US 3375695 A
Description (OCR text may contain errors)
United States Patent 3,375,695 METHOD OF COLD ROLLING George A. Knapp, Canfield, Ohio, assignor to Reactive Metals, Inc., a corporation of Delaware No Drawing. Filed Feb. 16, 1966, Ser. No. 527,738 5 Claims. (Cl. 72-365) This invention relates to cold rolling titanium, zirconium or alloys thereof. More particularly, the invention relates to a method of cold rolling sheets and thin plate up to about Ai-inch thick of relatively low ductility.
Titanium, zirconium and their alloys are attractive materials for many applications because of their unique properties. Thus, for example, high strength titanium alloys have become increasingly more important because they provide a higher strength-to-weight ratio than conventional structural materials. Among the foremost uses for titanium alloy sheet has been in the aerospace industry. Surface quality is an important factor in such applications and cold rolling is necessary to obtain good surface characteristics. However, cold rolling some materials is made difficult by their relatively high strength, hardness and crystalline structure. In particular, a problem has been encountered in cold rolling sheets and thin plates of these materials because extensive slivering at the ends of the sheet sometimes occurs. End slivering is very undesirable because it precludes further processing of the sheets and causes damage to the rolls in the rolling mills and thus, results in a high production cost. Historically high costs have been a serious impediment to the development of commercial applications for titanium, zirconium and their alloys.
In general, slivering of the ends during cold rolling is due to over-rolling at the end sections of the sheet. This occurs because there is always greater reduction at the ends and, therefore, the ends have a tendency to crack or sliver when the strain (or work) exceeds the critical strain limit of the material. End slivering does not occur with 'all titanium alloy compositions. It occurs with the less ductile materials and especially those which have a hexagonal-close-pack crystalline structure. This structure has only three sets of planes (1010), (103(1) and (0001) on which slip can occur and one slip direction, i.e., the . Alloys with this predominant crystalline structure generally have a high rate of work hardening. Certain alpha and alpha-beta alloys, and high strength grades of unalloyed titanium, have low limits of only a few percent for cold rollability before serious end slivering occurs. However, but for this end damage, these same materials would have capacity for to 35 percent cold rollability without internal damage.
Considerable effort has been made to avoid end slivering; however, little success has been achieved. One approach has been to bevel sheet ends to reduce the high localized rolling forces which occur and thereby reduce the tendency for critically straining the ends by overrolling. Another approach which has been tried is to raise the mill rolls when the sheet enters and leaves the mill. However, this results in slow production rates and considerable scrap loss due to the heavy ends which have to be sheared off. I
I have found that titanium and zirconium alloy products can be satisfactorily cold rolled with minimum end slivering or cracking by providing the ends of the sheet with metal tabs of higher ductility than the titanium or zirconium sheet or plate. The tabs are joined, as by welding, to the ends of the sheet or plate transverse to the direction of rolling, after which the sheet or plate is cold rolled to gauge. The t'abs may be removed after cold rolling.
3,375,695 Patented Apr. 2., 1968 As an illustration of the preferred embodiment of the invention, a commercial titanium alloy containing 5% aluminum, 2.5% tin and up to 0.2% oxygen was processed as described below.
The titanium alloy was provided 'as a sheet 0.04-inch thick, 36-inches wide and 120-inches long. It was annealed at a temperature of 1500" F. and. then air cooled, descaled and pickled. Unalloyed low strength titanium metal tabs 3-inches long and 36-inches wide were buttwelded to the end of the titanium sheet. The tabs were of commercially pure titanium which has a maximum oxygen content of 0.20% and is considerably more ductile than the titanium alloy sheet.
The so-prepared sheet was then cold rolled 15% to the desired gauge without end cracking or slivering. After cold rolling, the material was degreased to remove rolling lubricants and the end tabs were removed by shearing. After the ends were sheared, the titanium sheet was annealed at 1500" F. for minutes and then air cooled followed by descaling and pickling.
The welding of ductile tabs to the ends of a sheet prior to cold rolling avoids end slivering and the processing difficulties which result. Any material than can be welded to titanium and which is more ductile than the titanium alloy sheet may be employed. However, commercially pure, low strength titanium strip has been found to be very satisfactory. Similarly, sheets or thin plates of any titaniumor zirconium-containing material may be processed according to the invention; for example, sheets, etc. of such titanium alloys as Ti-8Al-1Mo-1V (alpha alloy) Ti-2Al-4Mo-4Zr (alpha-beta alloy) Ti-4 to 6A1 (alpha 'alloy) Ti-6Al-4V (alpha-beta alloy) Ti4Al-3Mo-1V (alpha-beta alloy) Ti5 to 7 Al-ZCb-lTa with or without. /2 to 1% Mo (alpha-beta alloy) may be cold rolled without end slivering by welding ductile metal tabs to the ends.
1. In the method of producing cold rolled sheets or the like of titanium, zirconium, and alloys thereof of good surface quality wherein the low ductility of the sheet renders it susceptible to end slivering and consequent disruption of the sheet processing operation, the improvement which comprises joining metal tabs of greater ductility than the sheet to ends of the sheet transverse to the direction of rolling and cold rolling the sheet whereby the ends of the sheet may be cold reduced to the same gauge as the remainder of the sheet without end slivering.
'2. A method according to claim 1 wherein the sheet is an alpha titanium alloy.
3. A method according to claim 1 wherein the sheet is an alpha-beta titanium alloy.
4. A method according to claim 1 wherein the sheet is high strength, unalloyed titanium.
5. A method according to claim 1 wherein the metal tabs are low strength, unalloyed titanium.
References Cited UNITED STATES PATENTS 2,993,269 7/1961 Kelley 29-424 3,021,887 2/ 1962 Maynard 29-423 RICHARD J. HERBST, Primary Examiner.
L. A. LARSON, Assistant Examiner.