• FACE

    A nonstandard term for WELD FACE.

  • FACE BEND TEST

    A test in which the weld face is on the convex surface of a specified bend radius.

  • FACE CRACK

    A crack that appears on the face of a weld or on the crown bead(s), which runs either parallel with (i.e., longitudinal) or perpendicular (i.e., transverse) to the direction of welding. 

  • FACE FEED

    The application of filler metal to the joint, usually by hand, during brazing and soldering. 

  • FACE OF WELD

    The exposed surface of a weld on the side from which the welding is done, regardless of the process.  See WELD FACE. 

  • FACE REINFORCEMENT

    Weld reinforcement on the side of the joint from which welding was done. See also ROOT REINFORCEMENT. 

     

  • FACE SHIELD

    A device positioned in front of the eyes and over all or a portion of the face to protect the eyes and face from arc light, weld spatter or expulsion, slag popping, or chipping and grinding. See HAND SHIELD and HELMET. 

  • FAHRENHEIT

    A thermometric scale on which 32o is the freezing point and 212o is the boiling point of water at standard atmospheric pressure.

    Fahrenheit temperature is converted to the Celsius temperature scale by the formula oC = 5/9 (oF -32).

    The formula to convert Celsius temperature to Fahrenheit is oF = 9/5 oC + 32. 

  • FALSE RESISTANCE

    The resistance of counter electromotive force. 

  • FAN

    A common name for the arc stream in atomic hydrogen welding. See ATOMIC HYDROGEN WELDING. 

  • FARAD

    A unit of measure of electrical capacitance equal to the capacitance of a capacitor with a potential of one volt between its plates when the capacitor is charged with one coulomb of electricity; formulated by physicist Michael Faraday in 1867.

  • FARADAY

    A measure of the quantity of electricity transferred in electrolysis per equivalent weight of the element or ion equal to approximately 96 500 coulombs of electricity. 

  • FARM IMPLEMENT REPAIR

    Farm implement repair is of ongoing importance to agricultural communities and the welding shops which serve them, and constitutes a challenging variety of repair work for the welder.

    The first step in the repair of farm implements is to identify the metal that the broken component is made of, and that will determine the process and filler metal required for the repair. Many components of farm implements are castings which are made of malleable iron, and should be brazed as described under CAST IRON, Malleable.

    Tractor Wheels

    Modern tractor wheels are fabricated with forged steel, aluminum, and sometimes magnesium, and can be readily welded. If a forged steel hub spoke breaks loose, the repair can be made with shielded metal arc welding (SMAW). See SHIELDED METAL ARC WELDING; See also ALUMINUM and MAGNESIUM.

    Older tractor wheels were made with cast iron hubs, with the spokes cast into the hub at the time the hub was made. The spokes were riveted to a steel rim, and repairs were made by brazing. If a spoke of an older wheel is broken loose in the hub, it should be cut free where it is riveted at the rim and then brazed to the hub, using as little heat as possible. After the brazing has been completed between the spoke and the hub, the other end of the spoke can be quickly welded to the rim with steel welding rods, and the distortion of the rim will be very slight. It is necessary, however, to wait until the spoke and the braze at the hub are cold before making the weld in the rim.

    Plowshares

    Plowshares are made with various grades of steel for service in different types of soil. One type of plowshare is called a crucible share, probably because it was originally made with crucible steel. Most of these shares are made of open-hearth steel containing approximately 0.55 to 0.65% carbon, varying with the manufacturer’s specifications.

    Another type is a soft-center plowshare. It is a tough plowshare with hard outer surfaces that will withstand rough usage. This type is made of three sheets of steel placed together; the center section is a low-carbon steel and the outside faces are steel with a higher carbon content. These three sheets of steel are preheated and welded together, using SMAW.

    A third type of plowshare is made of chilled cast iron (white iron) and is used in districts where the soil is partly composed of sharp sand. Chilled cast iron is very hard and very brittle, consisting largely of cementite. If used in a district where stones or rocks are part of the soil, this type would be subject to breaking.

    The soft-center share has a hard surface, and while not as hard as chilled cast iron, it is tougher. The crucible steel share is hardened throughout and is used in many soils where other types are not practical.

    Repairs

    If the point of the plowshare has worn off, it can be repaired by cutting off the old point and welding a new forged point to replace the old one.  If the edge is completely worn down and the point is gone, it may be necessary to use the “three-piece method” of repair, a process in which three new pieces of high-carbon steel are welded to the old share to build it out to its original shape. In this process, an edge piece, or blade, and two point pieces (one placed under the share and the other on top), are welded together to form a new point. High-carbon or alloy steel welding rods or electrodes are recommended for the edge and in building up the point; but if desired, low-carbon rods can be used on the land side where the wear is not as great.

    One-Piece Design

    Another method commonly used consists of welding a new part to the old share, which amounts to a rather wide cutting edge and point forged all in one piece. The worn portion of the share is cut off with a cutting torch, and the new section is clamped to the old section or held in a jig. The weld is made with a gas or arc torch.

    Forged Point

    If the cutting edge of the share is not so badly worn that an entirely new edge is necessary and only the point is worn away, the worn point can be cut off with the cutting torch and a new forged point welded to it. The original shape of the share should be carefully preserved so that it will have a controllable digging effect. These forged points are available in a grade of steel which can be heat treated and will produce an acceptable repair job. The electrode or welding rod must match the grade of steel in the plowshare as closely as possible. If they are not well matched, the repaired section might wear hollow or form a groove along the weld.

    Welding Rods and Electrodes

    Many welders make the mistake of welding parts, including forged points, to the plowshare with a welding rod or electrode that is too low in carbon. Most plowshares are heat treated after welding, and unless the weld metal is high enough in carbon content, it will remain soft and unaffected by the heat treatment. This means that there will be a soft spot which will wear to a greater extent than the harder metal on both sides of the joint.

    Low-carbon rods are not recommended for this type of work. Many high-strength rods and electrodes are available which contain more carbon, and some contain alloying elements such as chromium, nickel, and vanadium, all of which will produce a better grade of weld metal for these repairs. Although these rods are more expensive than the low-carbon grades, the rods should be selected to match the steel in the plowshare,

    the points, edges and other parts, (which are also expensive). This will accomplish the purpose of the repair, which is to make a serviceable joint. When a soft, low-carbon steel rod is used, the weld metal will not harden in subsequent heat treatment. Some welders make a practice of welding the land side of the share with low-carbon rod, and use a high-carbon rod on the edge and share portion. Even this is poor practice because the combination of unlike steels in the adjacent parts makes it impossible to harden the land side weld in any subsequent heat treatment.

    Heat Treatment

    After the weld has been made, it should not be hammered while still heated by the torch or arc, but should be allowed to cool, then reheated to the proper temperature and forged. During welding, strains are set up in the metal and the heat is irregular. If forging or hammering occurs just as the weld is completed, these strains have not yet adjusted, and the entire area surrounding the section being hammered is not at the same temperature. It may be at red heat immediately at the weld area, but this red tapers off to a black, or lower heat. For this reason, it is a much better practice to cool the weld; then reheat the workpiece and forge, reheat again, and cool; subsequently applying such heat treatment as may be necessary to produce the required hardness. Steel which is too high in carbon content and tempered to too great a degree of hardness may be too brittle for the purpose, so the exact heat treatment to produce the required hardness can only be determined by the knowledge and experience of the welder.

    Hardfacing

    Hardfacing a plowshare can increase the effective service life by three to five times, depending on the abrasiveness of the soil in which it is used. See HARDFACING.

    The metal used for hardfacing may be deposited on the underside of the plowshare, as indicated in Figure F-1, and on the top of the point, which will permit excellent scouring of the top of the share. In some localities welders prefer to deposit the hardfacing metal on the top and allow the underside to be sharp- ened by wear. In this application, the hardfacing must be ground smooth so that proper scouring will take place. In some soils scouring is not as important as in others, and the welder may find that a hardfacing deposit on the top side will be preferable.

    Another consideration is the type of metal which should be used for building up a badly worn implement. If the part were new, it would be necessary to hardface only the wearing surfaces with a grade of alloy suitable for its expected service. New parts, however, are not always hardfaced, or they are not hardfaced often enough to prevent the wearing down of the points and becoming blunt, dull, and very different compared to their original shapes. When in this condition, the point should built up to its original shape before the hardfacing metal is applied. 

    If an ordinary steel welding rod is used to build up the point, the weld metal will be much too soft to stand up during service, and the hardfacing might be pounded down into the softer undercoating. Special high-carbon steel or other alloy rods are made specifically for building up the point to its proper shape before hardfacing rods are applied to it. Since hardfacing rods are made of expensive metals, however, it is an acceptable practice to build up the part almost to its original shape with a less expensive metal which will answer the requirements for hardness and strength, and then overlay the surface with the hardfacing metal.

    Broken Gear Teeth

    A relatively simple job which frequently comes into the farm shop is repairing cast iron gears with one or more broken teeth. Gear teeth can be repaired or built up using the oxyacetylene welding process with a good grade of cast iron or bronze rod.  With either cast iron or bronze rod, the important requirement is using a flux. The metal should be deposited carefully to minimize postweld grinding. A No. 7 tip with neutral flame is recommended for this purpose.  The job of rebuilding or replacing the internal teeth on the power lift wheel of a plow is somewhat more difficult because it is impossible to grind the teeth to size after the rebuilding job is complete. The teeth must be carefully shaped and sized with the torch during rebuilding. A cast iron deposit seems to offer the only successful solution for jobs of this nature.

    Ensilage Cutter Blades

    Ensilage cutter blades which have been broken or nicked can be repaired using the following method:

    (1) Place a 6 mm (1/4 in.) square bar of medium carbon steel along the tapered side of the blade, with the blade laid flat and resting on the steel bar.

    (2) Make several tack welds with the arc welding torch.

    (3) Make an arc weld in the groove formed by the square steel bar and the tapered face of the blade.

    (4) Turn the blade to rest on the side to which the bar has been welded, which is the back of the blade.

    (5)Apply hardfacing. The hardfacing material fills the opening between the square steel bar and the old edge of the blade.

    (6) Grind on the back to smooth the hardfacing metal, and grind a new taper on the front of the blade to form an edge in the hardfacing. Blades can be repaired in this way even though badly chipped or nicked. Often the hardfacing on the back of the blade is applied with the torch. Cutter blades are ordinarily made of high-carbon steel, in the range of about 0.70 to 0.80% carbon.

    Based on the representative descriptions of these repair jobs, it is obvious that the job shop welder must master a variety of tasks, although almost every break will be in some way similar to the one which has previously been fixed. See CAST IRON, Arc Welding; CAST IRON, OXYACETYLENE WELDING, BRAZING,CARBIDE TOOLS; TOOL BRAZING, TOOL WELDING, HARDFACING, ELECTRODE, STEEL, Cast; MAGNESIUM ALLOYS. 

     

  • FATIGUE LIMIT

    A stress level below which the metal will withstand an indefinitely large number of cycles of stress without fracture. When stress is above the fatigue limit, failure occurs by the generation and growth of cracking until fracture results in the remaining structure. If the term is used without qualification, the fatigue limit is usually the number of cycles of stress necessary to produce a complete reverse of flexing stress. See FATIGUE STRESS. 

  • FATIGUE STRESS

    The maximum stress which a material will endure without failure no matter how many times the stress is repeated. 

  • FATIGUE TEST

    A destructive test used to measure the stress to cause failure by fatigue in a material, part, structure, or weldment after applying a fixed number of cycles of load. Generally, the stress to cause failure is plotted against the number of load cycles on a logarithmic scale. In fatigue testing, it is important to decide on and document the repetitive loading cycle, including base (minimum) load and peak (maximum) load, and frequency of loading. Loading is usually expressed as a ratio, R = maximum stress/minimum stress, considering compressive stresses as positive (+), and tensile stresses as negative (-), so that load reversals between tension and compression result in a negative (-) value of R (stress ratio).

    Testing for the fatigue strength of a material is so laborious that many materials have not been tested at all, so data is simply not available. In some cases the material has been tested by a user, and the resulting data is often treated as proprietary and is not available in general references or in the open literature. For a hard steel, a test of 2 x lo6cycles duration is necessary to establish a definite fatigue strength. For soft steel, a test of lo7cycles duration is necessary, while for aluminum and magnesium and many other non-ferrous metals and alloys, 5 x lo8 cycles may be necessary, since these materials exhibit an endurance limit, or stress below which the material could sustain an infinite number of loading cycles without failing.

    There are many types of fatigue testing machines. Most commonly used are those which use a rotating beam or rotating cantilever. These rotating tests give a completely reversed stress in which the maximum unit of tensile and compressive stress in the surface of the specimen is equal. The speed of rotation varies with this machine from 2000 rpm to 12 000 rpm.

    Fatigue test specimens can be of almost any size, depending on the amount of available material, although certain standard sizes (as opposed to non-standard, and especially, sub-size specimens) are preferred (e.g., by ASTM). Cross-sectional shape is generally, but not necessarily, round. Regardless of size and shape, to give the maximum and most repeatable test results, the surface of fatigue test specimens must be carefully prepared and finished so that they are free of holes, notches, abrupt changes of cross section, machine (kerf) marks and scratches, and even residual stresses from processing (unless these are expected to be used in service in the actual item). The slightest corrosion or flaw will greatly reduce the fatigue limit of a part in service.

  • FATlGUE

    The phenomenon of the progressive fracturing of a metal by means of a crack which spreads under repeated cycles of stress. Materials subject to vibration stress frequently fail at much, lower loads than anticipated. Investigation discloses that each material has a fatigue stress beyond which it is not safe for repeatedly loading it. 

  • FAYING SURFACE

    The mating surface of a member that is in contact with or in close proximity to another member to which it is to be joined. 

  • Fe

    Chemical symbol for iron. 

  • FEATHER

    See ACETYLENE FEATHER. 

  • FEED RATE, Thermal Spraying

    A nonstandard term for spraying rate. See SPRAYING RATE. See also THERMAL SPRAYING.

  • FERRITE

    A solid solution in which alpha iron is solvent; characterized by a body-centered cubic lattice structure. A pure form of iron, it is very soft, ductile and magnetic. Tensile strength is about 275 MPA (40000 psi). fee CAST IRON, Hard Spots; CAST IRON, and METALLURGY. 

  • FERRITE NUMBER (FN)

    An arbitrary, standardized value designating the ferrite content of an austenitic stainless steel weld (or base) metal. It should be used in place of percent ferrite or volume percent ferrite on a direct replacement basis. 

  • FERRO-CHROMIUM (FERRO-CHROME)

    A material containing iron and chromium used in manufacturing welding electrode coatings and alloy steels. 

  • FERRO-MANGANESE

    A material containing iron and manganese used in manufacturing welding electrode coatings and alloy steels.