Wire Rod Block Practice Example

 
Let us assume that you sent us an input form with your WRB data (for 6 mm wire) but with no pass dimensions. And let us say that we launched BYBLOCK obtaining exactly the "source" pass schedule (SPS) shown in this site (click here: it's in German, but language doesn't matter – just consider the numerical data).

The "basic" pass schedule (BPS) we will use is almost identical to the SPS. A number of minimal differences are due to the fact that the SPS comes from BYBLOCK in semi-automatic mode, while the BPS comes from BYBLOCK in manual mode: i.e. in the former oval and round dimensions are calculated, while in the latter they are manually copied from the SPS, thus inevitably introducing approximations.

Now the point is: where do we manually enter all this data? In the planet GAPS0600. Though, talking of planets, "enter" is an improper term: we should say "assign". For example, where the Sun (BYBLOCK) has in the source code something like

• INPUT "entry round speed";ERS [which is an input prompt],

your planet GAPS0600 has bluntly

• ERS=25 [which is a statement].

ERS is thus no longer a variable but a constant.

In this example we are not showing the BPS, i.e. the output of GAPS0600 with nominal roll diameters: you can create it yourself if you download the planet from this site. Instead we will show the satellite created by grinding 10 mm out of the diameters of the 4th and the 10th stand of the block. (Block stands are numbered 21 to 30 because we assume that before the block there is a 20-stand continuous bar mill.)

After launching GAPS0600 the following screen is displayed:

GAPS0600 - release 3.7 - copyright (C) 2002 Annibale Izzo
The author accepts no responsibility for any damage, howsoever 
caused, which may stem from the use of this program


Company name: Tweedledee Steel Company Ltd.
Machine identification: Block #1
Finished round diameter: 06.00 mm


For a given wire rod block and a given finished diameter
GAPS0600 calculates the necessary gap variations in case
of changed roll diameters.


k. to calculate gap variations
d. to exit the program

select choice

On pressing "k" we are prompted to enter the new roll diameters (or to confirm the nominal diameters):

INPUT NEW ROLL DIAMETERS

- for oval 21 -> new roll diameter [ ENTER to confirm 210 ]?
- for round 22 -> new roll diameter [ ENTER to confirm 210 ]?
- for oval 23 -> new roll diameter [ ENTER to confirm 210 ]?
- for round 24 -> new roll diameter [ ENTER to confirm 210 ]? 200
- for oval 25 -> new roll diameter [ ENTER to confirm 170 ]?
- for round 26 -> new roll diameter [ ENTER to confirm 170 ]?
- for oval 27 -> new roll diameter [ ENTER to confirm 170 ]?
- for round 28 -> new roll diameter [ ENTER to confirm 170 ]?
- for oval 29 -> new roll diameter [ ENTER to confirm 170 ]?
- for round 30 -> new roll diameter [ ENTER to confirm 170 ]? 160

   leader oval and finishing round should have the same roll diameters

do you want to change any entries (y/n)?

(Note that if we confirmed all the original diameters we would have created the BPS.) We just answer "n" and we obtain a third screen:

the output report will be saved in a file on disk,
with the extension .WRB

enter filename, without extension (max 8 chars):

We answer, for example, G200_160, and that's all. We have just created a new satellite. And this is how the satellite G200_160 looks:

B L O C K   D E S I G N   F O R   R O U N D   6 

   Gaps vs. roll diameters


Number of stands 10 
Initial section is a round from stand 20 
Entry round area 150 mm^2
    (d = 13.64 mm cold)
Entry round speed 25 m/s
Entry round temperature 1000 °C

Final round diameter 6 mm
Final speed 129.2 m/s
Rolling temperature - calculated
Theoretical mill throughput 101.0 t/h


Rolled stock: carbon steel with C = 1 ; Mn = 1 ; Cr = 1 [%]

The values of tau (reduction ratio between stand N and
stand N+1) are indicated at stand N - bottom right.
All together the reduction ratios are:

                       21->22   1.203700
  22->23   1.178900    23->24   1.203700
  24->25   1.183500    25->26   1.178600
  26->27   1.192000    27->28   1.177000
  28->29   1.204000    29->30   1.175700

Nominal roll diameters in mm
 210   210   210   210   170   170   170   170   170   170  

Nominal roll gaps in mm
 1   1   1   1   1   1   .5   .5   .5   .5  

Filename: G200_160.wrb
 

- RPF = 1 


          FINAL REPORT



 21  OV    b1t    h1t    b1r    h1r    r     maxw   gap   dnom   dwor   [mm]
           22.90 10.28  16.28   9.61 15.32  21.97   0.33  210    201.49

          cE3    area   slip   speed   revs  temp  K 31  P 8    M 139    N
         -60     129.1 1.0247  29049   2687  1000   306   76     1365    382 
    R% 13.94     mm^2          mm/s    rpm    °C   N/mm^2  kN    N m     kW
          bite angle [degrees] = 11.7
       HSC: 100; KSC: 4                                    tau = 1.2037 



 22  RD    drn           h1r    b1r          maxw   gap   dnom   dwor   [mm]
          12.14  A 30   12.14  11.46        13.44   1.00  210    199.89

          cE3    area   slip   speed   revs  temp  K 26  P 5    M 96     N
         -90     109.2 1.0148  34354   3235  1010   258   48     936     318 
    R% 15.44     mm^2          mm/s    rpm    °C   N/mm^2  kN    N m     kW
          bite angle [degrees] = 11.7
       HSC: 100; KSC: 4                                    tau = 1.1789 



 23  OV    b1t    h1t    b1r    h1r    r     maxw   gap   dnom   dwor   [mm]
           17.03  8.37  14.74   7.96 10.76  16.21   0.60  210    203.63

          cE3    area   slip   speed   revs  temp  K 34  P 8    M 133    N
         -128    89.67 1.0286  41821   3813  1020   331   74     1305    520 
    R% 17.85     mm^2          mm/s    rpm    °C   N/mm^2  kN    N m     kW
          bite angle [degrees] = 10.6
       HSC: 100; KSC: 4                                    tau = 1.2037 



 24  RD    drn           h1r    b1r          maxw   gap   dnom   dwor   [mm]
          10.16  A 30   10.64   9.37        11.15   1.48  200    191.51

          cE3    area   slip   speed   revs  temp  K 26  P 3    M 58     N
         -155    80.44 1.0128  46616   4590  1030   256   33     568     274 
    R% 10.29     mm^2          mm/s    rpm    °C   N/mm^2  kN    N m     kW
          bite angle [degrees] = 11.9
       HSC: 100; KSC: 4                            tau = 1.1835 x 210 / 170 



 25  OV    b1t    h1t    b1r    h1r    r     maxw   gap   dnom   dwor   [mm]
           13.20  7.47  12.47   7.00  7.70  12.55   0.52  170    164.72

          cE3    area   slip   speed   revs  temp  K 33  P 5    M 71     N
         -220    62.98 1.0288  59539   6710  1040   322   50     698     489 
    R% 21.71     mm^2          mm/s    rpm    °C   N/mm^2  kN    N m     kW
          bite angle [degrees] =  9.7
       HSC: 100; KSC: 4                                    tau = 1.1786 



 26  RD    drn           h1r    b1r          maxw   gap   dnom   dwor   [mm]
           8.60  A 25    8.60   8.05         9.02   1.00  170    163.03

          cE3    area   slip   speed   revs  temp  K 27  P 2    M 35     N
         -269    54.79 1.0138  68443   7909  1050   260   24     338     281 
    R% 13.01     mm^2          mm/s    rpm    °C   N/mm^2  kN    N m     kW
          bite angle [degrees] = 12.5
       HSC: 100; KSC: 4                                    tau = 1.192 



 27  OV    b1t    h1t    b1r    h1r    r     maxw   gap   dnom   dwor   [mm]
           10.75  6.40   9.90   6.09  6.11  10.46   0.19  170    165.04

          cE3    area   slip   speed   revs  temp  K 33  P 4    M 44     N
         -344    44.94 1.0242  83438   9428  1061   320   35     428     422 
    R% 17.97     mm^2          mm/s    rpm    °C   N/mm^2  kN    N m     kW
          bite angle [degrees] =  8.8
       HSC: 100; KSC: 4                                    tau = 1.177 



 28  RD    drn           h1r    b1r          maxw   gap   dnom   dwor   [mm]
           7.25  A 25    7.25   6.83         7.77   0.50  170    163.83

          cE3    area   slip   speed   revs  temp  K 27  P 2    M 23     N
         -413    38.90 1.0128  96400  11096  1070   263   18     221     257 
    R% 13.45     mm^2          mm/s    rpm    °C   N/mm^2  kN    N m     kW
          bite angle [degrees] = 10.3
       HSC: 100; KSC: 4                                    tau = 1.204 



 29  OV    b1t    h1t    b1r    h1r    r     maxw   gap   dnom   dwor   [mm]
            8.46  5.59   8.10   5.33  4.60   8.23   0.24  170    165.87

          cE3    area   slip   speed   revs  temp  K 33  P 3    M 30     N
         -523    31.62 1.0221  118598 13360  1082   324   26     290     404 
    R% 18.72     mm^2          mm/s    rpm    °C   N/mm^2  kN    N m     kW
          bite angle [degrees] =  7.7
       HSC: 100; KSC: 4                                    tau = 1.1757 



 30  RD    drn           h1r    b1r          maxw   gap   dnom   dwor   [mm]
           6.08  A 25    6.08   5.75         6.48   0.50  160    154.95

          cE3    area   slip   speed   revs  temp  K 27  P 1    M 13     N
         -580    29.09 1.0116  128910 15707  1092   261   12     124     205 
    R%  8.00     mm^2          mm/s    rpm    °C   N/mm^2  kN    N m     kW
          bite angle [degrees] =  9.3
       HSC: 100; KSC: 4




Block reduction ratio: 4.731773 
Global elongation coefficient: 5.156423 
Total power required (just for rolling): 3552 kW

DATE (MM-DD-YY): 01-13-2002
HOUR: 23:16:00


Processing time: 2 s

From this pass schedule we can verify:

• That the constant "entry round area x entry round speed" (150 x 25,000) is respected at any stand (area x speed = 3,750,000)
• That the product "dwor x revs x slip x area" at any stand is a constant (which is another way to represent the constant flow)
• That the ratio between the revs is exactly equal to the gear ratio tau

But our purpose here was to show how a satellite can suggest the proper gaps at each stand, when one or more stands have roll diameters different from the nominal values.

In our example we modified two diameters. Now we can build up a table with four columns: NRD and ARD (nominal and actual roll diameters); NRG and ARG (nominal and actual roll gaps):

From this table we can verify:

• The "lever" effect of two modified roll diameters affecting six roll gaps.
• The "stickiness" of the rounds towards maintaining the original gap, unless really forced like at stand #24: this comes from the way BYBLOCK was designed.

A good way to conclude this study, could be as follows: look at the second input screen, asking for new roll diameters. You will see a warning message:

"leader oval and finishing round should have the same roll diameters"

This message appears only when the last two stands have different roll diameters. You can easily understand this when you look at stand #30 in the final results. The finished round has: groove diameter 6.08, reduced diameter 6.08 and enlarged diameter 5.75. In brief, it is an empty, unacceptable round.

What happens is this:

• Roll diameter at stand #30 (with the finishing round) was diminished 
• To maintain constant flow, rotational speed of WRB motor must be raised 
• Therefore linear speed at stand #29 (with the leader oval) increases
• To maintain constant flow, oval area must decrease
• To decrease oval area, roll gap must be decreased
• But: decreasing gap at stand #29 results into an empty finished round

It's a checkmate: there is no way to fix this problem. The only thing to do is to grind the rolls at stand #29 down to the diameter machined at stand #30. This is the philosophy behind the warning message above.

A little tip, between you and me: keep roll diameter at stand #29 one mm (40 mils) lower than that at stand #30: 159 mm at stand #29 if you have 160 mm at stand #30.

Some final considerations. Would you like to see what happens if all the roll diameters in the WRB are reduced by the same amount? For example, 3 mm?

Let's launch our planet GAPS0600 again. We obtain a new satellite, from which we extract the following table:

From this table you can understand immediately why we dubbed it "malpractice" to set a WRB with nominal gaps after reducing all roll diameters by the same amount.

By the way, from a 6.08 mm groove this satellite produces a finished round with dimensions 6.08 x 6.06.