KR100376527B1 - Rolling method of steel plate after improvement of width error degree - Google Patents

Abstract

The present invention relates to a method for rolling deburring in thick plate rolling, and its purpose is to compensate for the gap between the rolls in consideration of both the thermal expansion shrinkage value and the amount of wear of the rolling rolls, thereby improving the width error width after rolling. In providing a method.

The present invention for achieving the above object first calculates the wear amount (WRwear) for the work roll, the wear amount (BRwear) of the support roll, the thermal expansion amount (WRther) of the work roll, and the heat shrinkage amount (WRcont) of the work roll. The technical gist of the method is to compensate for the gap between the work rolls, and then to perform the blasting rolling by setting the roll gap based on the work roll gap compensation amount.

Description

Rolling method of thick steel plate with improved degree of error

The present invention relates to a method for rolling deburring in thick plate rolling, and more particularly, to the width of the thick steel sheet which improves the width error after deburring by compensating the roll gap in consideration of both the thermal expansion shrinkage value and the wear amount of the rolling roll. It relates to a rolling method.

In general, slabs manufactured by continuous casting or crushing mills are produced as thick plates using reversible mills. In the rolling process for producing a thick plate product, even rolling and bread-rolling rolling are first performed by a rough rolling mill, and then the rolled-rolled rolled material is mapped to the final target dimension by a finishing mill. This will be described with reference to FIG. 1 showing the rolling process in the rough rolling process as follows.

That is, in the rough rolling process, as shown in Fig. 1, first, the slab 1a is evenly rolled in the plate length direction to uniformly select the thickness of the slab 1a so as to satisfy the bread-rolling rolling condition. The even-roll rolling finished material 1b is obtained by a so-called even-roll rolling step (X). Next, this is rotated 90 degrees horizontally to roll the even-rolled finished material 1b in the width direction to secure a predetermined width dimension. By the so-called bread-making rolling process (Y), bread-making rolling completed material 1c is obtained. Then, it is rotated 90 degrees horizontally, and the width finishing rolled material 1c is rolled in the longitudinal direction to obtain a predetermined thickness, length, and mechanical properties, followed by a finishing rolling process (Z) to obtain a target dimension. (1) is obtained.

The width degree of the width reduction rolling material 1c after completion of the width reduction rolling process (Y) described above has a direct effect on the length of the plate after rolling, and the width after the width reduction is greater than the rolling target width. Since the length of the product is shortened, the length of the product cannot be satisfied. In addition, when the width | variety of the width | variety rolled-in completed material 1c after width | emission is less than a target width, when cutting a steel plate in rectangular shape, the both edge portions of the width | variety rolled-in completed material 1c are cut | disconnected. Since the amount of crops to be cut by the cutter is small, the cutting surface becomes poor or the width is short.

There are various causes of the decrease in the width degree after the blasting rolling, such as the degree of roll gap setting, the accurate calculation of the spreading amount in the longitudinal rolling, and the roll gap change due to roll wear or thermal expansion. Among them, the biggest reason is that as shown in Fig. 2, the roll gap H of the thick plate rolling mill 10 continuously changes after the rolling rolls 11 and 12 are replaced.

That is, after the roll replacement, as shown in Fig. 2b, the thickness of the material after rolling shows Hb, but when the roll gap is changed due to thermal expansion and abrasion of the rolling roll, the roll is thermally expanded as the rolling progresses even if the roll gap set value is the same. Since the diameter becomes larger, as shown in Fig. 2A, the thickness becomes Ha and becomes thinner than the thickness of the initial roll replacement. In addition, as the wear of the roll increases as the rolling time elapses, as shown in FIG. 2C, the diameter becomes smaller and the thickness after the rolling becomes Hc, which is thicker than the initial roll replacement.

For example, assuming that the rolling work roll diameter is increased by 1 mm by adding up and down by thermal expansion, the actual roll gap is also reduced by 1 mm. In case of selecting slab with thickness × width × length of 220mm × 1600mm × 3000mm, and rolling the slab with the same rolling and width rolling target dimensions as shown in Table 1 without considering the spreading amount in the width direction for convenience, As described above, when the roll gap is reduced by 1 mm due to the thermal expansion of the roll, and without compensation of the roll gap, as shown in Table 2, the width after the width is reduced to 164 mm and 81.5 mm after the thickness is even and The result is a 19 mm wider value.

On the contrary, in the case where the roll wear amount is 1 mm due to the increase in the rolling amount, the width after the width is reduced by 19 mm.

On the other hand, the thermal expansion and wear phenomenon of the roll with the rolling time after the rolling roll replacement shows the aspect as shown in Figure 2d. As shown in FIG. 2D, the thermal expansion amount gradually increases after replacing the rolling rolls, and reaches a predetermined time, thereby achieving saturation and no further thermal expansion. On the other hand, the wear amount shows a phenomenon that the roll wear amount continues to increase with the rolling time. As a result, the diameter change of the roll is expressed as the sum of the roll diameter change amounts due to the thermal expansion and wear. As a result, roll abrasion and thermal expansion after roll replacement are the causes of variation in breading. Fig. 3 shows an example of the scatter diagram for the out-of-plane error caused by the width of the target thick plate.

Therefore, after replacing the rolling rolls, it is necessary to calculate and compensate the thermal expansion, shrinkage, and wear of the rolls by the rolling history in order to accurately expose the rolling rolls even if the rolling rolls change in diameter due to thermal expansion and abrasion. However, in order to compensate for the above roll gap, conventionally, an operator has been mainly performed by experience. However, since this method has a difference in proficiency for each operator, it is limited to rely on the experience of the operator.

Therefore, the present invention has been proposed to solve the above-mentioned conventional problems, and its object is to calculate the thermal expansion and wear of the rolling rolls after replacing the rolling rolls in a thick plate rolling mill, and to calculate this value to control the thickness during rolling and breading rolling. The present invention provides a method for rolling out a breading machine in which the breading error is improved by the roll gap compensation.

1 is a schematic diagram showing a rolling process in a conventional rough rolling process

Figure 2a to 2c is a schematic diagram showing the thickness change of the material according to the roll gap change of the thick plate rolling mill

Figure 2d is a graph of the change over time for the roll diameter of the thick plate mill due to thermal expansion and wear

Figure 3 is a scatter diagram of the width of the target steel sheet and the breadth error generated at that time

Figure 4 is a graph showing the thermal expansion change of the roll with time after replacing the work roll of the thick plate rolling mill

Figure 5 is a flow chart for the process of rolling process of the present invention

Figure 6 is a graph showing the variation of the width deviation according to the presence or absence of bread width rolling application according to the present invention

Explanation of symbols on the main parts of the drawings

1a ... slab (1a) 1b ... even rolling finished material

1c ...... Burning Rolling Finishing Material 10 ...... Thick Plate Rolling Mill

11 ...... Work Roll 12 ...... Support Roll

The present invention for achieving the above object is a rough rolling process for even rolling and deburring rolling in the roughing mill comprising a work roll and a support roll; and the final target dimension in the finishing mill for the demolition rolling material rolled in the roughing process In the manufacturing method of a thick steel sheet comprising a;

If the work roll that is currently working is a newly assembled work roll, set the thermal expansion amount (WRther) and the wear amount of the support roll (BRwear) to zero with the wear amount (WRwear) for the work roll, and If it is not an assembled work roll, the coefficient of wear (C _f1 ) of the work roll is obtained in advance through regression analysis from the relationship between the rolling history and the actual wear amount of the work roll before replacement and assembly. After determining the width (B) and the length (L) of the target rolled material and measuring the rolling load (P) for the material, the contact projection length (ld) and the diameter (Dw) of the rolled material and the work roll were obtained. Calculating the wear amount (WRwear) for the work roll by Equation 1;

Then, from the relationship between the rolling history and the actual wear amount on the support roll before replacement and assembly, the information on the wear coefficient (C _f2 ) of the support roll was obtained in advance through regression analysis, and then the total length (Lb) and Calculating a wear amount BR wear of the support roll through Equation 2 by measuring the diameter Db;

Then, the width (B) of the final target rolling material for the material to be rolled, the measured measurement temperature (Tm) of the rolling material, the contact projection length (ℓd) of the rolling material and the work roll, the rolling time (Tr) and Calculating the thermal expansion amount (WRther) of the work roll by contacting the work roll with the rolled material by substituting the coefficient of thermal expansion C _{r of} the work roll into Equation 3;

Measure the non-rolling time (Tc) that the actual rolling is not in progress for the rolled material, collect the amount of cooling water (Qc) per unit time and substitute the heat shrink coefficient (Cc) in the equation (4) according to the cooling during rolling stop Calculating a heat shrinkage amount WRcont of the work roll;

Compensation value for the gap of the work roll (RGcom) using Equation 5 from the wear amount (WRwear), thermal expansion amount (WRther), heat shrinkage amount (WRcont), and support roll wear (BRwear) for the work roll obtained as described above. Calculating; And

Calculate the gap of the work roll according to the gap compensation value RGcom of the work roll calculated as described above using Equation 6, and adjust the gap of the work roll according to the calculated value to roll the material to the final target rolling width. step; It relates to a breading machine rolling method that includes a breading machine error degree is improved.

Hereinafter, the present invention will be described in detail.

The present invention is very useful in the thick plate rolling process in which the evening and breading machine rolling is performed in the roughing mill, and the breading machine rolling material is finish rolled to the final target dimension in the finishing mill. Among them, the present invention is very useful for the breading roll in the reversible thick plate roughing mill 10 composed of a work roll 11 and a back-up roll 12 as shown in FIG. 2B.

The present invention first calculates the wear amount for the work roll (WRwear), the support roll wear (BRwear), the work roll thermal expansion amount (WRther), and the work roll thermal shrinkage amount (WRcont) to calculate the gap of the work roll from these calculations. Is compensated for, and then the roll gap is set by setting the roll gap based on the work roll gap compensation amount.

First, the steps of calculating the wear amount of the work roll and the support roll will be described.

The wear amount of the work roll of the present invention is governed by many factors such as rolling load, relative sliding with the rolled material, coefficient of friction of the work roll, and material of the roll. However, since the calculation of the wear amount of the work roll considering all these factors becomes very complicated, the present invention applies a calculation formula generally used.

That is, the calculation formula for the wear amount of the work roll of the present invention can be expressed by a simple equation as shown in Equation 1 as being proportional to the product of the rolling load per unit area and the contact number at the same point of the work roll and the rolled material.

[Equation 1]

P: rolling load (ton)

B: width of rolled material (mm)

L: length of rolled material (mm)

ℓd: Length of contact projection between rolled material and work roll (mm)

Dw: Diameter of work roll (mm)

C _f1 : wear factor of work roll

In Equation 1, P / (B · Ld) represents (rolling load) / (rolling area and roll contact area) and represents rolling load per unit area, and L / (π · Dw) represents (length of rolled plate) / ( Roll circumferential length) means contact recovery of the roll and the rolled material at the same point.

In addition, the work roll wear factor (C _f1 ) is a factor determined by the roll material, the relative slip state, and the rolling temperature. The regression analysis is performed in the relationship between the rolling history and the amount of wear on the work roll rolled before the new replacement. Obtain through The work roll wear coefficient was measured to have a value of about 1.091 × 10 ⁻³ to 1.189 × 10 ⁻³ , when the work roll reference diameter was 1160 mm.

On the other hand, the width B and the length L of the rolling material are the final target values of the rolling material to be rolled, and the rolling load P is the measured value.

Next, the wear amount calculation formula of the support roll is basically the same as the work roll, but since the object contacting the support roll is not a roll material but a work roll, the unit rolling load can be expressed as 'rolling load / support roll length'. It is composed together.

[Equation 2]

Lb: Overall Length of Support Roll (mm)

Db: support roll diameter (mm)

C _f2 : Support Roll Wear Factor

Here, the support roll wear coefficient (C _f2 ) is a factor determined by the roll material. The support roll wear factor (C _f2 ) is obtained by a regression analysis in the relationship between the rolling history and the amount of wear of the support rolls replaced after the rolling is completed. Actually, The support roll wear coefficient was 1.89 × 10 ⁻³ to 2.11 × 10 ⁻³ when the reference diameter was 2000 mm.

Next, the steps of calculating the thermal expansion and contraction amount of the work roll will be described.

Figure 4 shows the thermal expansion and thermal shrinkage of the roll in accordance with the rolling and the rolling stop after the actual rolling roll replacement. As shown in Fig. 4, after the rolling roll is replaced, the thermal expansion amount does not expand any more after reaching the initial limit point e, and the thermal expansion amount decreases due to shrinkage at the f point at which the rolling stops, and is below the limit value. It goes down. After the rolling starts at point g again, the thermal expansion amount of the roll is increased to rise to the limit point h again. This phenomenon occurs periodically with rolling and stopping rolling.

The thermal expansion calculation formula of the work roll is affected by a number of factors such as the temperature of the rolled material, the heat of processing, the heat of wear, the length of the rolled material, the non-rolling time between the passes and the thermal conductivity between the rolls. In order to construct the system, a large amount of data must be collected in the actual industry, and the calculation itself becomes very complicated.

Therefore, the present invention uses a simple equation by regression analysis of the performance. The thermal expansion of the roll by rolling shows a larger value as the rolling material temperature is higher, the larger the contact area between the rolling material and the roll is, and the longer the rolling time is.

[Equation 3]

Cr: Thermal expansion coefficient of work roll

Tm: Actual measured temperature of rolled material (Tm)

B: width of final target rolled material

ℓd: length of contact projection between rolled material and work roll

Tr: rolling time

Here, the roll thermal expansion influence coefficient Cr by rolling is measured in the relationship between the rolling history and the measurement thickness by measuring the actual thickness after rolling to a predetermined thickness in the rough mill. In this case, the thickness of the rolled material is measured using a micrometer or a radiation thickness meter provided on the rear of the finishing mill. In order to obtain the coefficient of thermal expansion, rolling materials of the same dimensions should be used, if possible. This is because, in the thickness calculation formula, the accuracy of the mill module may be a problem.

The thermal expansion coefficient of the said work roll was irradiated with 2.392 * 10 <^-3> -2.608 * 10 < ^-3 > when the roll diameter is 1160 mm.

The thermal expansion calculated value should be limited to a constant value α as shown in FIG. For example, the thermal expansion limit value (α) is different depending on the dimensional operating conditions of the rolling roll, but since the temperature of the working roll is usually controlled at 55 to 60 ° C., there is no big difference, so considering the above coefficient of thermal expansion Such as about 0.70 mm.

On the other hand, since the shrinkage calculation formula of the work roll shows a larger value as the roll surface area is larger, the amount of cooling water is larger, and the non-rolling time is longer, it is configured as in Equation 4.

[Equation 4]

Cc: heat shrinkage coefficient of work roll

Dw: diameter of work roll

Qc: Cooling water amount per unit time (Qc)

Tc: non-rolling time

Here, the roll shrinkage influence coefficient Cc is obtained by measuring the change of the roll gap by time while idling the rolling mill.

The roll shrinkage influence coefficient was a factor that is affected by the temperature of the cooling water according to the season, and 2.59 × 10 ⁻⁷ to 3.22 × 10 ⁻⁷ was examined as an appropriate value when the cooling water temperature was in the range of 15 to 30 ° C.

On the other hand, the support roll is indirect heat movement through the work roll without directly contacting the material, and because the cooling is continuously cooled by the cooling water, the temperature change of the support roll is very small and negligible so it is not calculated separately.

As described above, when the roll abrasion and thermal expansion calculation formulas are prepared, the work roll wear amount, support roll wear amount, work roll thermal expansion amount and shrinkage amount are calculated for each pass of the rolling, and the roll gap compensation amount (RGcom) is obtained using Equation (5). .

[Equation 5]

Then, a roll gap setting amount SD is obtained using Equation 6 to set a roll gap using a screw lowering drive device.

[Equation 6]

TH: thickness

RF: roll force

MM: mill module

So: Roll gap zero correction value

The roll gap setting procedure for the breadmaker rolling of the present invention for setting the roll gap through such a calculation process is shown in detail in FIG. 5.

As shown in Fig. 5, the breadmaker rolling of the present invention is the first step, and when the work roll is newly replaced, the work roll wear amount, support roll wear amount, and thermal expansion amount, which have been cumulatively calculated so far, are deleted and initialized.

Here, the reason for eliminating the support roll wear amount is because the roll gap is zero-adjusted again by using the screw lowering drive device after replacing the work roll so that the wear amount so far disappears by zero point adjustment. If it is used continuously without replacing the work roll, the work roll wear, support roll wear, work roll thermal expansion, and work roll shrinkage for the next rolled material are calculated according to the cumulative wear and thermal expansion performance to date. , And 4.

Then, after calculating the gap compensation amount of the work roll using Equation 5, the gap set value of the work roll is calculated using Equation 6, and the roll gap is set using the screw lowering drive device based on this set value. Rolling is carried out. After that, repeat the same process as before.

Hereinafter, the present invention will be described in detail through examples.

EXAMPLE

A slab with a thickness of 220 to 250 mm x width of 1500 to 2250 mm × length of 2500 to 4000 mm is produced using a thick plate rolling mill to produce approximately 500 sheets of thick plates with a thickness of 6 to 120 mm × width of 1500 to 4650 mm × length of 15000 to 45000 mm. In addition, it is shown in Figure 6 by measuring the width error according to the application of the present invention.

Figure 6 shows the effect before and after using the method of the present invention, before the improvement (Fig. 6a), the average width error 11.5mm, deviation (1σ) 12.5mm, after improvement (Fig. 6b) the average 7.1mm, deviation ( 1σ) 7.6mm, it can be seen that the breading accuracy is greatly improved.

As described above, in the present invention, the thermal expansion and wear amount calculation formula of the rolling roll after roll replacement is derived from the actual operation data, and the roll gap change amount is calculated from the wear and thermal expansion calculation formula of the roll during actual rolling, and then the roll gap is obtained using this value. By setting this, it is possible to control the exact thickness at the time of evening and spreading rolling, which contributes greatly to the spreading degree.

Claims (1)

The rough rolling process of even rolling and deburring rolling in the roughing mill including the working roll and the supporting roll, and the finishing rolling process of finishing the rolling rolling process of the explosive rolling material rolled out in the roughing process to the final target dimension in the finishing mill. In the manufacturing method of a thick steel sheet comprising a, If the work roll that is currently being worked is a newly assembled work roll, set the thermal expansion amount (WRther) and the wear amount of the support roll (BRwear) to zero with the wear amount (WRwear) for the work roll, and If the work roll is not assembled, the wear factor (C _f1 ) information of the work roll is obtained through regression analysis from the relationship between the rolling history and the amount of wear on the work roll before replacement and assembly. After determining the width (B) and the length (L) of the final target rolled material and measuring the rolling load (P) for the material, the contact projection length (ld) and the diameter (Dw) of the rolled material and the work roll were obtained. Calculating a wear amount (WRwear) for the work roll by Equation 1 below; [Equation 1] (P: rolling load (ton), B: width of rolled material (mm), L: length of rolled material (mm), ld: contact projection length of rolled material and work roll (mm), Dw: diameter of work roll) (mm), C _f1 : wear factor of work roll) From the relationship between the rolling history and the actual wear amount of the support roll before the replacement assembly, the wear coefficient (C _f2 ) information of the support roll was obtained in advance through regression analysis, and then the total length (Lb) and the diameter ( Calculating a wear amount (BRwear) of the support roll through Equation 2 by measuring Db); [Equation 2] (Lb: total length of support roll (mm), Db: support roll diameter (mm), C _f2 : support roll wear coefficient) The width (B) of the final target rolling material for the material to be rolled, the measured measurement temperature (Tm) of the rolled rolling material, the contact projection length (Ld) of the rolling material and the working roll, the rolling time (Tr) and the work Calculating the thermal expansion amount (WRther) of the work roll by contacting the work roll with the rolled material by substituting the thermal expansion coefficient C _r of the roll into Equation 3 below; [Equation 3] (Cr: coefficient of thermal expansion of the work roll, Tm: measured entry temperature (Tm) of the rolled material, B: width of the final target rolled material, Ld: contact projection length of the rolled material and the work roll, Tr: rolling time) Measure the non-rolling time (Tc) that the actual rolling is not in progress for the rolled material, collect the amount of cooling water (Qc) per unit time and substitute the heat shrink coefficient (Cc) in the following equation (4) to the cooling during rolling stop Calculating a heat shrinkage amount WRcont of the work roll; [Equation 4] (Cc: heat shrink coefficient of work roll, Dw: work roll diameter, Qc: amount of cooling water per unit time (Qc), Tc: unrolling time) Compensation value for the gap of the work roll using the following equation (5) from the wear amount (WRwear), thermal expansion amount (WRther), heat shrinkage amount (WRcont), and wear amount of the support roll (BRwear) for the work roll obtained as described above. Calculating; And [Equation 5] The roll gap setting amount SD according to the gap compensation value RGcom of the work roll calculated as described above is calculated by the following Equation 6, [Equation 6] (TH: exit thickness, RF: roll force, MM: mill module, So: roll gap zero compensation) Adjusting the gap of the work roll by this calculated value and rolling until the final target width is completed; Width width rolling method of the thick steel sheet is improved, characterized in that configured to include a width error.