RESEARCH Produces Better Vehicles
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THE,acklition of copper to steel has been found to increase both the yield and tensile strength, and the ratio of yield strength to tensile strength, without materially affecting the ductility. With additions of more than about 0.6 per cent. copper, steel, high in manganese and silicon, can be precipitation hardened without quenching in a liquid.
Because a super-saturated solution of copper in ferrite is 'obtained by very slow and uniform cooling, sections as large as 8-in, can be hardened throughout by tempering after normalizing. If a cast copper-steel contains less than 0.2 per cent. of carbon, it will be readily weldable. Copper-steels are more resistant to scaling during heat treatment than plain ca rb o n or carbon molybdenum steels.
Cylinder Liner Material
Nickel-chromium-alloy cast iron is being employed for enginecylinder liners mounted in aluminium-alloy cylinder blocks, because the expansivities of the two materials are similar. Advantages of resistance to wear and corrosion are also provided. Obviously, this combination provides good maintenance of metal-to-metal contact in the operating temperature range.
Moreover, the shrink fit required to accommodate nickel-chromium-alloy cast-iron liners in aluminium blocks is considerably less than that required for grey iron or steel liners. Other examples of the use of high-expansion types of nickel-chromium cast iron are with 18-8 stainless steel inserts.
Compression-ring materials for oil engines, have been developed with the object of obtaining greater strength and tension with no sacrifice of wearing ability. The decrease in ring widths calls for greater strength in order to avoid breakage under heavy combustion loadings. Moreover, tests have generally indicated that the employment of a higher unit-pressure wilt produce better sealing and longer life.
Ring Cast Irons
Metallurgical research and the development of centrifugally cast material with carefully controlled heat treatments, have brought ring cast irons with physical characteristics approximating to those of steel. Changes in alloying have made it possible to produce materials of varying qualities, so that a material can be selected with the desired characteristics for each application. The general result of this work is that piston ring material is now stronger than that produced before the war, and will give longer life, in addition to better performance.
Mass production of a new aluminiumalloy, having a compressive yield strength about twice that of ordinary structural steel, and a tensile strength greater than that of any aluminiumalloy now used, has recently been announced. The alloy has a compressive yield strength of about 67,000 lb. per sq. in.
A coating composition for vehicle refinishing, that prevents "bleed through" of maroons and reds, is now available. It is a pyroxlin product applied directly to the old red or maroon finish, and is fast-drying and extremely adhesive. The coating requires no special skill or technique in spraying.
For welding low-alloy cast steel or low-alloy, high-tensili, rolled steels in the flat position with a.c. or d.c. straight polarity, a new electrode has been developed. This is specially designed for high-speed welding of grooved joints and horizontal fillets. The electrode is available in four diameters, from 5-32 in. to f in.
Repairing Cast Iron
A cast-iron soldering rod, for repairing cracks in cast iron, has also been developed. It combines ease of application with satisfactory results, because it produces corrosion-resistant welds. It is also used for sealing and filling cracks and blowholes, and for building up, where high strength is not required. It melts at a low temperature-316 agrees C.—and tins rapidly. It has many applications in commercial vehicle repair and maintenance.
Black break is a condition in silicontungsten spring steel, which manifests itself in the form of black bands or areas on the surface of a fractured spring. Steels having black break are physically inferior. A study has been made to determine the cause of black break. The blackening is caused, it is found, by graphite.
The chemical composition of the steel affects it to a marked degree. Lowering the carbon, silicon and tungsten contents and, particularly, raising the chromium content, diminishes the tendency of the steel to precipitate graphite, and hence the tendency to black break.
Vast possibilities for making many different products at greatly reduced cost have been opened up by the technique of extruding cold steel, developed by the Germans. By this means, cold steel is made to flow under pressure in• the
same way, when extruded, as tin, lead, copper, brass and aluminium. The process has already been perfected in the United States, and will soon be ready for commercial use. Cold extrusionis carried out with mild low-carbon steel. The material is formed by pressure of a punch in an open die, a shoulder on the punch forcing the steel through the die opening.
The great discovery of the Germans lay in finding the method of lubricating the steel, so that it would flow through the die. This was achieved by a variation of the bonderizing process, which chemically transforms the surface of steel into an insoluble phosphate of the iron. The coating holds lubricant so as to form a film between steel and die.
Brazing Aluminium Another discovery is a new means for brazing aluminium sheets together. On one• side of the aluminium sheet is a layer of aluminium alloy, with a slightly lower melting point than the rest of the sheet. The two sheets are placed together with the alloy face on. the inner side. Then the assembly is heated to the point where the alloy will melt and fuse, but not hot enough to melt the sheetsthemselves. Heat is transferred to the sheets, through a metal die designed to fit them., at a fusing temperature of 580-620 degrees C.
Roplacement of the glass windows in vehicles by . acrylic resin sheets has done much to eliminate injuries from flying glass. Plastic panes have remained unscratched and unstained after months of use under temperature conditions ranging from —45 degrees F. to + 120 degrees F.
Pre-fabricated lorry bodies in 12-, 14and 16-ft. lengths are being assembled by dealers in America in 10 operations in 10 man-hours. The units arrive from the factory with the primer coat, ready to be finish painted. To assemble these bodies, foundation strips are first laid, and the steel-ribbed floor unit installed. Then the side panels, with or without doors, are placed in position, to be followed by the rear panel, which is then welded.
Welding on the Farm
Fitted out with a large stock of welders' supplies, a lorry is being used effectively in America in selling to farmers, factories and welding shops in the more remote areas, and is meeting with great success. A new brake-facing process has been invented, in which the brake facings are cemented to the shoes, eliminating rivets. More braking surface is thus provided, and the scoring of the drums eliminated.
Russia lays claim to a new method Qf welding by which it is possible to weld up to 650 ft. per hour, with an accompanying saving in power and increased quality. Two pieces are fused, after which the filler metal comes to the joint in a molten state. In America, brakes, clutches, doors and windscreen wipers are being operated hydraulically without preventive maintenance. It is believed that hydraulic actuation will eliminate some of the problems inherent in air systems, giving a better performance, and reducing maintenance.
The system operates at pressures between 800 and 1,100 lb. per sq. in., the pump operating or cutting out automatically when critical points are reached. The storage accumulator—au 8-in.diameter hollow steel ball—is divided
into two compartments separated by a diaphragm. One side confines the permanent charge of compressed air, acting as a spring against the oil stored on the opposite side of the ball.
The clean hardening of finished alloy steel parts with a light case and with minimum size change, is being achieved by the new process termed carhonitriding. The basic atmosphere is 20 per cent. CO, 40 per cent. H,, and 40 per cent. N,, to which are added carefully measured hydrocarbon gas and
ammonia. File-hard, wear-resistant surfaces arc achieved quickly at fairly low temperatures.
The process is said to be cheaper than liquid cyaniding, and to give a greater depth of hardenable case, in a given time, than in normal case-hardening. Distortion is minimized, and both plain carbon and alloy steels respond to the • process, which is not dangerous to the operators, as may be the case with fused cyanide salts. Wear resistance is greater than with normal hardening.