US2393675A - Art of cold die working scaled stainless steel - Google Patents

Description

ART OF GOLD DIE WORKING SCALED STAINLESS STEEL ames M. Fenner, South Euclid, nomad a. Griffiths, Cleveland Heights, and Arch W. Harris, Euclid, Ohio, assignors to The American Steel and Wire Company of New Jersey,

tion of New Jersey No Drawlng. Application February 14, 1945.

Serial No. 577,930

7 so as to coat 'the graphite particles with the a calcium stearate, the drawing preferably involv- This invention is concerned with the art of cold drawing wire from stainless steel rod and wire stock having scale on its surface of the type produced by its hot working and annealing under oxidizing conditions. This type of scale is formed on stainless steel rod that is hot rolled from a billet in air in the currently conventional mane ner, and also by annealing stainless steel rod and wire when no effective against air contacting it while it is at annealing temperatures. It is the type which prior to this invention had to be removed by pickling before the steel could be cold drawn into wire through a wire drawing die, because its brittle and abra-' sive nature made its drawing through the die commercially impracticable. The stainles steel with which the invention is concerned is any of the ferritic grades containing at least 12% chromium and any of theaustenitic grades, all of these grades producing the described scale type in forms that make it harder to remove it than do the forms produced on plain carbon and low alloy steels, and which make itmore destructive to wire drawing dies. Also, these stainless grades are inherently harder to draw than the other steels named, and prior to this invention they not only required more expensive pickling to remove the scale, but also required the extra steps of lead coating topermit their drawing, and the subsequent removal of the lead.

However, this invention this type of scale so it such stainless steel rod and wire during its cold drawing through a wire drawing die, but also so as to condition it so it permits drawing of such rod and wire without lead coating the latter.

'I'heprinciples of the invention may be understood from the advancement of specific examp es.

To cite one example, ferritic stainless steel of the straight 12% chromium grade is hot rolled in air from a billet into a inch diameter rod in the currently conventional fashion so its surface has the described type of scale. Then the cold rod bundle isimmersed in a strongly alkaline water solution'heated to from 180 F. to boiling temperature, the bundle being left in this solution for from 20 to 30 minutes. Next, while still wet with such a solution, the bundle is limed in the usual manner excepting that baking is necessary only to dry the lime solution. Finally, the rod from the bundle is dry drawn through tungsten carbide wire drawing dies using a lubricant consisting by weight of 80% calcium stearate, 15% graphite and 5% dry lime intimately mixed provides for treating I not only can be left on protection is provided ing heavier reductions in the first draft and with the succeeding draft reductions becoming lighter by comparison with the first, as the drawing progresses and the stock work hardens. The rod is 1; inch diameter and it is drawn in three drafts down to .192 inch diameter before annealing is required. by the work hardening eflect. Annealing is then carried out without cleaning the stock and with air contacting the stock at annealing temperatures to develop more of the described type of scale, and the stock is then again treated, limed and lubricated as described and drawn down in one draft to .1875 diameter which is the finished size. At this time simple acid cleaning with a water solution of either hydrofluoric, hydrochloric, sulphuric acids, etc., sufllc'es to remove the scale, lime and lubricant left on the finished wire.

As a second example, austenitic stainless steel of the 18-8 grade is similarly hot rolled into rods having a diameter of 1'; of an inch, but since this grade must be stabilized against carbide precipitation by quenching. from temperatures around 2100' F., the rod is heated to these temperatures and then quenched by passing it continuously through a strongly alkaline water so lution to both stabilize it and condition its scale for drawing. as was done in the first example by the more prolonged immersion. That is to say, ierritic steels cannot be quenched because they would harden, so in such instances the bundle is put while cold into the heated solution and so requires time to heat to the solution temperature,

. while austenitic steels often must and always can be quenched from very high temperatures. In this instance of austenitic steel it is enough to let the solution contact the rod for 5 seconds, remembering the. continuous nature of the immersion, and the heat left in the rod dries it. Therefore, the rod is rewet with the solution before the liming, or is wetted with some other wetting agentpromoting wetting of the rod with the lime solution during liming. It has been found preferable in all instances to have the rod wet with some good wetting agent prior to liming.

' Otherwise than noted, the 18-8 rod may be drawn and cleaned as was: the straight 12% chromium grade.

Now it will be noted that these examples show a that one characterizing feature of the invention is the discovery that the scale which in commercial practices is always formed as the result of processing the steel into rod or 'by its heat treatment and which has caused so much trouble in the prior art is conditioned so that it not only ceases to cause trouble, so it need not be removed, but also so it actually substitutes for the lead coating formerly necessary when th higher alloy stainless steel grades were die worked; so it becomes pertinent to more fully discuss the strongly alkaline water solution used for this conditioning. v

This solution may be made or a water solution of any alkaline substance providing the solution with sufficient alkalinity, and the degree of alkalinity may be determined simply by following the procedure described and adjusting the alkalinity until a value is found enabling successful drawing of the scaled rod. The required degree of alkalinity varies with the immersion time of the scaled rod in the solution and with the solution temperature, a lower degree being required with longer immersion time and higher temperatures and vice versa. However, the time in both batch handling and continuous immersion is limited in commercial work; and the solution temperature cannot exceed its boiling temperavides a degree of alkalinity making effective thetime values given in the two specific examples. A water solution of sodium hydroxide or sodium carbonate providing a similar degree of alkalinity may be substituted. Another commercial available alkaline detergent consists in per cent by weight of 41.40 NaaCOa, 29.60 NasPOaZHzO and 29' rosin soap; and about 5 to 8 ounces per gallon of water provides a solution that is also effective. In no event should the immersion time be so long as to remove substantial amounts of the scale being treated to make it substitute for lead coating during the drawing.

As indicated, it is important that such a so-- lution also be used to wet the rod and wire stock prior to liming, but this solution may be applied to the scaled stock cold when considered only as its being used for its function as a wetting agent during the liming. If possible the stock is preferably limed while still wet from its treatment with the solution at elevated temperature to condition its scale for drawing, but if it dries it should be rewet with the solution or its equivalent prior to the liming.

The lubricant used must be of such a nature as to function as a wire drawing lubricant under the heavy pressures and consequently high temperatures encountered in drawing the high alloy stainless steel grades here involved, and theme asoaevs specifically described does this. Others may be substituted providing they do not fall to function as a wire drawing lubricant during the cold drawing through the wire drawing die. For instance, any metallic stearate and graphite may be used, if the graphite is covered with the stearate.

We claim:

1. In the art of cold die working stainless steel stock having scale on its surface of the type produced by its hot working and annealing under oxidizing conditions, the improvement comprising contacting said scale with a strongly alkaline water solution at elevated temperature for a time less than removes substantial amounts of said scale from said stock, lubricating the stock and cold die working the lubricated stock, all with said scale on the stock.

2.1In the art of drawing wire from austenitic stainless steel rod and wire stock having the scale on its surface of the type produced by its hot working and annealing under oxidizing conditions, the improvement comprising quenching said stock from a temperature where its carbides are in solution by continuously passing it through a strongly alkaline water solution, liming the stock, lubricating the limed stock, and cold drawing the limed and lubricated stock through a wire drawing die,- all with said scale on the stock.

3. In the art of drawing wire from ferritic stainless steel rod and wirestock having scale on its surface of the type produced by its hot working and annealing under oxidizing conditions, the improvement comprising immersing the stock in a strongly alkaline water solution at temperatures of from F. to its boiling temperature for from 20 to 30 minutes, liming the stock, lubricating the limed stock, and cold drawing the limed and lubricated stock through a wire drawing die. all with said scale on the stock.

4. In the art of drawing wire from stainless steel rod and wire stock having scale on its surface of the type produced by its hot working and annealing under oxidizing conditions, the improvement comprising contacting the scale with a strongly alkaline water solution at elevated temperature, liming the stock while wet with this solution, lubricating the limed stock with a mixture of metallic stearate and graphite with the metallic stearate coating all the graphite particles, and cold drawing the limed and lubricated stock through a wire drawing die without lead coating the stock, all with said scale on the stock, the alkalinity, temperature and time of said contacting being adjusted so the scale draws through said die and substitutes for a lead coating.

JAMES M. FENNER. RONALD E. GRIFFITHS. ARCH W. HARRIS.