized, free-cutting steel used lo• shafts, gears, pins, nuts, etc. Can be carburized.
SAE / AISI 11L17. Leaded version of 1117 used for screw-machine ports, gears, shafts, pins, etc. Can be carburized.
SAE / AISI 1141. Medium-carbon, resulfurized, free-cutting steel used for shafts, nuts, bolts, etc. Can be hardened by heat treatment.
SAE / AISI 4140. Medium-carbon chromium-molybdenum alloy tiled used for studs, nuts, bolts, gears, wrenches, shafts, etc. Can be heat-treated.
SAE / AISI 41L40. Leaded version of 4140, free-machining type. I be heat-treated.
SAE / AISI 4145. Medium-carbon chromium-molybdenum steel used for studs, nuts, shafts, wrenches, gears, bolts, etc. Can be heat-treated.
SAE / AISI 41L45. Leaded version of 4145, free-machining type. Can be heat-treated.
SAE / AISI 4620. Low-carbon nickel-molybdenum steel used for gears, cams, pinions, and shafts. Excellent carburizing grade.
SAE / AISI 46L20. Leaded version of 4620, free-machining type. Can be carburized.
SAE / AISI 8620. Low-carbon nickel-chromium-molybdenum alloy steel used for gears, cams, shafts, and pinions. Excellent carburizing grade.
SAE / AISI 86L20. Leaded version of 8620, free-machining type. Can be carburized.
SAE / AISI 4340. Medium-carbonnickel-chromium-molybdenum it I I oy steel used for gears and shafting. Has high hardenability.
SAE / AISI 8642. Similar to 4340. Has high hardenability.
EF 4130. Aircraft-quality alloy steel.
EF 4140. Aircraft-quality alloy steel.
E 4340, EF 4620, EF 8740, and E 9310. All aircraft-quality alloy steels.
Rather than going into a lengthy description of all the characterr;tics and heat-treating properties of all the various grades of car-lion and alloy steels, the preceding tables can be used by the oiigineer or designer to determine strength, ductility, hardness, and heat-treatment temperatures for each SAE/AISI and ASTM steel listed. A metallurgist should be consulted prior to making a final design choice about the various steels used in important or critical applications.
Stainless steels: Uses by AISI number
Note: The stainless steels listed in the preceding tables typically are known by their three-digit SAE numbers, such as 201, 302, 304, 440, etc. The last three digits of the listed SAE numbers are the standard industry identification numbers and are used as such in the following usage summary.
Chromium-nickel stainless steels (austenitic)
- Low nickel, good corrosion resistance. High work-hardening rate. Excellent weldability.
- General-purpose type equivalent to 302.
203 EZ. Superior machinability. Good corrosion resistance. 216. Most corrosion resistant of all chromium-nickel-manganese stainless steels.
301. High work-hardening rate. Used in structural applications where high strength and resistance to atmospheric corrosion are required.
302. General-purpose stainless steel with good strength properties. Resistant to many corrosive conditions.
303. Free-machining type used in corrosive atmospheres, strong chemical solutions, many organic chemicals, most dyes, nitric acid, and foods.
303 Pb. Leaded version of 303 used for high-volume automatic machining operations.
304. Low-carbon variation of 302. Weldable with caution. Excellent resistance to a high number of corrosive conditions and chemicals.
304 L. Extra-low-carbon version of 304. Low carbon content prevents carbide precipitation during welding, which can produce cracks at the weld joints. Excellent weldability.
305. Good fabrication stainless for spinning, deep-drawing, and cold-heading operations.
- Used in high-temperature applications. Resistant to most acids.
- Higher alloy content improves the basic characteristics. Improved over 309 and 304 for corrosion resistance.
316. Best corrosion resistance of the standard stainless steels. Resists pitting and most chemicals. Used for paper-mill machinery parts and photographic industry parts and containers. High-temperature strength.
316 L. Low-carbon version of 316 that is welded more easily without carbide precipitation.
317. Higher alloy content than 316, providing more corrosion resistance.
321. This alloy is stabilized with titanium for weldments sublect, to severe corrosion. Excellent corrosion resistance to a wide variety of organic and inorganic substances.
347. Stabilized with Cb and Ta for use in the carbide precipitation range of 800 to 1500°F, with no impairment to corrosion resistance.
Chromium stainless steels (ferritic)
409. Developed for automotive muffler service and used in non-critical exterior parts. Economical and easily fabricated.
430. Most widely used of the non-hardenable types of chromium stainless steel. Good mechanical properties and heat resistance. Resistant to nitric acid, sulfur gases, and many organic chemicals, including foods.
430F Free-machining version of 430. Similar in properties to 430. 446. High resistance to corrosion and scaling at high tempera-I tires. Excellent in sulfuric atmospheres.
Chromium stainless steels (martensitic)
403. Excellent for highly stressed parts such as turbine blades. Good resistance to water and atmospheric corrosion.
405. Variation of 410 for improved weldability. Same corrosion resistance as 403.
410. Low-cost general-purpose stainless steel that is heat-treatable. Used where corrosion is not severe.
410 S. Same as 410 except lower carbon range for improvedweldabiliy.
414. Modification of 410 with more nickel to improve corrosion resistance. Can be heat-treated to Rockwell C 25 to C 43.
416. Free-machining version of 410 with corrosion resistance to food acids, basic salts, water, and most atmospheric corrosion products.
440 A, B, C, and F Series of high-carbon stainless steels. All are the same basic composition except carbon content. Can be heat-treated for high strength and high hardness. These steels are corrosion resistant only in the hardened conditions. 440 F is a free machining type used in many applications.
Low-chromium stainless steels
All these grades provide excellent corrosion resistance similar to the austenitic stainless steels and are capable of being heat-treated to various high-strength conditions with minimum distortion. They are generally furnished in the annealed condition for ease of machining. They develop their high-strength properties by aging at selected temperatures. They may be provided as vacuum arc-remelted steels for more demanding applications. They are used in many high-strength, anticorrosion applications. Among other uses, 17-7PH (ASTM A313) round wire is used for helical spring applications, and 17-7PH (ASTM A693) strip is used for flat spring applications.
High-strength, low-alloy (HSLA) steels
Typical HSLA steels, with data indicating their mechanical properties, are shown in Table 4.23. Although these are low-alloy grades of steel, they have excellent tensile strength and other properties, making them valuable in many applications. HSLA steels were developed more than 75 years ago by Krupp in Germany. Some of the older German ordnance steels could be classified as modern HSLA steels, and they also were copper-bearing to improve their resistance to atmospheric corrosion. The famous Mauser M1898 rifles produced for various South American countries had bare polished-metal receivers and bolts.
Many of the HSLA steels rely on carbon, manganese, and silicon contents to achieve the strengths associated with these special materials. Other alloying elements such as nickel, chromium, and copper are also present in some of these steels.
Structural steels with very high tensile strengths are referred to as ultra-high-strength steels. An arbitrary minimum yield strength level of 200 ksi has been established for these grades of steels. (Some ultra-high-strength steels fall below this arbitrary minimum.) Tables 4.24 through 4.30 give the mechanical properties of some ultra-high-strength steels. Many of these are considered high-quality specialty steels, with 4340 being used as the reference by which all other types of ultra-high-strength steels are measured. AISI type 4340 is used in critical applications, such as key components for aerospace vehicles and commercial and military aircraft.
Aluminum and Aluminum Alloys
Aluminum and its alloys are among the most used metallic materials, with countless applications and an extremely broad range of physical and chemical properties. Pure aluminum is a silvery white metal, light in weight, nontoxic, and easily cast, forged, and machined. The pure metal was first isolated in the laboratory in 1827. The method of extracting the metal by electrolysis of alumina dissolved in cryolite was discovered by Hall in 1886 in the United States. This method is still in use today and is known as the Hall process. Aluminum in its natural forms is the third most abundant material in the earth’s crust, exceeded only by oxygen and silicon.
Aluminum alloys are mandatory in many design applications of modern technologies. Many of the modern aluminum alloys are stronger than some steels on a volume basis and weigh only 34 percent (or one-third) as much as steel. The average density of aluminum alloys is 0.098 lb/in” and that of steel is 0.282 lb/in’. The electrical conductivity of aluminum is 60 percent that of an equal cross-sectional area of copper, which is the second best conductor of electric current. In order of electrical conductivity, the best four elements are silver, copper, gold, and aluminum, respectively.
Tables 4.31 through 4.38 show the physical properties of all the present aluminum alloys. Also included are the typical uses for all the wrought and cast types of aluminum alloys in use today. Figure 4.2 shows part of the SAE standard delineating alloy and temper designation systems for aluminum.
Copper and Copper Alloys
Copper and copper alloys are also among the most important and most used metallic materials. Almost all electrical components and electrical products contain parts made of copper or one or more of its important alloys. All the electrical industries worldwide depend on copper and copper alloys. Many new copper alloys have been developed over the past 30 or 40 years, with beryllium-copper alloys as one of the preferred materials in many electrical applications as a replacement for the phosphor bronzes. The phosphor, silicon, and manganese bronzes have many applications where strength and current-carrying ability, combined with corrosion resistance and nonmagnetic properties, are desired. Springs with a high fatigue-endurance limit and good electrical properties are made from the beryllium-copper alloys.
One of the most important uses for copper is in the electrical power distribution industries, where ETP no. 110 copper bus conductors are used to carry the electrical power for all electrical applications. The power distribution industries use such equipment as transformers, power stations, power transmission lines, mid electrical switch gear and control equipment. The electric motor industries are another large user of copper products.
Copper is one of the most important elements, with a specific gravity of 8.96 g/cm’ and weight of 0.324 lb/in’. It is the second-best conductor of electric current, exceeded only by silver. The copper metal is smelted from oxide, sulfide, and carbonate compounds halt, are found in their natural states as cuprite, malachite, azurite, and bornite. The most important compounds are the oxides and the sulfates (blue vitriol), the latter being used for agricultural poisons and water purification.
Magnesium and magnesium alloys have many applications where it moderate strength and light weight are required. These alloys find many applications in military and commercial aircraft, as well as i i i rockets and missiles (aerospace vehicles).
Magnesium is the eighth most abundant element in the earth’s i i is t. The metal is obtained by electrolysis of fused magnesium choride derived from brines, wells, and seawater. Magnesium is a silvery white, lightweight metal that is also fairly tough. It is one-third lighter than aluminum. The metal tarnishes in air and burns easily when in the finely divided state with a dazzling white flame. The specific gravity of magnesium is 1.738 g/em’, and its density is 0.063 11, 111′. Caution must be used when handling magnesium because of w flammability in air. Water should not be used to extinguish a magnesium fire.
Titanium alloys have a high strength-to-weight ratio. They are used as armor plate in modern war planes and propeller shafts, rigging, mill other parts of ships where high strength and resistance to salt water are required. Titanium metal is produced by reducing titanium tetrachloride with magnesium. Titanium is a lustrous, white metal with low density and good strength. The specific gravity of titanium is 4.54 g/cm3, with a weight of 0.164 lb/in’. The pure metal burns in air and is the only element that burns in nitrogen gas.
Titanium is used extensively in modern aircraft and aerospace vehicles, where a lightweight alloy with high strength finds many applications. Titanium is the ninth most abundant element in the earth’s crust.
The Unified Numbering System (UNS) for Metals and Alloys
The Unified Numbering System (UNS) provides a means of coordinating many nationally used numbering systems currently administered by societies, trade associations, and the producers of metal” and alloys, thereby avoiding confusion caused by use of more than one identification number for the same material or by having the same number assigned to two or more entirely different materials. Table 4.54 shows the primary series of numbers, and Table 4.55 lists the secondary division of some series of numbers. When you know the UNS number for a metal or alloy, you may use these tables to determine the prime material (metal) or classification by alloy represented by the UNS number.