The difference between continuous rolling constant and stacking coefficient and stacking ratio？

1 , continuous rolling and continuous rolling constant

A rolled piece is rolled on several rolling mills at the same time and kept rolling in a unit time for the rolling of the rolling mill through the equal volume of each rolling mill. The volume of metal passed in a unit of time (if it is the volume of metal passing in one second, it is called the metal second flow.) Calculated by:

V= (π Dn/60 ) S

Where V is the volume of metal passing through the mill per unit time, mm3 ;

D – roll working diameter, mm ;

n – roll speed, r / min ;

S —— section area of ​​the rolled piece, mm2 .

The volume of metal passing through each mill in a unit time is equal to a constant. This constant is called the continuous rolling constant. It can be expressed by the following formula:

K even = S1D1n1 = S2D2n2 = S3D3n3 . . . . . . =SnDnnn

In the actual rolling production, the continuous rolling constant is constantly changing due to the influence of the front slip and the continuous change of the hole type and the like. Therefore, the continuous rolling constant must be adjusted and corrected accordingly.

2 , stacking coefficient = stacking coefficient + drawing coefficient

For micro-stack rolling, when rolling, the rolling stock passing between the racks must meet the principle of equal flow of seconds.

,which is:

ν 1S1= ν 2S2= . . . = Ν xSx = K even

Where ν 1 , ν 2 , ν x are the rolling speeds of the respective rolling passes;

S —— the cross-sectional area of ​​the rolled piece;

K even – continuous rolling constant.

If the rolled piece is rolled simultaneously on two adjacent frames, and the second flow of the front frame is slightly larger than that of the rear frame, namely:

ν xSx >ν x+1Sx+1

In the case of a small section of the rolled piece, a free sleeve is created between the two frames, that is, a micro-heap phenomenon occurs. This rolling process is called micro-stack rolling.

In the production of wire rod mills, there are micro-stack rolling between pre-finishing or medium-rolling stands due to the hole design or the adjustment of the rolling mill. In the micro-stack rolling, the rolling state is described by the stacking factor K stack. The K stack is equal to the ratio of the back frame metal second flow to the front frame metal second flow rate of adjacent racks with continuous rolling relationships. When the K stack is >1 , it is rolled for pulling steel; when the K stack is <1 , it is rolled for stacking steel. The stacking factor of micropile rolling is usually 0.99 to 0.98 .

3 , stacking rate

The relative difference of the metal flow rate of two adjacent racks during continuous rolling, the stacking rate = (Vi + 1 – Vi) / Vi × 100 where Vi = FiDwini (1 + Shi) ship (1 + Sk) V is Metal second flow; F is the cross-sectional area of ​​the rolled product at the exit; Dw is the work roll diameter; n is the work roll speed; Sh is the forward slip rate. When the stacking rate is positive, it is called pull steel, the greater the absolute value is, the more serious the steel is. If the stacking rate is negative, it is called pile steel, and the larger the absolute value is, the larger the pile is.