METAL TYPES

The metals that Steelworkers work with are divided into two general classifications: ferrous and nonferrous. Ferrous metals are those composed primarily of iron and iron alloys. Nonferrous metals are those composed primarily of some element or elements other than iron. Nonferrous metals or alloys sometimes contain a small amount of iron as an alloying element or as an impurity.

FERROUS METALS

Ferrous metals include all forms of iron and steel alloys. A few examples include wrought iron, cast iron, carbon steels, alloy steels, and tool steels. Ferrous metals are iron- base alloys with small percentages of carbon and other elements added to achieve desirable properties. Normally, ferrous metals are magnetic and nonferrous metals are nonmagnetic.

IRON

Pure iron rarely exists outside of the laboratory. Iron is produced by reducing iron ore to pig iron through the use of a blast furnace. From pig iron many other types of iron and steel are produced by the addition or deletion of carbon and alloys. The following paragraphs discuss the different types of iron and steel that can be made from iron ore.

PIG IRON

Pig iron is composed of about 93% iron, from 3% to 5% carbon, and various amounts of other elements. Pig iron is comparatively weak and brittle; therefore, it has a limited use and approximately ninety percent produced is refined to produce steel. Cast-iron pipe and some fittings and valves are manufactured from pig iron.

WROUGHT IRON

Wrought iron is made from pig iron with some slag mixed in during manufacture. Almost pure iron; the presence of slag enables wrought iron to resist corrosion and oxidation. The chemical analyses of wrought iron and mild steel are just about the same. The difference comes from the properties controlled during the manufacturing process. Wrought iron can be gas and arc welded, machined, plated, and easily formed; however, it has a low hardness and low-fatigue strength.

CAST IRON

Cast iron is any iron containing greater than 2% carbon alloy. Cast iron has a high- compressive strength and good wear resistance; however, it lacks ductility, malleability, and impact strength. Alloying it with nickel, chromium, molybdenum, silicon, or vanadium improves toughness, tensile strength, and hardness. A malleable cast iron is produced through a easily as the low-carbon steels. They are used for crane prolonged annealing process. hooks, axles, shafts, setscrews, and so on.

INGOT IRON

Ingot iron is a commercially pure iron (99.85% iron) that is easily formed and possesses good ductility and corrosion resistance. The chemical analysis and properties of this iron and the lowest carbon steel are practically the same. The lowest carbon steel, known as dead- soft, has about 0.06% more carbon than ingot iron. In iron the carbon content is considered an impurity and in steel it is considered an alloying element. The primary use for ingot iron is for galvanized and enameled sheet.

STEEL

All the different metals and materials that we use in our trade, steel is by far the most important. When steel was developed, it revolutionized the American iron industry. With it came skyscrapers, stronger and longer bridges, and railroad tracks that did not collapse. Steel is manufactured from pig iron by decreasing the amount of carbon and other impurities and adding specific amounts of alloying elements. Do not confuse steel with the two general classes of iron: cast iron (greater than 2% carbon) and pure iron (less than 0.15% carbon). In steel manufacturing, controlled amounts of alloying elements are added during the molten stage to produce the desired composition. The composition of a steel is determined by its application and the specifications that were developed by the following: American Society for Testing and Materials (ASTM), the American Society of Mechanical Engineers (ASME), the Society of Automotive Engineers (SAE), and the American Iron and Steel Institute (AISI).Carbon steel is a term applied to a broad range of steel that falls between the commercially pure ingot iron and the cast irons. This range of carbon steel may be classified into four groups:

HIGH-CARBON STEEL/VERY HIGH-CARBON STEEL

Steel in these classes respond well to heat treatment and can be welded. When welding, special electrodes must be used along with preheating and stress- relieving procedures to prevent cracks in the weld areas. These steels are used for dies, cutting tools, milltools, railroad car wheels, chisels, knives, and so on.

LOW-ALLOY, HIGH-STRENGTH, TEMPERED STRUCTURAL STEEL

High-strength steels are covered by ASTM specifications. NOTE: This type of steel is much tougher than low-carbon steels. Shearing machines for this type of steel must have twice the capacity than that required for low-carbon steels

STAINLESS STEEL

This type of steel is classified by the American Iron and Steel Institute (AISI) into two general series named the 200-300 series and 400 series. Each series includes several types of steel with different characteristics. The 200-300 series of stainless steel is known as

AUSTENITIC.

This type of steel is very tough and ductile in the as-welded condition; therefore, it is ideal for welding and requires no annealing under normal atmospheric conditions. The most well-known types of steel in this series are the 302 and 304. They are commonly called 18-8 because they are composed of 18% chromium and 8% nickel.

The chromium nickel steels

Low-Carbon Steel . . . 0.05% to 0.30% carbon are the most widely used

and are normally nonmagnetic.

Medium-Carbon Steel . . . 0.30% to 0.45% carbon

High-Carbon Steel . . . 0.45% to0.75% carbon their crystalline structure

into two general groups.

One Very High-Carbon Steel . . . 0.75% to 1.70% carbon group is known as

FERRITIC CHROMIUM and the other group as MARTENSITIC CHROMIUM.

ALLOY STEELS

Steels that derive their properties primarily from the presence of alloying element other than carbon are called ALLOYS or ALLOY STEELS. Note, however, that alloy steels always contain traces of other elements. Among the more common alloying elements are nickel, chromium, vanadium, silicon, and tungsten. One or more of these elements may be added to the steel during the manufacturing process to produce the desired characteristics.

Alloy steels may be produced in structural sections, sheets, plates, and bars for use in the as rolled condition. Better physical properties are obtained with these steels than are possible with hot. These alloys are used in structures where the strength of material is especially important. Bridge members, railroad cars, dump bodies, dozer blades, and crane booms are made from alloy steel. Some of the common alloy steels are briefly described in the paragraphs below.

NICKEL STEELS

These steels contain from 3.5% nickel to 5% nickel. The nickel increases the strength and toughness of these steels. Nickel steel containing more than 5% nickel has an increased resistance to corrosion and scale. Nickel steel is used in the manufacture of aircraft parts, such as propellers and airframe support members.

CHROMIUM STEELS

These steels have chromium added to improve hardening ability, wear resistance, and strength. These steels contain between 0.20% to 0.75% chromium and 0.45% carbon or more. Some of these steels are so highly resistant to wear that they are used for the races and balls in antifriction bearings.

Chromium steels are highly resistant to corrosion and to scale.

CHROME VANADIUM STEEL

This steel has the maximum amount of strength with the least amount of weight. Steels of this type contain from 0.15% to 0.25% vanadium, 0.6% to 1.5% chromium, and 0.1% to 0.6% carbon. Common uses are for crankshafts, gears, axles, and other items that require high strength. This steel is also used in the manufacture of high-quality hand tools, such as wrenches and sockets.

TUNGSTEN STEEL

This is a special alloy that has the property of red hardness. This is the ability to continue to cut after it becomes red-hot. A good grade of this steel contains from 13% to 19% tungsten, 1% to 2% vanadium, 3% to 5% chromium, and 0.6% to 0.8% carbon. Because this alloy is expensive to produce, its use is largely restricted to the manufacture of drills, lathe tools, milling cutters, and similar cutting tools.

MOLYBDENUM

This is often used as an alloying agent for steel in combination with chromium and nickel. The molybdenum adds toughness to the steel. It can be used in place of tungsten to make the cheaper grades of high-speed steel and in carbon molybdenum high-pressure tubing.

MANGANESE STEELS

The amount of manganese used depends upon the properties desired in the finished product. Small amounts of manganese produce strong, free-achgining steels. Larger amounts (between 2% and 10%) produce a somewhat brittle steel, while still larger amounts (11% to 14%) produce a steel that is tough and very resistant to wear after proper heat treatment.

NONFERROUS METALS

Nonferrous metals contain either no iron or only insignificant amounts used as an

alloy. Some of the more common nonferrous metals Steelworkers work with are as follows: copper, brass, bronze, copper-nickel alloys, lead, zinc, tin, aluminum, and Duralumin. NOTE: These metals are nonmagnetic. COPPER

This metal and its alloys have many desirable properties. Among the commercial metals, it is one of the most popular. Copper is ductile, malleable, hard, tough, strong, wear resistant, machinable, weld able, and corrosion resistant. It also has high-tensile strength, fatigue strength, and thermal and electrical conductivity. Copper is one of the easier metals to work with but be careful because it easily becomes work-hardened; however, this condition can be remedied by heating it to a cherry red and then letting it cool. This process, called annealing, restores it to a softened condition. Annealing and softening are the only heat-treating procedures that apply to copper. Seams in copper are joined by riveting, silver brazing, bronze brazing, soft soldering, gas welding, or electrical arc welding. Copper is frequently used to give a protective coating to sheets and rods and to make ball floats, containers, and soldering coppers.

CARBON STEELS

Carbon steels are iron-carbon alloys containing up to 2.06% of carbon, up to1.65% of manganese, up to 0.5% of silicon and sulfur and phosphorus as impurities. Carbon content in carbon steel determines its strength and ductility. The higher carbon content, the higher steel strength and the lower its ductility. According to the steels classification there are following groups of carbon steels:

• Low carbon steels (C < 0.25%)

• Medium carbon steels (C =0.25% to 0.55%)

• High carbon steels (C > 0.55%)

• Tool carbon steels (C>0.8%)

Designation system of carbon steels Chemical compositions of some carbon steels Properties of some carbon steels

Low carbon steels (C < 0.25%)

Properties: good formability and weldability, low strength, low cost.

Applications: deep drawing parts, chain, pipe, wire, nails, some machine parts.

Medium carbon steels (C =0.25% to 0.55%)

Properties: good toughness and ductility, relatively good strength, may be hardened by quenching

Applications: rolls, axles, screws, cylinders, crankshafts, heat treated machine parts.

High carbon steels (C > 0.55%)

Properties: high strength, hardness and wear resistance, moderate ductility.

Applications: rolling mills, rope wire, screw drivers, hammers, wrenches, band saws.

Tool carbon steels (C>0.8%) - subgroup of high carbon steels

Properties: very high strength, hardness and wear resistance, poor weldability, low ductility.

Applications: punches, shear blades, springs, milling cutters, knives, razors. Designation

system of carbon steels

American Iron and Steel Institute (AISI) together with Society of Automotive Engineers

(SAE) have established four-digit (with additional letter prefixes) designation system:

LOW-ALLOY, HIGH-STRENGTH, TEMPERED STRUCTURAL STEEL

A special lowcarbon steel, containing specific small amounts of alloying elements, that is quenched and tempered to get a yield strength of greater than 50,000 psi and tensile strengths of 70,000 to 120,000 psi. Structural members made from these high-strength steels may have smaller cross- sectional areas than common structural steels and still have equal or greater strength. Additionally, these steels are normally more corrosion- and abrasionresistant. High-strength steels are covered by ASTM specifications. NOTE: This type of steel is much tougher than low-carbon steels. Shearing machines for this type of steel must have twice the capacity than that required for low-carbon steels

STAINLESS STEEL

AUSTENITIC

First digit 1 indicates carbon steel (2-9 are used for alloy steels); Second digit indicates modification of the steel.

0 - Plain carbon, non-modified

1 - Resulfurized

2 - Resulfurized and rephosphorized

5 - Non-resulfurized, Mn over 1.0%

Last two digits indicate carbon concentration in 0.01%.

Example: SAE 1030 means non modified carbon steel, containing 0.30% of carbon.

A letter prefix before the four-digit number indicates the steel making technology:

A - Alloy, basic open hearth

B - Carbon, acid Bessemer

C - Carbon, basic open hearth

D - Carbon, acid open hearth

E - Electric furnace

Example: AISI B1020 means non modified carbon steel, produced in acid Bessemer and containing 0.20% of carbon.

Chemical compositions of some carbon steels

SAE/AISI grade C, % Mn,% P,% max S,% max

1006 0.08 max 0.35 max 0.04 0.05

1010 0.08-0.13 0.30-0.60 0.04 0.05

1020 0.17-0.23 0.30-0.60 0.04 0.05

1030 0.27-0.34 0.60-0.90 0.04 0.05

1045 0.42-0.50 0.60-0.90 0.04 0.05

1070 0.65-0.76 0.60-0.90 0.04 0.05

1090 0.85-0.98 0.60-0.90 0.04 0.05

1117 0.14-0.20 1.10-1.30 0.04 0.08-0.13

1547 0.43-0.51 1.35-1.65 0.04 0.05