SU1659143A1 - Method of screw rolling - Google Patents

Abstract

The invention relates to rolling production, in particular to helical rolling of solid and hollow products. The purpose of the invention is to improve the quality of rolled products by reducing twisting. The heated billet is deformed in rolls installed at the feed and rolling angles and having a variable hardness along the length of the barrel. The change in the hardness of the rolls along the length of the barrel is related to the feed angles and the rolling of the mathematical dependence.

Description

The invention relates to rolling production, in particular to helical rolling of solid and hollow products.

The purpose of the invention is to improve the quality of rolled products by reducing twisting.

The heated billet is deformed in a helical rolling mill in rolls installed at the feed and rolling angles and having a hardness variable over the length of the barrel. The change in hardness along the length of the barrel rolls in zano with feed angles and rolling mathematical dependence

H; H,

24P-COS

(+ UY. UT

Rt 3iCi5in gpcco5 (cospcos5 |)

(b) (Xe in (arcco5 (cospcoS (f)) Ycosp cos i)

where H is the hardness in the i-th point of the roll surface:

Hi - hardness at the point of the surface of the shaft -. ka, taken as the base;

R, X, Y is the roll radius to the base point and its coordinates in a system whose center is at the intersection point of the roll axis and the mutual perpendicular to the rolling axis;

lo

.

AR, A d - changes in the radius of the roll and the corresponding shortest distance to the axis of the workpiece between the base and 1st points;

Ј - coefficient of ovality of the workpiece;

(p - the angle of the roll taper between the base and 1st points;

e is the shortest distance between the rolling and roll axes;

/, d - the angle of feed and the angle of rolling.

In the process of rolling in mills with skew-mounted rollers having a profile of variable length along the barrel, the billet is subjected to the twisting action of the rolls.

The amount of twisting is determined by the value of the twist angle of the product, determined from the condition

e

0 R7 /

h

e

. .ii)

 G „H

Yo

about

§

J

Oj

where RH, Rx, Ri, rH, rx - the radius of the roll and the workpiece;

 - coefficients of tangential and axial velocity; ;,

m.U- projections of the unit vector of the circumferential side of the roll;

Fi, Fx is the cross-sectional area of the workpiece. From this condition, it follows that a decrease in the twist angle occurs with a decrease in the integrand.

The most optimal variant is RX „RH

(2)

This condition can be fulfilled by adjusting the tangential velocity coefficient rjr along the length of the deformation zone to compensate for this change in the ratio of the roll radius to the corresponding radius of the workpiece.

The value of the tangential velocity coefficient is determined by the presence of plastic (caused by tangential rolling) and geometric (due to the geometry of the deformation zone) slip. In this case, the regulation of the coefficient of tangential velocity along the length of the deformation zone consists in creating rolling conditions that ensure a change in the coefficient of friction along the surface of the contact between the roll and the rolled stock. Experimental data shows that an increase in the hardness of the material of the roll surface is accompanied by a decrease in the coefficient of friction of the roll-roll pair. It was established that the change in the tangential slip coefficient is adequate to the change in the hardness of the rolls,

Therefore, dependence (2) is represented as

Ri ri p

nRi tfr Hi w

where Ri, Ri are the radii of the roll in the base and -th sections of the roll;

P, P are the corresponding radii of the workpiece (the shortest distance from the roll surface to the rolling axis);

t / n, Wm are the coefficients of the tangential velocity, in the base and tth sections;

Hi, Hi - roll surface area in the base and i-th sections,

Considering that

 AR and i + D g expression (3) can be written as

1 + -M.

H | T + Ri

Hi

1 +

well

P

(four)

(five)

This means that, in order to improve the quality of rolling, the change in the hardness of the surface of the rolls must be in accordance with the change in their profile and the shape of the workpiece.

in the deformation center, i.e. correspond to the shape of the rolls, mill setting and rolling mode. These parameters include feed angles ft, rolling d, roll radius and taper R and p corresponding to this radius. shortest distances r to the axis of rolling, the shortest distance between the axes mi rolling and roll.

Taking into account these parameters and expression (5), propose expression (1) to determine the hardness of the rolls along the entire deformation zone.

The change in hardness can be both monotonous and discrete. At the same time, the proposed change in hardness makes it possible to reduce its difference between adjacent areas, which has a positive effect on the rolling conditions and product quality. The preparation of rolls with such a hardness distribution can be carried out

5 using zone heat treatment, electrospark alloying, surfacing with various materials, banding, mechanical hardening and their various combinations.

The use of rolls with the proposed hardness distribution allows changing the coefficient of friction along the surface of the contact of the rolls and rolled products, thus ensuring the necessary (with

5 points of view of improving the quality of rolling) the nature of the change along the deformation zone of the tangential velocity coefficient. This can significantly reduce rolling curl and improve accuracy.

0 of its geometric dimensions.

PRI me R. The screw rolling mill with TPU-140 mushroom-shaped rollers, whose axes are turned to an angle of 15 ° and a rolling angle of 10 °, pierce 10 mm jSl 10 mm of ZOXGSA heated to a temperature of 112x14 mm. The roll-in radius is 400 mm, the workpiece radius is 46 mm. Rolls are biconically calibrated

0 with the angles of taper of the inlet and outlet sections respectively 13 ° and 6 ° 30. To estimate the twisting, a longitudinal groove of 2 mm depth is made on the blanks before heating.

5 Rolls are used with the distribution of hardness according to the proposed mathematical dependence. For the base point take the point of the roll surface in the section of pinching, having a hardness of 180NB. The distribution of hardness is ensured by rolling the barrel of the roll with rings of various grades of steel: 35, 40x, 18xGSA, H25N15, ZH2V8, ZOGHGSA.

Claims (1)

As a result, it was established that the angle of drilling is 6 °, the difference in thickness is 8.2%, which is 6 and 2 times smaller than the prototype, respectively. The share of defective pipes for external defects and the difference in wall thickness decreased, respectively, 3.6 and 1.7 times. Claim method A method of helical rolling, including the deformation of a heated billet in rolls, installed at feed and rolling angles and having a variable hardness along the length of the barrel, characterized in that, in order to improve the quality of rolling by reducing twisting, the workpiece is deformed in rolls, the hardness is changed along the length of the barrel which is related to the feed angles and rolling with mathematical dependence  + uR H, H, 0 five 0 five   COs (Qrc (.t44 b | apcco5 (cosf3eoeiS | - |) (1-tЈ) (Xem (arcco5 (co5 |% cos J) l + Yeospcosi) where HI is the hardness at the 1st point of the roll surface; Hi is the hardness at the point of the roll surface taken as the base; R, X, Y is the roll radius to the base point and its coordinates in a system whose center is at the intersection point of the roll axis and the mutual perpendicular to the rolling axis; AR, Dg - changes in the radius of the roll and the corresponding shortest distance to the axis of the workpiece between the base and s points; p is the angle of the taper of the roll between the base and 1st points; Ј - coefficient of ovality of the workpiece; e is the shortest distance between the rolling and roll axes; ft, b - feed angle and rolling angle.