JPS605361B2 - Method for predicting fold end position of slab crop in rolling process - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rolling process, particularly a method for directly holding the folded end portion of a slab crop in a blooming process using a universal mill.

As is well known, the tip of the ingot is subject to strong segregation due to the casting process, so even when it is formed into a slab by blooming, the tip of the slab (on the biting side during top rolling)
The strongly segregated part remains in an elongated form.

Further, both the leading end and the trailing end (the bottom side) of the slab have complicated deformed shapes as shown in FIG. That is,
The planar shape is a fishtail shape, and the thickness shape is an overlapped shape and includes the mechanical pipe M (hereinafter, the planar shape is referred to as a fishtail, and the thickness shape is referred to as an overlapped shape). The above-mentioned deformed shape part called slab crop and strongly segregated part are defective as a product, so
It will be truncated after the final reduction pass.

By the way, the shearing position of the crop is different between the leading end crop and the trailing end crop.

Since the rear end crop hardly has a problem with strong bias, it is sufficient to shear it at the position of the folded end P of the crop (the inner end of the mechanical pipe M). On the other hand, in the case of the tip crop, the strongly segregated part exists on the back side from the position of the fold end part P of the crop. The hard corner portion to be cut off is predetermined by the standard as the size and weight from the tip of the ingot. When an ingot is subjected to blooming rolling, the strongly polarized portions are also stretched as a matter of course. Therefore, with regard to the tip crop, shearing must be performed at a position q of the slab corresponding to the position of the strongly segregated part to be cut off, which is determined for the ingot. However,
The crop shear position P or q changes depending on the ingot specifications, slab dimensions, reduction pass schedule, etc., so it is very difficult to understand it quantitatively. The shear length is determined empirically. However, since this standard shear length is only a rough guide and lacks reliability, in reality, it is necessary to first shear at a dimension slightly smaller than the standard shear length and then visually inspect the sheared part. Therefore, according to this conventional method, the number of times of shearing increases, resulting in extremely low work efficiency.Shearing is performed at a dimension that is several minutes larger than the standard dimension. If this is done, only one shearing is required, but of course this method cannot be adopted as it would cause the cutting to be cut off more than necessary.
There has been a strong desire to research a method for accurately predicting crop truncation length.Past research has made it quite clear how to optimize the pass schedule and ingot end shape, which are the main factors for cropping. However, there is nothing that has sufficiently clarified the crop truncation length quantitatively.By the way, regarding the tip crop, the relationship between the folding end layer P of the crop and the shearing & falsification has been investigated by Sardine et al. It is well established and reliable.

In other words, the cross-sectional area of the part to be cut off as the tip crop determined for the ingot is A, and the standard size q'
, when the cross-sectional area of the rolled slab is , the shear position q of the slab can be found as a position from the leading edge of the slab using q'XA poison. The final layer P of folding of the crop corresponds to the leading edge of the ingot. Therefore, the shearing position q can be easily and accurately predicted based on p in relation to the rolling reduction amount. Therefore, whether it is a front end crop or a rear end crop, if the fold end portion layer P of the crop can be accurately predicted, the shear position of the crop can be accurately predicted. In other words, the accuracy of the crop shear position depends on the prediction accuracy of the layer at the end of the fold of the crop. An object of the present invention is to accurately predict this crop fold end portion layer P, thereby making it possible to accurately predict the shear position of the crop.

The present invention is based on the formula below, which was derived by taking into consideration various characteristics of blooming by a universal mill that have been discovered through many years of research and experimentation. The gist of the present invention is to predict the layer at the end of the crop fold based on the above-described method.

However, n: suffix 1 to i indicating the number of rolling passes; rolling passes i+1 to j when the thickness of the entrance side of the slab is Hp or more; rolling pass △Lo when the thickness of the slab entrance side is smaller than Hp; Qn = 1 When, the amount of increase in overlapping length △Lf uniformly increases in each of the 1st to ith rolling passes; When Q'n = 1, it increases uniformly in each of the 1st to jth rolling passes. Increase in fishtail length Qn; Correction coefficient Q'n for overlap length due to difference between tail-side clip and biting-side crop; Correction regarding fishtail length due to difference between tail-side crop and biting-side crop Coefficient Hn; Inlet thickness of the slab in each rolling pass Hp; Inlet thickness of the slab at which the deformation amount of the end face starts to decrease when an experimental slab with a flat end face is rolled down with the inlet thickness changed from large to small. .

Ho: When an experimental slab with a flat end face is rolled down with various entry thicknesses, the end face does not deform. 8: Stretching correction coefficient for overlap length 8′: Stretching correction coefficient for fishtail length ; Correction coefficient y due to fishtail entrainment; Filling factor 6 due to the presence of air bubbles at the end of the slab; Medium expansion dimension K due to thick reduction; Fishtail length conversion factor of 6 The first term indicates the overlap length Lp (see FIG. 2, 0), and the second term indicates the fishtail length Lf (see FIG. 2, 1).

In other words, the present inventor has determined that ``the length dimension between the crop end S and the folded end P, the overlap length Lo and the fishtail length Lf as well shown in FIG.
(Characteristic 1) "It revealed that.
In addition, the inventor stated, ``The overlap length and fishtail length are formed by thick reduction and medium pressure reduction, but if you analyze the relationship, the overlap length peak will be the same as the thick reduction. The fishtail length Lf has a large effect, but medium pressure has almost no effect, while the fishtail length Lf
Not only medium pressure but also thick pressure has a large effect (Characteristic 2).

” was revealed. This is because the slab becomes increasingly flattened in one direction as the number of rolling passes increases. In other words, when thick reduction is performed, the overlap length Lo increases and the slab expands in the middle direction, and when medium pressure reduction is performed, the fishtail length Lf increases, and the middle expansion due to thick pressure reduction increases the thickness of the slab. This is added as an increase in tail length. Of course, intermediate expansion in the thickness direction also occurs due to medium pressure reduction, but this expansion in the thickness direction has almost no effect on the increase in the overlap length Lo due to the directionality of flattening the slab. Therefore, the first term indicating the overlap length Lo in equation 1' is related to the overlap length based only on thick reduction.

On the other hand, the second term indicating the fishtail length (3.△L
. -Q'n) is related to the fishtail length based on medium pressure, and (K6) is related to the fishtail length based on medium spread based on Atsho. By the way, when an ingot is bloomed by a universal mill, the shape of the crop changes as shown in FIG.

Note that although the actual number of rolling passes is 10 or more, for the sake of explanation, it is shown as being completed in four rolling passes. Explaining based on the figure, the ingots shown in Figures 3a and a' have fishtails and overlaps due to the first rolling pass, as shown in Figures 3b and b'. The area around the tip (same as the area around the rear edge) protrudes forward (the central part of the tip maintains a flat shape). In the second rolling pass, as shown in Fig. 3c and c', the protruding portions (=
crop) will curve inward. Furthermore, in the third rolling pass, as shown in FIGS. 3(d) and 3(d), the protruding portions on both sides of the fishtail are further curved inwardly, while a fold line 1 is formed at the center of the overlap. In the final rolling pass, as shown in Fig. 5e and e', the protruding part of the fishtail curves deeper inward, while the overlap line 1 bends inward (the occurrence of mechanical pipe M). ).In this way, both the overlap length Lo and the fishtail length Lf are cumulatively increased each time the number of rolling passes is increased.

Therefore, if the amount of increase in the overlap length Lo and the fishtail length Lf for each rolling pass is known, the length L between the cropped end S and the folded end portion layer P can be predicted. However, it is difficult to directly determine the amount of increase in overlap length and the amount of increase in fishtail length in each rolling pass. therefore,
The present inventor has clarified that this can be derived from the following way of thinking. That is, prepare a slab for each rolling pass that has the same thickness and flat end surface as the entrance plate of each of the first to fourth rolling passes in FIG. (as shown, the end faces are not flat), these slabs are subjected to only thick reduction in each reduction pass.

``The crop increase amount at this time is △ for each reduction pass,
ΔLo2, ΔLo3, ΔLo4 (generally Δmount n), and each increase amount can be set equal to the increase amount of the actual overlap length (characteristic 3-1). ” Also, in the same way as above, prepare slabs with flat end faces that are the same as the entrance side plate thickness dimension and entrance side plate middle dimension of each of the first to fourth rolling passes in Fig. 3, and prepare these slabs for each rolling pass. Perform only medium pressure reduction for each reduction pass. ``The amount of crop increase at this time is determined for each reduction pass by △Lf, △L et al., △Lf3
, △Lf4 (generally △Lfn), and each of these increases can be set equal to the increase in fishtail length (in this case, the increase in fishtail length due to middle widening is not taken into account). (Characteristic 3-2).
”Furthermore, the present inventor has determined that the amount of increase in the overlap length Δgn and the amount of increase in the fishtail length ΔLm are:
We have discovered that it exhibits very interesting properties.

In other words, ``When performing thick reduction by changing the entry side plate thickness (Hn), the overlap length △gon becomes as shown in Figure 4 (Characteristic 4).'' {I} When HhZHp (Mr. When the entrance plate thickness Hh is sufficiently thick compared to the roll diameter 2R),
In this case, since the entrance plate thickness Hh is sufficiently large, the rolling force by the rolling roll does not penetrate to the center of the slab, and only the surface layer of the slab is stretched, and the increase in overlap length △ mountain n is the size of Hn. Regardless of the value, it will be a constant value △Buddha.

[B] When Hp, the rolling force from the rolling roll penetrates to the center of the slab and stretches not only the surface layer but also the center of the slab, so the overlap length The amount of increase ΔLon decreases as the entrance side plate thickness decreases, and finally the amount of increase ΔLon of the overlap length becomes zero.

When Shiichi OSHnSHo, In this case, the central stretch of the slab is visible. It is larger than the layer stretching and overlaps. The amount of increase ΔLon in the pull length is negative.

The broken line in the figure is experimentally confirmed, but theoretically. It is certain that we can draw a curve like this above. Ru.

The value of △Lo above is basically given as the relationship between the rolling roll radius R and the rolling amount Δh for each rolling pass (basically means when coefficients such as Qn, 8, y, etc. are not taken into consideration. ).

In other words, △Ko is basically {a) When HnZHp, that is, when the rolling pass is 1st to i-th, △Lonia,〉R
・Ah However, a, is a coefficient, and when Qn=1, 0.18Sa
,≦0.30, preferably a,=0.24.

'b) When OSHhSHp ~ In other words, the rolling path is i+
For the 1st to i-th cases, the above formula cannot be applied to the cape kite/bulk OSHnSHo, but since the overlap length in this range is negligible, the above formula can be used instead. can do.

In addition, the values of the entrance side plate thickness Ho and Hp are Ho=P, △h+
It is given by P2R Hp=P3zoR・△h.

P,, P2, P3 are coefficients determined by rolling conditions and are 1.
0SP, S2.0, preferably P, = 1.50.1SP
2SO. 3 preferred〈P2:0.24.0SP3〉5.
0, preferably P3=4.3.

On the other hand, if medium reduction is performed on the same machine as described above with Bn in the entry side plate changed, the fishtail length ΔLpn (in this case, thick reduction is not performed, so the shape is the same as overlap).
is basically given by: △Lpn2a,〉Mamegenshita However, R': Medium pressure reduction roll radius △b: Medium pressure reduction amount.

However, since it is considered that Hp is always greater than Hp in the entrance plate, there is no need to set boundary conditions such as a and b under the thick reduction. Therefore, the above characteristics 3-1, 3-2,
4, the overlap length is basically given by, and the fishtail length is basically given by.

Another thing that must be taken into consideration here is the effect of the middle expansion due to thick reduction on the fishtail.

As a result of experiments, the middle expansion dimension 6 according to Atshoshita is calculated using the following formula 6 = a
It became clear that it is given by 2(H-h).

However, a2;0.1Sa2SO. 4 Preferably a2=0.15
H; ingot thickness h; final slab thickness and 6 affects the fishtail length as the value K6 multiplied by the conversion factor K.

However, K; kyo≦K≦member Preferably K= Therefore, the above formula regarding the fishtail length {31
is modified as follows.

Now, in order to calculate the actual L from the L given by the above equation (Equation 11), regarding the overlap, the coefficient Qn, 8
, Regarding the fishtail, the coefficients Q'n, B'
, y, many elements need to be considered.

Regarding the coefficients Qn and Q'n, as mentioned above, the coefficients Qn and Q'n are the correction coefficients related to the overlap length due to the difference between the crop on the tail side and the crop on the biting side, and the correction on the fishtail length. It is a coefficient.

The crop length on the bottom side and the crop length on the biting side are Generally, the former is longer than the latter. However, the present invention provides a comparison between the two. revealed the rate.

That is, Qn and Q'n are both 0.15 to 0.7, preferably 0.5 on the biting side, when the bottom side is set to 1.
becomes.

{For the rho coefficients 8 and 8', As mentioned above, the coefficients 8 and 8' are Regarding variations and fishtails This is the stretch correction coefficient.

The present inventor has clarified this stretch correction factor.

In other words, regarding overlap, the mechanical The value is different before and after the pipe occurs. Ru.

When the entrance plate thickness at the time of mechanical pipe generation is Hm When h>Hm; 8=1 earth When hS value; 8=lower is given by

On the other hand, regarding the fishtail, since no mechanical pipe is generated, 8' is uniformly given by 8'=chapter.

Regarding the coefficient y, As mentioned above, the coefficient y is the value of the slab Oribe. The inventor determined that the filling rate due to the presence of air bubbles, etc. is, when this filling factor is small, it Proportionally overlapping length, fish It is clear that both tail lengths decrease. I made it clear.

This differs depending on the type of ingot and the differences between the bottom crop and the biting side crop; for the biting side crop of semi-killed steel, y=0.8, and for the others, y=1.

0 Regarding the coefficient f, As mentioned above, the coefficient f is the Fisch This is the correction coefficient due to tail involvement. Ru.

As is clear from Figure 3, fishtail curling means that as the reduction pass progresses and both sides of the fishtail protrude, it loses its rigidity and therefore curves inward due to medium pressure.This curvature is noticeable. The amount of protrusion of the fishtail decreases as the temperature increases, so this must be taken into consideration.

The inventor clarified the following about the coefficient vine. Ta.

When h > 200 to 300; f = 1; When h mi 200 to 300; the above formula ■
By modifying [3', the above equation '1} can be obtained.

A specific example of formula '1) when the inventor conducted rolling under the following rolling conditions was as shown in formula [5}.

Rolling conditions 1 Shoshita roll radius R, R'; 130 length 2
Rolling speed: 38 pm to 43 Pm 3 Rolling temperature: 1050 pm 0 However, = 1.5△h + 0.2R Qn, Q'n; For the bottom side crop, Qn = Q n = 1 For the bite side crop, Qn = Q n = 0.5 Hm; 30 竇■ 6; 0.15 (one hour per day) f: When h > 300, f = l When hmi 300, f = Hosoushoku 2 The formula derived in this way {1 Based on this, find the length L between the end of the slab crop and the end of the fold, and calculate this L'
Based on this, the crop truncation position P or q was calculated and the crop truncation weight W was calculated. weight) was very accurately matched.

FIG. 5 shows a comparison with the crop cut-off weight W' when shearing is performed at a conventional standard shear length. The rolling conditions for the experiment shown in FIG. 5 are as follows. Ingot: 19 in the killed steel final slab; 140 broadside reduction roll radius R, R'; 130 rib rolling speed; 38 pm to 48 Pm rolling temperature; 1050 q○ As detailed above, the slab in the rolling process according to the present invention The method for predicting the failure of the folded end part of a crop is based on the formula '1), which was derived by fully considering the various characteristics of rolling found in the course of many years of research, so the crop shear and calendar based on that prediction are As is clear from the experimental results, it is possible to carry out the method with extreme accuracy.

This not only allows slabs to be removed without waste, but also improves the accuracy of component assurance, reducing the integrated yield from steel manufacturing to products by 0.5.
% can be improved. In addition, the formula [11
In addition to blooming, thick plate rolling in a plate mill is conceptually applicable to bloom rolling and the like.

[Brief explanation of drawings]

Figure 1 is a perspective explanatory view showing the shape of the slab crop, Figure 2 is a perspective view showing the shape of the slab crop.
Fig. 1 is an explanatory diagram showing a fishtail, Fig. 2 is an explanatory diagram showing a central cross-section of Fig. 1, and Fig. 3 is an explanatory diagram showing a river overlapping.
Figures a'-e and e' are explanatory diagrams of the crop that changes with each rolling pass. FIG. 4 is a graph showing the relationship between the entrance plate thickness Hn and the overlap length Δyun in blooming rolling, and FIG. 5 is a graph showing the experimental results. Figure 1 Figure 2 Figure 5 Figure 3 Figure 4

Claims (1)

[Scope of Claims] 1. A method for predicting the position of the end of the fold in the rolling process based on the following equation that derives the length L between the end of the slab crop and the end of the fold. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ However, n: Suffixes 1 to i indicating the number of rolling passes; rolling passes i+1 to j when the thickness of the entrance side of the slab is greater than Hp; the thickness of the entrance side of the slab is smaller than Hp When rolling down pass ΔLo; When αn = 1, the amount of increase in overlap length ΔLf that increases uniformly in each of the 1st to i-th rolling passes; When α'n = 1, each of the 1st to jth rolling passes The amount of increase αn in the length of the fishtail that increases uniformly in the rolling pass; the correction coefficient α′n for the overlap length due to the difference between the crop on the bottom side and the crop on the biting side; Correction coefficient Hn for the length of the tail; thickness Hp of the entrance side of the slab in each rolling pass; when an experimental slab with a flat end face is rolled down with its entrance side thickness varied from large to small, the amount of deformation of the end face begins to decrease Slab entrance thickness. Ho: Entrance plate thickness β at which the end face does not deform when an experimental slab with a flat end face is rolled down with various entry thicknesses; Stretching correction coefficient β′ related to overlap length; Stretching correction coefficient ξ related to fishtail length; Fishtail Correction coefficient γ due to entrainment; Filling rate δ due to the presence of crop air bubbles; Width expansion dimension K due to thick rolling; Fish tail length conversion coefficient of δ.