JPH02179303A - Manufacture of thick steel sheet having discontinuous projections in length direction - Google Patents

Abstract

PURPOSE:To prevent generation of lap flaws, etc., and to effectively manufacture a thick steel sheet by rolling a stock by a specific light drafting amount from the rolling start to the pass one less than the final pass and then rolling the stock by a specific strong drafting amount in the final pass. CONSTITUTION:A thick steel sheet 1 having discontinuous projections 4 in the length direction is manufactured by multipass reversal rolling by use of caliber rolls. In that time, the sheet 1 is rolled by a light drafting amount ht shown by the inequality I from the rolling start to the pass one less than the final pass. Then, the sheet 1 is rolled by a strong drafting amount Ht shown by the inequality II at the final pass. Where, ht: a light drafting amount (mm) from the rolling start to the pass one less than the final pass to bring an outlet side sheet thickness to be (t)mm, Rs: projection height allowable limit value (mm) of the intermediate pass preventable against generation of lap flaws, alphat: print percentage (%) when an outlet side sheet thickness is made to be (t)mm, Ht: drafting amount (mm) to bring an outlet side sheet thickness in the final pass to be (t)mm, Rt: necessary projection height (mm) as a final product. Hence, industrially useful effects are obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing a thick steel plate having protrusions discontinuous in the length direction on at least one surface thereof.

[Prior Art] Demand for steel plates having discontinuous protrusions on at least one surface in the length direction has increased in recent years as a material for civil engineering and construction to improve adhesion to concrete, and as various floor plates for construction. It's increasing.

Conventionally, hot-rolled thin steel plates with a thin wall thickness and narrow width, called striped steel plates, have been used as steel plates with protrusions for civil engineering and construction materials. It is thick and wide.

It is expected that demand for thick steel plates having discontinuous protrusions in the longitudinal direction will increase.

As a method for manufacturing thick steel plates with irregular cross sections, for example, JP-A-62-
Publication No. 40903 discloses a method for manufacturing this using a rolling mill that can be recombined with 4 to 5 stages, and Japanese Patent Laid-Open No. 61
Japanese Patent Publication No. 119311 discloses a method that can form protrusions with less roll damage and a preferable height.

However, the former method relates to a method for manufacturing a thick steel plate in which continuous protrusions are formed in the length direction.
Unlike the present invention, the present invention does not relate to a method of manufacturing a thick steel plate having discontinuous protrusions in the length direction thereof.

Although the latter method concerns the production of steel plates with discontinuous projections along their length, the formation of the projections is basically carried out in the final stand of the hot strip mill.
It is carried out in one bus by Caliber Roll.

[Problem M to be solved by the invention] The protrusions of a thick steel plate having discontinuous protrusions in the longitudinal direction are removed at the final stand in the case of a continuous mill, or in the case of a single multi-bus reversible rolling mill. is the final pass, and it is possible to form it in one pass using a caliber roll.

However, since the protrusions are formed by only one pass of rolling, the width and thickness of the product that can be manufactured are limited due to the maximum possible reduction in one pass rolling, restrictions on slab dimensions due to the structure of the heating furnace, etc. Dimensions such as length are significantly restricted, and furthermore, wasted time occurs in the rolling process, resulting in a significant decrease in productivity.

In addition, when rolling is performed by one bus in the finishing mill of a rolling line having two rolling mills, one for roughing and one for finishing, the distribution of the number of rolling passes is significantly biased toward rough rolling, resulting in a significant decrease in productivity. .

When a thick steel plate having longitudinally discontinuous protrusions is rolled in multiple passes using a multi-pass reversible rolling mill, the following problem occurs. That is, in general, the amount of reduction in each pass in multi-pass reversible rolling is determined by the rolling load and rolling torque in the early stage of rolling, and in the late stage of rolling.

It is determined by the shape of the protrusion to be formed. In rolling using caliber rolls, the caliber shape is transferred to the steel plate depending on the amount of reduction in each pass. That is, as shown in FIG. 7(a), projections 4 are formed on the surface of the thick steel plate 1 by rolling the thick steel plate 1 with an upper work roll 2 on which a caliber is formed and a flat lower work roll 3. be done.

However, as shown in FIG. 7(b), this protrusion 4 is crushed during rolling in the next pass, and as shown in FIG.
Wrap flaws 5 as shown in the enlarged cross-sectional view in FIG. 3(c) occur.

This lap flaw 5 does not disappear in the subsequent rolling, but rather is promoted, becomes 1 to 2 mm deep, and clearly remains on the product. Furthermore, if the protrusion formed in the previous pass and the protrusion formed in the next pass overlap in a certain range, the protrusion 4 will be damaged as shown in FIG.

Therefore, it is an object of the present invention to solve the above-mentioned problem and to solve the problem that wrap flaws and damage to the protrusions occur when a thick steel plate having discontinuous protrusions in the longitudinal direction on at least one surface is subjected to multi-bus reversible rolling. The object of the present invention is to provide a method that can be manufactured efficiently without any problems.

[Means for Solving the Problems] The present inventors have developed a method for processing a thick steel plate having discontinuous protrusions in the longitudinal direction on at least one surface thereof by multi-pass reversible rolling, thereby causing lap flaws and damage to the protrusions. We conducted extensive research in order to develop a method that could be manufactured efficiently without any additional steps. As a result, the first finding was obtained.

(1) The relationship between the height of the protrusion and the depth of the lap flaw can be estimated from the caliber, that is, the shape of the protrusion. Therefore, the transfer characteristics of the caliber shape to the steel plate, that is, the printing rate (protrusion height/rolling amount x 100), determined by the caliber shape, the thickness of the rolling entry and exit sides, etc., are taken into consideration.

Each pass from the start of rolling to before the final pass is controlled by a predetermined reduction amount so that the height of the protrusion generated by the reduction in each pass is kept to a fraction of the final required height. By applying the following light pressure reduction, it is possible to prevent the occurrence of lap flaws and damage to the protrusions.

(2) If the final pass is performed under strong pressure that can form a predetermined protrusion shape, taking into consideration the print rate, protrusions having a predetermined shape and height can be formed.

The present invention has been made based on the above-mentioned findings, and includes a thick steel plate having discontinuous protrusions on at least one surface thereof in a predetermined shape for forming the protrusion shape. In the method of manufacturing by multi-pass reversible rolling using a caliber roll having a caliber of It is characterized by rolling with a strong rolling reduction amount ΔH2 shown in the following equation (2).

However, Δht: Light reduction amount to make the exit side plate thickness tmm from the start of rolling to before the final pass (,a) ΔR3R3 Tolerable limit value of protrusion height of intermediate pass that can prevent lubricating (no) αC = exit side plate thickness Printing rate when tnn is (ΔHt: Reduction amount to make the exit side plate pressure 8 mm in the final pass (n-) ΔRL: Height of the protrusion required for the final product (■) Next, start rolling. The reason why the amount of reduction up to the final pass and the amount of reduction during the final pass are determined as in equations (1) and (2) above is shown in FIG. 5(a) as a plan view and as shown in FIG. 5(b). )
5(a) is a sectional view taken along line A-A in FIG. 5(c).
A thick steel plate 1 having lattice-like protrusions 4 (maximum height 4!IIB) discontinuous in its length direction as shown in the BB cross-sectional view in Figure (a) is manufactured using a multi-pass reversible rolling mill. I will explain the side when doing so. FIG. 2 is a graph showing the relationship between the exit side plate thickness and the print rate in each pass when rolled by this rolling mill. As is clear from FIG. 2, the printing rate is inversely proportional to the exit side thickness of the rolled material. Third
The figure is a graph showing the relationship between the height of the protrusion and the depth of the lap flaw in the intermediate pass. As is clear from Fig. 3, if the height of the protrusion in the intermediate path is set to about 1- or less,
It is possible to prevent wrap flaws from occurring. FIG. 4 is a graph showing the relationship between the average reduction amount and the depth of lap flaws at intermediate bus numbers, based on FIGS. 2 and 3 above. As is clear from FIG. 4, if the rolling reduction amount is about 5 m or less, the occurrence of lap flaws can be prevented, or even if lap flaws occur, the depth can be tolerable.

FIG. 1 shows a thick steel plate 1 having the above-mentioned longitudinally discontinuous lattice-like protrusions 4 with a target finishing thickness of 25. It is a graph showing each rolling pattern when manufactured using four types of rolling patterns with a target protrusion height of 3 mm. A indicated by a 0 mark in FIG. 1 is a case in which rolling is performed by the method of the present invention under light rolling from the start of rolling to before the final pass, and under heavy rolling in the final pass to form protrusions of a predetermined height. It is.

Also, B indicated by an X mark, C indicated by a Δ mark, and D indicated by a 0 mark.
is a comparative example, in which in the initial and middle rolling process from the start of rolling to before the final pass, strong or medium reduction with a reduction amount of 8 m or more was applied, and the final pass was performed with a strong reduction or medium reduction of 6 m or more. This is the case when it is rolled further.

The condition of the protrusions on the product thus rolled was examined, and the results are shown in Table 1.

In addition, wrap flaws of 0.4 to 1.0 mm occur, and the protrusions are severely damaged. On the other hand, in the case of A, the protrusion height is approximately the target value, no lap defects occur, and no damage occurs to the protrusion.

Based on the results shown in FIG. 1 and the characteristics shown in FIGS. 2 to 4, in the present invention, rolling is performed with a light reduction amount Δht shown in the following equation (1) from the start of rolling to before the final pass, Next, it was decided that the final pass would be rolled with a strong reduction amount ΔHt shown in equation (2) below.

In Table 1, the magnitude of the reduction in the reduction pattern is in the order of strong reduction>medium reduction>light reduction>light reduction. In addition, the protrusion shape was evaluated as follows.

0 mark: Good Δ mark: Slightly poor However, Δht: Reduction amount (wI) to reduce the thickness of the exit side plate to tmm from the start of rolling to before the final pass ΔR5R5 Tolerable limit value of protrusion height in the intermediate pass that can prevent lubricating (un) αt: The thickness of the exit side plate is ta+ The printing rate when The permissible limit value ΔR3 of the protrusion height of the intermediate pass to be obtained is determined by the depth of the lap flaw shown in FIG. 3 that is permissible as a final product. Light reduction amount Δh
It is preferable that t be 51III+ or less, particularly 3m++ or less. Based on the various characteristics described above, the following can be further derived.

That is, as shown in FIG. 2, the printing rate α, where the exit side plate thickness is jan, is inversely proportional to the exit side plate thickness of the rolled material. Therefore, by setting the light reduction amount Δht in each pass from the start of rolling to before the final pass to be relatively large in the initial stage of rolling when the plate thickness is thick, and decreasing the reduction amount as the plate thickness becomes thinner as the passes progress. , rolling efficiency can be increased.

Next, the present invention will be explained with reference to examples.

[Example] From a slab with dimensions of 150 mm thick, 1945 mm wide, and 3650 m long, a slab with a thickness of 25 nn, a width of 2500 mm, and a length of 1
6,000mm and the maximum height of the protrusion is 4m.
A thick steel plate made of high-strength steel with a tensile strength of 50 kg/nn2 and having discontinuous lattice-like protrusions in the longitudinal direction shown in the figure was subjected to a rolling pattern Nn shown in Table 2 by the method of the present invention. 1 and Nα2.

For comparison, Table 2 also shows examples in which finish rolling was performed in one pass, and the respective rolling efficiencies.

FIG. 6 is a graph showing the exit side plate thickness in each finish rolling pass of Invention Examples &1 and Nα2, where the X mark indicates Nα1 and the O mark indicates Nα2. In Table 2 and Figure 6,
Invention example Nα1 is an example in which the amount of light reduction in finish rolling is kept almost constant, and example NQ2 is an example in which the amount of light reduction in finish rolling is varied depending on the plate thickness.

"Rough/Finish J" in the rolling efficiency evaluation column of Table 2 means:
The value of the ratio of the rough rolling load (required rolling time) to the finishing rolling load (required rolling time) is shown. When this value is less than 1.0, it means that the finish rolling load is high, and when this value is 1.0 or more, it means that the rough rolling load is high.

Moreover, "efficiency" in the same column is an index indicating the rolling efficiency of each side when the rolling efficiency of the present invention example Nα1 is set to 100.

In Inventive Example Na 1, the reduction in each pass from the start of rolling to before the final pass in finish rolling was performed with a light reduction amount of about 2.3 wn in all passes, and the reduction in the final pass was performed with a strong reduction amount of 13 nn. It was done by The required number of passes is 7 passes. In Inventive Example &2, the rolling reduction of each pass from the start of rolling to the final pass in finish rolling is as follows:
The protrusion height allowable limit value ΔR5 is set to 0.0000, which prevents lap defects from occurring.
5no, and the light reduction was varied within the range of 2.5 to 4.0n11 for each pass, and the final pass was performed with a strong reduction of 13 mm.

As a result, in the case of the present invention example Nα2, the number of light rolling passes can be reduced to 5 passes, which is 2 passes less than the present invention example Nα1, and the rolling efficiency can be increased by 23% compared to the present invention example Nα1. Ta.

On the other hand, in the case of Comparative Example 1 in which finish rolling was performed in one pass, inventive example N [2
As a result of requiring 9 passes, which is a large number of passes, and extremely increasing the rolling load of rough rolling, the rolling efficiency was 14 compared to Invention Example Na 1.
% decreased.

As mentioned above, this invention is not limited to the case where a caliber roll is used as an upper work roll and a thick steel plate having protrusions on the upper surface side is manufactured. Of course, the present invention can also be applied to the production of thick steel plates having protrusions, or to the production of thick steel plates having protrusions on their upper and lower surfaces using caliber rolls as the upper and lower work rolls.

[Effects of the Invention] As described above, according to the present invention, a thick steel plate having discontinuous projections in the length direction on at least one surface is lapped by multi-pass reversible rolling using a caliber roll. This provides an industrially useful effect in that it can be manufactured efficiently without causing scratches or damage to protrusions.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the rolling pattern according to the method of the present invention together with the rolling pattern of a comparative example, and FIG. 2 is a graph showing the relationship between exit side plate thickness and printing rate. Figure 3 is a graph showing the relationship between the height of the protrusion and the depth of the lap flaw, Figure 4 is a graph showing the relationship between the amount of rolling reduction and the depth of the lap, and Figure 5 (a) is discontinuous in the length direction. 5(b) is a sectional view taken along line A-A in FIG. 5(a), and FIG. 5(c) is a sectional view taken along line A-A in FIG.
), FIG. 6 is a graph showing the exit side plate thickness for each pass showing an embodiment of the present invention, and FIGS. 7(a) (b)
(C) is an explanatory diagram showing a state in which a lap flaw occurs, and FIG. 8 is an explanatory diagram showing a state in which a protrusion is damaged. In the drawings, 1... Thick steel plate, 2... Upper work roll, 3...
...Lower work roll, 4...Protrusion, 5...Wrap flaw.

Claims (1)

[Claims] 1. A thick steel plate having discontinuous protrusions in the length direction on at least one surface thereof is processed by using a caliber roll having a caliber of a predetermined shape for forming the protrusion shape. In the method of manufacturing by pass reversible rolling, rolling is performed from the start of rolling until before the final pass with a light reduction amount Δh_t shown in the following equation (1), and then, in the final pass, a strong reduction amount ΔH_t shown in the following equation (2) 1. A method for producing a thick steel plate having longitudinally discontinuous protrusions, the method comprising: rolling a thick steel plate with discontinuous projections in the longitudinal direction. Δh_t≦ΔR_s/a_t×100 (
1) ΔH_t≧ΔR_L/α_t×100...
(2) However, Δh_t: Light reduction amount (mm) to make the exit side plate thickness tmm from the start of rolling to before the final pass ΔR_s: Tolerable limit value of protrusion height in intermediate passes that can prevent lap defects (mm) α_t: Printing rate (%) when the exit side plate thickness is tmm ΔH_t: Reduction amount (mm) to make the exit side plate thickness t mm in the final pass ΔR_L: Height of protrusions required for the final product (mm) 2. Each pass from the start of rolling to before the final pass is
2. The method for manufacturing a thick steel plate having longitudinally discontinuous protrusions according to claim 1, wherein the light reduction amount Δh_t is 5 mm or less based on the formula. 3. The method of manufacturing a thick steel plate having longitudinally discontinuous protrusions according to claim 1, wherein the light reduction amount Δh_t of each pass from the start of rolling to before the final pass is changed according to the plate thickness.