NO141691B - PROCEDURE FOR TREATING A CONTINUOUS CASTED COPPER BAR - Google Patents

Description

The present invention relates to a method for treating a continuously cast copper rod which, when it comes out of the rolling mill, has an oxide layer on the surface and where the oxidized rolled rod with a temperature of approx. 540°C is passed through at least one treatment zone comprising an elongated, open-ended channel for introducing a colder, liquid treatment mixture containing a reducing agent, the oxidized rolled rod being brought into contact with the liquid mixture to simultaneously convert the oxide layer to metal with the rod cooling to a temperature below approx. 93°C, and as the mixture is continuously recycled.

By known methods for the production of continuous

cast copper bar becomes the bar that comes out of the casting appa-

usually rated the hot rolled immediately after casting. When the rod is exposed to the atmosphere, it oxidizes, and a glow scale forms on the surface, comprising a mixture of red cupric oxide and black cupric oxide. This glow plug must be removed or brought back to a metallic state before the rod can be drawn into wire that is accepted as a commodity. Removal of the oxides is also necessary to prevent excessive wear on draft nozzles etc.

Different methods have been tried to remove the oxide glow scale from the surface of copper-containing products. It should be mentioned that the term "copper" here is also intended to include copper alloys. Examples of previously proposed methods for removing scale are the following. 1) Mechanical removal of the glow plug by sandblasting, scraping or the like.

2) Pickling

3) Treatment with reducing vapors.

4) Cooling with an aqueous solution of methyl alcohol.

Thus, US patent document no. 3,623,532 indicates a system where acid pickling is used to remove scale from a copper rod by immersing the rod in a dilute aqueous acid solution, e.g. sulfuric acid or citric acid, after the cast bar has come out of the rolling mill, but before it reaches the winding device. In the known pickling process, the heat contained in the rod is used to speed up the chemical reaction.

Under these conditions, the copper oxides are removed from the surface by a combined mechanical-chemical process, i.e. partly by peeling due to the difference in thermal contraction of the oxides and the copper substrate, and partly by dissolution of the oxides. Typically, in less than a second, the rod must be cleaned and cooled from approximately 540°C to room temperature.

The used acid is then returned to the tank and pumped through the heat exchanger back to the injectors. To maintain optimal cleaning conditions, the pickling solution is continuously regenerated to keep the copper content and acid concentration at predetermined levels. This is carried out by passing the used solution through an electrolysis unit and periodically adding new acid to the system.

The above-mentioned pickling process has been used with successful results, but in order to reduce operating costs due to the necessary use of acid-resistant materials, to avoid ecological problems associated with getting rid of waste acid, and to produce a product with a more stable high quality, tried to develop alternative methods for acid pickling.

Other methods using one or more reducing gases or vapors for treating oxidized copper rod are discussed in US Patent Nos. 3,546,029, 3,562,025, 3,620,853 and 3,659,830. In these patents, it is stated that oxide scale is removed by first exposing the rod to reducing gases or vapors at high temperature and then immediately quenching the rod in a cooling bath before exposing it to the ambient atmosphere.

Although the reduction with gas offers some advantages in relation to acid pickling, there are other disadvantages that come with such systems. The gases or vapors which are stated to be suitable for the reduction of copper rod are e.g. flammable, toxic or both, and therefore require special treatment to avoid explosion, impact on the heart or lungs etc. In addition, an oxygen-free atmosphere must be provided at high temperatures, which requires special sealing devices to completely delimit the rod and the reducing gases so that neither entry of oxygen from the atmosphere nor escape of the trapped gases into the atmosphere occurs. Another disadvantage of systems with reducing vapors is the fact that the production rate is lower than with liquid contact systems.

US-PS 3433683 specifies the use of an aqueous solution of 1-5 volume percent methyl alcohol in the heat treatment of copper and copper alloys. The patent claims that when heated copper is cooled in a solution containing methyl alcohol, the oxides on the surface of the hot metal are converted to metal, so that the copper in the oxides is recovered. Experiments indicate, however, that such a treatment is not satisfactory without the inclusion of a pH-modifying agent.

It is an object of the present invention to provide an improved method for treating continuously cast copper rod with a liquid treatment mixture, where the disadvantages of corrosive acid pickling as well as the complex conditions and dangers associated with reduction in the vapor phase are avoided. The invention can be used in connection with continuously cast ingots, rods and wire, for the production of products of high quality, with great regularity and with less expenditure.

According to the invention, this is achieved with a method as stated in the introduction, which is characterized by the fact that a diluted aqueous mixture containing propanol is used as the liquid mixture that is brought into contact with the oxide layer, preferably together with either polyhydroxy alcohols, ketones, alkyl and alkanol amines , secondary and tertiary amines, or a combination of two or more of these substances, with the mixture's pH being kept at at least 7.

Continuously cast copper bar is usually passed through one or more rolling mills immediately after it has emerged from the casting machine while it is still hot, e.g. at a temperature of approximately 816°C. The bar comes out of the rolling mill at a temperature of approximately 540°C and is fed into a first zone where it is quenched with the non-acidic treatment solution. It should be mentioned that with the previously used acid pickling system it was necessary to use oil-removing devices, e.g. an air stream, to avoid the pickling solution being contaminated with the lubricating oil used in the rolling mill. With the present invention, there is no need to keep the lubricant away from the treatment solution. If desired, the air treatment can thus be omitted when the lubricant from the bar rolling mill is miscible with the treatment solution.

It should also be mentioned that while the impact of the acid pickling introduced significant amounts of copper into the pickling solution which had to be removed, the present treatment is significantly more efficient and non-corrosive and leads to far less metal input to the treatment solution. In contrast to acid pickling, the treatment solution used will therefore not necessitate continuous renewal using electrolytic equipment to remove excess copper from the solution.

The oxidized copper bar that comes out of the rolling mill is almost immediately subjected to a combined cooling and cleaning treatment in one or more zones. The hot rod is passed through a line with devices for injecting treatment solution. In this way, the treatment liquid immediately comes into contact with and rapidly cools the hot copper rod. Non-acidic, liquid treatment mixture can be pumped through the cooling line in the same direction as the rod is moved, being the smallest in the first zone, exposing the hottest part of the rod to the coldest treatment solution, as this increases the heat transfer and thereby increases the thermal stresses exerted on the oxide glow shell due to the large temperature difference between the rod and the treatment liquid. The pumping speed of the treatment fluid is regulated to allow a moderate rise in the temperature of the fluid leaving the line, e.g. a rise of about 6 to 34°C. The subsequent treatment zones can be arranged to pump treatment solution in a direction parallel to the rod movement as described for the first zone, or in countercurrent to the rod movement through the system, as will be described in more detail below. In the first zone, the treatment mixture can optionally be pumped through the cooling line in countercurrent to the bar movement through the system. Combinations of counter-flow and co-flow in different treatment zones can also be used. Optionally, the pumping speed of the treatment mixture in the first treatment zone can be regulated to effect little or no reduction within the first zone of the temperature of the hot copper rod, or to effect a smaller temperature reduction in the first treatment zone than in any of the other treatment zones in which significant cooling occurs place. The important thing is that there must be sufficient contact time between the rod and the treatment solution so that the rod's temperature is lowered to below approximately 93°C to prevent renewed oxidation. The operating parameters that can be varied to satisfy a given production rate include: the temperature of the incoming treatment solution, its flow rate, and the number of treatment zones. After the rod comes out of one or more of the arranged treatment zones, it can, if desired, be cleaned with water and treated with wax before it is coiled up. Either alternatively or after the possible cleaning with water, lubricating water-miscible wax material can be used in water solution or a suitable solvent if desired or combined with the treatment mixture and used together with this without harmful effects.

The non-acidic treatment mixture is composed to carry out both cleaning and cooling and may optionally, as mentioned, also include a lubricating material. As mentioned, the pH in the solution is kept above 7 and preferably between 9 and 11. If necessary, the pH can be regulated by adding predetermined quantities of alkali metal hydroxides and inorganic and organic salts of alkali metal hydroxides, such as e.g. sodium hydroxide or sodium carbonate.

In addition to the above-mentioned organic scale removers, the treatment mixture also advantageously contains surface-active agents, chelating agents, etc., especially when the production rate is high. The greater the production rate, the greater the pumping rate through each of the cooling lines. Water-soluble or emulsifiable waxes or the like can

is also added to the treatment solution to protect the clean rod surface before winding. In general, the amount of wax added is small, i.e. of the order of 0.1% by weight of the mixture. Alternatively, the waxing can be carried out separately after the cleaning.

The temperature of the liquid treatment solution is maintained at about 4 to 93°C. The treatment solution is continuously recycled and filtered as explained later. Devices for heat exchange are arranged in the recirculation system to cool the treatment solution before its introduction into the treatment zones.

The liquid treatment mixture used in the method preferably contains a major proportion of water, e.g. 90 percent by volume or more. However, the ratio between water and additives is not critical and can be varied. The essential feature of the treatment solution is its ability to quickly remove heat from the hot rolled bar so that the oxide layer is exposed to a shock and at the same time react with the oxide that remains on the surface to reduce it to metal so that a clean rod free of oxide scale.

The cleaning additives used are preferably water-soluble. N-propanol has been found to give particularly good results alone and especially in combination with polyhydroxy alcohols such as e.g. glycerol, glycol etc. The ratio between propanol and polyhydroxy alcohol is not critical and can vary within wide limits, e.g. from 7:1 to 1:1. The preferred polyhydroxy alcohols are those which have 2 or 3 hydroxyl groups such as e.g. ethylene glycol, propylene glycol, diethylene glycol and glycerol.

Among usable ketones can be mentioned acetone, propanone, butanone and pentanone, alone together with propanol or in combination with other ketones, or in combination with one or more polyhydroxy alcohols such as e.g. glycerol, glycol 6.1. The ratio between ketone and polyhydroxy alcohol is not critical and can be varied within wide limits. The primary, secondary and tertiary alkyl and alkanol amines preferably have up to 6 carbon atoms 1 each alkyl or alkanol group. Preferably, the alkyl or alkanol groups have from 1 to 3 carbon atoms, and preferred

2 carbon atoms. The ratio between amines and alcohols is not critical and can vary within wide limits, e.g. from 1:1 to lr'

The present invention clearly offers advantages in relation to the previously used methods, and thus relatively cheap unalloyed steel can be used in the treatment plants in contrast to the more expensive stainless steel grades required for acid treatment. It is also not necessary to use complicated equipment for air treatment, cleaning or waxing. Nor is there any need for special shielding for high temperatures, or equipment for gas development and quenching which was necessary for the vapor phase reduction.

In relation to the use of an aqueous solution of methyl alcohol, an improved result is achieved, and by keeping the pH of the mixture at at least 7, the formation of free acids is avoided.

In the following, the invention will be described in more detail with reference to the attached drawings, which illustrate equipment for carrying out the method.

Fig. 1 shows a schematic flow diagram in a plant for carrying out the method according to the invention, and illustrates a three-zone system whereby the rod is cleaned and cooled in each of the zones. Fig. 2 shows a section through a first treatment zone for treatment of the copper bar that comes out of the rolling mill and in which the treatment fluid is pushed forward in co-flow with the bar's movement. Fig. 3 shows a section through an apparatus used in the transition between the first two treatment zones, with pressurized atomization nozzles for spraying treatment fluid onto the rod coming out of the first zone. Fig. 4 shows a section through an apparatus which is used in the transition between the last two treatment zones and through which the copper rod passes before winding, the treatment fluid being introduced into the rod line in countercurrent to the advance direction for the rod. Fig. 5 shows a section through part of the third processing zone through which the copper rod passes before winding, and also shows a wax treatment section before winding.

With reference to the drawings, in which corresponding reference numbers denote corresponding elements in the various figures, fig. 1 schematically shows a plant 10 for continuous casting, where molten metal is formed into a cast ingot 12 in a casting machine 11. The ingot is rolled in the rolling mill 13, which reduces the cross-sectional area of the ingot and simultaneously increases its length to form the cast rod 14. The cast bar 14 is then subjected to a treatment according to the present invention by being fed from the rolling mill 13 into the first treatment zone 15 - 17. The second treatment zone 17 - 19 serves for further treatment of the bar 14. The third, treatment zone 19 - 21 receives the bar 14 for further processing. Then, if necessary, the rod 14 is cleaned and/or treated with wax in the apparatus 21 and sent to pinch rollers 22, the rod guide mechanism 23 and the winding device 24. Between the first and second treatment zones, there is

a treatment with pressurized liquid (fig. 2).

While the rod 14 moves towards the winding device 24, the treatment solution from the tank 30 is continuously recycled through the plant 10. The treatment solution is pumped from the tank 30 through the line 32 by means of the pump 31 to the water-cooled heat exchanger 33 through the line 34. The treatment solution is sent through the line 35 to each of the treatment zones 15 -17, 17-19, 19 - 21 through respective lines 36 - 39. Return lines 40 and 41 lead the treatment solution back to the tank 30 for further recycling.

The plant outlined above represents an example where three zones are used to bring the hot rod 14 into direct contact with the liquid treatment mixture. In this case, the treatment fluid is carried in co-flow with the rod in the first zone 15 - 17 and in counter-current to the rod in the second zone 17 - 19 and the third zone 19 - 21. However, all three zones can easily be constructed so that they push liquid treatment fluid in countercurrent to the movement of the rod. Furthermore, each of the zones can be changed so that the fluid passes either in countercurrent or cocurrent to the rod's movement. Furthermore, the plant can work with two zones, or possibly just one zone, where cleaning, cooling and coating can be carried out simultaneously. As an example, zones 15 - 17 can be used for cleaning and partial cooling and zone 17 - 19 for cooling and wax treatment^-En. a large temperature difference is achieved when the hot bar enters the cooling line where the colder liquid is brought into contact in co-flow. This first temperature shock promotes the breakdown of the oxide glow shell on the bar surface.

Fig. 2 shows a detailed section through an apparatus that can be used at the entrance to the first processing zone 15 - 17 through which the bar 14 passes for cooling and cleaning, and the unit 15 comprises a housing part 50 with an entrance wall 51 which abuts the housing part of the rolling mill 13, further an exit wall 52

and a guide plate 53, each of which has openings arranged in line to receive the rod 14 from the rolling mill 13. The nozzle 59, which can be used with air, steam or other gases, is placed in and extends through the opening in the entrance wall 51. The air nozzle 59 surrounds the path P in which the rod from the rolling mill 13 is guided. The die

59 comprises a cylindrical housing part arranged in abutment against the entrance wall 51 and a threaded part 62 with a small diameter protrudes through the opening in the entrance wall 51 into the housing part of the rolling mill 13. The nut 6 4 engages with the external threads of the threaded part 62 for to hold the nozzle 59 in place. The cylindrical housing part 61 defines the opening 65 which is arranged in line with the path of movement P of the rod, and the opening 65 is recessed at 66. The recess 66 and the opening 65 are connected by means of a chamfer 68. The supply pipe 69 is connected to the recess 66 through the opening 70

in the nozzle housing part 61. The nozzle insert 71 is threaded into the recess 66 and defines a rod opening 7-2 which is aligned... in line with the path P and the rod opening 65 in the nozzle housing part 61. The inner end of the nozzle 71 forms the tapered part 74 which is sized and shaped to correspond to the tapered portion 68 of the nozzle body portion 61. The diameter of the nozzle insert 71 corresponds approximately to the diameter of the recess 66 in the nozzle 61 with their respective threaded portions, and the nozzle insert 71 is reduced in its outer diameter at 75, between the tapered part 74 and the threaded part 76. An annular supply chamber 78 is thus formed between the nozzle insert 71 and the nozzle housing part 61, which is in connection with the supply pipe 69. The flange 79 extends radially outward from the reduced diameter part of the nozzle insert 71 into the annular supply chamber 78, and the flange 79 is provided with shards at intervals around its circumference. The flange 79 acts as a guide flange and is normally placed near the opening 70 in the nozzle housing part 61. When the nozzle insert 71 is guided as far as possible into the nozzle housing part 61, the flange 79 will move past the opening 70 and slow the fluid flow from the supply pipe 69. The tapered part 74 on

the nozzle insert 71 will also be placed close to the tapered

part 68 on the nozzle housing part 61 and this also acts to limit the flow of fluid from the annular supply chamber 68 into the rod opening 65 of the nozzle 61. Thus, when air, steam or other gas under high pressure flows through the supply pipe 69 from the supply source, both volume velocity and current injection speed into the rod opening 65 could be controlled by moving the nozzle insert 71 inwards or outwards from the nozzle housing part 61. When a usable setting is achieved, the lock nut 80 can be rotated on the threads of the nozzle insert 71 and pressed against the nozzle housing part 61 to lock the nozzle insert 71 in position .

It is thus seen that the nozzle 59 acts to reduce the amount of lubricant carried by the rod 14 out of the rolling mill 13 to a minimum by bringing an annular air flow in general

in a direction opposite to the direction of movement of the rod 14.

As previously mentioned, this air flushing treatment can be omitted if desired when the treatment mixture is miscible with the lubricating oil, as is the case here.

When the rod 14 is moved along the path P and passes from the nozzle 59 through the housing part 50, it will be controlled by the guide plate 53 which defines an opening that surrounds the path P. The guide plate 53 comprises a guide sleeve 86 placed in the opening and defines an annular converging opening 88 for guiding the front end of the rod 14 which first enters the cooling line 16 from the nozzle 59 along the path P. The bottom wall 89 in the housing part 50 comprises a drain pipe 90 which acts to carry away any oil or treatment fluid that could accumulate.

At the exit wall 52 of the housing part 50, injector devices are arranged for the continuous introduction of the treatment solution Vcooling line 16.

The injector devices comprise an injector nozzle 100 connected to the outlet wall 52 and comprise the nozzle housing part 101, the nozzle transition 102, and the nozzle insert 104. The transition 102 and the nozzle insert 104 each delimit rod openings 105 and 106 which are. arranged in line with the rod path P.. The rod opening 105 in the upper;

the gangway 102 exits in the tapered portion 108 while the outside of the insert 104 converges to the tapered portion

109 which is dimensioned and shaped to correspond to the tapered part 108. The housing part 101 defines the threaded bore 110 into which the insert 104 is screwed, and the countersink 111. The annular space between the insert 104 and the countersink 111 forms the annular supply chamber 112,

and the opening 114 is connected to the supply line 36 and leads out into the annular supply chamber 112. The supply line 36 serves to connect a source for treatment,

high pressure fluid with the annular supply chamber 112, and the treatment solution flowing to the annular supply chamber 112 flows between the tapered portions 108 and 109 of the adapter 102 and the insert 104 into the rod opening 105 of the adapter 102, and along the path P

for the rod 14. The flow direction of the treatment solution that flows out through the tapered annular nozzle 116

constituted by the tapered portions 108 and 109 are generally directed along the path P into the cooling conduit 16, which acts to create a flow of treatment solution through the rod-

the wire 16 along the rod 14 in the same direction as the movement of the rod. The line 16 is kept in an almost filled state while the rod is passed through it.

In fig. 3 shows a detailed section through an apparatus

17 arranged between the first processing zone 15 - 17 and the

another processing zone 17 - 19, and a house part 120 is shown

provided with openings arranged in line formed in the entrance

the wall 122 and the exit wall 124, as well as a guide plate 125 which roughly corresponds to the guide plate 53 in fig. 2, around the rod path P. Atomizing nozzles 126, 128 arranged above the rod path P -opposite-

set sides of the guide plate 120 are arranged to direct a stream of treatment solution under high pressure towards the rod 14 which

passes. The effect of the atomization section is to remove oxide scale that has been detached from the surface of the rod 14 after the temperature shock in the first treatment zone 15 - 17.

The pre-dusted liquid emitted by the nozzles 126, 128 also corrects

the incoming treatment solution from lines 16, 18 towards

the openings 130 arranged in the bottom wall 132 of the housing part 120 for return to the tank 30 (fig. 1) through the line 40. By partially separating the oppositely supplied treatment solutions, the tendency to foam formation is reduced to a minimum. Air devices 134, 136 which are connected to the interior of the housing part 120 are arranged on the top wall 138. The guide plate 125 hangs down from the top wall 138 in the housing part 120 and comprises a guide sleeve 139 arranged in the opening which delimits an annular converging opening 140 in order to start by steering the front end

of the rod 14, as previously mentioned. The treatment solution that enters the apparatus 17 through the line 18 comes from the apparatus 19, as can be seen from fig. 4. The apparatus 19 comprises a housing part 150 provided with openings arranged in line formed in the entrance wall 152 and the exit wall 154. The injector nozzle 160 is connected to the entrance wall 152 and is identical to the injector 100 in fig. 2, except that it is arranged so as to inject treatment solution into the cooling line 18 in countercurrent to the direction of movement of the rod 14. The supply line is connected to the line 38 to carry treatment solution to the injector 160. A flow accelerator 170 is connected to the exit wall 154 on the housing part 150 and comprises the housing part 171 and the nozzle body 172. The nozzle body 172 extends through the opening of the exit wall 154 and delimits the opening 173 along its length, and is located in line with the rod path P. An annular groove 174 is turned down in the outer surface of the nozzle body 172, and several openings 175 extend from the annular groove 174 towards the rod opening 173, at an angle directed moi;.-housing part ISO. S.trøm =—- - ning axis accelerator housing part 171 surrounds the annular opening 174 so that an annular supply chamber 176 is defined between the housing part 171 and the nozzle body 172. The supply line 178 is in connection with the opening 179 which runs out into the annular supply chamber 176 and flows through openings 175 out into the rod opening 173. Openings 175 are arranged so that the speed of the treatment solution flowing into the rod opening 173 is directed towards the housing part 150, and this induces

a fluid flow through the rod opening 173 towards the housing part 150. • Liquid in the line 20 will thus further be brought to flow towards the housing part 150.

The outlet line 180 is connected to the housing part 150 through

the bottom 182. The air opening 184 is connected to the housing part 150 through the top wall 186. Treatment fluid that has flowed in"

in the housing part 150 from the flow accelerator 170 or from the cooling line 20 will thus be emptied away through the line. 180. Correspondingly, gases that may be present in house-

the part 150 is vented through the vent opening 184. It must

it is mentioned that under normal operating conditions the rod 14

leaving the second treatment zone 17 - 19 in an approximately clean state at a temperature lower than that at which some particularly

renewed oxidation of the rod can take place at the exit from the final treatment zone, e.g. 66°C. A third processing zone approximately identical to the second processing zone can optionally be arranged for increased production speed. For the sake of completeness, it is mentioned that the third zone can be a combined treatment and cleaning zone approximately as shown in the previously mentioned US patent document No. 3,623,532 (fig. 5) modified to receive the non-

acidic treatment solution used here, or as shown in fig. 5, an apparatus 21 comprising a housing part 200 divided by means of guide plates 201, 202. The entrance wall 203, the exit wall 204

and the guide plates each delimit openings arranged in line around the rod path P, so that the rod 14 can pass through the housing part. Guide sleeves 205, 206 which are carried by the guide plate 202 and output

the wall 204 guides the front end of the rod 14 along the path P. The injector 207 which is placed in the entrance wall 203 to-

the injector 160 in fig. 4, and treatment solution from the tank 30 enters the injector 207 through the line 39 under pressure and is connected to the line 20 through which the rod 14 passes. The direction of flow for the treatment liquid is in countercurrent to the movement of the rod. However, the liquid can instead be made to flow in cocurrent with the direction of movement of the rod.

A wax application nozzle 208 is provided in the guide plate 201 on

downstream side of injector 207. Wax application nozzle 208

is corresponding to the nozzle 59 in fig. 2. Line 209 communicates with a wax supply source (not shown) for supplying wax under pressure to wax application nozzle 208. The surface of rod 14 is thereby coated with wax as it passes. An outlet line 210 in the bottom 211 of the housing part 200 leads unused wax back to the supply source (not shown). If desired, a nozzle corresponding to the nozzle 59 in fig. 2 is placed immediately after the wax application step to blow excess wax away from the rod 14 and dry it. However, this can be omitted, as the rod has retained sufficient latent heat for self-drying after coiling.

The air opening 211 in the top wall 212 of the housing part 200 serves

to lead gases out from the housing part 200 to the atmosphere. The equipment that comes after the combined treatment-wax application device that is discussed here comprises pinch rollers 22, rod control mechanism 23 and winding device 24, schematically shown in fig. 1 in the drawings. These devices are described in detail in US Patent No. 3,623,532. It may be mentioned that the wax application device can be omitted when the treatment mixture used has added a miscible lubricating material which reduces further oxidation to a minimum and acts as a lubricant for subsequent threading operations.

For additional protection, a separate growth step can be used if desired.

In the following, examples of a liquid mixture shall be given

and its use in the method according to the invention - EXAMPLE 1

Preparation of a non-acidic treatment solution took place as follows:

A concentrate of a treatment solution contained the following components in the indicated quantities:

t 9,460 1 diluted aqueous solution containing approximately 2% of.

the above concentrate was prepared in a container to provide a circulation rate through the system of approximately 1135 l per my. The pH of the diluted treatment solution was adjusted to 10 by adding sodium hydroxide. 4.5 kg of calcium acetate was added to suppress foaming.

EXAMPLE 2

The treatment solution prepared in accordance with example 1 was introduced into the tank 30 in fig. 1 shown in the drawings and was continuously recycled through the system at a rate of approximately 1135 kg per minute. my. The working conditions under stable equilibrium conditions were the following:

Periodic analyzes of the treatment solution that was recycled showed that the copper content built up to approximately 40 ppm, which is far less than what occurs with acid pickling. The oxide scale was continuously removed by filter devices arranged in the pump outlet. Refreshing solution was periodically added to the system (approximately 19 l/hour).

The copper rod which had been treated in the manner described was found to be uniformly free of oxide scale. A significant advantage lies in the possibility of working at much higher production rates than the previous technique with the removal of glow scale by means of vapor phase reduction and without the disadvantages that automatically accompany both the acid pickling method and/or the vapor phase reduction method occurring.

Claims (2)

1. Procedure for treating a continuously cast copper rod which, when it comes out of the rolling mill, has an oxide layer on the surface and where the oxidized rolled rod with a temperature of approx. 540°C is passed through at least one treatment zone comprising an elongated, open-ended channel for introducing a colder, liquid treatment mixture, containing a reducing agent, the oxidized rolled bar being brought into contact with the liquid mixture to convert the oxide layer to metal while the rod is cooled to a temperature below approx. 93°C, and as the mixture is continuously recycled, characterized in that it is brought into contact with the oxide layer as a liquid mixture. a diluted aqueous mixture containing propanol is used, preferably together with either polyhydroxy alcohols, ketones, alkyl and alkanol amines, secondary and tertiary amines, or a combination of two or more of these substances, as the mixture's The pH is maintained at at least 7. 2. Method as stated in claim 1, characterized in that the pH of the mixture is kept between 9 and 11.