FR2582579A1 - METHOD FOR COATING STEEL ROD-CORE WITH OTHER METAL - Google Patents

Abstract

THE SUBJECT OF THE INVENTION IS A PROCESS FOR COATING A STEEL CORE STUD OF MEDIUM OR HIGH CARBON CONTENT WITH ANOTHER METAL. A BATH OF HOT WATER 56 IS USED AT A TEMPERATURE BETWEEN APPROXIMATELY 70C AND THE BOILING TEMPERATURE AND, PREFERABLY, APPROXIMATELY 90 TO 96C, THEN A COOLING IN WATER 72 IS CARRIED OUT AT A TEMPERATURE LOWER THAN THE TEMPERATURE OF THE FIRST BATH, AND PREFERREDLY, AT ROOM TEMPERATURE. THE COATED MATERIAL IS SENSITIVELY FREE OF OXIDE PARTICLES OR SPONGIOUS PARTICLES ON THE SURFACE, WHICH IS BAD AND THE STEEL CORE IS PRACTICALLY FREE OF ACICULAR TRANSFORMATION PRODUCTS WHICH ALLOWS THROUGH TREATMENT CONTINUOUS SON.

Description

The present invention relates to a method for

  made of steel rod-core coating with a

  other metal so as to resist the formation of harmful oxides

  sible. We already know for various reasons, to wear a

  metal rod with another metal in order to obtain certain

  advantageous properties of the core material as well as the surface or other desired characteristics of the coating material, while deriving certain economic benefits from the relatively limited use of the coating material which is generally more expensive (see especially US 3,714,701, 4,227,061 and 4,331,283). In known methods, the use of one or two metal coating tapes of a material such as

  copper, for example, which is preheated and can be pre-

  form to allow solid phase bonding around the circumference

  a member of a preheated core rod which may be of steel.

  For many uses, the diameter of the coated product is reduced, for example by a drawing operation, to thereby obtain a uniformly coated product having the same properties.

desired dimensions.

  One of the problems with a continuous coating process, particularly with medium and high carbon steel cores, is that slow cooling stages are used to prevent hardening. of the steel core have also caused the formation of inadmissible proportions of oxides

on the surface of the coated material.

  It has already been sought to obtain a clean stem surface for subsequent treatment by cleaning

  chemical, for example by stripping or mechanical removal.

  of the oxide layer on the surface. It is also known to enclose the entire slow cooling zone in an enclosure containing an inert or reducing atmosphere. These ancillary treatments of the main process are

quite tedious.

  The Applicant has previously suggested passing the coated rod after a suitable reduction of the temperature by air cooling, through a reducing atmosphere chamber containing, for example, cracked ammonia in order to reduce the coating layer. oxides previously formed to its original metallic form. A significant problem with such a way of approaching the problem is that the reduced metal layer is porous and mechanically

  unstable as a direct result of the gaseous reduction process.

  This layer tends to disintegrate during the subsequent stretching or deformation stage to form flakes on the surface or dust which is highly objectionable and may interfere with subsequent treatments or the use of

coated product.

  While it has previously been known to cool steel products by soaking them in boiling water in order to effect reasonably rapid cooling while avoiding the undesirable formation of acicular transition products, it has not previously been suggested to use immersion in boiling water of the coated steel products in order to achieve the objects of the invention (see in particular: Tendler: "Controlled Cooling of Rods", Wire Journal, February 1981, pages 84-91; "Hardening of Rail Steels by Quenching in Boiling Water ", Industrial Heating, March 1981, pages 8 to 10 and Economopoulos et al," The EDC process: Metallurgical Background and Industrial Applications ", Wire

  Journal, March, 1981, pages 90 to 95.

  Nevertheless, there is still a great need and very

  real for a production process of a clean continuous article

  naked that can be treated later and

  use without cumbersome cooling enclosures

  a special atmosphere or without chemical or mechanical cleaning to eliminate the formation of oxides or the loss of metal by formation of the oxide or formation of a spongy metal which must then be removed or dropped

of himself.

  The present invention has solved the above problem.

  After bonding the coating material to the steel rod, the coated product is immersed in hot water which is at a temperature slightly lower than or equal to the boiling temperature of the water. After cooling, the product is immersed in a second medium

  immersion which may be water at a reduced temperature.

  The first immersion is at a temperature of about 71 ° C depending on the carbon content of the steel core being processed, and a range of 90 to 96 ° C is preferred. The cooling action is preferably performed under

atmospheric pressure.

  The process is particularly effective for medium and high carbon rods

that we use as a nucleus.

  Accordingly, the main objects of the invention are: to provide an improved process for resisting the undesirable formation of oxides on the surface of the coated steel product; to resist the formation of oxides on the surface

  coated products without the need for chemical removal steps.

  oxides such as pickling or oxidation mechanical removal stages prior to further processing such as drawing; to provide such a method whose use is economical and whose use is effective; producing a glossy coated surface and preventing the formation of a reduced surface layer of reduced spongy metal;

  - to provide such a process which eliminates the need

  air-cooling or other means of re-

  chilling such as placement in an inert or reducing atmosphere; and - to achieve other goals that will emerge from the

  description which follows with reference to the attached drawing in which:

  Figure 1 is a cross section of a product prepared by the present invention; and

  FIG. 2 is a partially schematic view of

  of an installation intended to be used with the process

of the invention.

  As used herein, the term "medium carbon steel" refers to steel containing about 0.16 to 0.30% carbon, and "high carbon steel" refers to steel having a carbon content.

more than about 0.30%.

  While the method of handling the individual coating tapes and the core rod as well as the solid state bonding method thereof are not part of the present invention and can be used.

  any acceptable means upstream of the single refrigeration process

  according to the invention, reference will be made to a means

  coating to make the description more complete.

  The particular means that is represented is described in

U.S. Patent 4,227,061.

  As seen in Figure 1, the final product consists of one or more coating tapes 2,4

linked to a kernel 6.

  In the embodiment shown in FIG. 2, a steel core 10 which may be a rod is conveyed by a cleaning station 12 which cleans the

  outer surface of the stem 10. The stem that can

  dement come from a reel of material not shown, progresses in the direction indicated by the arrow. It is required to make a solid bond with the coating metal strips 18 and 20 between the connecting rollers 14 and 16, each having a groove for receiving a portion of the core assembly and the coating tape. The coating strips 18 and 20 are either cleaned or have been cleaned during a part of the process and passed between tension rollers 24 and 26 respectively and then by electrically excited electrical contact pads 34 and 35 respectively which serve to heat the ribbons 18 and 20 by resistance and are excited by a current source 36 and leads 30 and 32. The source

  current 36 is also connected to the link rolls.

  its 14 and 16 by a conductive wire 38 to form as well

  the low voltage end of the circuit.

  The stem-core is also preheated. We

  preheating by an electric induction coil

  The end cap 44 is provided with a tubular inlet through which a gas can be introduced into the tube 18 which prevents oxidation of the rod. A positive pressure chamber 46 is provided in the zones receiving the rod 10 of the coating strips 18, 20 and is made to receive a reducing gas which is resistant to oxidation.

  rod and ribbons before binding.

  In a preferred embodiment, the steel core 10 is constructed of medium or high carbon steel. Among the preferred coating materials are metals that are not sensitive to the cooling rates caused by immersion in hot water and do not undergo surface oxidation when exposed to water or water. aqueous solution of a buffered base suitably at temperatures ranging from

  ambient to the boiling point of water, the material

  which may be, for example, a Monel alloy. The preferred coating material is selected from copper, alloys

  copper, nickel and nickel alloys.

  After bonding, the coated product 50 comes out of

  connecting equipment and passes through a tran-

  with an inert or reducing gas such as amine

  cracked moniac. The composite material which progresses

  At a speed of about 14 to 18 m / min, the first through-flow tank 52 passes through an overflow tank 52 which contains water 54 at substantially the same temperature as water 58 in the first immersion tank. 56. The cracked ammonia from chamber 51 is also admitted to vessel 52 and overflows water 54. Thus, both water 54 and ammonia protect the coated product 50 from corrosive or oxidative environments. The tank 56 contains water 58 to

  a temperature between about 71 C and the boiling point.

  With pure water, the boiling point is 100 C under a pressure of 1 bar. Preferably, the temperature of the water is between about 90 and 96 C. While the article

  composite 50 emerges from the connecting equipment, its

  is normally between about 900 and 982 C or more. Cooling with hot water is sufficient,

  considering the temperature of the water and the duration of the

  mersion, to reduce the steel core to a temperature

  less than about 593 C in the first tank of

  56. The composite rod is then passed through

  cooled 50 in a second tank 66 to overflow the

  full which contains water and a gas such as nitrogen in the space above the water. The rod 50 is then admitted into the second cooling tank 72 containing water 74 at a reduced temperature with respect to the water 58 and, preferably, less than about 27 ° C. or

ambient temperature.

  The tanks 52, 56, 66, 72 and 76 can be

  any suitable material such as stainless steel

  for example, and can be substantially rectangular seen in plan. Vats 52, 56, 64 and 66 generally have a tight cover on top while vats 72 and 76 can be opened or closed. It should be noted that between the moment when the coated steel core emerges from between the rolls

  14, 16 until it leaves the second cooling tank

  72, this core does not experience any significant exposure to corrosive or oxidative environments. In the example shown, this result is achieved by the gaseous environment of protection in the chamber 51 and by maintaining the coated product 50 in the protective atmosphere and / or under the water level in the tanks 52, 56, 66 and 72. Openings are made in the walls of the tanks 52, 56, 66 and 72 to allow the passage of the coated rod 50.- Optionally, one can provide closure means. As far as the water 58 leaves the tank 56 on the upstream side, it is received in the tank 52 to discharge the overflow. This water is indicated by "54". A second overflow spill 66 is divided by a partition 67 and contains high temperature water 68 from the upstream vessel 56 and cooler water 69 from the downstream vessel 72. The pipes, 71, 64 and the pump 62 allow the water 54 of the tank

  52 and the water 68 of the tank 66 to return to the tank 56.

  The water coming out of the tank 72 through the adjoining wall

  cente to the overflow tank 66 enters this tank

  66 as the water 69 and can be withdrawn by a drain 70.

  A quantity of water 74 is admitted into the third overflow spill tank 76 in the form of water 78,

  with possible discharge by emptying 79.

  Suitable sources of replenishing water

  (not shown) and heating devices

  For example, immersion heaters (not shown) such as immersion heaters, steam heaters, or heat exchangers may be provided for start-up and adjustment. The heat contained in the coated stem may be adequate to maintain

  water 58 at the desired temperature.

  Optionally, the coated product 50 may be passed through a metering stage (not shown) to trim the superfluous coating material such as externally projecting fins. The cooled rod can then be wound on a reel 80. The composite can be subjected to an operation

  drawing directly at the exit of the cooling station.

  dissement, or after rewinding on the coil 80 for storage and / or transport for further processing. The residence time (at the rate of progression indicated above) of any segment of the coated rod in the tank 56 is about 15 to 50 seconds, and

  preferably from about 25 to 45 seconds.

Example

  To further elucidate the nature of the invention,

we will give an example.

  There may be provided a coating chain which may be of any suitable type to advance the rod and the ribbing (s) to be attached to the rod, including the appropriate preheating means and the connecting rollers. The core may be a C1060 steel core rod having a diameter of about 8.7 mm and two facing tapes each having a width equal to

  about half of the circumference of the steel rod.

  The coating tapes can be, in copper CDA 102

  having a width of 15.87 mm and a thickness of about 0.8 mm.

  The steel core is preheated to about 98.degree. C. for example by high frequency induction heating and the copper strips are heated to about 650.degree. C. for example by resistance heating. The outlet temperature of the coated product between the bonding rollers is about 9270 C. The coated shank has a diameter that is about 91% of the sum of the shank diameter and the thickness of the two ribbons. initials involving the reduction

  performed during the passage between the connecting rollers.

  The coated rod is advanced at about 16.5m / min. The first water cooling bath contains water and is about 200 mm wide,

  about 152 mm deep and about 9 m long.

  It contains water at a temperature of about 94 C. Each segment of the coated rod stays in hot water for about 33 seconds as it passes through the first cooling tank and comes out at a temperature of approximately 510 to 538 ° C. The coated rod is then preferably introduced into another cooling water which is in a trough having a width of approximately cm and a depth of 15 cm to a depth of 240 cm.

  length, and containing water at room temperature.

  It can be seen that the coated product is devoid of accumula-

  annoying superficial oxides and that its appearance

is clean.

  It is conceivable that the process of the invention provides efficient cooling of the composite in a manner that reduces the temperature of the steel core while resisting formation of the acicular transformation product.

  and also by resisting any notable oxidation or possible

  embarrassing effect on the outer surface of the

  coating. It is still conceivable that we realize all these results.

  without the need for chemical cleaning of the product such as stripping or mechanical cleaning and avoiding air cooling with subsequent reduction of the oxide in the cracked ammonia

  example a spongy product that can be embarrassing.

  It will further be appreciated that if desired, cooling may be carried out under a pressure other than atmospheric, provided that the corresponding boiling water temperatures are adjusted and,

  although these modifications are intended for specific cases

  In particular, they are considered as encompassed by the scope of the invention. On the other hand, some additives can be introduced which can change the boiling point. When it comes to "coolant" and its boiling weight, it is desired to include water with or without additive and under atmospheric pressure and under a different pressure, as well as the boiling points that the water will have. with such additives or under modified pressures. It is conceivable that if for reasons of convenience, there is shown an arrangement comprising two ribbons

  18 and 20, it might be possible to

  make the coating with a single strip or

with more than two strips.

  It is further conceivable that if it has been a question of a "rod-shaped" core and generally of a substantially cylindrical section, one could use

possibly other profiles.

  It goes without saying that various modifications can be made to the embodiments described and represented,

  without departing from the scope of the invention.

Claims (16)

  A method of coating a steel core rod (10) with at least one coating tape (18,20) of another metal, by preheating said core rod and said tape, by installing the tape around the core and making a solid-phase bond (14, 16) of said coating tape to the core (10) while the core and ribbon are advancing, characterized in that after said bonding, said coated steel rod is immersed in a first cooling liquid bath (56) at a temperature between about 70 C and the boiling temperature of said coolant, and said   rod coated in a second bath of coolant   (72) having a lower temperature than the first cooling liquid.   2. Method according to claim 1, characterized in that water with or without additives is used as   first and second coolants (56,72).   3. Method according to one of claims 1 or 2, characterized   in that the first immersion in water is carried out at a temperature between about 71 and 100 C.   4. Method according to one of claims 3 there, characterized   in that the cooling water of the second bath is at   a temperature below about 27 C.   Method according to one of Claims 4 to 4, characterized   in that two coating tapes (18, 20) are used.   6. Method according to one of claims to 5, characterized   in that the first immersion is carried out at a temperature of about 90 to 960 C.   7. Process according to any one of the claims   1 to 6, characterized in that a coating material selected from the group consisting of   copper, copper alloy, nickel or nickel alloy.   8. Process according to any one of the claims   1 to 7, characterized in that the temperature of the steel core is reduced to less than about 593 ° C.   in the first cooling bath.   9. Process according to one of the reverendicationslà 8, characterized   in that the first cooling is carried out sensi-   under atmospheric pressure.   10. Process according to any one of the claims   1 to 9, characterized in that the coating is carried out on a steel rod which is a medium grade steel or high carbon.   11. A method according to any one of claims 1 to 10,   characterized in that the coating is carried out on a rod   of steel containing more than approximately 0,16% of carbon.   12. Process according to any one of the claims   1 to 11, characterized in that the second cooling with water is carried out substantially at room temperature.   13. Process according to any one of the claims   1 to 12, characterized in that the rod coated with the first cooling bath is advanced speed of about 13.5 to 18 m / min.   14. Process according to claim 11, characterized in that a steel rod (10) having a diameter is used. less than about 1.27 cm.   15. Process according to one of claims 1 to 14, characterized   in that each part of the coated rod stays in the cooling hot water bath for about at 50 seconds.   16. The method of claim 15, characterized in that said residence time in hot water is about 25 to 45 seconds.