SU1446176A1 - Method of heat treatment of steel - Google Patents

Abstract

The invention relates to heat treatment of materials and can be used in the steel industry in the production of cold-rolled thin sheet of mild steel. The purpose of the invention is to increase plasticity in the case of shafts by improving the crystallographic texture of the steel. The essence of the invention is that in a known method of heat treatment of a sheet, including heating, holding and cooling, heating is carried out to a temperature T A + B C, where A, B and C are proportional coefficients of resistivity steel before heating, and for steels having 6g 380 - 580 MPa, the proportionality coefficients choose A 1032.1 Ci B -21.1 S / MPa, C 0.32 C (MPa), and for steels having 68 581-880 MPa, these coefficients, respectively, choose A 560.1 ° C i B 7.7 ° C / 1Sa and C -0.03 ° C C / (MPa). 1 tab. S (L 4 O) Od

Description

The invention relates to the heat treatment of materials and can be used in the ferrous metallurgy in the manufacture of cold rolled thin sheet of mild steel.

The purpose of the invention is to increase rmacity during stamping by improving the crystallographic texture of steel,

The essence of the invention lies in the fact that according to the method of annealing of cold-rolled low carbon steel, including the determination of the initial time resistance to j pBBOM of the initial temporary resistance to rupture 5 EiarpeBj exposure and subsequent cooling, heating, ve, tsut to a temperature higher than the beginning of recrystallization (T °, C) which is determined by mathematical dependencies

Т 1032J - 21.1 бе, 0, 10 - for steel5 with initial temporary tensile strength of 380-580 ml

T 560.1 7.7 & „- 0.036 10

for steelS having an initial temporary resistance of razrygou 581-850 MPa, the initial temporary resistance to rupture of steel before heating MPa-Yu-5

1032.1 and 560., 1 coefficients, from 21.1 and - coefficient OED

C / mnaj

0.32 and 0.03 - coefficients /

 c / (MPa)

Given the coefficients in the mathematical dependence and the permissible deviation from the calculated temperature in the range not exceeding. 10 C in the direction of its increase and in the price of E, obtained experimentally | while processing experimental statistical early,

Cold-rolled low-carbon steel grade 08U or OVkp used, for example, in the production of shadow masks of color television picture tubes, is used with a very EH range of values of the original tensile strength of steel 380-880 MPa. So, in the production of shadow; slotted masks used steel strip with an initial temporary tensile strength of 380-580 in the production of shadow masks with round holes (masks of the delta structure) - 581-380 MPao. For each

g

0

50

five

0

five

0 5

, five

The initial temporal resistivity requires its optimal annealing temperature for the shadow masks. Exceeding the heating temperature to a value greater than the resulting formula allows for increased warping of the masks, their adhesion to one another and defects on defects. Uneven transparency of the masks during subsequent editing and stamping. High temperature leads to the growth of colonies of cementite, which increases the probability of formation impulses when stamping masks. A decrease in the heating temperature to a value lower than the formula allows leads to a marriage due to a defect in the Slip Line during subsequent editing and stamping of those. new masks. In this case, in the annealed steel, unfavorable ratios of crystallographic orientations Pj ,, are obtained, which determine the ability of the metal to be stamped.

In the invention, carrying out annealing with cold-rolled low-carbon steel, or at temperatures of the onset of recrystallization (700-1050 C) according to the indicated formula, allows to obtain annealed metal without flow area in the Stress-strain diagram. This will avoid the operation of the Training and prevent the formation of a defect in the Slip Line on the Stamping operation. Punching steel without prior operation; training is very important especially in the production of shadow slotted masks. The training of masks, even with a slight compression, causes the formation of wrinkles, uneven deformation of the holes and lintels, due to which masks are rejected before the defect. Uneven transparency.

Transverse specimens with dimensions of 300x20x0.15 mm are cut from cold-rolled mild carbon steel grade 08U or 08kp with a width of 565 mm and a thickness of 0.15 mm, and temporary tensile strength is determined. Then, shadow masks are made from the steel strip by photo etching, i.e. 500x x 400mm tablets with a network of numerous etched holes. For a steel strip having an initial temporary tensile strength of 380-580 MPa, shadow masks with slotted holes are etched, and with initial temporary tear resistances equal to 581-850 MPa, shadow masks with round holes are etched ( ). Made masks are sorted in batches with the same initial temporal resistance to rupture. From each batch, the masks are typed in bags of five pieces each and installed on a continuous conveyor furnace mesh conveyor. Taking into account the initial temporal tensile strength of the steel strip, for each batch, using the formula obtained, determine the required heating temperature and shading masks. Packages of shadow masks are heated to the temperature determined by the formula, taking into account the deviations allowed by the formula within the limits of not more than ± 10 С over the whole volume of the package of shadow masks.

After heating to a predetermined temperature, the mask packs are kept in

20 due to defect Slip lines due to the formation of a yield point (9-11%) in the Stress-strain diagram. In this case, a low ratio P, ix / Pr, oc

within 10 minutes, cooled to 20–40 ° C, 25 (7–12), and the yield of the stamps is separated from one another, the bottom drops sharply to 66–69%. Casting is correct in roller correcting Example 1 (experiment 2). From chilling machine and stamping (spherization - for- nal-rolled low-carbon stripes on the screen area of a color picture tube — 0810 steel, 565 mm wide, and a thick TV). Then, masks with a control-30 of 0.15 mm thickness cut the transverse blast and the reject rate and the yield after the Stamping operation are determined.

Steel test results for

Shadow masks, treated with a known photo-etching method, are also made by the proposed methods, given in tabeous slit masks in the amount of egg. In the experiments carried out in parallel with the masks, samples were annealed in batches;

The samples are 300x20x0.15 mm in size and determine the temporary tensile strength of the discharge machine, which is 380 MPa. From a steel strip of a rolled strip with a size of 300x20x xO, 15 mm and 20x20x0.15 mm, in order to determine the length of the platform, on the voltage-deformation diagram and crystallographic texture

2050 pcs. The masks of this batch are sorted into packages according to five masks in the rolls, which are installed on the grid conveyor of a continuous through-pass horizontal furnace with electric heating and a safe atmosphere. By the formula, the required temperature of heating and holding of shadow masks of steel annealed according to the obtained formula is determined.

The ability to shampovka steel for shadow masks is evaluated by the intensity ratio, which is cut from Pr ,,, iK, unfavorable Pc, ooi, ° steel strip of the same batch, from favorable intensities for stamping crystallographic landmarks. the goal is the yield point length in the stress-strain diagram, as well as in terms of the yield yield and the number of defects in the Stamping operation.

1-21,1.380.10 + 0.32 (380.)

692-i: lO (° C).

Along with masks, samples of 300x20x are placed on the conveyor of the furnace.

55

determine the length of the flow area on the stress-strain diagram 1 and the ratio of the intensities of crystallographic orientations (, 0. Packages with masks and obC can be seen from the table during the heat treatment of cold-rolled low carbon steel under conditions of heating and holding at temperatures.

determined by the mathematical dependence, the yield during subsequent stamping is maximum (88-92%), and the number of defects (experiments 2, 5, 7 and 10) is minimal (8-12%). In these experiments, the maximum intensity ratio of the crystallographic orientations Pr, / P (18-20) and

there is no flow area on the stress-strain diagram. In the case of the exit of the heating temperature and the exposure of the shadow masks for the upper one (experiments 1.6 and 9) or for the lower one (experiments

3,4 and 8) the limit allowed by mathematical dependence during subsequent stamping results in an increased number of scrap either by defect Uneven transparency, or

by defect Slip lines due to the formation of a yield point (9-11%) on the stress-strain diagram. In this case, a low ratio P, ix / Pr, oc

(7-12), and the yield for stamping decreases sharply to 66-69%. Example 1 (experiment 2). From cold-rolled low carbon strip steel grade 0810 width of 565 mm and a thickness of 0.15 mm cut cross-section

(7-12), and the yield for stamping decreases sharply to 66-69%. Example 1 (experiment 2). From cold-rolled low carbon strip steel grade 0810 width of 565 mm and a thickness of 0.15 mm cut cross-section

The samples are 300x20x0.15 mm in size and determine the temporary tensile strength of the discharge machine, which is 380 MPa. From steel strip me2050 pcs. The masks of this batch are sorted into packages according to five masks in the rolls, which are installed on the grid conveyor of a continuous through-pass horizontal furnace with electric heating and a safe atmosphere. The formula determines the required temperature of heating and holding of shadow masks.

xo, 15 and 20x20x0.15 mm, cut from the steel strip of the same batch with the aim

1-21,1.380.10 + 0.32 (380.)

692-i: lO (° C).

Along with masks, samples of 300x20x are placed on the conveyor of the furnace.

xo, 15 and 20x20x0.15 mm, cut from the steel strip of the same batch with the aim

determine the length of the flow area on the stress-strain diagram 1 and the ratio of the intensities of the crystallographic orientations (, 0. Packages with masks and PSI I Ooj / l gO

the samples are heated to a temperature of 695 ° C, held for 10 minutes, cooled to a temperature of 30 ° C with a speed of 5U

tew (30) / min. they separate the masks from one another, subject them to editing in a roller-correcting machine and to a staff. On the annealed samples, the crystallographic texture and the length of the yield point are determined. In this case, the intensity ratio of the crystallographic orientations Р {f iг / PJ-dd J is iS ,, on the stress-deformation diagram, there is no area, the yield point, and the extrusion during stamping is 88%,

PRI me R 2 (experiment 5). From cold-rolled low-carbon strip steel grade 08U, width 565 W and thickness, I cut off transverse images of dyes of size 300x20x0., 15 No. 4 and determine the temporary resistance of the discharge ,. which is 480 MPa. Shaped slit masks in the amount of 1050 fflTj are made of the steel strip, which are sorted into packages of five masks each and installed on a conveyor of continuous passage

Noah furnace. The required temperature of heating and holding of shadow masks is determined by mathematical dependence:, 1-2K 1 -480 -10-NE, 3.2 (480 -1 O)

- 757 ± 10 (° С)

Together with the masks, an image of a 300x20x xOj15 and 20x20x0 15 mm sized image is placed on the conveyor of the furnace to determine the crystallographic texture to the length of the area. Packages with masks and samples are heated to 755 ° C, hold 10 microns of cold: wait to 30 ° C at a rate of 30 ° / MHHs separate the pegs from one another, straighten them in a roller correcting machine. In this case, the ratio: e: the intensity of the HOSJ crystallographic orientations is 19 in this case. In the diagram pp lagyie — deformation there is no flow area. Ptivke equal to 89%.

EXAMPLE 3 (test 10) From cold-rolled low carbon strip steel grade 08kp, width 565 k and thickness O, 15 mm, transverse specimens of 300x20x0e 15 mm are cut and the initial temporal resistance to fracture is 880 MPa, steel clocks make shadow masks delta structure766

There are 1000 pcs in quantity, which are sorted into packages with five masks in each and installed on the conveyor of a continuous furnace. The desired temperature of heating and holding of shadow masks are determined by mathematical dependence.

., 1 + 7.76b-0,, 1 + 7, 7-880 x x10- -0.03 (880 10-) (° С).

Packages with masks are heated to 1005 ° C, held for 10 minutes, cooled to 30 ° C with a speed, the masks are separated from one another, they are straightened in a roller-straightening machine and stamped. The yield of fflTaNfflOBKe pr is 90%.

Thus, it has been experimentally proven that when using the proposed method, a high ratio of intensity of crises of Pp / va / P is provided, thereby increasing the ability to stamp annealed untreated low carbon steel.

The proposed method makes it possible to obtain a training for annealed low-carbon steel with an improved crystallographic texture, due to which the ability to stamping increases dramatically. Carrying out annealing of cold-rolled low carbon steel at temperatures above the beginning of recrystallization in. The knowledge of the initial time tensile strength, determined experimentally by the mathematical formula, allows to obtain annealed metal without a flow area on the Stress-strain diagram. This avoids the Training operation, prevents the formation of a Slip line defect in the Stamping operation and dramatically improves the ability metal to stamping.

In comparison with the known method, cases of increased spoilage during stamping of products from annealed steel are excluded, which allows to obtain a maximum suitable code.

Invention Formula

The method of heat treatment of steel, predominantly cold-rolled low carbon, including heating to a predetermined temperature, holding at this temperature and cooling.

7

characterized in that, in order to increase the plasticity during stamping by improving the crystallographic texture of the steel, the heating is carried out to a temperature

TA

where A, B, and C are the proportionality coefficients, depending on time

mIQ 8

against steel rupture (ig) before heating and at 5 380-580 MPa, they respectively constitute 1032.1 ° Cj 21.1 С / MPa and О, 32 ° С / МГ1а, and at dj 581-880 Ша they constitute 560, 1 C-, 7, / s / Ш1а and -0.03 s / MPa

14

08 kn

850

Also

580

Claims (1)

Claim The method of heat treatment of steel, mainly cold-rolled low-carbon, including heating to a predetermined temperature, holding at this temperature and cooling, 144617 6 characterized in that, in order to increase the ductility during stamping by improving the crystallographic texture of the steel, heating is carried out to a temperature where A, B and C are proportionality coefficients jq depending on the tensile strength of the steel (i ₈ ) before heating and at = 380-580 MPa, they respectively amount to 1032.1 ° C; 21.1 ° С / MPa and 0.32 ° С / МГ1а ⁷ , and for d> ₈ = 581-880 MPa they are 560.1 ° С ·, 7.7 ° С / MPa and -0.03 ° С / MPa ⁷ . Experience steel grade Initial tensile strength - Shadow Mask Type Number of masks per lot The temperature determined by the formula, C optimal maximum minimal 1 0810 380 Crevice 1250 692 702 682 2 08U 380 2050 692 702 682 3 08U 380 1700 692 702 682 4 08U 480 eleven _ 1200 757 767 747 5 0810 480 _ eleven_ 1050 757 767 747 6 08U 480 - ⁿ - 2000 757 767 747 7 08U 1 581 Deltastructure 1800 906 916 896 8 08U 581 Deltastructure 1600 906 916 896 9 08 kp 880 Also .900 1005 1015 995 10 08kp 880 _P__ 1000 1005 1015 995 eleven 08U 420 Crevice 650 Famous Method 12 0810 530 _eleven_ 510 thirteen 08 kp 780 Deltastructure 450 14 08kp 850 Also 580 9 . ⁱ⁰ Continuation of the table Experience Actual temperature of heating and holding of masks, ° C - The ratio of the intensity of crystallographic orientations The length of the yield plate on the stress diagram strain,% ---——---- Defective stamping of shadow masks by defects,% Yield for stamping shadow masks % Breaks Slip lines Uneven transparency 1 700-710 8 1,5 16 0 18 66 2 690-700 18 0 12 0 0 88 3 675-685 7 9.5 19 thirteen 0 68 4 735-745 6 9.0 20 17 0 63 5 750-760 19 0 eleven 0 0 89 6 760-770 1,0 18 0 fifteen 67 7 900-910 20 0 8 0 0 92 8 890-900 Yu eleven 16 18 0 66 9 1010-1020 12 1,5 17 0 14 69 10 1000-1010 18 0 10 0 0 90 eleven 480-490 3 0 100 100 0 0 12 360-370 4 0 100 100 0 0 thirteen 390-400 4 0 100 100 0 0 14 410-420 2 0 100 100 0 0