US2153702A - Fastening device - Google Patents

Description

G, C. TIGHE gpm u, w39.,

FASTENING DEVIGE .Filed may 22, 1935 Patented Apr.l 11, 1939 PATENT OFFICE mesne ts,

Rustless Iron and Steel Corporation of America, a corporation of Del'- Application May 22, 1935, Serial No. 22,855

3 Claims.

v This invention relates to fastening devices such as studs, bolts, screws and. pins.

Among the objects of my invention is the pro- -vision of fastening devices such as bolts, screws,v

5 studs, pins and the like which are provided with corrosion-resistant and/or heat-resistant portionsthat are adapted to withstand the conditions encounteredv in use, which are strong, tough and readily fabricated from available stock and which are less expensive in material costs,

working costs and machining costs than hereto- I fore known devices of the character indicated.

. The invention accordingly consists-in the combination of elements, features of construction and l5 arrangement of parts and in the several steps and the relation of each of the same to one or more of the others as described herein and shown in the accompanying drawing, the scope of the `application of which is indicated in the following claims.

In the accompanying drawing Figures 1,'2, 3 and 4 respectively represent a bolt, a'screw, a pin anda stud, embodying. the novel features of my invention. As conducive to a clearer understanding of certain features of my invention it may be. noted at this point that in the .aviation and automobile trade, in the dairy, soda-fountain, hospital and kitchen equipment and in the manufacture of a variety of electrical and mechanical machines, testing devices and instruments, there is a demand for screws, bolts, pins and other fastening devices which are strong, corrosion-resistant'and wear resistant and, in many instances, which present a bright, polished head pleasing to the eye.

The demand forA fastening devices such as bolts, pins and studs having either head portions,

40 shank portions or threaded end portionsvwhich are resistant to the effects ofcorrosive agents, either at normal or exceedingly high temperatures, is at present largely supplied by rustless iron and steel products. Rustless iron and steel fastening devices, however, are exceedingly expensive because of the comparatively high initial cost .of the metal and because of the rather great expense of machining thestock metal as by turning, cutting and threading in the manufacture of the desired deviceaarticles or products.

Similarly, this demand for fastening devices having exposed' heads of bright polished metal is supplied by brass, copper and 'iron bolts, screws and pins plated with nickel or chromium. The

@5 brass or copper fastening devices are soft and are (ci. s5-1) but poorly adapted to the conditions encountered in actual use.

Bolt heads of these-metalsare nicked and damaged by wrenches and other tools employed in positioning the bolt. The slotted portions of 5 screws are quickly worn away and otherwise damaged, thereby effectively inhibiting the ready placement and removal of these screws. Similarly, the exposed heads of pins are scratched,

dented and otherwise defaced. s 10 'I'he nickel-plated or chromium-plated iron or steel bolts are of greater strength and have greater resistance to wear than the plated brass or copper fastening devices but the plated surfaces of these screws and bolts-are soon scratched 16 and broken, exposing the underlying ferrous metal. Under the corrosive attack of the atmosphere or other corrosion-fostering media, the exposed ferrous metal rusts disiiguring the head of the fastening device and ultimately causing 20 the plated metal to peel off and expose the greater portion of the underlying ferrous metal. This metal immediately rusts and further disfigures the head ofv the device. Y

A part of the demand' for fastening devices havingy bright, polished heads is supplied by bolts, .pins and screws fashioned of rustless iron and steel. These fastening devices are exceedingly expensive because of the great initial cost ofthe metal employed and because of the comparatively great expense of working and `machining this metal. For example, the production ccst of a bolt fashioned of rustless iron or steel amounts to about six times that of a likebolt fashioned of low-carbon steel. Because of this great cost differential the use of rustless iron and steel fastening devices is severely limited.

One of the outstanding objects of my invention is the provision of fastening devices of the o character indicated having exposed portions which are resistant to corrosion and scaling at both normal and high temperatures, which lend themselves to rapid and emcient production ernploying' a minimum of expensive corrosion-resistant metal and which, for the bolts, screws and pins, have head portions that take a bright nish and that are suiiiclently hard and strong to withstand' the impact and strain of a wrench or other tool without tearing or distortion. 50

In the practice of my invention a fastening device such as bolt lll (see Fig. l) is provided with a rustless iron or steel head portion lila and a low-carbon steel shank portion lilb. The head and shank portions of the bolt ane welded together as at Ilc. The end ofthe bolt is threaded as at Ind.

The rustless iron or steel head portion of the bolt analyzes approximately, 10% to 30% chromium, 0% to 20% nickel, .03% to .3% carbon, with or without supplementary additions. of aluminum, copper, manganese, molybdenum, silicon, tungsten and the like in small amounts and the balance substantially iron. Good results are achieved both where the head portion of the bolt is fashioned of iron or steel comprising essentially 10% to 30% chromium with minor quantities of the additional ingredients and the balance iron, and where it is fashioned of an austenitic'chromium-nickel iron comprising essentially 10% to 30% chromium, 7% to 20% nickel and the balance iron. For most purposes the austenitic chromium-nickel iron is preferred because of its superior working characteristics, an austenitic iron analyzing approximately. 18% chromium, 8% nickel, and the balance substantialy iron being preferably lemployed. 'The straight chromium iron, however, is considerably less expensive and is employed where less severe working operations are encountered.

vSuch an iron ordinarily analyzes about 14% chromium, .10% carbon and the balance iron, although in certain lspecial applications an iron having a higher chromium content is used.

In the production of a fastening device in accordance with `the provisions of my invention a length of rustless iron or steel rod is butt-welded to a length of low-carbon iron or steel forming a composite rod of rustless iron and low-carbon steel. By butt-welding is meant a particular form of electric welding in which a current of great density is passed through two pieces of metal in abutting relation. The weld is clean, strong and in no way brittle. Satisfactory results are achieved in butt-welding lengths of rods ranging in thickness from very smallrods to rods of about six inches in diameter. The limits imposed as to the size of bars or rods which are satisfactorily welded, is the welding apparatus available rather than any limitation inherent in the metals welded.

Where a portion of the fastening device is fashioned of the straight chromium iron or steel there is some hardening of the Weld metal as it cools from the weld temperature down to normal temperatures. Likewise, back from the weld itself there is a zone which has been raised above the critical point of the metal and as the metal of this zone cools from above the critical point it is inclined to harden. Further back from the weld there is another zone of metal which has been raised to a temperature just beneath the critical point. This metal in cooling is tempered and softened somewhat. A minimum variation in hardness along the rustless iron portion of the composite product is achieved for the straight chromium iron or steel where metal of the higher chromium and lower carbon contents is employed.

Where the aus nitic chromium-nickel iron or steel is employed as material for either the head or the shank of the fastening device substantially no hardening of the weld metal or hardening or softening of the metal back of the weld is experienced as a result of the welding operation. An austenitio chromium-nickel steel does not harden by heat-treatment. so that in cooling y from a weld temperature there is no hardening effect. This metal hardens by working, however, and where a length of austenitic chromiumnickel rod is welded to a length of low-carbon iron or steel a hardness resulting from the working of the metal into a rod is partially lost as the result of the heating during welding This softening or tempering effect is minimized by accomplishing the welding operation as rapidly as possible. With a quick welding operation the austenitic alloy iron is maintained at a high temperature for a minimum of time and because of the structural sluggishness of this metal very little softening results.

After the welding operation is complete the composite bar or rod is preferably ground to free it of excess weld metal and then headed either by hot or cold operations. In the production of bolts up to about three-'quarter inch in diameter the rustless iron or steel portion is cold-upset to eiect a desired bolt head. Where larger bolts are .produced the rustless iron or steel portions of the composite rod are preferably hot-worked to achieve desired heads.

In the vfurther production of a bolt the lowcarbon iron or steel shank is cut to a desired length and threaded in any suitable manner. These cutting and threading operations are rapidly and efficiently conducted because of the inherent ease with which low-carbon iron,or steel is machined as compared with rustless iron and steel. The head of the bolt is then given a .desired polish as a finishing operation.

My composite bolt having a rustless iron or steel head 'and a low-carbon iron or steel shank is strong, tough and durable. It presents a head which is resistant to corrosion under a variety of corrosion-fostering conditions met with in use. It is resistant to scaling at high temperatures. It is sufficiently hard to withstand the repeated strain of wrenches employed in positioning and removing the bolt with a minimum of scratching, tearing or other defacing of the bolt head. In addition, such a bolt is produced at a cost comparable to a like sized bolt of iron or steel having a chromium or nickelplated surface and at a cost not prohibitively in excess of the low-carbon iron or steel. bolts which are not resistant to corrosion.

My improved bolt is of wide utility and is employed where bolts having hard, strong heads, which are ornamental in nature and pleasing to the eye 'are desired. For example, bolts of this character are used in automobile bumpers, trunks, tire carriers and the like, they are employed in stoves, refrigerators, cabinets and in similar kitchen and household equipment and they are employed in shelves, cabinets, benches in a variety of apparatus and equipment used in hospitals and dairies. Similarly, these bolts are employedl in numerous indoor and outdoor architectural applications where the bolt head is exposed to the elements.

As illustrative further of my invention attention is directed to Fig. 2 where there is indicated a machine screw I I having a rustless iron or steel head portion I Ia and a low-carbon iron or steel threaded shank portion IIb. The rustless iron or steel head portion and low-carbon iron or steel shank portion are welded together as at Ilc, illustratively appearing up within the head portion.

In Fig. 3 there is indicated a pin I2 comprising a rustless iron or steel head portion I2a and a low-carbon iron or steel shank portion I2b. The shank is pierced as at I2c providing an opening for the key. The rustless iron or steel forming the head portion of the pin and the low-carbon iron or steel forming the shank portion are u aisance united in a weld as at 62d, where illustratively the weld appears adjacent the head of the pin.

A composite stud fashioned of rustless iron and low-carbon steel is illustrated as i 3 in Fig. 4 where a short rustless iron or steel threaded portion 93a and a', long shank portion I 3b having a threaded end part i`3c are welded together as at i3d. Such a stud is of special utility in internal combustion engines, steam turbines, boilers, superheaters, electric motors and the like where y high local heating of a fastening device is encountered and where strength and resistance to scaling at high temperatures are required.

Thus it will be vided in this invention fastening devices, such as bolts, screws, studs, and pins, and a method of producing the same, in which the various objects hereinbefore noted together with manypractical Patent No., 2,155,702.`

advantages are successfully achievedgIt will be seen that these fastening devices are especially useful throughout a wide field of household, industrial and architectural applications where fastening devices subjectr to high local heating or devices presenting'bright, polished heads, pleasing to the eye and fully resistant to the corrosive conditions encountered in use, are desired. It will further be seen that these fastening devices lend themselves to emcient and economical production at a minimum increased cost over heretofore known fastening devices which are in no way resistant to corrosion, and at a costsubstantially less than the cost of fastening devices completely fashioned of a single corrosion-resistant metal.

While as illustrative of the practice of my invention the head portion andshank portion of mycon'iposite fastening device are respectively of rustless iron or steel and low-carbon iron or steel, it will be understood that anyone of high-carbon steel,

`medium-carbon steel or even low-alloy steel may beemployed as the base metal part. Also, that where desired, as where highlocal heat conditions are encountered and wherea head having seen that there has been proa bright nlsh is not required as in certain boiler, automotive and electrical machinery apparatus, the head portion is fashioned of low-carbon steel While the shank portion or the threaded end portion of the same is fashioned of rustless iron or steel.

Likewise, while the head and shank of my fase tening device are illustrated as being welded together at a. point on the shank immediately adjacent the head portion, it will be understood that where desired the weld may be made to appear within the head portion or adjacent to or within'the threaded portion of the shank where this construction is deemed desirable. 'Ihe particular location of the weld between th rustless iron and low-carbon steel portions is best determined empirically by welding and heading dierent relative lengths of rustless iron or steel and low-carbon iron or steel bars.

As many possible embodiments may be made of my invention and as many changes may be made in the embodiments hereinbefore set forth it is to be understood that all matter described herein or shown in the accompanying drawing is to be interpreted as illustrative and notas a limitation.

I claim:

1. In manufactures -of the class described, a fastening device comprising an austenitic rustless iron or steel portion and an iron or steel portion butt-welded thereto.

2. In manufactures of the class described, a fastening device comprising a portion of rustless iron anaylzing approximately, 10 per cent to 3G per cent chromium and the balance iron, and a steel portion butt-welded thereto.

3. In manufactures of the class described, a fastening device comprising a head portionof austenitic rustless iron analyzing approximately, 1U per cent to 30 per cent chromium, '7 per cent to 20 per cent nickel and the balance iron, and a shank portion of steel butt-welded thereto.

GEORGE C. TIGEE.

GEORGE c. TIGHE.

April 1J., 1959,

It is hereby certified that the name of the assignee in the above rnm-n bered patent was erroneously described and specified as "Rustless Iron and Steel Corporation of'America" and specified as Rustless Iron land, a corporation of Delaware whereas sadname 'should have been described and Steel- Corporation, of Baltimore, ilary-t as shown by the record of assignments in this office; and that the said Letters `Patent should be read with this correcton thereinthat the same may -Patent Office. A

conform'to the recordof the case inthe (Seal) Henry Van Arsdale Acting Conunssioner of Patents.

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