US2175620A - Treatment of sheets, thin bars, and the like - Google Patents

Description

UNITED STATES PATENT OFFICE TREATMENT OF SHEETS, THIN BARS, AND THE LIKE Russell R. Smith, Hillard E. Miller, and Ralph H. G clder, Ashland, Ky., assignors to The No Drawing. Application March 10, 1937,

Serial No. 130,216

1 Claim. (Cl. 148-8) Our invention relates to a treatment for that the sheet is later enameled, plated, bondersheets, thin bars'and the like,'by which we preized or otherwise treated. pare them for such subsequent treatment as en- Since the pickling bath usually contains sulameling, painting, ducoing, bonderizing, nickelphuric acid, either alone or in combination with 5 plating, galvanizing, cadmium plating and alloy other acids such as muriatic acid, the reaction 5 plating. Sheets which are ultimately to be used of the acid on iron or steel will form sulphates or for any of the above named purposes must be of chlorides which are not removable with lime. very high quality, in order that the various coat- We have found that the various above menings will adhere well to the base metal. It is tioned deleterious results may be eliminated by a .o then necessary to reduce the metal to the proper cyanide neutralizing bath. For this purpose, thickness and to have the final sheet perfectly we prefer to use sodium cyanide, although poclean, so that it will bond with the coating which tassium cyanide or other cyanide solutions will is t be app]ied accomplish the same purpose. The afore-men- Briefly, we prefer to carry out our process on tioned sulphates are readily soluble in a solu- 13 sheets, strips, thin bar and the like in the foltion of sodium cyanide and they are therefore 15 lowing manner: Commencing with a slab, we hot removed from the surface of the sheet and th roll this slab, for example, on a continuous hot sheet is left chemically clean. strip mill or a hot sheet jobbing mill, to thin bar The neutralizing bath, which contains a suitgauge. We then pickle the material and then able cyanide such as sodium cyanide, is prefreduce it to final sheet gauge either on a cold or erably held at a temperature of from 140 to a hot mill. If the preliminary steps of this proc- 180 F. although higher or lower temperatures ess as above outlined have been carried on so may be used, and is maintained at a strength of that we now have a long strip of metal, we may om 1 t0 u ce f od m yanide per proceed directly to normalize, while if we have on of Solution- The p ture of the bath short lengths of metal, we prefer to stitch them will depend upon the type of drying to which 25 so as to produce 'a long strip. We then northe product is to be subjected, and also upon the malize the strip and pickle it. We then prefconcentration of the solution. We have found erably pass the strip through a hydraulic spray of that very much weaker concentrations may be cold wtaer at high pressure (for example 300 used and also that concentrations up to one or 3 lbs. per square inch) and then through a low more c s per al could be used- Experi- :0 pressure cold water spray (for example 80 lbs. ence has shown, however, that increased amounts per square inch) in order to wash it. We then of sodium cyanide do not materally improve the pass the sheets or strip through a tank containproduct. The sheets are immersed in the cyanide ing a cyanide solution and then again wash the tank from four to five seconds, up to thirty-five trip d dry it by passing it through parallel or forty seconds, depending on the speed with 35 high pressure jets delivering either hot air, steam, Which the strip passes through the tank. The or high pressure hot water, and then through a Speed With wh h t e St p passes through the drying furnace which is maintained at a temtank is a function of the preceding pe s,

I perature sufficient to complete the drying of the namely normalizing and pickling.

sheet. The sheets may then pass through several An after treatment of cyanide neutralized 40 loop pits and are then sheared to length. sheets may comprise, for example, a temper roll It will be noted that in the above series of through one or more passes of temper mills, steps, we pass the sheets or strip through a tank which may be of the two, three or four-high containing a cyanide solution. The purpose of variety. These passes may be made with water,

this cyanide solution is to neutralize the sheets with steam, with gas, or dry. The sheets may after the pickling step. It has been usual to then be roller levelled. Another after treatment use a lime bath for pickling purposes, but we have which we have found to be desirable involves the found that a lime bath is not always satisfactory, after treatment discussed above, followed by box because it merely neutralizes the portions of free annealing at temperatures from 809 to 1450" F.

5 acid which remain on the sheets and does not sheet temperature. Various gases may be introremove the usual pickling. deposit or smudge. duced into the annealing box to prevent oxi Furthermore, since lime is but slightly soluble in dation of the sheet surface. water, it adheres to the sheet as free lime which Another after treatment which we have found. later causes trouble because it promotes rust desirable may include the treatments above outand has other detrimental effects, in the event lined, followed by a further temper rolling on 55 two-, three-, or four-high mills, either wet or dry or both, and a roller leveling.

We have found that the box annealing step changes any traces of sodium cyanide which may remain on the sheet into sodium carbonate.

Where the sheets are to be subsequently galvanized, they are prepared as outlined above. Various routings may be used preceding the cyanide treatment, depending on the temper required in the galvanized product. After the cyanide treatment, the sheets are dried by one or more of the aforesaid mentioned drying media and roller leveled in preparation for the galvanizing operation. We have found that cyanide treated sheets are free from injurious sulphates and as a result the characteristics of the galvanized product are very much improved. We have noted an improved adherence of the galvanized coating and have been able to obtain a better control of the coating and an improved appearance. The galvanizing operation may, of course, be done with sheets or coils.

We may use our sodium cyanide neutralizing in the preparation of thin bar for cold reduction either in sheets or coils. For this purpose the sodium cyanide is used as a neutralized after pickling, as above outlined, and the sheets rolled from thin bar so treated, will have a better appearance due to the fact that a clean white thin bar is used. In this product we have noted im proved bonderizing characteristics, improved en amel bonding, improved plating characteristics and greater resistance to rust. The thin bar referred to above, may vary from .050 to .250 in thickness and may be up to 96 inches wide.

The above mentioned cold reduced sheet may be used with the heat treatment or it may be normalized and box annealed at various temperatures up to 1450" F. or it may be box annealed alone. In addition, various tempering processes may be included at certain stages of the operation.

It is to be understood that modifications may be made in our process without departing from. the spirit of our invention and that we intend to be limited only by the appended claim.

What we claim as new and desire to secure by Letters Patent is:

A process of cyanide neutralizing pickled iron and steel sheets to be subsequently coated, in which the cyanide solution is maintained at a temperature from 140 F. to 180 F., at a concentration of from .120 to .150 ounce per gallon of solution, and in which the duration of the 3;..-

from 4 to 40 seconds.

RUSSELL R. SMITH. HILLARD E. MILLER. RALPH H. GELDER.

neutralizing step is