DE1533015B1 - PROCESS FOR MAKING CORROSION RESISTANT SEALER NICKEL COVERS ON STEEL TAPE - Google Patents

Description

The composition of the slurry and the method of applying it to the tape are in accordance with the parent patent application. As mentioned earlier, the slurry must first be dried at a low temperature, and it is important that it does not evaporate as it dries. Preferably the slurry contains a binder both to bind the nickel powder in the slurry layer formed on the belt and to better suspend the powder in the slurry. Methyl cellulose has proven to be a suitable binder for this purpose. If the slurry contains methyl cellulose, the dried slurry layer must be heated to drive off the methyl cellulose. This may be accomplished by heating at 250 to 450 ⁰ C carried out in a reducing atmosphere before the hot compaction. The inventive annealing of the dried layer at 500 to 650 ^° C. ensures complete removal of the methyl cellulose, with the residual carbon content of the layer being reduced at the same time. It can be assumed that such cleaning of the nickel layer leads to the improved corrosion resistance of the coating compared to the previously known.

Some exemplary embodiments of the invention are described in detail below:

example 1

First, a creamy slurry was prepared with the following composition:

100 ml water,
275 g nickel powder,

0.75 g methyl cellulose,

0.75 ml of polyoxyalkylated polyalkalene glycol.

The specific bulk density of the nickel powder was 1.8 g / cm ³ and the particle diameter was 3 to 4 μm.

The slurry was applied to degreased, cold rolled and annealed strip of mild steel applied with a width of 76 mm and a thickness of 1.6 mm in an approximately 0.23 mm thick layer. The coated tape was air dried at about 60 ° C, in. 380 ° C for 5 minutes Reducing atmosphere of cracked ammonia and then annealed by rolling in Warm compressed air. It has been found that there is a temperature loss between the oven and the rollers of 10 to 20 degrees results, so that the actual rolling temperature was between 360 and 370 ° C. The roller diameter was 203 mm and the roller pressure was about 340 kg per millimeter Tape thickness.

The densified tape was then annealed in cracked ammonia at 700 ° C for 1 hour, followed by cooled and then cold rolled to a thickness of 0.76 mm. The final thickness of the coating on the tape, which had an excellent surface area, was 0.038 mm. A sample of the coated The tape was immersed in boiling water for 6 hours, whereupon it was found that the Coating was essentially impermeable and had negligible porosity.

Example 2

First, a creamy slurry of the following composition was prepared:

200 ml water,

1.5 g methyl cellulose,
525 g nickel,

1.5 ml polyoxyalkylated polyalkylene glycol,

1.5 ml silicone anti-foam emulsion,

1 ml 0.880 normal ammonia.

The slurry was sprayed onto three test pieces of steel belt according to Example 1, whereby a surface layer of 0.3 to 0.33 mm in thickness resulted. The strips were dried in air, calcined at 381-385 ⁰ C in cracked ammonia and by rolling in hot air according to Example compacted. 1 The roller pressure was between 283 and 306 kp per millimeter of strip thickness.

The compacted pieces of tape were then annealed for 1 hour at 700 ⁰ C in cracked ammonia, then cooled and cold rolled as a lubricant at a thickness reduction of 50% using white spirit. The test pieces were then galvanically chrome-plated in the conventional manner with a 0.25 μm thick coating and subjected to the so-called CASS test (copper-accelerated acetic acid salt spray test, according to British Standard 1224: 1965, Appendix F). After 16 hours, all three samples had a protective value number of 9 according to the following series of guidelines, in which the individual protective value numbers are compared with the number of punctiform rust spots on a sample with a surface area of 200 cm ² :

35

40

45

Protection value number Number of rust spots 10
9 0
2
r ö
7th
6th
5 O
12th
24
60

Example 3

First, a creamy slurry of the following composition was prepared:

475 g nickel powder,
200 ml water,

2 g methyl cellulose,

1.5 ml polyoxyalkylated polyalkylene glycol.

This slurry was applied to the steel strip in such a way that it ran over a kind of weir onto a hot-rolled, 102 mm wide and 1.4 mm thick steel strip which had previously been _{pickled in 10% HNO 3} to remove the scale. The layer thickness of the slurry was 0.36 to 0.38 mm.

The test tape was dried in air, calcined in cracked ammonia at 419 ° C. and hot-compacted in air as in Example 1. The roller pressure was about 368 kp per millimeter of tape thickness. Subsequently, the strip was annealed for 1 hour at 700 ⁰ C in cracked ammonia, cooled and cold rolled as a lubricant then with a thickness reduction of 50% using white spirit. Of the

coated strip was 0.25 μπα thick Electro-chrome plated layer and then subjected to the CASS test according to Example 2. After 16 hours the test tape had a protective value of 9.

Example 4

First, a creamy slurry was prepared with the following composition:

100 ml water,

237.5 g nickel powder, 1 g methyl cellulose,

0.75 ml of polyoxyalkylated polyalkalene glycol.

The slurry was transferred to two test pieces of a cold-rolled and annealed steel strip of 76 mm width and 1.58 mm thickness, the previously degreased and pickled for 30 seconds in 10 ° / ₀ HNO ₃ and was then rinsed. The pickling took place in order to roughen the strip surface and in this way to increase the adhesion of the nickel-ao coating. After drying at 6O ⁰ C, the thickness of the layer was 0.43 mm to 0.48.

The samples were then calcined for 10 minutes at 600 ± 5 ° C in cracked ammonia and cooled to 410 ° C, then transferred to a roll stand, the rolls of which had a diameter of 203 mm, and in air at a roll pressure of 352 or 352 mm. 404 kp per millimeter of strip thickness and a rolling speed of 3.0 m / min. The densified strips were then annealed in cracked ammonia at 700 ° C for 1 hour and cold rolled _{using white spirit as a lubricant at a thickness reduction of 50 ° / 0.} Both sample tapes were then galvanically chrome-plated with a 0.25 μm thick layer and subjected to the acetic acid salt test (according to British Standard 1224: 1965, Appendix H). This test is less difficult than the CASS test, ie 16 hours of the CASS test corresponds to 96 hours of the acetic acid salt test. The protective value of both test tapes was 9, corresponding to the number series given in Example 2 after 120 hours in the acetic acid salt test, ie after a corrosive attack that was stronger than the test tapes of Examples 1 to 3. This results in the advantageous effect of the - Annealing before hot compaction.

Claims (5)

1 2 layer is re-compacted by cold rolling. Dem- patent claims: according to the process according to the main patent registration, the sintering, rolling and second sintering 1. Process for producing corrosion-resistant by two other process steps, namely a dense nickel coating on steel strip, with 5 hot densities and subsequent annealing, replaced with a powder layer on the steel strip. In general, the sintering takes place at 700 ⁰ C and wear, sintered, compacted by cold rolling and more, so that the hot compacting must take place at a temperature below this value after further sintering by cold rolling; is compressed, wherein the nickel powder as water, this temperature may be quite low and containing paste is applied and for example be at least 25O ⁰ C before sintering i _0, there is, however, is dried, after patent application generally somewhat higher. About 500 ⁰ C in air is P 14 58 275.3-24, characterized However, oxidation gekennzeich- place so that übern et at 500 ° C, that the grout in known increasing temperatures in the hot compacting manner and dried, the coated strip at a protective gas or reducing atmosphere at a temperature of 250 to 650 ⁰ C, at temperature i ₅ must be carried out. temperatures over 500 ⁰ C, preferably in reducing the coated strip, prior to Warmverdich- Atmosphere, hot-rolled and annealed and for a short time at the aforementioned temperature Layer is compacted by cold rolling. being held; hot compaction then takes place 2. The method according to claim 1, characterized directly from the glowing heat. records that the coated tape before the 20 It has now been found that at a sufficiently high Hot rolling annealed at 500 to 65O ⁰ C and pressure during hot compaction and a is then hot rolled in a heat. sufficiently high temperature the powder particles themselves 3. The method according to claim 1 or 2, characterized with each other and with the strip to be coated that the annealing ^{connect at 600 to 700 0} C, although it takes place at too high a pressure in the. 25 The coating cracks, but the coating is stuck to the 4. The method according to any one of claims 1 to 3, tape adheres. The pressure required depends on the characterized in that the cold rolling in strip thickness and the roll size from and changes two or more stages takes place and the coated essentially with the root of the tape thickness and Band is annealed between every two stitches. of the roll diameter. The one for hot compaction 5. The method according to any one of claims 1 to 4, 30 required pressure can, however, easily by experiments characterized in that the coated are determined. Annealed strip after final cold rolling The coated strip is annealed will. preferably at 600 to 700 ⁰ C, ie below the Temperature at which significant sintering occurs. 35 Cold rolling can be done in two or more stages take place, with the coated tape between each two stitches is annealed. In the first stage, the Coating, for example, up to 70 to 85% of the theoretical maximum density and in the second stage up to The invention relates to a method for being compressed to the maximum density. Making Corrosion Resistant Dense Nickel Over- It is inevitable that as a result of cold rolling pulls on steel belt, where a powder layer occurs in the coating of the belt, the steel strip is applied, sintered, by cold rolling compressed and, after further sintering, the material makes it less corrosion-resistant than cold-chip rolling is re-compacted, the nickel-free material 45. Preferably this will be powder Applied as a water-based paste and in front of the layered steel strip to further increase its Sintering is dried, according to the patent application corrosion resistance therefore a final one P 14 58 275.3-24. Subjected to stress relief annealing. According to the procedure of the main patent application. The present invention makes it unnecessary to the steel strip can be heated to sintering temperature with an essentially 100 ° / _{0 igen 50.} Nevertheless, density of the nickel coating can be produced, ie the annealing can also be carried out at higher temperatures, the nickel coating has almost the theoretically ^{possible maximum density, for example up to 800 °} C., and is therefore not porous. However, sintering then already results and such a high density gives the tape the economic advantages of the method in terms of corrosion resistance, but for the production of which a lower temperature is lost. In a similar way, four steps, namely sintering, rolling and the strip can optionally also be warm instead of further sintering and rolling. be cold rolled, yet it is in view of a It has now surprisingly been found that about 100 ° / ₀ strength density is not not necessary to heat the tape sintering the dried slurry ever more than 700 ⁰ C, is required. According to the invention, therefore, the layer dried according to the method according to the invention by rolling the strip with a layered steel strip has a good corrosion-increased temperature, but below the sintering temperature resistance; however, it was found that the temperature of the layer densified. In particular, the corrosion resistance can be further improved in accordance with the invention in that the slurry layer per se, if the dried slurry is dried in a known manner and the coated band 65 carrying band is compacted to 500 to at a temperature of 250 to 650 ^{0 before hot} C, at a temperature of 650 ° C, ie as high as possible, but below the temperatures above 500 ⁰ C, preferably in a reducing sintering temperature of the dried layer, heated atmosphere, hot-rolled and annealed and the is.