Fig. 276.—Steps in scarfing and preparing to weld an eye on the end of a rod.
Points on Welding
1. Use a clean, deep, compact, coke fire.
2. Clean the fire every half hour.
3. Make the scarf» short arid thick, rather than long and thin. Scarfs should not he longer than V/4 times the thickness of the stock.
4. Round the surfaces of scarfs so slag will be squeezed out- rather than trapped in the weld.
5. Heat the irons to a Rood welding he-at, yet do not burn them.
6. Bring both irons up to the welding heat at the same time.
7. Have the scarfed sides of the irons down in the fire just before removing them.
8. Before welding the irons t<>gether, shako off any sla« or impurities by quickly nipping the tongs against the edge of the anvil.
9. Steadying the pieces over the edges of the anvil will help get them accurately and quickly placed.
10. Strike light or medium blows when irons are at the welding heat. Simply forcing the parts together is all that is necessary. Heavy blows mash the irons.
11. Work fast; keep the hammer on the anvil within easy reach.
12. In ease of failure to stick, do not continue hammering. Reflux and try again, being sure the fire is in good shape, and that you heat the irons hot enough.
318. Drawing and Shaping Steel Shares.—Steel plowshares are sharpened by heating and drawing the edge. The share should be placed in the fire so that only the portion to be drawn is heated. This is best done hy placing the share fiat with the edge over the center of the fire, and by banking up under the share with green coal. The share should not be placed in a vertical position with the edge down.,
/The share should be hammered on top, beginning at the point and working back toward the heel, heating and hammering only a small section at a time. The share should not be heated above a cherry red, and care should be exercised not to dent the top side of the share with hammer marks any more than necessary.
It is important in sharpening a share to get the point shaped so that it will have the proper suction. It should slope down ward until the tip end is about Yt to % in. below the lower edge of the landside. The point should also be bent out toward the land slightly, usually about ^s to in., to give the plow what is known as land suction. In case of a walking plow, the outer corner or wing of the share should have a small flat surface that bears on the ground and helps to support the outer side of the plow. Sulky or tractor plowshares require little or no such wing bearing.
319. Hardening the Share.—A soft-center steel share may be hardened by heating about 2 in. along the cutting edge to a dull red and then dipping it in water, cutting edge straight down. Some smiths heat the whole share to a dull red before dipping.
Solid crucible-steel shares should be hardened very little if at all. There is danger of breaking during hardening. Also, it is easy to get them too hard and brittle, which may result in breakage in use.
320. Sharpening Chilled Shares.—Chilled iron shares cannot be forged. They must be sharpened by grinding or chipping on the top side. Chilled iron shares are comparatively cheap and are commonly discarded after they are sharpened once or twice.
321. Sharpening Harrow Teeth,—Spike-tooth harrow teeth that have sharp points and sharp square edges are much more effective than teeth that have become blunt and rounded from long use. Harrow teeth are easily sharpened by forging at a cherry-red heat.
They will stay sharp longer if hardened by heating the points back from 1 to 3 in. to a dull red and dipping in water. There is some danger, however, of making them so hard and brittle that they may break in use.
There are many different kinds and grades of iron and steel used in implements and other farm equipment. To be better enabled to repair such equipment, a mechanic should know something about the different kinds of iron and steel and their properties and uses.
322. Pig Iron.—The first step in the manufacture of iron and steel is to extract the iron from the iron ore, which is mined in various parts of the world. This is done by means of the modern blast furnace. The molten iron accumulates at the bottom of the furnace and is drawn off into sand molds and allowed to cool and form short, thick bars known as pig iron. Pig iron is then used as the source from which other kinds of iron and steel are made.
323. Cast Iron.—To make castings, the pig iron is remclted, together with small amounts of scrap iron, and poured into molds of the desired shape and then allowed to solidify. Cast iron is used extensively because it is cheap and can be readily molded into complicated shapes. It is hard and brittle and cannot be bent. It cannot be forged or welded in the forge fire, but it can be welded with the oxyacetylene torch. It crumbles when it is heated to a bright red or white heat. It can be drilled and sawed easily and also filed easily after the hard outer shell is removed. The quality of cast iron can be controlled by varying the amounts of scrap iron and steel mixed with pig iron when it is melted. ,
324. Chilled Iron.—Chilled iron is cast iron that has been made in special molds, sometimes water-cooled molds, that cool the outer portions of the casting rapidly,- thus making the surface of the casting very hard and wear resistant. Chilled iron is used for bearings on certain farm machines and for shares and moldboards of plows that are to be used in gravelly or stony soils.
325. Malleable Iron.—Malleable iron is cast iron of special composition that has been treated, after casting, by heating for a long period. This prolonged heating removes some of the carbon from the surface of the casting and reduces its brittleness. Malleable castings are softer and tougher than plain eastings and can be bent a certain amount without breaking. They are also more shock resistant.
326. Wrought Iron.—Wrought iron is practically pure iron with only very small amounts of carbon or impurities. It is made by removing the carbon and impurities from pig iron. The best grade of wrought iron comes from Norway and Sweden where the purest iron ores are rained. Wrought iron was formerly used extensively by blacksmiths, but, because of its high price, its use at present is quite limited. Wrought iron has about 0.04 per cent carbon.
327. Mild Steel.—Mild steel, also known variously as machine steel, low-carbon steel, soft steel, and blacksmith iron, is the common material used by blacksmiths. It is made by removing practically, but not quite, all the carbon from pig iron. To remove it all would be much more expensive. It contains from about 0.1 to 0.3 per cent carbon, not enough to enable it to be hardened to any appreciable extent by heating and quenching in water. It can be bent and hammered cold to some extent and can be forged and welded in the forge. It is a little more difficult to weld than wrought iron.
328. Tool Steel.—Tool steel is made from pig iron by first removing all the carbon and practically all the impurities and then adding a definite, known amount of carbon. Tool steel contains from about 0.5 to about 1.5 per cent carbon. It is granular in structure instead of fibrous or stringy. It must not be heated higher than a bright-red or low-orange heat, or it will become honeycombed and therefore weak and brittle. The higher the percentage of carbon the harder the steel may be tempered, and the more difficult it is to weld. Blacksmiths' tools, such as hammers and cold chisels, are commonly made of steel having from 0.5 to 0.9 per cent carbon. Taps and dies and such tools are made of steel having 1 to 1.25 per cent carbon. The carbon content of iron and steel is designated by points, one point being one-hundredth of 1 percent of carbon. Thus a 50-point. carbon steel contains 5%oo or one-half of 1 per cent of carbon.
329. Distinguishing between Grades of Steel.—A good way to distinguish between the various grades of steel is to grind them on a grinding wheel and note the sparks that are given off. Sparks from wrought iron are light yellow or red and follow straight lines. Sparks from mild steel are similar but more explosive or sprangled. Tool steel gives off sparks that are lighter in color and still more explosive. The higher the percentage of carbon in steel the brighter and more explosive are the sparks.
330. Soft-center steel consists of a layer of mild steel welded between two layers of high-carbon steel. The outside surfaces can therefore be hardened, while the center remains comparatively soft and tough. It is used in moldboards of plows and in cultivator shovels where it is desired to have a very hard outer wearing surface combined with toughness and strength.
331. Alloy Steels.—Small amounts of one or rnoro other metals, Fia. 277.—Different grade« of iron and such a« tungsten, nickel, chromium, silicon, vanadium, etc., are commonly The hi«her the carbon content of the steel, mixed with steel to form alloy steels. ^£ighter Md """ ox*>loaivo the These metals are used in steel to give certain desirable properties, such as great, strength, resistance to corrosion, toughness, and resistance to shock.
309. (a) Why should the welding lire be deep, clean, and compact? (b) How often should the fire be cleaned when welding?
310. (a) What is meant by scarfing? (6) What are the characteristics of a good scarf? (c) Why are long thin pieces hard to weld? (d) Why are irons usually upset before scarfing?
311. (a) What materials may be used for welding flux? (6) When and how is it applied? (c) Just how does a flux assist in welding? (d) What kinds of iron and steel, if any, may be welded without flux?
312. (a) What precautions should be observed in heating irons for welding? (b) What should be done in case one iron heats faster than the other? (c) Why should the »scarfs be down instead of up just before the irons are removed from the fire for welding?
313. How may the welding heat be recognized?
314. (a) Outline the process of making a welded chain link or a ring. (6) What is the general shape of the link scarf? (c) Why is it important to have the ends lapped at about 90 dcg. when they arc being welded? (d) Why is the link given a sharp rap over the edge of the anvil just, after it is taken from the fire and before the ends are welded together? (c) Why should the weld be started with only medium and not heavy blows? (J) How may the welded |>art of a link or a ring be neatly and amoothly finished?
316. (a) Explain and be able to demonstrate how to quickly take two irons out of the fire and place them accurately on the anvil for welding. (6) Should the thin edges of the scarfs be welded down first or last, or at some other time? Why? (c) After a weld is completed in a round rod, just how should the welded section be neatly smoothed and brought to size?
316. (a) What are common causes of failure in welding? (6) What procedure would you recommend in ease irons do not stick at the first, attempt to weld? At the second or third attempt?
317. (a) Just how would you proceed to make a welded eyebolt? (6) How may the work be done to prevent marring and drawing the stem next, to the eye?
318. (a) Just how should a steel plowshare be placed in the fire for heating? (6) How much of the share should be heated at a time? (c) What is the proper forging heat for steel plowshares? (d) Should the share be hammered on the top or on the bottom side? (e) What important points should be observed in shaping the share?
319. (a) How may plowshares bo hardened? (6) What kind of shares should be hardened very little if at all? Why?
320. How are chilled iron shares sharpened?
321. (a) How are spike-tooth harrow teeth sharpened? (6) Should they bo hardened? If so, how?
322. (a) What is pig iron? (6) How is it made? (c) For what is it used?
323. (a) How are castings made? (b) What are some of the important properties or characteristics of cast iron?
324. (a) What is chilled iron, and how is it made? (b) What, are the main uses of chilled iron in farm machines?
326. (a) What special property does malleable iron have? (6) How are malleable castings made?
327. (a) How is mild steel made? (6) By what other name« is mild steel commonly known? (c) What are its important properties or characteristics?
328. (a) llow is tool steel made? (6) What are the chief differences between tool steel and mild steel? (c) How is the amount of carbon in tool steel commonly designated? (d) How much carbon is contained in steel used for making black-smithing tools like hammers and cold chisels?
329. Just how may one distinguish between the various grades of stocl?
330. (a) What is soft-center steel, and how is it made? (b) What are its particular advantages over other kinds of steel? (c) In what parts of farm machines is it commonly used?
331. (a) What is an alloy stoel? (b) What materials or metals are commonly used in making alloy stoels? (c) In what respects may allow steels be better than plain steels?
Schwarzkopf: "Plain and Ornamental Forging." Radebauoh: "Repairing Farm Machinery." Friese: "Farm Blacksmithing." Harcourt: "Elementary Forge Practice." Boss, Dent% and White: "Mechanical Training/ Smith, Robert H.: "Agricultural Mechanics." S»xvii>ge and Alltox: "Blacksmithing."
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