Technology & Engineering
Carbon Steels
Carbon steels are iron-carbon alloys containing up to 2% carbon, making them the most common and widely used type of steel. They are known for their strength, durability, and affordability, and are used in a wide range of applications, from construction and manufacturing to automotive and infrastructure. Carbon steels can be further classified based on their carbon content and properties.
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8 Key excerpts on "Carbon Steels"
eBook - PDFFundamentals of Modern Manufacturing
Materials, Processes, and Systems
- Mikell P. Groover(Author)
- 2016(Publication Date)
- Wiley(Publisher)
Steel castings usually fall into this carbon range as well. ~ ~ 800 120 100 80 60 40 20 240 220 200 160 120 80 600 400 200 0 0.2 0.4 0.6 % Carbon (C) 0.8 1.0 Tensile strength, MPa Hardness, HB Tensile strength, 1000 lb/in 2 . Hardness Tensile strength ■ Figure 6.12 Tensile strength and hardness as a function of carbon content in plain carbon steel (hot-rolled, unheat-treated). 108 | Chapter 6 | Metals 2. Medium Carbon Steels range in carbon between 0.20% and 0.50% and are specified for applica- tions requiring higher strength than the low-C steels. Applications include machinery compo- nents and engine parts such as crankshafts and connecting rods. 3. High Carbon Steels contain carbon in amounts greater than 0.50%. They are specified for still higher-strength applications and where stiffness and hardness are needed. Springs, cutting tools and blades, and wear-resistant parts are examples. Increasing carbon content strengthens and hardens the steel, but its ductility is reduced. Also, high Carbon Steels can be heat treated to form martensite, making the steel very hard and strong (Section 26.2). LOW ALLOY STEELS Low alloy steels are iron–carbon alloys that contain additional alloying elements in amounts totaling less than about 5% by weight. Owing to these additions, low alloy steels have mechanical properties that are superior to those of the plain Carbon Steels for given appli- cations. Superior properties usually mean higher strength, hardness, hot hardness, wear resistance, toughness, and more desirable combinations of these properties. Heat treatment is often required to achieve these improved properties. Common alloying elements added to steel are chromium, manganese, molybdenum, nickel, and vanadium, sometimes individually but usually in combinations. These elements typically form solid solutions with iron and metallic compounds with carbon (carbides), assuming sufficient carbon is present to support a reaction.
eBook - PDFFundamentals of Modern Manufacturing
Materials, Processes, and Systems
- Mikell P. Groover(Author)
- 2019(Publication Date)
- Wiley(Publisher)
6.2.3 | STEELS As defined earlier, steel is an alloy of iron that contains carbon ranging by weight between 0.02% and 2.11% (most steels range between 0.05% and 1.1%C). It often includes other alloying ingredi- ents, such as manganese, chromium, nickel, and molybdenum; but the carbon content is what turns iron into steel. Hundreds of compositions of steel are available commercially. For purposes of organ- ization here, the vast majority of commercially important steels can be grouped into the following categories: (1) plain Carbon Steels, (2) low alloy steels, (3) stainless steels, (4) tool steels, and (5) specialty steels. PLAIN Carbon Steels These steels contain carbon as the principal alloying element, with only small amounts of other elements (about 0.4% manganese plus lesser amounts of silicon, phos- phorus, and sulfur). The strength of plain Carbon Steels increases with carbon content. A typical plot of the relationship is illustrated in Figure 6.12. As seen in the phase diagram for iron and Ladle Molten steel Tundish Submerged entry nozzle Water-cooled mold Molten steel Solidified steel Water spray Cooling chamber Withdrawal rolls Bending rolls Guide rolls Mold flux Continuous slab Slab straightening rolls Cutoff torch Slab ■ Figure 6.11 Continuous casting: steel is poured into tundish and distrib- uted to a water-cooled continuous casting mold; it solidifies as it travels down through the mold. Thickness of slab is exaggerated for clarity. Section 6.2 | Ferrous Metals | 107 carbon (Figure 6.4), steel at room temperature is a mixture of ferrite (α) and cementite (Fe 3 C). The cementite particles distributed throughout the ferrite act as obstacles to the movement of disloca- tions during slip (Section 2.3.3); more carbon leads to more barriers, and more barriers mean stronger and harder steel.
eBook - PDF- Harry Cather, Richard Douglas Morris, Mathew Philip, Chris Rose(Authors)
- 2001(Publication Date)
- Newnes(Publisher)
There are three main groups: Low Carbon Steels containing up to about 0.25% carbon by weight: They have moderate strength and excellent fabrication properties and are used in great quantities for bridges, buildings, ships and other vehicles. The great majority of all steel used (over 90%) falls in this group. Medium Carbon Steels containing between 0.25% carbon and 0.60% carbon by weight: They have greater strength and hardness but less ductility. They are therefore also more difficult to fabricate than the low Carbon Steels. They are used to manufacture products such as gears and rails, which need better wear resistance. High Carbon Steels containing between 0.60% carbon and 1.4% carbon by weight (although steels with greater than 0.8% carbon are rare): They have the highest strength and hardness but the least ductility and toughness of the three groups. They are used to manufacture springs, dies and cutting tools where high hardness and wear resistance are important. Better materials have generally taken their place. Note: In all our future discussions we will assume that the proportions of elements in any alloy are given in terms of the weight of material rather than volume. Microstructure of steels Iron is polymorphic and forms different crystal structures over different temperature ranges as was seen under ‘Polymorphism (allotropy)’, Chapter 3. The structural changes also exist when carbon is dissolved in the iron structure. The dissolved carbon forms interstitial solid solutions. The proportion of carbon that exists in the BCC ferrite form is much less than can dissolve in the FCC austenite form. We can see this in the thermal-equilibrium diagram for the iron–carbon system (Figure 5.2.1). When the solubility limit of carbon in either ferrite or austenite is exceeded, a compound, Fe 3 C, forms between the excess carbon and iron. This is called iron carbide, or cementite . It has a composition of 6.67% carbon by weight.
eBook - PDF- Vladimir B. Ginzburg, Robert Ballas(Authors)
- 2000(Publication Date)
- CRC Press(Publisher)
56 CHAPTER 4 4.6 Tool Steels Tool steels can be defined as a class of carbon, alloy, or high speed steels that are capable of being hardened and tempered [6,7]. These steels are commonly used to make a variety of tools for cutting, shaping, forming and blanking of materials at either ordinary or elevated temperatures. Tool steels are also used for a variety of other applications where high hardness, strength and toughness are required along with resistance to wear, abrasion and softening at elevated tempera-tures. These properties are generally attained with high carbon and alloy contents. Tool steels can be grouped into eight main categories as shown in Table 4.6, which also provides the chemical composition for these grades. Table 4.7 shows the mechanical properties of some selected tool steels. Table 4.6 Chemical composition of tool steels [6, 7].
eBook - PDF- J. Carvill(Author)
- 2014(Publication Date)
- Butterworth-Heinemann(Publisher)
6.1.4 Alloy irons The strength, hardness, wear resistance, temperature resistance, corrosion resistance, machinability and castability of irons may be improved by the addition of elements such as nickel, chromium, molybdenum, vanadium, copper and zirconium. 6.2 Carbon Steels 6.2.1 Applications of plain Carbon Steels These are alloys of iron and carbon, chemically combined, with other elements such as manganese, silicon, sulphur, phosphorus, nickel and chromium. Properties are governed by the amount of carbon and the heat treatment used. Plain Carbon Steels are broadly classified as: low carbon (0.05-0.3%C), with high ductility and ease of forming; medium carbon (0.3-0.6%C), in which heat treatment can double the strength and hardness but retain good ductility; and high carbon (> 0.6%C), which has great hardness and high strength and is used for tools, dies, springs, etc.
Available until 4 Dec |Learn moreManufacturing Technology
Materials, Processes, and Equipment
- Helmi A. Youssef, Hassan A. El-Hofy, Mahmoud H. Ahmed(Authors)
- 2011(Publication Date)
- CRC Press(Publisher)
Engineering Materials and Their Applications 65 rods,. and. a. multitude. of. machine. parts . . The. toughness. and. formability. of. high-carbon. steels.(<0 .8% .C).are.quite.low,.but.the.hardness.and.wear.resistance.are.high . .High-carbon. steels. find. application. in. hammers,. chisels,. drills,. punches,. files,. cutters,. knives,. saws,. wire,. and. dies. for. all. purposes . . Properties. that. are. typically. developed. in. plain-carbon. steels.are.given.in.Table.4 .4. b. . Alloy.steels:.Alloy.steels.contain.appreciable.quantities.of.alloying.elements.in.addition.to. carbon. .They.include.the.following.categories . . 1 . . High-strength. low-alloy. structural. steels. (HSLA):. HSLA. steels. contain. insufficient. carbon.and.alloying.elements.to.be.hardened.effectively.by.quenching.to.martensite,. and.hence.they.rely.on.chemical.composition.rather.than.heat.treatment.to.develop.the. desired.mechanical.properties.in.the.as-rolled.condition . .HSLAs.find.applications.in. large. welded. structures,. where. the. size. precludes. subsequent. heat. treatment . . These. applications.require.high.yield.strength,.good.weldability,.acceptable.corrosion.resis-tance.and.limited.ductility,.while.hardenability.is.of.no.concern . . . These. steels. contain. slightly. more. phosphorus. and. silicon. than. carbon. steels,. thereby.strengthening.the.ferrite.network,.and.raising.the.yield.strength.to.about.50%. above.that.of.carbon.structural.steels . .HSLA.steels.can.be.made.corrosion.resistant. (8 times.as.compared.with.that.of.plain.carbon.steel).by.proper.addition.of.P,.Cu,.Si,. Cr,.V.and.Mo . .For.this.reason,.HSLAs.are.known.as. weathering steels . .Because.of. their.high.yield.strength,.weight.saving.of.20%.to.30%.can.often.be.achieved.with.no. sacrifice.of.strength.and.safety . . . Rolled. and. welded. HSLA. steels. are. now. being. used. in. automobiles. and. railway. cars.to.save.weight,.and.for.bridges,.towers,.pressure.vessels,.and.building.structures.
- George Murray(Author)
- 1997(Publication Date)
- CRC Press(Publisher)
The design engineer is usually not inter-ested in how the steel is manufactured, the deoxidation practice nor the micro-structure, but is more involved with the required strength level, such as those spec-ified in ASTM standards. 2 PROCESSING Certain processing terms may help the design engineer in his or her materials selection procedure. In addition, the design engineer must be aware that the prop-erties can vary considerably, depending on the process to which the steel has been subjected. The most pertinent processing parameters will be summarized in the following. 1. Heat Treatment: The properties of all carbon and alloy steels depend on the type of heat treatment given the steel. These treatments involve air cooling and quenching in water or oil, usually followed by tempering (heating) procedures. The tempering temperature is of most importance, as illustrated in Fig. 1 , which shows the wide variation in hardness obtained at different tempering temperatures and carbon content. Although the plain Carbon Steels are widely used in the non-heat-treated hardened state (i.e., annealed and normalized), they also find considerable use in the heat-treated state. Cutlery is a good example since hard (and thus sharp) conditions can be achieved in thin sections by quenching from a suitable elevated temperature. Toughness (lack of brittleness), if needed, can be achieved by sub-sequent tempering operations. 2. Hardenability: The hardenability of a steel is a measure of the depth to which a steel can be hardened. Good hardenability is achieved by adding alloying elements such as nickel, chromium, molybdenum, and, sometimes, vanadium and tungsten. Thus, the alloy steels have a high quenched hardness and strength throughout thick sections (up to a few inches) and correspondingly are used for shafts, thick disks, load supporting rods, etc.
eBook - PDF- Ajeet Singh(Author)
- 2017(Publication Date)
- Cambridge University Press(Publisher)
Some alloying elements like copper (Cu), chromium (Cr), lead (Pb), magnesium (Mg), manganese (Mn), molybdenum (Mo), nickel (Ni), phosphorus (P), silicon (Si), and sulphur (S) are added to improve the properties of steels and such steels are called alloy steels. Low and medium alloy steels have these constituents less than 10 per cent, while high alloy steels have more than 10 per cent. Classification of ferrous and non-ferrous metals is given below: Engineering Materials 23 Metals Ferrous Wrought iron Carbon steel Cast iron Alloy steel Stainless steel Low carbon steel Medium carbon steel High carbon steel Ductile Grey White Malleable Low alloy Medium alloy High alloy Non-Ferrous Aluminium alloy Copper alloy Miscellaneous metals Non Metals Wood Plastics Rubber Ceramics Synthetic Thermo-plastic Thermo-setting Natural 2.4 Ferrous Metals Iron and Iron alloys (called steels) are most commonly used metals. Wrought iron is the purest form of Iron. Mild steel is the most commonly used steel. High Carbon Steels, alloy steels, and cast irons have high percentage of carbon as shown in Figure 2.1. Percentage of Carbon (Not to scale) 0 0.15 0.45 0.8 1.5 2.3 3 4 Wrought iron Low carbon steel Medium carbon steel High carbon steel White cast iron Cast iron Grey cast iron Figure 2.1 Percentage of carbon and name of ferrous metals Fundamentals of Machine Design, Volume I 24 2.5 Wrought Iron Wrought iron has a very low percentage of carbon (0.01) and is used for ornamental work, chain links, crane hooks, water, steam pipes, etc. It is a tough, malleable, and ductile material and can be easily forged and welded. It is not suitable for shocks. Ultimate tensile strength of WI is between 250–500 MPa and the compressive strength about 300 MPa. 2.6 Carbon Steels Carbon is the main hardening element in steel. If its percentage is more than 0.85, it increases the hardness and tensile strength, but decreases ductility and weldability.
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