JPS5945445B2 - Shape control method in cold rolling of metal - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a shape control force method in cold rolling of nut-IJ joints of metals, particularly steel plates.

The flat shape of the sl-IJ tube after cold rolling is an important quality characteristic as well as the accuracy of the plate thickness.

Therefore, many studies have been conducted and patents have been filed to improve these quality characteristics.

There is a similar trend in shape control, and a lot of research has been conducted, but conventional shape control methods use a shape detector in rolling mills with a shape detector, and by the operator in rolling mills without a shape detector. Observe the shape during rolling by visual judgment, and if the shape is no longer flat, usually correct the roll spacing, roll pending force, or supply of cooling water and lubricating oil to improve the shape of the strip. do.

A major drawback of such conventional shape modification force methods is the adjustment of cooling water and lubrication conditions of the plates and rolls for shape modification purposes.

There are two types of lubricating oil supply systems for cold rolling mills: the so-called recirculation system and the direct force type.

Particularly in the case of recirculation systems, roll cooling, strip cooling and lubrication are usually carried out with solutions containing rolling oil.

Therefore, by adjusting the pressure and flow rate of the roll cooling water, which affect the shape of the strip, the lubrication state, that is, the coefficient of friction between the roll and the plate will be changed.

In some cases, the lubrication condition deteriorates significantly, and as a result, the lubricating oil film between the rolls and plates is no longer maintained, and the rolls and plates come into direct contact, causing scratches on the strip surface due to so-called metal contact, which significantly deteriorates the product value. There are cases.

Also, even if the lubricating oil film does not break, if the lubrication condition deteriorates,
The amount of heat generated by rolling increases, and this heat changes the roll temperature, which changes the amount of roll thermal expansion and may result in a change in the strip shape.

Furthermore, the lubrication performance is affected by temperature, and as the temperature increases, the lubricity deteriorates and the amount of heat generated further increases, creating a repeating vicious cycle, which may actually deteriorate the shape of the strike IJ tube.

The temperature of the strip during rolling not only affects the lubrication state but also the quality characteristics of the finished product.3 For example, if the strip temperature at the exit of the finishing mill is too low, moisture will remain during rolling and this will cause the surface of the steel plate to deteriorate. When oxidized, an oxide film may remain as a pattern on the surface of the strip, making it unusable as a product.

It also affects the mechanical properties of the steel plate.

Therefore, for the strip temperature and roll temperature, target temperatures are determined in advance based on the relationship between temperature and heat scratches, roll life, etc. for each material to be rolled, and the amount of cooling coolant is changed. Alternatively, it is preferable to control the temperature to be below or within the target temperature by changing the rolling conditions themselves.

As explained above, the temperature of the NuI-IJ tube during cold rolling is an extremely important factor, and must be maintained at an appropriate value.

It is undesirable to change the Null-IJ knob temperature solely for the purpose of maintaining the shape, which is one of the required quality characteristics of the product.

The main components of the present invention are to control the strip temperature during rolling to a value that is preferable from the viewpoint of not only the shape but also the quality characteristics of the finished product and the stability of the rolling operation, and to control the shape by anticipating the effect on the shape. It supplies the equipment to do so.

An example of the conventional shape adjustment force method will be explained with reference to FIG.

This figure is an example of a reversible cold rolling mill, and the strip S
is fed out from the unwinding machine 1 and rolled by the rolling roll 3,
It is being wound up by winding machine 2.

? , 8 is a so-called roll coolant equipment for lubrication and cooling.

6 is a roll position control device, and 5 is a so-called roll bending device that applies force to both ends of the roll to deform the roll.

If this rolling mill has a shape detector, the shape detector 4
If the shape is not in the desired condition, the operator visually checks the shape, and if the shape is not in the desired condition, the lever roll position control device 6. Through the roll coolant regulators 7 and 8 and the roll pending force regulator 5, these conditions are changed to maintain a good shape.

These corrections are usually made manually, but may also be made automatically by the controller 12 using information from the shape detector.

The present invention will be explained in detail according to FIG.

Numbers 1 to 8 in the figure are the same as in FIG.

Reference numeral 10 denotes a device that collects various data during rolling and provides it to the arithmetic device 11 and the arithmetic device 13 as information for calculation.

The various data include rolling mill current, voltage, rolling force, steel plate tension, coolant concentration, flow rate, and pressure.

Additionally, if there is a measuring device, the information is the temperature from the Nutrip thermometer on the exit side of the rolling mill, and the geometric dimensions and mechanical properties of the rolling rolls.

One component of the present invention is that the computing device 11 estimates the known rolling and conveying temperatures from this information.

Here, the well-known rolling and transfer equations are solved for the temperature of the strip and rolls, but it is necessary to determine the so-called heat transfer coefficient experimentally, and the inventors determined the heat transfer coefficient from data during actual rolling. It was confirmed that the estimated temperature agreed well with the actual measured value.

Below, the well-known formulas related to rolling and transmission used in the present invention (1970-1972 Spring Lecture on Plastic Working, Proceedings 41-44)
Page) and the comparison between the temperature estimated by calculation and the actual measured value will be described in detail.

Possible causes of temperature changes in the strip and roll during cold rolling include ■ Cooling by cooling water, air, and lubricating oil ■ Heat conduction between the strip and roll ■ Frictional heat generation between the strip and roll ■ Heat generated by processing the strip during rolling It will be done.

First of all, regarding the temperature of the strip, ■ Cooling with cooling water, etc., is θ2- θa + (θ, -θa) e-A1 ・
・・・・・・・・・・・・(1) Here, it is expressed as A=2a/pCh, and if you calculate A for each minute time and substitute it into equation (1), the temperature at any time can be calculated. Calculated.

◎ Heat generation due to processing can be expressed as ideal deformation work.

θ The amount of heat generated by friction is calculated using Hill's torque formula,
If we convert the difference between μ=0 and other cases into heat, we get Lμm2KfmRΔh (007+132r
) pJF-.

Here, β is the distribution ratio of Masatsu heat between the roll and the strip, assuming that it is distributed at the ratio of β to the roll and (1-β) to the strip.In practice, it means a correction coefficient between calculation and actual measurement. It is something that has.

Regarding the strip temperature, the heat transfer between the strip and the rolls mentioned above can be ignored because the contact time per unit length of the strip is extremely short.

Next, regarding the temperature of the roll, assume that the temperature distribution is uniform in the circumferential direction and in the roll movement, and consider this to be a one-dimensional problem only in the radial direction.

The heat conduction equation for the cylinder is as follows: The boundary conditions include frictional heat generation, heat conduction, and cooling by cooling water, and if we introduce the isolateral heat transfer coefficient aB and the equivalent coolant temperature θE, we can convert this (4X5) into a v-type If we use simultaneous difference approximation, we can solve the simultaneous-order force equation (6>>(8)).

This equation is a three-term force equation and can be solved using Thomas' method.

Note that θ: humidity temperature, h: plate thickness, J: heat equivalent of work, α
: Heat transfer coefficient, τ, t: Time, R roll diameter, ρ
: Density, Kfm: Deformation resistance, C: Specific heat, ε: Strain, Example of comparing the null-IJ knob temperature and roll surface temperature calculated using the formula above the contact arc length of the two rolls and the strip with the actual measured values. are shown in Figs. 3 and 4, and both are in good agreement.

FIG. 3 shows the strip temperature, and the actual value was measured 2 minutes after the end of rolling.

FIG. 4 shows the roll surface temperature.

Estimated temperature of st'J tube and roll and calculation device 1
1. Compare the temperature given as the target value to the temperature given as the target value, and if there is a difference, find the heat transfer coefficient that should be corrected to the target temperature,
The required amount of coolant is determined from the relationship between the heat transfer coefficient and the amount of coolant, which was separately determined experimentally, and the coolant regulator T
, 8°9 to adjust the coolant amount.

FIG. 5 shows an example of the relationship between the amount of coolant and the heat transfer coefficient, which was experimentally clarified by the inventors.

According to the findings of the inventors, the strip coolant is effective for modifying the strip temperature, and therefore the strip coolant is mainly regulated through the regulator 9.

Further, since the roll temperature does not have much influence on the temperature of the sl-IJ tube, a 7°8 roll coolant regulator is operated to adjust the coolant amount to control the roll temperature.

Further, if the temperature of the Null-IJ tube during rolling can be measured, the actual measured temperature and target temperature are compared, and if a difference occurs, control is performed using the method described above.

By the method described above, the strip temperature and roll temperature are kept constant.

In this case, there is no compensation for keeping the shape of the strip good, but according to the findings of the inventors, the shape is usually kept good, and even if the shape becomes bad, the degree of damage is slight, and the simple shape control device described below It is possible to always maintain a good shape.

The shape control device will be explained below.

The shape is observed based on the signal from the shape detector 4, and if the shape is not good, the arithmetic unit 13 determines the amount of correction of the roll bending force and roll position necessary for shape correction, and the roll bend adjuster 5 and the roll position adjuster Drive 6,
Correct each.

The present invention has further advantages in the following points.

That is, the comparator 14 monitors the correction amount for shape control obtained by the arithmetic unit 13, and if the correction amount becomes too large and cannot be corrected, for example, the usage limit of the roll bender has been reached, the roll target can be adjusted within a practically possible range. Correct temperature.

Specifically, the relationship between the roll bend force and the roll temperature is determined separately, the roll temperature target value is corrected based on this relational expression, and the temperature control device again controls the roll temperature to the corrected target temperature.

As previously explained, if the roll temperature is controlled using roll coolant, it is possible to control the roll temperature without significantly affecting the strip temperature.

The specific effects of the present invention will be described below.

The inventors particularly investigated the relationship between strip temperature and rolling speed using a hard material that requires a high rolling force, and at the same time investigated the occurrence of slip defects on the strip surface.

The results are shown in Figure 6, where the strip temperature is 120°.
When the temperature exceeds -130°C, the lubricating oil film between the roll and the strip cannot be maintained, and slip defects occur on the surface of the Null-IJ joint due to direct contact or any metal contact between the roll and the strip.

For this reason, in the conventional rolling method, it was necessary to reduce the rolling speed, but in the rolling method of the present invention, the IJ tube temperature is actively controlled by adjusting the amount of cooling coolant, etc. High-speed rolling is now possible without slip defects.

G1 indicates the rolling method according to the present invention, G2 indicates the rolling method according to the conventional method, and the mark X indicates the occurrence of slip.

The material is a hard material with C=0.12%. The details of the present invention have been explained above using a recirculation system as an example of a reversible cold rolling mill and a rolling oil lubrication system. It is of course possible to apply the invention.

[Brief explanation of drawings]

Figure 1 is a block diagram explaining the conventional shape adjustment method;
The figure is a block diagram of an apparatus for carrying out the method of the present invention, Figure 3 is a graph showing the results of comparison between the calculated value and the measured value of the strip temperature against the rolling speed in tandem rolling to explain the present invention, and Figure 4 is the same. Figure 5 is a graph showing the relationship between the amount of coolant and heat transfer coefficient, and Figure 6 is a graph showing the relationship between strip temperature and rolling speed. be. 1... Winding machine, 2... Winding machine, 3.
...Rolling roll, 4...Shape detector, 5
・・・・・・Roll benzo ink device, 6・・・・・・
Roll position control device, 7... Roll coolant equipment, 8... Roll coolant equipment, 9... Strip coolant equipment, 10
... Information input/output device, 11 ... Arithmetic device, 12 ... Shape controller, 13 ... Arithmetic device, 14 ... Comparison vessel.

Claims (1)

[Claims] 1. When cold-rolling a metal strip, the temperature of the metal strip +7 and the rolling roll is controlled in advance based on the relationship between the temperature and the quality characteristics of the finished product for each rolling material, using a cooling control device for the metal strip and rolling roll. In addition to controlling the cooling amount, rolling conditions, etc. to achieve the determined set temperature, the shape of the metal strip is controlled by operating the roll bending device and roll position adjustment device, and the amount of correction of the roll pending car and roll position is controlled. A shape control method in cold rolling of metal, characterized in that the target values for the temperature control of the metal strip and the rolling roll are corrected within an allowable range when the temperature control becomes uncontrollable due to these manipulated variables.