DE1273827B - Process for the production of tapes from magnesium alloys which can only be hardened by cold forming - Google Patents

Description

Process for producing strips from only by cold working hardenable magnesium alloys The invention relates to a method for Manufacture of strips from magnesium alloys that can only be hardened by cold forming, the z. B. 3% Al, 1% Zn, 0.2% Mn, by rough rolling at 426 bis 204 ° C or above the recrystallization temperature to 118 to 143 ° / o above the Final thickness and finish rolling at a temperature below 204 ° C or the recrystallization temperature.

So far, when rolling from such magnesium alloys Cast ingots of moderate dimensions only produced short sheets or plates.

It is also known to produce a ductile shape of one made of a magnesium alloy sheet, the reduction in thickness is very hot Metal and the final stage of this operation in a temperature range from 4 to 177 ° C after previous annealing, followed by another annealing. Even there is a relatively large reduction in thickness at one above the recrystallization temperature temperature and the metal is usually annealed at 260 to 482 ° C. Annealing could be omitted for hot rolling over 315 or 260 ° C. After hot rolling or after this subsequent annealing, rolling to the final thickness took place below the recrystallization temperature.

There has heretofore been no viable method of rolling out such just by Cold stretching of hardenable magnesium alloys into strips and subsequent winding to a covenant while avoiding undesired twinning or at the same time occurring uneven grain growth after subsequent unrolling to a flat track and after heating, as is the case for the usual bending and deformation processes is required. Twinning and irregularity occurring in certain places Grain growth has a detrimental effect on the flatness and also on the mechanical Properties of the tape.

Therefore, the aim of the invention is to provide an improved method of manufacture of a strip made of the specified magnesium alloys without these unfavorable properties.

The inventive method in a novel sequence of process stages is characterized in that the finish rolling in one pass takes place, during which the temperature of the tape from about its recrystallization temperature is reduced out to below its recrystallization temperature, and that the rolled and so cooled band is wound directly into a bundle, whose Radius is at least 50 times the strip thickness.

The tape can then be laid flat when it is later unwound from the waistband and after all customary deformation work, if necessary with heating, or with a number of additional rolling operations without local twinning or irregularity Grain growth are processed further.

A cast ingot made of magnesium alloys is used to carry out the process according to the invention, in particular with the following nominal compositions and ASTM codes: AZ 31: 3% Al, 10 / () Zn, 0.2% Mn, remainder Mg, AZ 61: 6% Al, 1% Zn, 0.15% Mn, remainder Mg. HK 31: 3 ° / a Th, 0.7% Zr, remainder Mg, HK 11: 10 /, Th, 0.7% Zr, remainder Mg, HM 21: 2 ° / o Th, 10 /, Mn , Remainder Mg, ZE 41: 4% Zn, 0.5% Zr, 0.4 SE, remainder Mg (RE applies to rare earth metals), ZE 10: 10/0 Zr, 0.12 ° / o SE, remainder Mg.

The ingot is subjected to a solution heat treatment at about 454 ° C the almost complete dissolution of the alloy metals occurs. The glow time depends depends on the volume and shape of the ingot and is generally about 10-20 Hours, including the time it takes to heat up from room temperature Solution annealing temperature, where you can @ _ .:. -. , - _. . . -. .

Lasts 4 to 6 hours.: # After the solution heat treatment, the is still warm Bars up to the last stitch, possibly in multiple stages up to reduction the desired final thickness hot-rolled at a temperature at which the metal crystallizes can. This is followed by the winding of the tape into a waistband for the purpose of better HandlingY You have to do this before the last pass, then the watnig-rolled. :- Band.; Warpn: - wound up, so unwound and then further hot rolled or if necessary set aside and let cool. For further rolling, the collar is previously heated again above the recrystallization temperature of the tape.

In this temperature range, rough rolling takes place up to about 118 to 143%, preferably about 125%, of the final thickness. In order to prevent a Recrystallization is the finish rolling of the hot-rolled strip in a cold rolling mill in one go after cooling to a temperature just above its minimum recrystallization temperature, d. H. the temperature below which the material does not recrystallize, regardless of the degree of cold deformation applied and the annealing time, so that it finally emerges at a suitably low temperature.

The rollers are cooled e.g. B. by means of permeating or permeating a chilled lubricant so that the tape when it lasts Stitch is finished rolled to the final thickness, gives off heat to the rollers and this at a temperature slightly below the recrystallization temperature, e.g. B. at about 135'C In the case of the alloy AZ 31, it leaves again.

The strip rolled in this way is wound up into a bundle whose radius is at least 50 times the tape thickness. -This tape has cheap mechanical ones Properties. It can be unwound well for making shaped or drawn Objects without the occurrence of undesired twinning and sporadic grain growth use.-.

The following example explains the method according to the invention. A cast ingot with a thickness of 305 mm, freed from the casting skin; a width of 1016 mm, a length of 1930 mm and a weight of 1021 kg made of a magnesium alloy composed of 3 % Al, 10 /, Zn, 6.2% Mn, the remainder being Mg, at .454 to 482 for about 16 hours ° C solution annealed and then hot-rolled at about 4454 ° C between rolls with a diameter of 686 mm. With the first stitches, the bar was cross-blocked and at the same time spread out to 1295 mm, while at the same time reducing its thickness to - 239 mm. A lubricant made from a 10% aqueous solution of a polyglycol was applied to the rollers, the temperature of which was estimated to be about 60.degree. The surface speed of the rollers was about 243 m / min. The cross-blocked billet was then longitudinally rolled in 18 passes and its thickness reduced to 4.57 mm. The strip temperature @ dropped to about 287 ° C. during hot rolling. After the 18th stitch, the 287 ° C warm, now about 97 m long tape was wound up on a reel with a dome diameter of 610 mm. The warm rolled up strip was then placed in a furnace heated to 343 ° C. and then finish-rolled in five additional passes on a rolling mill. The first four of these stitches consisted of hot rolling at temperatures between 282 and 343 ° C, with the tape being rewound after each stitch. At the first stitch, the, -thickness decreased from 4. ° 5'7. on, 3.55 xnm, in the second from 3.5 to -2.74 mm; ' with the = third = from 2.74 to 2.23 mm and with the fourth from 2.23 to 1.78._ min. For the fourth stitch it was wound up and cooled to a temperature between 193 and 232 ° C and then for the fifth and last stitch its thickness was reduced to 1.32 mm and its temperature to 104 to 126 ° C. This temperature decrease was achieved by transferring heat from the strip to the rolls, which were cooled to about 37.degree. C. and 48.degree. C., and by regulating the rolling speed to about 152 m / min. Eventually the tape was at a temperature between. about 104 and 126 ° C - reeled onto a 610 mm thick dome. The length of the belt was about 305 m.

Samples of the tape had the following strength properties Crushing State @B °° # "limit (kp / m m = ) (kp / Mm ') ( kp / MM2) (° / o) Rolled 29.53 23.20 19.69 3 to 5 Annealed ...... ) ... 28.83 21.80 18.28 15 *) Annealed for 1 hour at 129 ° C. Unwound samples of the tape, which had been heated to about 315 ° C. before a farming operation, had a smooth surface free of twinning or sporadic grain growth. The tape was easily deformed by bending and pulling without cracking.

Claims (2)

Claims:. 1: Method of making tapes-from only magnesium alloys which can be hardened by cold working, e.g. B. 3% Al, 1% Zn, 0.2 ° / p Mn contained by rough rolling at 426 to 204 ° C or above the recrystallization temperature to 118 to 143% of final thickness and finish rolling at a temperature below 204 ° C or the recrystallization temperature n e t that the finish rolling takes place in one pass, during which the temperature . of the tape .from approximately its recrystallization temperature to below its recrystallization temperature is reduced, and that the rolled and thus cooled strip immediately closes. one Bundle is wound, the radius of which is at least 50 times the tape thickness. 2. The method according to claim 1, characterized in .that the warning rolled strip to a temperature of 14 to 111'C above its minimum recrystallization temperature cooled and that the thus cooled recrystallized tape with further cooling; as stated in claim 1, is rolled to the desired final thickness. Into consideration Drawn pamphlets: U.S. Patent Nos. 1941608, 2 294 648.