US2656949A

US2656949A - Lined container and welded joint therein

Info

Publication number: US2656949A
Application number: US131144A
Authority: US
Inventors: Glenn W Leupold
Original assignee: AO Smith Corp
Current assignee: AO Smith Corp
Priority date: 1949-12-05
Filing date: 1949-12-05
Publication date: 1953-10-27
Anticipated expiration: 1970-10-27

Description

Oct. 27, 1953 e. w. LEUPOLD LINED CONTAINER AND WELDED JOINT THEREIN Filed Dec. 5, 19 49 INVENTOR- Glenn YKLe PoZd BY M 9 ATTORNEYS Patented Oct. 27, 1953 UNITED STATES PATENT OFFICE LINED CONTAINER AND WELDED JOINT THEREIN Glenn W. Leupold, Milwaukee, Wis., assignor to A. 0. Smith Corporation, Milwaukee, Wis., a corporation of New York Application December 5, 1949, Serial No. 131,144

1 Claim. (01. 220-64) 2 nally through a portion of a container and its flanged connection;

Fig. 2 is a sectional view of a portion of a container having a threaded fitting and illus- The inventionisparticularly adaptable to joints 5 trating another embodiment of the invention; employed in tanks, vats or containers of varying and sizes wherein connection portions such as man- Fig. 3 is a longitudinal sectional view of a ways, flanges for various openings and the like, portion of a wall of a large container such as a are secured to the body of the tank or vat. If tank in which an alloy band is employed around the bearing surfaces of the connection portions the circumstance of the tank to join the tank are coated with ceramic or vitreous enamel, for sections together. instance, any blow or impact to which the con- With reference to Fig. l the wall I of the nection portions are subjected while in use, may container is of ordinary carbon or mild steel cause the vitreous enamel coating to become while the flanged connection 2 is of a metal chipped or cracked thereby subjecting the metal which resists corrosion, such as stainless steel. beneath the chipped 0r cracked coating to cor- The wall of the container and the connection rosive attack. To remedy this, it has been the are joined by the fusion butt weld 3. The metal practice to make the connection portions of a of the joint is of particular importance in that metal which is resistant to corrosion from the it is preferable to use an alloy for the weld which liquid carried or stored in the tank or vat. Freis compatible to metals having dillerent coefiiquently the metal employed for this purpose is cients of expansion. stainless steel {which has a different coefiicient As an example, one such alloy which has been f m l p i n than the metal fr m which found to be suitable for fusion welding mild steel the balance of the structure is fabricated. This t t inle steel comprises substantially the folin turn has led to the employment of joints of lowing: varying forms between the different metals to j prevent crazing of the enamel coating generally '70 to 80% nickel bonded to the metal which is not corrosion re- 10 to 18% chromium sistant, an example of such metal being low car- 9% iron maximum boil or mild steel. 0.5% copper maximum The principal object of this invention there- Remainder residuals fore is to provide an improved joint which may be employed in structures having a vitreous en- An alloy of the above c mposition has a coamel protected metal member and an alloy corefficient of thermal expansion substantially the rosion-resistant metal of diiferent coeificients of [:3 same as that of mild steel while stainless steel thermal expansion. has a coefficient of thermal expansion substan- Another object is to provide a joint between tially 50 per cent greater. an enamel protected meta]. member and an alloy It has been discovered that the above alloy corrosion-resistant metal of different coeificients may be used advantageously to form a fusion of thermal expansion in which the enamel may 40 butt weld between the diiferent metals. In makextend part way across the joint or, if desired, ing such a weld the width of the inner surface entirely across the joint. l of the weld 3 is made considerably greater than The discovery that an enamel protected metal the width of the outer surface 5. Across the weld member and an alloy of corrosion-resistant metal there is a gradation of the composition of the of different coefiicients of thermal expansion may kg it which makes possible t carrying be united y a fllSlOIl butt Weld Which the over of the vitreous enamel lining onto the weld ename; Goa-ting extends part Way across the joint deposit for a substantial distance, for instance, or entirely across the same is a substantial and approximately aeross half the Width of the inner important contribution to the art. urfa of the Weld The invention Will be described in connection t is known in the enameling art that when with a container of t e bo yp for p p applying a vitreous enamel to carbon steel a o illustration ground coat must first be used before firing the h p n in drawin illu rat s typic l cover coat. It is also known that the ground embodiments of the invention in which: coat is generally not acid resistant while the Figure 1 is a sectional view taken longitudicover coat is. Vitreous enamel may be applied directly to certain alloy steels such as stainless steel.

In the practice of the invention it is preferable to first join the body I of the container to the flanged connection 2 by a fusion butt weld 3 having an inner surface 4 of substantial width. The metal of the weld deposit will be diluted by the metals which are being joined so that the weld metal nearest the carbon steel of the body I will take on characteristics more nearly those of the carbon steel than will the weld deposit metal at a line adjacent the corrosion-resistant metal of the connection fitting where the characteristics of the weld deposit metal will be more nearly like that of the corrosion resistant metal. The effects of this dilution serve to make the Weld deposit metal a bufiering agent between two metals possessing substantially different coefficients of expansion and to provide a zone of gradual change from metal of the one coefficient to metal of the other.

A vitreous enamel lining B is next applied to the inner surface of the Wall I of the container. As stated above a ground coat must be used when coating carbon or mild steel with vitreous enamel. In the preferred practice of the invention the ground coat is first applied to the inner surface of the container and also for a short distance across the inner surface of the fusion Weld 3. The cover coat is next applied to the ground coat and then fused in any suitable man- It has been found that the Weld deposit metal extending from approximately the center of the surface 4 to the corrosion-resistant connection fitting 2 is, by virtue of the effects of dilution of the metal of fitting 2 with the metal of the weld deposit, resistant to attack from corrosion. Therefore, it is unnecessary to carry the enamel lining over the entire surface 4 of the joint 3 although this may be done if desired, The latter is illustrated in Fig. 2 wherein a threaded connection 1 is shown as welded to Wall 8 of a container by weld 3.

In Fig. 3 there is shown a portion of the wall of a substantially large tank which has been fabricated from two tank sections. Walls 9 of the tank sections are generally of carbon steel and are joined together by circumferentially extending bands In and II of a suitable corrosionr resistant alloy such as stainless steel which are joined by welds 3 to the respective tank sections according to the above described process. and .then joined to each other by a fusion weld 12. The metal of the weld deposit I2 is preferably of the same constituency as that of the bands In and I I.

The invention provides a joint which may be used for example in a container the body of which is fabricated from a relatively inexpensive metal such as mild or carbon steel. Connection fittings of a corrosion-resistant metal are joined to the body of the container by a fusion butt weld and subsequently the inner surface of the body portion is provided with a vitreous enamel lining to protect the body from corrosion. Heretofore, tapered joints have been utilized in joining connection members to the body of the container and then the inner surface was enamel lined. The invention provides an ordinary fusion butt weld in joining metals of different coefiicients of thermal expansion in which the weld deposit metal is an alloy compatible with the metals being joined so that the alloy weld deposit acts as a buffering agent between the metals in that there is a gradation of composition of the weld deposit from one side of the weld to the other.

Various embodiments of this invention may be employed within the scope of the following claim.

I claim:

In a corrosion resistant metallic structure hav- 4 ing a fusion weld deposit therein, a carbon steel body having a surface subject to corrosion when unprotected, a body having a corrosion resistant alloy steel surface adjacent said carbon steel surface, a fusion weld deposit between said bodies and presenting a surface zone of substantial width between said surfaces in which there is a gradation of allo s content providing a gradual change in the coefficient of thermal expansion from that of said carbon steel surface to that of said alloy steel surface, and a protective coating of vitreous enamel fused and bonded to said carbon steel surface and extending for at least a substantial distance across said surface zone of said weld deposit,'the gradation in coefficient of thermal expansion of the surface zone covered by said vitreous enamel serving to prevent injury to the enamel from thermal expansion differentials, and

the alloy content of the exposed surface metal adjacent the edge of said coating being sufficient I to substantially resist corrosion without further protection.

GLENN W. .LEUPOLD.

Number Name Date 1,896,411 Maskrey Feb. '7, 1933 2,214,002 Trainer et a1 Sept. 10, 1940 2,356,047 Geisinger et al -s Aug. 15, 1944