SU1433990A1 - Method of treating rolled plate - Google Patents

Abstract

The invention relates to methods for the thermal deformation processing of steel and can be used in the manufacture of rolled products. The purpose of the invention is to improve the quality of rolling by preventing the formation of microcracks. The essence of the invention is that in the production of rolled products, cyclic bending parameters (radius and number of bending cycles) are selected taking into account the relative elongation of steel in the pre-preformation state and are determined by the ratios R (h / 08c / 0-625h and N 0 , 64 (tPR / h), where the relative elongation of steel} R is the bending radius -.- ba, h is the thickness of the rolled product, N. is the number of bending cycles. The deformation parameters are limited by the fact that for certain N and RS (critical) steel cracks are formed. (L

Description

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I The invention relates to the thermal deformation treatment of steel: And can be used in the manufacture of sheet metal. ; The purpose of the invention is to improve the quality of rolled products by preventing the formation of microcracks. : The essence of the invention is that the cyclic bending parameters of rolled sheet (radius and h | 1 layer of bending cycles) are selected taking into account the relative elongation of steel in the pre-deformation state — and are calculated by the formulas:

h 578

 R 625h;

N 0.64 (-p-)

Where

R - h is the relative elongation of steel, abs. five

rolled bending radius, mm; thickness of rolled stock, mm; N is the number of bending cycles. The limitation of the deformation parameters is due to the fact that with certain deformation parameters (critical)} microcrack formation occurs in steel.

In the case of monotonic deformation (uniaxial expansion), the formation of microcracks occurs when the deformation constitutes on average 0.2 of the total relative elongation of steel at break. Then, under cyclic tension-compression, the maximum permissible deformation parameters are defined as

 Milking

 0,2s /,

()

de

40P

N

Aon / maximum permissible degree of deformation, abs; five

maximum permissible number of bending cycles; relative lengthening of steel, abs.

When bending, the strain distribution over the cross section of the sample is non-uniform: on the surface it is maximum, and in the center it is minimal and zero.

The degree of one-time deformation (Ер) on the sample surface during bending is determined by the formula

R

h

55

(2)

where h is the sheet thickness, mm; R is the bending radius, mm. The average strain over the sample cross section is determined as the arithmetic mean of the maximum and minimum strain, i.e.

R

SSR2

then according to equation (1)

0.2s / 1

Avr

P

(3)

will get

(BUT)

OR

R.DEP 40p

O.AJ.

(five)

The value of the maximum permissible degree of one-time deformation (maximum) is determined at N op (the minimum possible number of cycles), i.e.

. Max

-R, AOG, - O.A

learning formula (3), we get:

(7)

0, A or R

A on

those. bending radius must be greater than b / 0,8sG.

The lower limit of the bending radius () is called (: one of the conditions for the onset of plastic metal flow, i.e.

(9)

"." KC

h 217

where h is the sheet thickness, mm;

ir deformation, corresponding to the onset of plastic flow, abs.

According to GOST 1497-84, the onset of plastic flow corresponds to a relative elongation of 0.2% (0.002 abs). Then from the formula (8) and (9) it follows that

W "Kt

0.8-0.002

 625h

(ten)

and from formula (8) and (10) it follows that the bend radius should be

O7G

: 625h ..

(eleven)

Determines the maximum permissible number of bending cycles at Ep p.i.on (at

 E

r dvp

t-p is the number of cycles is 1).

-j1433990.

From equation (6) follows (erection — Example. Steel billets, the right and left parts squared) 10G2C1 with a thickness of 8 mm is heated to

950 C, incubated for 30 minutes,

 P Nd (, p (0.4 /), (12) is cooled to room temperature

with speed . In this case, (-.04 then, the relative elongation of steel

 . equal to 30% (or 0.3 abs). Elongation can be defined as

taking into account formula (3), we have the P test for rarefaction.

and non-destructive methods (na.,.,. (fi. Pf statistical, magnetic, gnitno-statistical and others).

2R Substituted values for R15 elongation (0.3 abs) to inequality

™ Ndag, 0.64 (s / ---). (15) (11), we get: 33.4 R: 5000. According to.

experimental conditions accept

From formula (12), it follows that with R 70 mm, then the number of cycles for the bending treatment of rolled products by cyclic bending according to formula (15) is 4.5. The number of bending cycles should be 2%. The hardening of the steel is 10%.

Claims (1)

R 1 BUT be no more than 0.64 (). Preliminary Formula of the Invention The specified conditions of deformation restrictions are „ The method of processing sheet procation parameters is given in the initial / 9t: one mainly of low carbon steel content (according to the value of / - o - “- ch and low-alloy steels, including steel elongation and exposure, h g, heating, cooling, cooling, formation state). This is a guarantee. one . -deformation flexible with given radii It avoids the occurrence of micro. i- g -, g-. catfish bending and the number of cycles, cracks in steel. „ yy -,.,, -} n start, distinguishing with The proposed selection of deformation ju - , that, in order to improve the quality of the pro- kata by preventing obrazarazom .. l, yy nn microcracks, before deformation Hire after necessary thermobab, to. -, measure the relative elongation of the run; subject to deformation. gy i - o, and the deformation is carried out with a ical bend. Before deformation op-35 "h- im J-M the bending radius determines the relative elongation of the st. whether for stretching in this state.i / g about j tic p, / o p / 0, o o bZj p. After that, by formulas (8) and (13) the maximum permissible values are determined, where h is the thickness of rolled metal, deformation parameters.40 and with the number of cycles N 0.64 (P R / h).