- - AGRICULTURE CORE CURRICULUM - - (CLF2000) Advanced Core Cluster: AGRICULTURE MECHANICS (CLF2350) Unit Title: Metalworking _____________________________________________________________________________ (CLF2353) Topic: Types and Properties of Common Time Year(s) Metalworking Materials 1 Hours 1 / 2 / 3 / 4 _____________________________________________________________________________ Topic Objectives: Upon completion of this lesson the student will be able to: Learning Outcome #: (H-1) - Identify samples of cast iron, mild steel and aluminum. Special Materials and Equipment: Graph paper, pencil, ruler, compass, small sheet metal piece, scribe or scratch awl References: Burke, Stanley R., & Wakeman, T. J. (1990). MODERN AGRICULTURAL MECHANICS (2nd ed.). Danville, IL: Interstate Publishers. Phipps, Lloyd J., & Reynolds, Carl L. (1990). MECHANICS IN AGRICULTURE (4th ed.). Danville, IL: Interstate Publishers. Evaluation: Quiz by instructor and evaluation of student participation in discussion. TOPIC PRESENTATION: Types and properties of common metalwoking materials A. Sheet metal is thin gauge metal used to form ducting, boxes, and machine guards by bending, folding, and otherwise manipulating. 1. Types of Sheet Metal Commonly Used in Agricultural Mechanics a. Galvanized or zinc-coated mild steel is the most common type used in the industry. It is available in thickness gauges from 16 ga. to 28 ga. Galvanized mild steel sheet metal is commonly used to build tool boxes, planter boxes, brooders, and anything else requiring durable yet thin metal sheets. b. Uncoated mild steel sheet is also available in 16 ga. to 28 ga. This sheet can be used for fence-siding, and other projects which will ultimately be painted. c. Copper and brass sheet is often used to do decorative sheet metal work such as name plates and signs. d. Aluminum sheet metal, available in different alloys, is also used in decorative applications. It does not rust or corrode easily but is brittle and may crack when worked improperly. In addition to the fastening techniques listed below, aluminum sheet can be welded with a MIG type welder. 2. Material Fasteners Used with Sheet metal a. Rivets are used to great advantage with all sheet metal work. Normally the rivet should be the same material as the metal. 1) Size the rivet to fit the rivet hole very close. 2) The rivet should extend 1 1/2 diameters through the sheet metal, then riveted over to form head and hold metal together. b. Blind rivets or "pop rivets" are also used in hard-to-get-at places. These are available in steel, stainless steel, and aluminum. c. Sheet metal screws provide the ability to easily take the pieces apart and then put them back together. Using a sharp punch to make a hole instead of punching or drilling the pilot hole for the screw provides more material for the metal screw to "bite" into and improves the holding strength. d. Machine screws and stove bolts also provide a secure joint and will support more weight than a sheet metal screw. They are also used to attach sheet metal to wood or heavier metal. B. Metalworking Terms a. Stength refers to the ability of a metal to hold loads without breaking. Steel is strong, but lead is weak. b. Hardness of a metal refer to its ability to resist penetration, wear, or cutting action. c. Malleability refers to its ability of metal to be rolled, forged, hammered, or drawn without cracking or breaking. Gold is the most malleable metal. d. Ductility refers to the abililty of a metal to be stretched without breaking. Baling wire is very ductile. e. Coldwork - Most of the metalwork done in drilling, taping, bending, and forming is done without heat. As metal is worked cold it becomes harder and will tend to crack if done too much. This is called, work hardening. f. Heat Treatment - Any heating and controlled cooling process that is designed to produce special properties of hardness, softness, or alteration of the strength of a metal. g. Tempering - a metal hardening process done by controlled heating and controlled cooling; it is done to relieve stress in the metal. C. Iron 1. Types of Iron Commonly Used in Agricultural Mechanics a. Cast Iron - coarse-grained steel with a 2-6% carbon content. It is brittle and therefore best used under compression pressure rather than tension. Types of cast iron include gray and white. Cast iron is commonly used for machine parts and hydrants. D. Carbon Steel 1. Carbon steels are iron which contain a specified percentage of elemental carbon. a. Low carbon steel (mild steel) - contains .05 to .30 percent carbon. Its soft, tough, and mallable characteristics make it suitable for rivets, screws, nails, and low strength machine parts. Used in bar, square, and flat stock it is the most common steel used for a variety of repairs and proects around the agricultural mechanics shop. b. Medium carbon steel - contains .30 to .70 percent carbon. It is used to make bolts, axles, hammers, and screwdrivers. E. Shapes and Sizes of Steel 1. Mild steel is available in the form of bar, square, and flat stock. This type of stock is measured by its thickness and width. Common lengths are 8 and 16 feet. 2. Sheet steel is available by thickness (gauge) and, as the name implies, is sold in sheets. 4 feet by 8 feet is common. 3. Angle iron, channel iron and "I" beams are forms of mild steel that are measured by thickness, width and-web (internal dimension) size. This form of mild steel is commonly used in agriculture to make frames for equipment and machinery. 4. Round tubing and pipe are commonly used in agriculture for irrigation, fence posts, and transport of fuels. Tubing is generally smaller and is measured by outside diameter (OD) and wall thickness. It is more commonly used in fuel lines and low pressure, low flow water systems. Pipe is generally larger and is measured by inside diameter (ID) and wall thickness. Pipe is used in irrigation as well as fence and building construction. 5. Square tubing is measured by wall thickness and outside dimensions. Square tubing is used for construction of gates and light-duty frames such as bench tops. F. Aluminum 1. Alloys of aluminum - consist of aluminum plus the addition of small quantities of other metals (copper, silicon, manganese, and others) normally less than 7% or 7% added metal to obtain specific alloys. a. Cast alloys are the basic aluminum material which cast parts are made of by heating to its melting point and pouring in a mold. b. Wrought alloys are derived from cast alloy but heated to a specific temperature and then formed by rolling, forging, and/or extruding through a die. ______________________________________________________________ ACTIVITY: 1. Examine samples of different metals of various sizes and shapes, and use technically correct terms to describe them. ______________________________________________________________ 7/17/91 YNJ/CC/tf #%&C