RU2288795C2 - Rolling roll operation method - Google Patents

Abstract

FIELD: rolled stock production, possibly in sheet rolling shops including continuous five-stand rolling mill and skin pass rolling mill whose rolling rolls have the same structure.

SUBSTANCE: exploitation of rolling roll comprises steps of alternating its operation in mill stands at regrinding and remounting as working layer of roll is spent. At first rolling roll is operated in skin pass rolling mill. When working layer of roll is spent no more than by 14%, roll is remounted to fifth stand of continuous five-stand rolling mill where roll operates until 15 - 28% of its working layer is spent. After that roll is remounted in second stand where it operates until its working layer is spent by 29 - 39%. Then roll is remounted to fourth stand of mill where it operates until 40 - 50% of its working is spent. Exploitation of roll is terminated in first stand of continuous five-stand rolling mill where roll operates until complete spending of working layer or till minimum design diameter of roll.

EFFECT: improved strength of rolling rolls, lowered specific consumption of rolls, reduced quantity of rejected cold rolled strips by surface flaws.

1 ex, 1 tbl

Description

The invention relates to sheet rolling production and can be used to operate the work rolls of four-roll stands of cold rolling mills.

A known method of operating a work roll of a continuous four-roll cold rolling mill. The method includes the alternation of fillings of the work roll in the mill with regrinding. As the roll wears out and regrinds, the roll is rearranged in stands, starting from the latter against the direction of rolling [Polukhin P.I. and others. Sheet rolling and roll service. - M .: Metallurgy, 1967, p. 284-285].

The disadvantage of this method is the low durability of the work roll.

There is also known a method of operating a work roll, including its work in the stand, determining the amount of wear and resurfacing with removal of 1.7-2.2 of the maximum amount of wear. As the diameter and hardness decrease, the roll is rearranged against the direction of rolling from the finishing stands to the draft [Auth. USSR Certificate No. 1342549, IPC V 21 V 202, 1987].

The specified method also does not guarantee high roll resistance, but complicates the operation of the rolling stock of the rolling department. For its implementation, careful measurement of the profile of each worn roll is required, which requires a lot of time.

The closest in technical essence and the achieved results to the proposed invention is a method of operating a work roll of a continuous multi-stand mill, including alternating its work in mill stands with resurfacing and rearrangements in stands, starting from the latter, as the barrel hardness decreases, characterized in that the permutation produced by reducing the hardness of the barrel by 1-4 units. HSD, and after working in the last stand, the roll is rearranged into the second stand and then sequentially along the stands in the rolling direction and its operation is completed after being moved from the penultimate to the first stand of the mill [RF Patent No. 2131312, IPC B 21 V 28/02, Publ. 06/10/99, Bulletin No. 16] - prototype.

The specified method also does not ensure the achievement of the required task associated with increasing the resistance of the roll due to difficulties in its practical implementation and limited scope.

The disadvantages of this method are as follows.

1. The use of this method greatly complicates the operation of the rolls in connection with the need to control on each roll the hardness of the barrel. Measuring the hardness of the roll is an additional step. It cannot be produced after the rolls are rolled out of the stand due to the known hardening of the roll barrel surface and its surface wear obtained when working in the stand. In both cases, measurement inaccuracies are possible. Therefore, it is necessary to make measurements on roll grinding machines (VSH) after the end of the grinding cycle. Such a measurement takes from 6 to 10 minutes, which additionally lengthens the roll grinding cycle by the specified time and reduces the performance of the VSH. Introduction to the technology of total hardness measurement of all rolls entails the need for an additional increase in the staff of the roller grinding workshop (GSM) to perform this operation.

In addition, the work roll for each stand has its own individual profiling. As mentioned above, the hardness of the rolls can be measured only after grinding is completed, i.e. after giving the roll the required profiling and if after measurements it is revealed that its hardness has decreased by more than 1-4 units HSD, you will need additional unproductive regrinding of this roll to another profiling for another stand.

It should also be noted that the vast majority of models and types of hardness testers leave traces of measurements on the surface of the barrel of the polished roll, which can also cause another additional polishing.

2. The second disadvantage of this method is the difficulty of providing the conditions for the rearrangement of the rolls over a narrow range of hardness changes of 1-4 units. HSD, commensurate with the error (± 2 units of HSD) of measuring hardness with ball hardness testers. Under these conditions, there is no full guarantee that the specified conditions for moving the roll to the next stand are met correctly.

3. The third disadvantage of this method is to reduce the range of its applicability when using mill rolls made using modern hardening technologies (manufactured by NKMZ, Stemhoff, JSW, etc.), which have a depth of more than half the depth the hardness of the working layer is uniform (its change does not exceed 2 units of HSD). For these rolls, the known method is not applicable. The scope of the known method is for rolls with a working layer depth of not more than 50 mm.

4. The start of operation of the work roll from the last stand of a continuous cold rolling mill, the rolling force in which is at the level of the rest of the mill stands does not contribute to the relaxation of internal stresses generated during hardening at the roll manufacturer during heat treatment. The consequence of this is a decrease in roll resistance.

The proposed method of operating a work roll below eliminates the aforementioned disadvantages.

The technical task of the invention is to further increase the resistance of the rolls while simplifying the method of moving the rolls in the stands of continuous and training mills, the technical problem is solved by regulating the moment of the rearrangement of the rolls in the stands of the mills based on the depth of the working layer produced by regrinding of the roll, which achieves the technical effect of increasing the rolling resistance roll and reduce its specific consumption per 1 ton of cold rolled steel.

Hereinafter, by the depth of the working layer of the roll (by radius or diameter), we understand the difference between the radii (diameters) of the new working roll before its first filling in the mill and the roll taken out of service at its last filling.

The problem is solved in that during the operation of the work roll, including the alternation of its work in stands of a continuous five-stand and training mills with resurfacing and rearrangements in stands, starting from the working stand of a training mill, as the working layer is polished according to the invention, the roll is moved to the fifth stand of a continuous mill after working out and grinding a maximum of 14% of the working layer depth, after the roll is operated in the last mill stand, where it is operated until 15-28% of the working layer is worked out, it is rearranged they are placed in the second stand, where it is used up to 29-39% of the working layer output, after which the roll is rearranged in the third stand of the continuous mill, where it is operated upon reaching 40-50% of the working layer output and rearranged in the fourth stand, where it is used up to 51 -80% of the working layer. The roll ends its operation in the first mill stand and is decommissioned either by a fully developed working layer, or by a minimum structural diameter.

Known and proposed technical solutions have the following common features.

1. Both technical solutions are ways of operating the work roll.

2. Both technical solutions involve alternating the work of the roll in the stands of a continuous mill with regrinding.

3. The route of movement of the rolls along the stands of the continuous mill (with reference to the five-stand mill) is the same in both technical solutions: 5 → 2 → 3 → 4 → 1.

The differences of the proposed method from the prototype are as follows:

1. Operation of the newly commissioned work roll does not begin with the fifth stand of the continuous mill, but with the work stand of the training mill (provided that the diameter of the work rolls of the training mill is structurally equal to the diameter of the work rolls of the continuous mill). Small reduction during training (<2.5%), the possibility of relaxation of internal stresses and a low probability of band breakage provide the roll with relatively easy and safe operating conditions to achieve a maximum of 14% production of the active working layer. According to the prototype, the operation of the roll begins with the last stand of the continuous mill with unsafe operating conditions for the roll, which can reduce its durability.

2. Transferring the roll to the last stand of the continuous mill from the training mill and each subsequent rearrangement of the rolls in the stands of the continuous mill is carried out upon reaching the specified percentage of working layer development, established experimentally, which excludes the procedure for measuring the hardness of all the rolls heaped in the stand (as is done by the prototype) with all the disadvantages mentioned above and simplifies the operation of the rolling farm.

3. The operation of the roll in the first mill stand is continued until the minimum structural diameter is reached, and not until the working layer is fully developed (if the roll is calcined to great depth).

These distinctive features exhibit in their entirety new properties that are not inherent in them in the known sets of features, and consist in increasing the resistance of the rolling roll while simplifying the procedure for moving the rolls along the mill stands and a wider scope of the method.

The essence of the invention is as follows.

The route of roll rearrangements along the mill stands should provide the solution of the following problems: to ensure high surface quality of rolled strips, high roll resistance, not to limit the mill productivity by the reduced linear speed of the penultimate mill rolls due to their small diameters, especially if the rolling in the last mill stand is carried out with small reductions and the linear speed of the strip in the last stand of the mill is slightly different from the speed of the penultimate stand.

In addition to natural wear and tear, the roll during operation in the mill stands receives various damages (bells, cuts, punctures) due to injury to its barrel during strip breaks. To remove the aforementioned defects, it is necessary to unplannedly remove significant volumes of the working layer from the roll barrel. It should be taken into account the fact that with a decrease in the hardness of the roll barrel, the depth of damage penetration deep into the roll decreases.

The probability of strip breakage in the inter-stand spaces of the continuous camp increases with the number of the inter-stand gap when moving along the mill line from the first stand to the fifth. For this reason, it is advisable to increase the roll resistance to install it in the first along the mill stand. On the other hand, in the last (finishing) mill stand, it is necessary to have rolls with maximum hardness that resists the appearance of prints on the surface of the roll barrel and to ensure high quality of the surface of the strips.

The operation of training cold-rolled strips is a finishing operation. For this reason, new rolls are installed with maximum hardness in a temper mill. In addition to ensuring the high quality of the surface of cold-rolled strips, this contributes to the relaxation of internal stresses generated in the rolls during quenching at the manufacturer of the rolls during heat treatment and not completely eliminated during aging of the rolls before putting them into operation.

There, the rolls are operated in relatively safe conditions (low probability of breaks, low contact loads) upon reaching a maximum of 14% removal of the working layer. During operation, the maximum relaxation of internal stresses in the body of the rolls is achieved.

After operation in a tempering mill, such a roll has a barrel hardness almost equal to that of a newly commissioned roll, and it is rearranged into the fifth stand of a continuous five-stand mill.

As the roll is operated in the last mill stand, fatigue stresses accumulate in the active layer of the roll barrel due to strip breaks and trauma to the roll surface. If the roll is further operated in this stand, then the surface of the roll will begin to collapse, its durability and quality of cold-rolled strips will decrease. However, in the process of work, in between the fillings, the roll is polished, part of the damaged layer is removed and this sets a certain parity between the accumulation of internal stresses and their relaxation. It has been experimentally established that if the roll is continued to work in the fifth mill stand until more than 28% of the working layer removed during resurfacing is used, then an irreversible accumulation of internal stresses will occur in the roll body, which can lead to breakage, delamination, and premature decommissioning.

To avoid this, after working in the fifth stand and grinding, the dump of 15-28% of the working layer of the roll is transferred to the second stand of the mill, operating at lower speeds, reductions and a lower level of contact stress.

When working in the second stand, the roll does not get damaged, while maintaining high hardness, because the probability of strip breaks in the first interstand space due to the large thickness of the strip is minimal. For the most complete removal of the accumulated fatigue stresses and damage, the roll is operated in this stand, alternating fillings with resurfacing until 29-39% of the working layer is removed from the barrel by grinding. Then the roll is transferred to the third mill stand. The likelihood of damage to the surface of the roll in this stand somewhat increases, but the roll has already lost up to 39% of its working layer, its hardness has decreased, and therefore, the penetration depth of damage to the roll barrel, received by it with possible strip breaks, decreases. In addition, as the roll is used, traces of damage are gradually polished, which makes it impossible to significantly increase internal stresses. The operation of the roll in the third mill stand is continued upon reaching 40-50% of the total removal of the active working layer of the roll, after which the roll is transferred to the fourth mill stand. It was experimentally confirmed that with an increase in the removal of the working layer from the surface of the roll over 50%, the hardness of the roll barrel decreases to less than 90 units. HSD, and it is no longer suitable for operation in the penultimate stand of a continuous mill.

When this condition is met for the specified percentage of grinding of the working layer, the roll enters the fourth stand of the mill with high hardness (more than 90 HSD units), sufficient to ensure the surface quality of cold-rolled strips and having up to 50% of the active working layer, less prone to brittle damage . Since it is precisely on this section of the curve that changes the hardness of the roll barrel from the depth of the working layer, an intensive decrease in the hardness of the barrel begins, the roll is operated only until the removal of 51-80% of the depth of the working layer of the roll, depending on the technology of quenching of the rolls adopted at the manufacturer. Further operation of the roll in this stand would lead to a deterioration in the surface quality of the cold-rolled strips due to a significant decrease in its hardness. In addition, due to a decrease in its diameter during refining, it is possible to limit the maximum rolling speed and reduce the productivity of the mill, because in the case of small reduction in the last mill stand, the difference in speeds between the last and the penultimate mill stands is insignificant and in fact the fourth mill stand determines the maximum rolling speed. Therefore, the roll is transferred to the first stand, where it completely produces a hardened layer. The level of contact stress in the first stand is low, because it compresses the hot-rolled non-riveted strip, a decrease in the hardness of the roll does not significantly affect the surface quality of the rolled strips. In it, the roll is operated with regrindings and fillings until the working layer is completely removed by grinding (during operation of the roll) or is taken out of operation upon reaching the minimum design diameter if the roll is calcined to a great depth.

All of the above indicates that the proposed technical solution meets the criterion of "significant differences".

An example implementation of the invention

Two new work rolls with a barrel diameter of 615 mm and a hardened layer depth of 70 mm by diameter according to the manufacturer's certificate (NKMZ) are poured into the working stand of the temper mill 2030 and cold-annealed strips of 0.5-2.5 mm thick are trained with periodic resurfacing. The working layer of the rolls is 615 / 2-550 / 2 = 65 mm per diameter, where 550 mm is the minimum structural diameter of the roll.

After 18 resurfacing, the depth of the working layer of the roll decreases by 9 mm in diameter or 13.8% and the rolls are rearranged in the fifth stand of a continuous five-stand mill 2030, where they continue to operate with periodic resurfacing. The diameter of the rolls at the time the rolls were moved to the fifth stand was 606.0 mm.

During the operation of the rolls in the fifth mill stand, 18 regrindings are performed. The diameter of the rolls decreases to 597.0 mm. The total removal of the working layer during resurfacing since the start of operation of the rolls was 18.0 mm in diameter or 27.7%. During the operation of the rolls, they received surface damage and their further operation under conditions of high speeds and high contact loads could lead to fatigue destruction of the surface and premature decommissioning of the rolls. To avoid this, the rolls from the fifth stand are rearranged into the second stand of the mill and continue their operation. After 29 regrinding of the rolls and a general removal of the working layer of the rolls of 25.2 mm in diameter or 38.8%, the rolls acquired a diameter of 589.8 mm. The portion of the working layer damaged during operation in the fifth mill stand was completely removed during resurfacing. Since the total removal of the active working layer from the roll was 38.8% each, they are transferred to the third mill stand. During operation, the rolls in the third stand undergo 2 strip breaks and their surface is partially injured. However, due to the decrease in hardness of the roll barrel, the strip breaks in front of the third stand do not cause deep damage to their working layer and due to the gradual removal of damage during resurfacing, additional internal stresses do not accumulate in the roll body. The work of the roll in the third stand is alternated with resurfacing. After 16 resurfacing, the roll diameter decreases to 582.6 mm. At the end of the operation of the rolls in the stand, the total depth of the ground layer was 32.4 mm or 49.8% of the original depth of the working layer and the rolls were transferred to the fourth stand of the mill. The work of the rolls in the stand is also alternated with resurfacing with a decrease in diameter to 567 mm. After 31 resurfacing, the total removal of the riveted layer was 73.8%. An optional hardness test showed that it had dropped to 86 units. HSD. Further operation of the roll in this stand would lead to a deterioration in the surface of the cold-rolled strips and, first of all, for the “imprints” defect due to the reduced hardness of the surface of the roll barrels and the possibility of sales and injury to the surface of the rolls at a high level of contact stress in the stand hardening of rolled metal.

For this reason (due to the impossibility of further operation of the rolls without reducing the surface quality of the cold-rolled strips), the rolls were transferred to the first mill stand. In the first mill stand, the operation of the rolls was carried out to achieve a minimum structural diameter of 550 mm and were written off as scrap metal. With the specified method of operating the rolls, the specific consumption of rolls per 1 ton of rolled stock was 1.0 kg / t.

Other options for implementing the method, including those discussed above, and indicators of their effectiveness are shown in the table.

Table No. p / p The removal of the working layer from the rolls when they are rearranged in continuous stands (stands 1-5) and training mills,% Specific consumption of rolls, kg / t Sorting of cold-rolled strips by surface defects,% Dress. mill crate 5 crate 2 crate 3 crate 4 crate 1 one 2 3 four 5 6 7 8 9 one 5 10 twenty thirty 60 one hundred 1.38 0.11 2 3 12 eighteen 28 66 * one hundred 1.45 0.14 3 9 fourteen 28 39 84 * one hundred 1.06 0.31 four 13.8 27.7 38.8 49.8 73.8 one hundred 1.0 0.29 5 5 fifteen 29th 40 51 one hundred 0.79 0.10 6 7 twenty 34 46 68 one hundred 0.86 0.27 7 fourteen 28 39 fifty 80 one hundred 0.99 0.32 8 16 32 41 62 81 one hundred 1.32 0.35 9 twenty 34 45 66 84 one hundred 1.25 0.72 10 10 37 46 76 90 * one hundred 1.14 1.13 11 (prototype) Not regulated 1.22 0.29 Note: * - during operation of the rolls, detachment of the rolls was observed with their premature decommissioning.

As follows from the data given in the table, the smallest specific consumption of rolls per 1 ton of rolled metal (0.79-1.0 kg / t) and the average percentage of sorting of cold-rolled strips by surface defects (0.1-0.32%) provide the inventive method of operating a work roll (options 4-7).

When using rolls according to options 1 and 2 during the swapping of rolls with a lower percentage of grinding of the working layer in the working stand of a temper mill and in 5, 2, 3 stands of a continuous five-stand mill, the specific consumption of rolls per 1 ton of rolled products increases and amounts to 1.38-1.45 kg / t rental. However, the level of sorting of cold-rolled strips by surface defects is minimal and amounts to 0.11-0.14%. The increased consumption of work rolls per 1 ton of cold-rolled steel is associated with a low (compared with the claimed option) level of grinding of the working layer of the rolls before filling them in stand 4. Further operation of such rolls with increased hardness led to their damage, significant removal to remove damage, and in some cases, to the detachment of the rolls with their premature decommissioning. However, when the rolls are operated in stand 4 with a high barrel hardness (due to the low level of grinding of the working layer), the work rolls are less susceptible to local damage, which causes periodic defects. This explains the lowest percentage of sorting of cold-rolled strips by surface defects.

When operating rolls according to option 3, their specific consumption per 1 ton of rolled products and the sorting level by surface defects of cold-rolled strips approaches the claimed variant.

When using the rolls according to options 8-10 and rearranging the rolls in the stands, with a large percentage of grinding of the working layer in the working stands of the temper mill and in 5, 2, 3 stands of a continuous five-stand mill (as compared with the claimed variant), the specific consumption of rolls per 1 ton of rolled metal also increases and amounts to 1.32-1.14 kg / t of rolled metal. At the same time, the level of sorting of cold-rolled steel according to surface defects obtained due to a decrease in the hardness of the barrel of the work rolls in stand 4 is also increasing. they were prematurely decommissioned by exfoliation.

When operating work rolls according to the prototype, the roll resistance averaged 1.22 kg / t, the sorting of cold-rolled strips by surface defects was at the level of roll operation according to the proposed technical solution.

The technical and economic advantages of the proposed method of operating a work roll are to increase its durability, reduce the sorting of cold-rolled strips by surface defects and reduce the specific consumption of rolls per 1 ton of rolled products, and also generally allow to increase production profitability by 3-7%.

Claims (1)

A method of operating a work roll, including alternating its work in stands of a continuous five-stand and training mills with resurfacing and rearrangements as the working layer is developed, characterized in that the operation of the roll is started from the training mill, after generating and grinding a maximum of 14% of its working layer, the roller is rearranged the fifth stand of a continuous five-stand mill, in which 15-28% of the working layer is exploited before working out and grinding and rearranged into the second stand of the mill, in which they are exploited folding and grinding 29-39% of the working layer, then the roll is rearranged in the third mill stand, in which 40-50% of its working layer is exploited before generation and grinding and rearranged in the fourth mill stand, after production with grinding in which 51-80% of the working its layer is rearranged in the first mill stand, in which it is exploited until the working layer is fully developed or the minimum structural diameter is reached.