US1860292A - Steel vesel and method of producing the same - Google Patents

Description

fPatented May 24, 1932 UNITED STATES FRITZ NEUHAUS, 0F BmLIN-TEGEL, GERMANY STEEL VESSEL AN D METHOD OF PRODUCING THE SAME No Drawing. Application filed July 5 1928, Serial No. 290,686, and in Germany September 19, 1925.

This application is a continuation in part of copending applications'Serial Nos. 86,932 and 86,924, filed on February 8, 1926, for steel vessels or tanks, and steel alloy and method of producing the same.

This invention relates to vessels or tanks which are adapted to contain fluids, and which are subjected in use to high pressures and temperatures. Such vessels are used especially in cracking oils and in other chemical operations, as well as in high-pressure steam' boilers and like containers. The object of the invention is to produce a vessel having great strength even when subjected to the high temperatures to which such containers are subjected in use.

In the design of such vessels, it has been the practice heretofore to compute the required wall thickness on the basis of the yield point of the steel at ordinary temperatures. The yield pointof' ordinary steel, however, decreases rapidly with increase in temperature, so that where the vessel is actually to be used at a temperature of 500 0. its yield point at that temperature will be only a fraction of the yield point at ordinary temperatures. This fact has been recognized, andhas been taken care of simply by using a large factor of safety, the thickness of the walls being therefore two or three times as great as would be necessary if the vessel were to be used only at ordinary temperatures. This practice necessarily results "in excessive and unwieldy thickness of the walls.

There are three known ways of manufacturing or fabricating such tanks, namely, by riveting, by forging, and by welding.

When plates are riveted together to form a vessel of this type, it is found that the seam and rivet holes cannot be kept sufliciently tight to avoid leakage, this being due to the thickness of the steel plates required for strength, a'ndto the internal stresses set up by the change in temperature to which the vessel is, subjected in use. Riveted tanks have the metal to hammer-welding,

therefore been found impractical and unsatisfactorjs' With the forged construction, the vessel may be forged from a-single steel billet. This is not only a very expensive process, but it has been found impossible to forge out of one piece vessels of the size needed in the industry. It has therefore been necessary to build up a tank of several forged hoops, uniting them .by riveting, which results in the drawbacks above mentioned.

Welding can be done by means of electricity or by the forged hammer-weld process, but electric welding, either spot-welding or fuse Welding, will not produce a satisfactory Vessel where the walls are thick, since the seams are not tight under pressure, and the structure of the steel is changed by the intense heat of the process and the steel is thereby weakened. The forged hammer-weld construction has been extensively and successfully used .formaking such vessels where the thickness of the walls has not been too great, but the difliculty of making a seam by hammer-welding increases With the thickness of the walls, with the result that it is very difiicult to obtain a reliable seam by this method where the walls are over 2 or 3 inches thick.

It has therefore been necessary to devise means which will permit the reduction of-the wall thickness without a corresponding reductionin the strength of the tank wall. This has in the past been done by employing special steels whichhave a sufficiently high yield point at high temperatures. Of the alloys used to form such special steels, chromium and nickel are the ones most commonly used. Considerable amounts of these alloys are necessary, however; for example, 3 to 5 per cent of nickel is generally added, and this addition greatlyfreducesthe susceptibility of practical matter, the known alloy steels could not be used in making welded containers, but

so that as a have been used only in making forged con- 1 tainers. Furthermore, while the addition of these alloys increases the strength at ordinary temperatures, the yield point of nickel steel decreases rapidly at temperatures of 300 C. and higher, so that eventually a point is reached at which the steel is but little stronger than ordinary carbon steel.

Low-carbon steel is also impractical for use in constructing oil cracking tanks, since even at normal temperatures its yield point is loW, and the yield point declines rapidly as the temperature rises. An advantage in the use of low-carbon steel is that it may be readily welded especially by the most desirable form of welding known as hammer-welding. Hammer-welding, when properly done, gives seams of greater strength than are obtainable by electric welding, but until now no material other than low-carbon steel has been found which, in the thickness and strength required, may be successfully hammerwelded.

The present invention is based on the discovery that certain vanadium alloys have an inordinately high yield point at high temperatures, and that such alloys may be successfully hammer-welded in a manner to be described. The-inventor has succeeded in producing a hammer-Welded container which, at the temperatures employed, is of greater strength than other steels, not excepting nickel steel. To form-such a container, a low-carbon steel containing a small amount of vanadium is used. It has been found that such an alloy can be readily hammer-welded by the use of water gas, and, at the same time, has a relatively high yield point above 400 C. The preferred proportions of the principal alloys in the steel are as follows:

Carbon .1% to 25% Vanadium .1% to .3%

Example? Carbon .1% to 25% Vanadium .1% to .3% Manganese to .7

Example 3 I Carbon [1% to 25% Vanadium Y .1% to 3% Manganese .3% to .7 Silicon Trace to .4%

The third combination is especially suitable for steel castings which, while having a high yield point at high temperatures, can

be successfully hammer-welded. The vanadium is usually added to the iron while in a molten condition, the percentage of carbon, manganese and silicon being controlled in the same manner as in other steel: The silicon serves to give density'to the steel when cast.

After the addition of the alloys, the metal is cast and rolled into sheets from which plates of appropriate size are cut. These plates are then raised to welding temperature by the use of a suitable gas, preferably Water gas, and are hammer-welded together to form vessels of the desired shape and size,

Alternatively, the metal may be cast into plates of such shapes that they may be used directly in the fabrication of such vessels.

The advantages, in lower cost for a given tors are to a great extent counterbalanced by the increased strength of the alloy, so that the cost of metal in a container made by the present process is but little in excess of the cost of the metal in a low-carbon steel vessel of equal capacity and strength, and this excess is morethan balanced by the reduced cost of welding and working the thinner plates.

In addition to the economy in cost, the strength of a vessel made in the above manner is less erratic at high temperatures than is the case with a vessel made of nickel steel, and is hence afar safer. container to use where high temperatures are combined with high pressures. It will be evident that a container of any desired size and shape may be made in the above described manner.

In the foregoing description, tanks adapted to be used in cracking oils have been es-- pecially mentioned,-but it will be obvious that tanks made according to the invention may also be used in other chemical operations, as well as for steam boilers and similar vessels.

Having described the invention, what is claimed as new is:

1. As a product of manufacture, a vessel adapted to withstand great pressure at high temperatures, said vessel being formed of hammer welded steel plates containing substantially. 2% of vanadium.

2, As a product of manufacture, a vessel adapted to withstand great pressure at high temperatures, the said vessel being formed from hammer welded steel plates containing substantially 2% vanadium and substantially 2% carbon.

3. The method of making a steel vessel which comprises forming plates from steel containing from .1% to .3% of vanadium and a low percentage'of carbon, and hammer welding said plates together to form a vessel.

4. The method of ni'aking a steel vessel which comprises forming plates from low- DR. FRITZ NE UHAUS.