GB2174933A - A method of cladding a steel core rod - Google Patents

Abstract

A method of cladding a steel core rod 10 with at least one cladding strip 18, 20, composed of another metal, comprising preheating said core rod 10 and said strip 18, 20 positioning said strip around said core rod and effecting solid-phase bonding of said cladding strip to said core rod, subsequently immersing a resultant clad steel rod 50 in a first cooling liquid quench 56 at a temperature of from about 160 DEG F (70 DEG C) to the boiling temperature of said cooling liquid. Preferred cladding materials given are copper, copper alloys, nickel and nickel alloys. Rod 10 is cleared at station 12, heated by induction coil 40; strips 18, 20 are heated by resistance heating through electrically energised shoes 34, 35, and are bonded to core rod 10 by rolls 14, 16. Clad rod 50 passes through chamber 51 containing an inert or reducing gas, overflow tank 52, a hot water quench tank 56, second overflow tank 66 and a second quench tank 72 with water at a lower temperature, and a third overflow tank 76. <IMAGE>

Description

SPECIFICATION A method of cladding a steel core rod The present invention relates to a method for cladding a steel core rod. In particular the invention relates to the cladding of such rods with another metal in such fashion that formation of objectionable oxides is resisted.

It has been known for various reasons to clad a metal rod with another metal so as to obtain certain beneficial properties of the core material along with the surface or other characteristics of the cladding material while effecting certain economic benefits through the relatively limited use of a generally more expensive cladding material. General examples of such cladding methods can be seen from U.S.

Patents Nos. 3,714,701; 4,227,061; and 4,331,283. In known systems it has been suggested to employ one or two metal cladding strips composed of a material, such as copper, which strips are preheated and may be preformed to enable solid phase bonding about the circumference of a preheated core rod member which may be composed of steel.

For many uses, the clad product is reduced in diameter, as by a drawing operation, in order to provide a uniformly clad product of the desired dimensions.

One problem which has been encountered with respect to continuous cladding processes, with particular emphasis on medium and high carbon steels core materials, is that the required slow cooling procedures employed to avoid hardening of the steel core have also resulted in the formation of objectionable levels of oxides on the surface of the clad material. It has been known to try to obtain a clean rod surface for further processing by subsequent chemical cleaning, for example, by pickling, or by mechanically removing the surface oxide layer. it has also been known to enclose the slow cooling zone entirely in an inert or reducing atmosphere.

These adjuncts to the main process are quite cumbersome.

It has also previously been suggested to pass a clad rod, after suitable reduction of temperature by air cooling, through a reducing atmospheric chamber containing, for example, cracked ammonia, in order to reduce the previously formed oxide layer to the original metallic form. However, a significant problem with this approach is that the reduced metallic layer may become porous and mechanically unstable as a direct result of the gaseous reduction process. Such a reduced metallic layer will tend to disintegrate during subsequent drawing or deformation processing to form a surface flake or dust which is highly objectionable and can interfere with subsequent processing or use of the clad product.

It is also known to quench steel products in boiling water to effect reasonably rapid cooling while avoiding undesired formation ofaciculartransition products, although it has not been previously suggested to employ boiling water quenches in respect of clad steel products in order to accomplish our objectives.

See generally, Tendler, "Controlled Cooling of Rods", Wire Journal, February, 1981, pp. 84-91; "Hardening of Rail Steels by Quenching in Boiling Water" Industrial Heating, March 1981, pp. 8-10; and Economopoulos et al., "The EDC Process: Matallurgical Background and Industrial Applications", Wire Journal, March, 1981, pp. 90-95.

There remains, therefore, a very real and substantial need for a process of producing a clean, continuously clad steel product which may be further processed and employed without cumber- some special atmosphere containing cooling e~nclosures or subsequent chemical or mechanical cleaning operations to eliminate oxide involvement or loss of metal either to oxide formation or through formation of metal sponge which is subsequently removed or falls off.

It is an object of the present invention at least to mitigate the problems of such prior art processes.

Accordingly, the present invention provides a method of cladding a metal core rod with at least one cladding strip composed of another metal, comprising preheating said core rod and said strip, positioning said strip around said core rod and effecting solid-phase bonding of said cladding strip to said core rod, subsequently immersing a resultant clad steel rod in a first cooling liquid quench at a temperature of from about 1600F (70 C) to the boiling temperature of said cooling liquid.

Desirably said clad material is subsequently immersed in a second cooling liquid quench at a temperature below said first cooling liquid quench.

Thus, in a preferred embodiment, subsequent to effecting bonding of a cladding material to a steel rod, the clad product is immersed in a hot water quench which is at, or slightly lower than, the boiling temperature of water. The product thus cooled is then immersed in a second quenching media which may be water at a reduced temperature. The first quench is at about 160 to 2120 F (70 to 1 000C), the actual temperature selected depending on the carbon content of the steel core being treated, and preferably at about 195 to 2050F (90 to 96 C). The quenching action is preferably accomplished at atmospheric pressure.

The process is particularly effective when medium or high carbon steel rod is employed as the core material.

The present invention has been found to provide an improved method for resisting undesired oxide formation on the surface of a clad steel product, and to resist oxide formation on the clad products surface without requiring either chemical oxide removal procedures, such as pickling, or mechanical oxide removal procedures before further processing such as drawing.

The present invention has also been found to provide such a system which is economical to employ and efficient to use, enables production of a bright clad surface and avoids creation of the surface layer of reduced metal sponge.

Still further, the invention has been found to provide such a process which eliminates the need for using air cooling or alternative cooling means such as inert or reducing atmosphere containments.

In order that the invention may be more readily understood, and to that further features thereof may be appreciated, an embodiment of a method of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a cross-sectional illustration of a clad rod made by a method of the present invention; and Figure 2 is a partially schematic illustration of a system adapted for use with a method of the present invention.

As used herein the term "medium carbon steel" will refer to steel having about 0.16 to 0.30% carbon and "high carbon steel" will referto steel having a carbon content of greater than about 0.30%.

The manner of handling individual cladding strips and a core rod, as well as the method of solid bonding the same forms no part of the present invention and any acceptable means may be employed upstream of the unique cooling process of the present invention. However, reference will be made to a means of effecting cladding in the interest of completeness of description. The specific means illustrated is disclosed in U.S. Patent No. 4,227,061.

As is shown in Figure 1, the final product will consist of one or more cladding strips 2, 4 bonded to a core rod 6.

As illustrated in Figure 2, a steel core 10, which may take the form of a rod, is passed through a cleaning station 12 which cleans the exterior surface of the rod 10. The rod, which may conveniently be provided from a reel of material (not shown), travels in a direction illustrated by the arrow A. The rod 10 and cladding strips 18, 20 are fed separately to a bonding station, comprising bonding rolls 14, 16, whereat solid bonding of the rod is effected with the metal cladding strips 18, 20 in the bonding rolls 14, 16. Each of the bonding rolls is provided with a groove to receive a portion of the cladding strip-core assembly. The cladding strips 18, 20 are either cleaned or have been cleaned as a part of this process and are passed through tensioning rolls 24, 26, respectively.The strips 18, 20 are then heated by passing through electrically energized contact shoes 34, 35, respectively, which heat the strips 18, 20 by resistance and are energized by a power source 36 via wires 30, 32. The power source 36 also is connected to bonding rolls 14,16through wire 38 in order to provide the low potential end of the heating circuit.

The core rod 10 is also preheated by means of an electrical induction coil 40 around which is supported a nonconducting tube 42. An end cap 44 is provided with a tubular inlet 45 through which a gas which inhibits oxidation of the rod may be introduced into tube 18. A positive-pressure chamber 46 is provided within the regions receiving the rod 10 and the cladding strips 18, 20 and is adapted to receive a reducing gas which resists oxidation of the rod and strips prior to bonding.

In practice of the present invention the steel core 10 may be composed of a medium or high carbon steel. Among the preferred cladding materials are those metals which are not sensitive to the cooling rates resulting from a hot water quench and do not suffer oxidation when exposed to water or a suitably buffered water base solution of temperatures ranging from ambient to the boiling point of the water or buffered solution, such as monel, for example. The preferred cladding material will be a material selected from the group consisting of copper, copper alloys, nickel and nickel alloys.

After bonding, a clad product 50 emerges from the bonding station and passes through a transition chamber 51 containing an inert or reducing gas, such as cracked ammonia. The composite material, which preferably is travelling at about 45 to 60 feed per minute (14to 19 metres per minute), then travels first through an overflow tank 52, and then to a first quench tank 56. The overflow tank 52 contains water 54 essentially at the same temperature as the water 58 in the first quench tank 56. Cracked ammonia from the chamber 51 also enters the overflow tank 52 and overlies the water in that tank. Thus, both the water 54 and ammonia protect the clad product 50 from corrosive or oxidizing environments. The first quench tank 56 contains water 58 at a temperature of about 160 F(70 C) to boiling point.With pure water the boiling point will be 2120F (100 C), at one atmosphere. The water temperature is preferably at about 195 F (90 C). The product 50 as it emerges from the bonding equipment typically has a temper ature of about 16500 to 1 8000F (890 to 9800C) or greater. The hot water quench achieved in the first quench tank 56 is sufficient in terms of water temperature and dwell time to reduce the temperature of steel core rod to less than about 11 000F (595 C). The cooled composite rod 50 is then passed through a second overflow tank 66 which contains water and a gas such as nitrogen in a space overlying the water.The rod 50 then passes through a second quench tank 72 which has water 74 at a lower temperature than the water 58 and preferably less than about 80 F (27 C) or at ambient temperature. A third overflow tank 76 may also be provided.

The tanks 52,56,66,72 and 76 may be made of any suitable material, such as stainless steel or a coated steel, and may be generally rectangular in plan. The tanks 52, 56, and 66 will generally have a sealed top closure whilst the tanks 72 and 76 may be open or closed.

It is contemplated that from the time a clad steel core emerges from the bonding rolls 14, 16 until it emerges from second quench tank72, no significant exposure to corrosive or oxidizing environments will occur. In the form illustrated, this is accomplished by the protective gaseous environment in chamber 51 and bf maintaining the clad product 50 under the protective atmosphere and/or water surface level in tanks52,56,66and72.

Openings are provided in the walls of the tanks 52, 56,66 and 72 to permit the passage of clad rod 50 therethrough. If desired, some sealing means may be provided betwen adjacent tanks. Water 58 that emerges from the tank 56, on the upstream side, is received in the overflow tank 52. The second overflow tank 66 is divided by a wall 67 and receives elevated temperature overflow water 68 from the first quench tank 56 on the upstream side and and cooler overflow water 69 from the second quench tank 72 on the downstream side. Suitable pipes 60, 71,64 and a pump unit 62 permit water 54 from the tank 52 and water 68 from the tank 66 to be returned to tank 56.

Water emerging from tank 72 at the wall adjacent overflow tank 66 will enter overflow tank 66 and may be withdrawn from that tank through a drain 70.

Also, some of the water 74 may enter the third overflow tank 76 and may be discharged through a drain 79.

Suitable sources of makeup water (not shown) and heating means (not shown) such as immersion heaters, steam heaters, and heat exchangers, for example, may be provided for startup and adjustment. In some circumstances the heat of the clad rod may be adequate to maintain the water 58 of the first quench tank 56 at the desired temperature.

The clad rod 50 may, if desired, be passed through a skiving stage (not shown) in order to trim any superfluous cladding material, such as fins, projecting from the exterior thereof. The cooled rod may then be wound on a take-up reel 80. The clad rod 50 may be subjected to a drawing operation either directly from the cooling station or may be rewound on the reel 80 for storage and/or transport prior to further processing.

The dwell time (at the above-stated travel rate) of any segment of the clad rod in the first quench tank 56 will be about 15 to 50 seconds and preferably about 25 to 45 seconds.

In order to provide further guidance as to the nature of the invention, an example will be considered.

A cladding line which may be of any type suitable for advancing a rod and strip or strips of cladding material to be bonded thereto, including appropriate preheating means and bonding rolls was provided.

A core rod member consting of a C1060 steel core rod having a diameter of about 0.3444 inches (8.75 mm) and two cladding stripe each having a width of approximately one half of the circumference of the steel rod were used. In this example, the cladding strips were composed of CDA1 02 copper having a width of 0.625 (76 mm) and a thickness of about 0.032 inch (0.8 mm). The steel core rod was preheated to a temperature of about 18000F (980 C) by radio frequency induction heating and the copper cladding strips were heated to about 1 2000F (650 C) by resistance heating.The exit temperature of the clad product from the bonding station was about 1700"F (925 C). The resultant clad rod had a diameter of about 91 percent of the sum of the original diameter of the rod and the original thickness of both of the cladding strips, the reduction being effected during passage through the banding rolls.

The clad rod was advanced at a rate of about 55 free per minute (16.75 metres per minute) to a first water quench tank containing water and having a width of about 8 inches (200 mm), a depth of about 6 inches (150mm) and a length of about 30 feet (9.1 metres). The water in the first quench tank was at a temperature of about 2000F (95 C). Each nominal segment of the clad rod has a dwell time in the quench water of about 33 seconds as it passes through the first water quench and emerges at a temperature of about 950 to 10000F (510 to 540"C).

The clad rod was then introduced into a further water quench in a trough which was about 8 inches (200 mm) by 6 inches (150 mm) deep by 8 feet (2.4 mm) long and contained water at ambient temperature. The resultant clad product was found to be substantially devoid of objectionable accummulations of surface oxides and to have a clean appearance.

It will be appreciated that a method of the present invention provides effective cooling of a clad rod in a manner which reduces the steel core temperature while resisting formation of acicular transformation products and also while resisting any significant or potentially burdensome oxidation formation on the exterior surface of the cladding material. It will further be appreciated that this is accomplished while not requiring either chemical cleaning of the product, such as by pickling, or mechanical cleaning and while further avoiding air cooling with subsequent reduction of the oxide cracked ammonia, for example, to produce potentially troublesome sponge.

It will further be appreciated that, if desired, the quenching may be accomplished at other than atmospheric pressure with a corresponding adjustment of the temperatures of the water and such modifications, while special cases, are contemplated as falling within the invention. Alsos, certain additives which may alter the boiling point may be provided. Reference herein to "cooling liquid" and its associated boiling point shall be deemed to encompass water with or without additives and such water under atmospheric or different pressures and the boiling points which such water will have with such additives or under influence of such pressures.

It will be appreciated that while for convenience of illustration a system involving two distinct clad strips 18, 20 has been illustrated, if desired, the cladding may be accomplished with a single strip or with more than two strips.

It will further be appreciated that while reference has been made herein to a core which is "rod form" and generally the rod will be of substantially cylindrical configuration, other profiles may be employed if desired.

Claims (18)

1. A method of cladding a metal core rod with at least one cladding strip composed of another metal, comprising preheating said core rod and said strip, positioning said strip around said core rod and effecting solid-phase bonding of said cladding strip to said core rod, subsequently immersing a resultant clad rod in a first cooling liquid quench at a temperature of from about 1 60 F (70 C) to the boiling temperature of said cooling liquid.

2. A method according to claim 1, further comprising subsequently immersing said clad rod in a second cooling liquid quench at a temperature below said first cooling liquid quench.

3. A method according to claim 1 or 2, wherein water with our without additives is used as said cooling liquids.

4. A method according to claim 3, wherein said first immersion is effected in water having a temper ature of from about 1600F (70 C) to 2120F (100 C).

5. A method according to claim 3 or 4, when dependent upon claim 2, wherein said second immersion is effected in water at a temperature below about 800F (27 C).

6. A method according to any one of claims 1 to 5, wherein two cladding strips are used.

7. A method according to any one of claims 1 to 6, wherein said first quench is effected at a temperature of about 1950 to 2050F (90 to 960C).

8. A method according to any one of claims 1 to 7, wherein the cladding material is selected from the group consisting of copper, copper alloys, nickel and nickel alloys.

9. A method according to any one of claims 1 to 8, wherein the temperature of said core rod is reduced to less than about 11 000F (595 C) in said first water quench.

10. A method according to any one of claims 1 to 9, wherein said first water quench is effected at about atmospheric pressure.

11. A method according to any one of claims 1 to 10, wherein said core rod is a steel rod.

12. A method according to any one of claims 1 to 11, wherein said core rod is formed from a material selected from the group consisting of medium carbon steel rod and high carbon steel rod.

13. A method according to claim 2, or any claim dependent thereon, wherein said second quench is effected at about ambient temperature.

14. A method according to any one of claims 1 to 13, wherein said clad rod is advanced through said first quench liquid at a rate of about 45 to 60 feet per minute (14to 19 metres per minute).

15. A method according to any one of claims 1 to 14, wherein said core rod has a diameter less than about 1/2inch (13mm).

16. A method according to any one of claims 1 to 15, wherein each portion of said clad rod has a dwell time in said hot liquid quench of about 15 to 50 seconds.

17. A method according to claim 16, wherein each portion of said clad rod has a dwell time in said hot liquid quench of about 25 to 45 seconds.

18. Apparatus for manufacturing a clad rod according to claim 17, comprising means for feeding a core material and at least one cladding strip to a bonding station, means for effecting bonding of the cladding strip to the core material, and at least one quench tank for containing a first cooling liquid at a temperature of from about 1600F (70 C) to the boiling point of such liquid, and at least one second tank for containing a second cooling liquid at second temperature below the temperature of said first cooling liquid.

18. A clad rod whenever produced by a method according to any one of claims 1 to 17.

19. Apparatus for manufacturing a clad rod according to claim 17, comprising means for feeding a core material and at least one cladding strip to a bonding station, means for effecting bonding of the cladding strip to the core material, and at least one quench tank for containing a first cooling liquid at a temperature of from about 1600F (70 C) to the boiling point of such liquid.

20. Apparatus according to claim 19,further comprising at least one second tank for containing a cooling liquid at second cooling liquid of a temperature below said first cooling liquid.

21. A method of cladding a steel rod substantially as herein described with reference to the accompanying drawings.

22. A clad steel rod substantially as herein described with reference to and as shown in the accompanying drawings.

23. Apparatus substantially as herein described with reference to and as shown in Figure 2 of the accompanying drawings.

24. Any novel or combination of features disclosed herein.

Amendments to the claims have been filed, and have the following effect: (a) Claims 1,2, 19,20 above have been deleted or textually amended.

(b) New or textually amended claims have been filed as follows: (c) Claims 3 to 18 and 21 to 24 above have been re-numbered as 2 to 17 and 19 to 22 and their appendancies corrected.

1. A method of cladding a metal core rod with at least one cladding strip composed of another metal, comprising preheating said core rod and said strip, positioning said strip around said core rod and effecting solid-phase bonding of said cladding strip to said core rod, subsequently immersing a resultant clad rod in a first cooling liquid quench at a temperature of from about 1 60 F (70 C) to the boiling temperature of said cooling liquid and subsequently immersing said clad rod in a second cooling liquid quench at a temperature below said first cooling liquid quench.