DE1583429B1 - Process for the production of a cold-rolled steel sheet with good dimensional stability - Google Patents

Description

The invention relates to a method for producing a preferred temperature range for the work

a cold-rolled steel sheet having good shape _v conditions- is that the winding with stability and a low yield strength, does not age, 700 carried out to 750 ° C and annealing at 670 to 71o ⁰ C with a content of less than 0.12 percent by weight will. ,.

Carbon, below 0.6 percent by weight manganese and 5 percent by weight of the steel of the above composition is vanadium, the remainder being iron, blocks from unkilled, semi-calmed or unavoidable impurities, which covers cast steel. If necessary, sheet metal is first hot-rolled, wound up and the steel melt is cooled before the addition of vanadium, further pickled and cold-rolled, finally deoxidized, the silicon content in the steel being annealed and surface-rolled. io 0.08 ° / ₀ and the aluminum content at 0.02 ° / ₀

The good dimensional stability "of a steel sheet must be characterized so that the steel is not calmed, otherwise it is characterized by the fact that its low yield point and mechanical properties and the purity of its modulus of elasticity are greater / so that it deteriorates after the press" steel and the growth of the crystal _{deformation maintains the given F (} qrm. D, a the knitted grains would be disturbed.

limit -at load "cfes' ^£ sheet, for example 15 With a carbon content of about 0.12 ° / ₀ would be, aging between the OberfläelfönWälzen in the production yield is too high, whereby the dimensional stability and the subsequent press forming, is would .the deteriorated. a manganese content exceeding 0.6 ° / ₀ yield strength of the steel sheet after its Her ¹ would directly make the steel too hard and reduced to considerable position ^and:! 'beisrjielsweise perform additional surface contaminants the Va & adiumvon vanadium prevents aging This leads 20 additional binds.. the vordazu in the steel as an impurity, that the formation of drawing handenen nitrogen, called avoided in a falling below and the ductility is maintained at the deformation. the lower limit of 0.01 ° / ₀ the desired WIR Λ It is already Process known (USA.-patenting. Would not be achieved. Exceeding the ™ font 2 666 722), in which a non-aging, un- The upper limit of 0.15 ° / ₀ no longer improves the effect of the killed steel with a vanadium content of between 25 vanadium. The decarburization is hot-rolled and 0.01 and 0.15% and the produced deoxidation of the steel is slowly cooled by the band at reduced pressure. The final temperature is controlled so that degassing takes place, so that the temperature during hot rolling is between 871 and 927 ° C, the addition of vanadium is not necessary. .-so that the tape reaches the take-up device with a temperature that is not below 816 ° C. In order to avoid aging, the process of slow cooling begins, steel block of the above-described combination, before the metal has reached a temperature, setting of the sheet produced at a temperature of well below 816 ° C. 680 to 760 ° C, preferably from 700 to 750 ° G

Another reference (Epstein, "Journal wound. Thereafter, the hot-rolled,. Aufof Metals", vol. 2, p. 830, 1950) states that the Auf-.35. wound sheet steel cooled, pickled and cold-rolled, the winding temperature should be ^{above 760 ° C.} which is followed by an annealing treatment, which is carried out in

It is also known (J ο ηΐ s, "Journal of Temperaturgrenzen between 630 and 730 ⁰ C, vorzugsthe Iron and Steel Institute", Vol. 174, p. 9, 1953) that, wise. Between 670 and 710 ⁰ C, is carried out if the steel after hot rolling is not at a temperature that can be A higher annealing temperature would lead to an increased low temperature, by cooling with water spraying at the same time become coarser to grains. · Lead to an increase in nitrogen in solid solution.

Thereby, the yield strength is lowered while, despite the addition of vanadium would such a * in the steel is over 760 ⁰ C jedcoh steel sheet due to aging as well as a sheet of conventional ^ lying coiling cementite in the solid. 45 unkilled, unquenched steel. An annealing treatment in the condition eliminated ', whereby a precipitation of a temperature below 630 ⁰ C would be a down carbon during cooling after annealing in fixed setting of the yield point is prevented despite the solution according to the invention and the steel ages. If the coiling temperature is to be prevented, on the other hand the coiling temperature would be too low, ie lower than 68O ⁰ C for the formation of stable vanadium nitride, the crystal grains in the 50 extremely long annealing times required, hot-rolled sheet not sufficiently, the atmosphere for the annealing is not subject to any

and the vanadium nitride does not become oxidized until the annealing process is subject to special restrictions, if however an oxydiedem Cold rolling eliminated, using a very long glowing gas atmosphere, must go through times are required! a suitable cover is provided for

With the known; The methods are-therefore-before; -, 55 that the surface of the steel sheet does not oxidize, The listed properties that the cold-rolled The annealing time depends on the annealing temperature; will Sheet steel should have, not achievable. annealed at the upper temperature limit, it is sufficient

The object of the present invention is a short glow time, while with the glow therefore, in the machining conditions for the lower limit temperature, a longer annealing steel sheet set so that the finished product is required a 60 duration, but the desired duration high dimensional stability due to a low yield point, recrystallization and softening within exhibits to the exclusion of aging. 16 hours is reached.

According to the invention, this object is achieved when using the drawing and the following

drive of the type mentioned above is thereby solved, the present invention will be described in more detail by way of examples the winding of the hot-rolled sheet at 65 refines.

a temperature of 680 to 760 ⁰ C and the annealing Fig. 1 shows the dependence of the grain size,

carried out at a temperature of 630 to 730 ⁰ C, the yield point and the change in the yield point is. by aging from the winding temperature;

F i g. 2 shows the dependence of the same quantities on the annealing temperature.

example 1

A hersestellter in a converter steel mil 0.07 _^0/0 C, 0.01% to Si. 0.35% Mn, 0 ~ 013% P, 0.015 ° / ₀ S, 0.005 ° / ₀ AI. 0.042 ° / ₀ V, 0.0028% N, remainder iron and unavoidable impurities is cast into a block, pre-rolled and rolled into a slab, which is ^{hot-rolled at 900 to 86O 0} C to a 2.5 mm thick sheet. After winding, cooling, cold rolling and annealing, the sheet is surface-rolled with a reduction ratio of 1% to its final thickness of 0.8 mm. The grain size, the yield point and the increase in the yield point are determined on the steel sheets produced in this way if the sheet is artificially aged ^{at 100 ° C. for 1 hour.}

The winding temperatures were varied over a range of 600 to 820 ° C, in each case the annealing temperature following cold rolling is 690 ° C. The influence of the annealing temperature is examined with annealing for 4 hours in a temperature range of 600 to 780 ° C, the winding temperature after hot rolling is 720 ° C in each case.

From the F i g. 1 and 2 it can be seen that the invention selected temperature ranges for winding and annealing the production of a dimensionally stable Allow steel with a low yield strength, whereby the steel does not age.

Example 2

A steel made in a converter, consisting of 0.05% C. 0.01% Si. Ö ", 27% Mn, 0.014% P, 0.013% S, 0.004% Al, 0.028% V, 0.0023% N, balance iron and unavoidable impurities becomes too potted in a block, pre-rolled and rolled into a plate. The winding follows the hot rolling at 720 ° C. The bundle is then cooled, annealed at 700 ° C. for 4 hours and then added to a reduction ratio of 1% to the final thickness of 0.8 mm.

In the table below, line I shows the mechanical properties of this steel, which is labeled I, and line II shows those of a steel of the same composition, but without vanadium, i.e. the properties of a conventional, unkilled steel labeled II is designated. Under the listed in the third column aging, the increase in yield strength is meant by an artificial aging of 1 hour at 100 ⁰ C

Tabel

stole Stretch limit
kg / mm ² Aging
kg / mm ² tensile strenght
kg / mm ^s strain
in·/. Erichsen value
in mm Cone bowl value
in mm I.
II 14.9
21.3 0.1
6.3 31.2
33.1 48.3
45.0 11.2
10.6 37.2
37.9

The above values show that the vanadium steel sheet produced according to the present invention is very good has a low yield strength, shows no aging and is comparable to conventional non-killed steel Has values for tensile strength, elongation and deep-drawability.

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Claims (2)

Patent claims: 1. Process for the production of a cold-rolled steel sheet with good dimensional stability and low yield strength, which does not age, with a content of less than 0.12 percent by weight carbon, less than 0.6 percent by weight manganese, and 0.0.1 to 0.15 percent by weight vanadium, the remainder Iron and unavoidable impurities, whereby the sheet is first hot-rolled, wound and cooled, further pickled and cold-rolled, finally annealed and surface-rolled, characterized in that the winding of the hot-rolled sheet is at a temperature of 680 to 76O ⁰ C and the annealing at a temperature from 630 to 730 ° C. 2. The method according to claim 1, characterized in that the winding at 700 to 750 ° C and the annealing is carried out at 670 to 710 ° C. 1 sheet of drawings