Advanced Practice in Metal Processing
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Notable Among Advances in Current Metallurgical Progress is the Growing Industrial Use of Working Systems Designed to Economize in Time and Material and to Diminish Rejects. Internal-combustion-engine Production Has Already Benefited by These Innovations
AN infra-red spectrometer has been developed for the analysis of hydrocarbons. This instrument ' enables quantitative or qualitative analysis to be made of high-octane fuels and similar complex mixtures, for which chemical analysis proves too difficult or takes too much time. An electric Nei gauge is accurate to within 5 per cent„ even under extreme conditions of climate and altitude. The gauge makes it • possible to carry just the right amount of fuel, so that the weight ordinarily provided for surplus fuel is convertible to pay-load.
Continuous-cast Bronze A continuous casting process has been developed for producing uniform mill length rods of a number of bronze alloys, formerly obtainable only as sand, permanent-mould or centrifugal castings. The rods can be made on automatic screw machines, and render feasible great economies and improved production. In the casting process, the metal is continuously withdrawn from the bottom of a crucible, passed through a die, and cut into lengths by a travelling cut-off device.
• A grease fitting has been introduced for use on heavy vehicles. It combines the most advantageous features of lubrication fittings used on war-time equipment—a ball check flush with the top of the fitting to prevent dirt or foreign matter from lodging in the opening and being forced into the bearing; a large grease passage, allowing greater volume of Lubricant flow; a bearing pad for couple jaws, equalizing distribution or wear on both jaws and the fitting itself; and a noncollapsible spring that cannot be forced out.
From U.S.A. comes a new steering trailer, the Hoobler undercarriage. This is a mechanical device for the support of van, high-side, flat-top and tank semi-trailers. It allows drivers of long vehicles to make rightward turns easily, even into narrow streets, without any of the tyres touching either kerb. The rear fifth wheel is designed so as to support the rear end of the trailer bed, and is the connecting link between the undercarriage and semi trailer. Pull is all on the rear fifth wheel, and this connection allows the undercarriage to swing as a unit.
A new aluminium product is employed for pressure-bleeding motor vehicle hydraulic brake systems. Charged from an airline, the unit carries its own air pressure, thus simplifying the servicing of such brakes. With one job completed, it is readily transported to the next.
A new hydraulic steering control renders easy the steering of large vehicles provided with big tyres. The steering wheel is employed solely as a valve lever for regulating the flow of oil forced into wheel cylinders to operate the front axle.
To ensure even and quick penetration of small or complicated parts in case-carburizing, a new" installation employs a high-pressure fan immediately below the work, so as to swirl carburizing gas at the required temperature into every crevice of the charge. In one instance, it is claimed that a 40 per cent, increase in output was obtained on transmission gears, spindles, etc., and the parts emerged free from scale.
Pre-cleaning of metals in advance of welding maintains the contact resistance uniform, and lessens electrode pick-up. For this cleaning, an etch paste is being produced. It can be painted on to metal, and washed off with water. A corrosion-resistant coating for aluminium alloys is being produced by simple immersion, calling for no electric current, and giving considerable resistance to attack.
Commercial cerium, more commonly known as " mischmetal," has been experimented with and employed in both aluminium and magnesium as a minor alloying element. Difficulties, such as proper alloying methods and accurate analysis. of the cast product, have been overcome, and it is possible that the addition of cerium will become standard in a range of light alloys, because certain properties have definitely been improved upon in both cast and wrought parts.
Metallic-zinc Pigments Of the methods available for the protection of iron and steel in use, it is now being claimed that the employment of paints so richly pigmented with metallic zinc as to constitute practically a galvanized coating offer distinct possibilities particularly in the prevention of corrosion fatigue.
Magnesium alloys are now being cast by a continuous casting process, even when direct liquid cooling is used. Continuous casting is definitely being used on a production basis, and improvements are said to result from its use, as well as technical and economic advantages. A new method of metal fabricatia is known as tangent bending. It is a cross between press forming and straight bending, in which the metal flows during the bending operation, its shape being controlled by a die.
A practical, precision machine with a' planetary grinding head called the jig grinder has been developed, and has rendered commercially possible the final positioning and sizing of holes in hardened work on a machine-shop basis.
Negative radial-rake angles in face milling have been found to. produce 4 stronger cutting tips, When tungsten carbide tools are used. The power required at the cutting edge is higher for the negative radial-rake cutter than for cutters with positive radial-rake angles, but the cutters with the negative rake angles will stand up longer at the higher speeds. Wear and failure at high speeds on the cutting edges of a positive rake-angle cutter soon increase its power consumption above that of a cutter with negative rake angles. The best surface finish in highspeed milling is produced with a negative radial-rake angle cutter at cutting speeds between 500 and 800 ft, per min.
Simplified involute Splining Involute splines are being broached in a hardened, bell-shaped hob. After the forging has been machined in turret lathes, the bore is broached to form the involute splines in the hub in the soft condition. Cylinder heads and sleeve cranks are being machined from light alloy castings. The special design of the cylinder head is necessitated by the use of sleeve valves that move on the cylinder heads with a combined reciprocating and turning motion, so that the heads may be likened to fixed pistons. To provide for the cooling of the heads when the engine is in use, the castings are hollow. Each casting has a ringgroove machined in it, and in the finished engine it carries two sparking plugs.
Flame gouging and welding as a means for removing and repairing structurally unsound areas in critical castings have reduced casting repair costs. The more searching inspection• methods now in general use have shown that repair welding can be eliminated to a great extent by provision for sub-sectioning and weld location in the casting design. Flame gouging-welding techniques for casting repair are being rapidly developed.
Carbon chromium and nickel • chromium-molybdenum steels remain standard for ball and roller bearings, despite experiments with numerous alternative steels. Alloy steels are being increasingly used for automobile bolts because of their hardenability, although there is no difference in ductility or, in general, in fatigue strength.
Aluminium permanent-mould castings were standard parts in many mobile engines before the 1914-18 war. It is expected that, because of a great reduction in the price of castings, they will be used in many new applications in the new automobiles. Close co-operation between foundry and•consumer, and of certain operations that directly bear on low-cost production are expected. to facilitate this,
Aluminium, overhead, garage doors constitute a new and excellent outlet for this metal. Apart from the lightweight feature of aluminium for such a structure, the mechanism of the door is installed in a small metal box that can be placed in an upper corner out of the way. This allows for low garage styling.
A new high-tensile machining steel is delivered beat-treated with a guaranteed tensile strength of 56 tons/sq. in., or even higher. It is easily machined, reliably homogeneous, and uniformly hard. It is used for crankshafts, gears, shafts, and miscellaneous parts.
To speed up the operation of checking crankshaft bearings, a special checker has been invented. The crankshaft is placed on four rotating discs, and a number of indicators is brought into position and the crankshaft is revolved. One indicator can be furnished for each bearing. The four discs roll, on accurate and supersensitive ball bearings. The bases are made in two lengths, 42-in. and 64-in.•Larger checkers can be made if required.
New All-purpose Electrode
An all-purpose mild-steel electrode for welding and repairing east iron is quite new and entirely different in operating properties from any other. It fuses well with either mild or mediumcarbon steel, so that it is ideally suited for uniting cast iron with other types of steel. With a yield point of 22 tons/ sq. in., the deposited metal has an ultimate tensile strength of 25 tons/ sq. in, (roughly double that of a good grade of cast ifV32). It can be employed with either az. or d.c. machines (straight or reverse polarity on dg.), and works well at low amperage, thus minimizing the dilution effect at the fusion zone, and permitting better quality machining. Reverse polarity on de. current produces a smooth bead with deep penetration. On d.c. straight polarity, penetration is less, higher beads are built, and there is less spread in the fusion zone. In either instance, as with a.c. current, a sound, deep weld can be obtained for any good quality of cast iron.
Motor-engine crankshafts are being forged in large high-speed forging presses. In some instances only three blows are needed in place of the 12 to 15 necessary with a steam hammer.
A method of silver-soldering tubularsteel parts in a furnace has been perfected; the parts are of heat-treated 1 per cent. chromium steel. The silver soldering is carried out at 650 degrees C., and the joint produced has extremely high-tensile and shear strengths after the operation.
A degreasing plant incorporates an activated-carbon unit for recovering the trichloretbylene. As the system is completely enclosed, no harmful vapours escape into the shop, and about 90 per cent. of the trichlorethylene is recovered.
A new alloy is designed for facing valves of internal-combustion engines. It contains nickel, chromium, cobalt and tungsten, and is applied by welding into a groove cut in_ the valve head. Temperatures of 540 to 820 degrees C. are said to have little effect on the hardness of the alloy.
A new metal sorter identifies steels, and metals and alloys of non-ferrous type by using the triho-electric effect. The sample to be tested is rubbed against a metallic specimen of known character. When the two objects differ in chemical or other metallurgical content, an. electric current is generated and registered. When the two parts are of identical type, no current is registered. The instrument does not injure finished products in testing, and is controlled by a unit containing a measuring circuit, an electronic bias supply, and a timing circuit operated by a thy ratron.
Nuts and bolts are prevented from sticking as a result of corrosion by means of an anti-freeze paint, with which they are first treated.
A high lead, tin-free alloy is being introduced for crankshaft bearings, and is capable of standing up under heavy loads at high speed. It contains 35 to 40 per cent. lead, 41 to 5 per cent. silver, the balance being copper with a trace of iron. By special casting machine process, it is coated on both sides of 0.075-in, steel strip, and then formed into bearings.
Potassium titanate is being advocated as a coating for welding rods. It is milled so fine that 96 per cent, passes through a 200-mesh screen. In addition to the atandard qualities of rutile coatings, it is also featured for am stabilization.
A method of coiling and stretching cold rolled strip into tubular forms has been perfected. It permits the making of spirally coiled tube with inor outside fins; open seamed coils; or edges overlapped with protrusions either inside or outside.
Continuous Battery Charger .
Civilians may soon have a battery charger that remains in the motor vehicle to supply continuous power. The charger is one that was used during the war on all types of vehicle and radio set.
To cheek the accuracy of piston rings, an electronic instrument is being manufactured which actually inspects the truth of periphery and the width of gap of a specific size of ring by automatic means. The piston ring is inserted inside a master ring of correct dimensional quality, which is rotated by a power-driven roller. The gauging functions are performed by scanning beams of light directed on to phototubes which energize electronic circuits to illuminate three signal lights. The inspection cycle per piece is less than five seconds LS.