We sale steel billet shear 2018
Analysis of the causes of shearing and cracking of continuous casting billet
First, the problem description
Four-machine four-flow continuous casting machine, the main production specifications are 150mm*150mm billet, the flame cutting is used in the early stage, the cutting temperature is 800-900°C, and the heating is repeated to 1000 degrees after rolling.
Now it is changed to continuous casting and rolling technology. By increasing the temperature of molten iron, increasing the drawing speed, reducing the cold zone, etc., the temperature of the slab is increased. The shearing temperature of the continuous casting billet is 950-1050 °C, mainly producing steel grade Q235-20MnSi steel. Ford 45 degree billet hydraulic shears are directly subjected to ultra-high temperature shearing, and the internal crystallization of the billet is unknown.
Recently, the four-stream continuous casting machine has problems such as uneven shear surface and cracking of the billet corner, and it appears in batches of several consecutive furnace numbers. The four streams simultaneously have more uneven shear planes, and sometimes single or double streams appear.
2. Analysis and solution of high temperature shearing problem of continuous casting billet
Based on years of research experience and technical discussions of experienced engineers and technicians in the industry, and with reference to a large number of related literatures, it is concluded that the shear plane unevenness and corner cracks of continuous casting billet are mainly caused by the following reasons:
1, the quality of molten steel
At present, small and medium-sized steel mills mostly use medium-frequency furnace steelmaking, that is, the medium-frequency furnace is used to melt the scrap iron, and the internal element content is adjusted to achieve the purpose of steel recycling. However, due to the variety of scrap iron and more impurities, the slag inclusions are easily formed in the molten iron, and the distribution of alloy elements is not uniform, which causes the content of molten iron alloy elements in each furnace to be different, resulting in slag inclusion, internal cracking and skin stomata in the continuous casting process. The quality defects cause the defects such as flowering head, folding, pitting and internal cracking in the continuous casting billet. Generally, the blast furnace converter and the refining furnace manufacturers rarely appear in this situation, and the quality of molten iron is the main cause.
Solution: Through the sampling of the slice, the internal quality of the steel slab is examined and analyzed in detail. If the quality defects such as stomata, slag inclusion and internal crack are found, the process should be adjusted immediately and the process is qualified.
2, the temperature of the billet
If the temperature of the billet is too high, the internal solidification rate of the continuous casting billet is too low, and the crystal layer on the surface of the billet is too thin. During the shearing process, the too thin outer shell is easily cracked under shear pressure, and the inner molten iron overflows at the incision portion. Applying to the surface of the steel billet, causing the billet to be uneven or molten iron, occasionally a small slag will accumulate in the upper right corner of the cutting head, which will easily cause corner cracks in the force section of the cutting head.
In the continuous casting and rolling process, the temperature of the continuous casting blank at the cutting edge is about 980~1050 °C. According to the characteristics of the steel, it is a "hot brittle" sensitive zone at 900-1200 °C. Since S and Fe form FeS in steel, FeS+S will produce eutectic reaction at 985 °C. When the shell is subjected to external force, it will crack along the grain boundary and seriously affect the plasticity of the steel. If the Mn in the steel is sufficient, S is dispersed into the matrix in the form of MnS. The melting point of MnS is as high as 1620 ° C, which can avoid the "hot brittle" sensitive zone of 900 ~ 1200 °C. Therefore, when the S content in the steel decreases or the Mn/S ratio increases, the high temperature plasticity of the steel will be improved, and the unevenness of the shear surface will be reduced or even eliminated. The temperature of the tundish steel of 280 furnace Q235 steel was randomly counted, among which 156 furnaces exceeded 1550 °C, and only 8 furnaces were found, which accounted for 5.13%. The analysis found that the shear surface unevenness occurred only when Mn/S was low and the temperature was high. This is because the excessive casting temperature causes the columnar crystal of the continuous casting billet to develop, the center segregation, the center loose, the center crack, and the internal structure of the billet deteriorate, resulting in a decrease in plasticity.
Solution: Check the solidification rate of molten iron at the shearing position of the billet by nailing test. If the solidification rate is too low, the shell surface of the billet is too thin. It is recommended to adjust to 2/3 or more of the billet crystallization to avoid splitting and folding.
3. Changes in steel grades
According to the statistics of many users, the incidence of uneven surface shearing of Q235 steel continuous casting billet is much larger than that of 20MnSi steel. It can be seen that the chemical composition of steel is an important reason for the uneven shear surface of continuous casting billet.
4, the impact of chemical composition
Through statistical analysis of the Mn/S ratio of 300 furnace steel, it is found that Mn/S ≤ 20 accounted for 87.18%, and the Mn/S ratio of steel with a large amount of shear surface unevenness was 15 or less, generally 11-13. However, the Mn/S of 20MnSi steel is relatively large, so the defects of uneven shear surface basically occur in Q235 steel. The low Mn/S ratio is the main reason for the uneven shear surface of Q235 steel continuous casting billet.
Solution: Control the ingredients strictly according to the internal control requirements, so that Mn/S ≥ 20, and ensure (P + S) < 0.050%.
5. Effect of oxygen content in steel
The billet has high oxygen content, poor plasticity, and easy cracking, so it is also prone to uneven surface shear. This is because the solubility of oxygen in solid iron is small, and oxide inclusions are easily formed. Oxide inclusions can deteriorate the cutting performance of steel and make steel brittle. In addition, FeO and FeS can form a low-melting eutectic at 950 ° C, which is very hot and brittle. When the oxygen content in the steel exceeds 30 × 10-6, the brittle transition temperature rapidly increases. Therefore, the steel with higher oxygen content is prone to unevenness of the shear surface during the shearing process.
Solution: Prevent the molten steel from being peroxided, improve the intrinsic quality of the steel, and ensure that the temperature of the tundish steel is not more than 1550 °C.
6, the impact of the cutting edge of the cutting machine
When the same number and the same casting machine are used to pull steel, the influence of the above factors is the same, but sometimes the four-flow simultaneous cracking unevenness and corner cracking occur. This is due to the fact that some flow cutting edges are too large or the cutting edges are sharp and blunt, and the occurrence of uneven shear plane unevenness in 20MnSi steel slabs also verifies this situation.
Solution: Check the cutting edge condition of the shearing machine every shift to ensure that the gap between the upper and lower cutting edges is 0.5~0.7mm, the edge of the cutting edge is blunt and R≯0.5mm, and the gap of the steel plate shearing back plate copper slide should not exceed 0.15mm, the maximum copper plate The amount of wear must not exceed 6mm
7, crystallizer and water cooling system
The temperature of the cooling water of the crystallizer does not match the water pressure, the number of the second cold water nozzles, the layout, the water spray method, etc., causing the temperature difference between the plane temperature and the corner of the continuous casting billet to be too large, and the corners are prone to cracks. In addition, due to poor water quality, nozzle fouling is easily blocked, resulting in uneven cooling in the secondary cooling zone. The shape of the nozzle, the height of the nozzle, the depth of immersion, and the angle of inclination of the spout hole of the nozzle all affect the fluctuation of the liquid level of the crystallizer. Excessive fluctuations cause the slag of the meniscus and the uneven cooling of the shell, resulting in corner cracks in the billet.
Solution: Improve the sprinkler system, reduce the temperature difference between the plane and the corner, adjust the nozzle height
8. Influence of vibrator on the quality of billet
According to the experience provided by many companies, the vibration amplitude of the continuous casting machine vibrator does not match the ratio of continuous casting speed, which will cause cracking and corner cracking of the billet.
Solution: Adjust the vibrator frequency
Induction furnace is used for smelting or insulating ferrous metals, non-ferrous metals, sponge iron, such as scrap iron, scrap steel, copper, aluminum and so on. Complete working equipment such as continuous casting machine, rolling mill, mainly used for the production of billet, steel bar, angle steel, H-beam, I-beam, etc. Using KGPS, IGBT, single or double power supply technology, PLC (Siemens) can be realized throughout the monitoring.
Main supply list: 2 sets of electric furnace body, 2 sets of hydraulic or mechanical tilting electric furnace mechanism, 1 set of control platform, 1 set of intermediate frequency control cabinet (6 pulse 1, 12 pulse 2, 24 pulse 4), low voltage control cabinet (6 pulse 1, 12 pulse 2, 24 pulse 4), 1 set of capacitor cabinet, 4 or 8 water-cooled cables; 1 water temperature alarm, 1 leakage alarm; 1 crucible mold, 1 liquid One batch of pressure steel pipe, one set of copper row, three water tanks. Transformer, cooling tower, furnace builder, furnace lining ejector, furnace cover.
KGSP Induction Electric Furnace
GW-8-4000-0.5J KGSP Induction Electric Furnace
GW-1-750-1JJ Medium frequency coreless electric furnace
GW-50-22000-0.2J No induction melting furnace
GW-0.25-160-1JJ melting electric furnace
GW-1.5-1000-1J Medium frequency induction furnace
| NO. |
Electric
Furnace
Type |
Input
power
(KW) |
input
voltage
(V) |
Input
current
(A) |
Rated
power
(KW) |
DC
current
(A) |
DC
voltage
(V) |
Melting
rate
(T/H) |
working
frequency
(HZ) |
working
voltage
(V) |
cooling water
pressure(MPA) |
Rated
capacity
(T) |
Power
consumption
(KWH/T) |
Power
Supply |
Furnace
body |
| 1 |
GW-0.25-160/1JJ |
180 |
380
(6 Pulse) |
256 |
160 |
320 |
500 |
0.24 |
1000 |
750 |
0.1~0.15 |
0.25~0.3 |
0.25 |
790 |
| 2 |
GW-0.5-250/1JJ |
280 |
380
(6 Pulse) |
400 |
250 |
500 |
500 |
0.4 |
1000 |
1500 |
0.1~0.15 |
0.25~0.3 |
0.5 |
770 |
| 3 |
GW-0.5-250/1J |
280 |
380
(6 Pulse) |
400 |
250 |
500 |
500 |
0.4 |
1000 |
1500 |
0.1~0.15 |
0.25~0.3 |
0.5 |
770 |
| 4 |
GW-0.75-400/1JJ |
400 |
380
(6 Pulse) |
650 |
400 |
800 |
500 |
0.6 |
1000 |
1500 |
0.1~0.15 |
0.25~0.3 |
0.75 |
770 |
| 5 |
GW-0.75-400/1J |
400 |
380
(6 Pulse) |
650 |
400 |
800 |
500 |
0.6 |
1000 |
1500 |
0.1~0.15 |
0.25~0.3 |
0.75 |
770 |
| 6 |
GW-1-500/1JJ |
550 |
380
(6 Pulse) |
800 |
500 |
1000 |
500 |
0.8 |
1000 |
1500 |
0.1~0.15 |
0.25~0.3 |
1 |
750 |
| 7 |
GW-1-750/1JJ |
800 |
380/690
(6 Pulse) |
1200/
700 |
750 |
1500/
850 |
500/
880 |
0.9 |
1000/
500 |
1500/
2600 |
0.1~0.15 |
0.25~0.3 |
1 |
720/660 |
| 8 |
GW-1-750/1J |
800 |
380/690
(6 Pulse) |
1200/
700 |
750 |
1500/
850 |
500/
880 |
0.9 |
1000/
500 |
1500/
2600 |
0.1~0.15 |
0.25~0.3 |
1 |
720/660 |
| 9 |
GW-1.5-1000/0.5JJ |
1100 |
690
(6 Pulse) |
912 |
1000 |
1140 |
880 |
1.2 |
500 |
2600 |
0.1~0.15 |
0.25~0.3 |
1.5 |
700 |
| 10 |
GW-1.5-1000/0.5J |
1100 |
690
(6 Pulse) |
912 |
1000 |
1140 |
880 |
1.2 |
500 |
2600 |
0.1~0.15 |
0.25~0.3 |
1.5 |
700 |
| 11 |
GW-2-1500/0.5JJ |
1650 |
690
(6 Pulse) |
1360 |
1500 |
1700 |
880 |
1.7 |
500 |
2600 |
0.1~0.15 |
0.25~0.3 |
2 |
675 |
| 12 |
GW-2-1500/0.5J |
1650 |
690
(6 Pulse) |
1360 |
1500 |
1700 |
880 |
1.7 |
500 |
2600 |
0.1~0.15 |
0.25~0.3 |
2 |
675 |
| 13 |
GW-2-2000/0.5JJ |
2200 |
690
(6 Pulse) |
1400 |
2000 |
2275 |
880 |
1.9 |
500 |
2600 |
0.1~0.15 |
0.25~0.3 |
2 |
650 |
| 14 |
GW-3-2500/0.5JJ |
2750 |
690/950
(6 Pulse) |
2275/
1700 |
2500 |
2840/
2080 |
880/
1250 |
2.56 |
500 |
2600/3200 |
0.1~0.15 |
0.25~0.3 |
3 |
610/560 |
| 15 |
GW-3-2500/0.5J |
2750 |
690/950
(6 Pulse) |
2275/
1700 |
2500 |
2840/
2080 |
880/
1250 |
2.56 |
500 |
2600/3200 |
0.1~0.15 |
0.25~0.3 |
3 |
610/560 |
| 16 |
GW-4-3000/0.5J |
3300 |
690/950
(6 Pulse) |
2730/
2040 |
3000 |
3410/
2500 |
880/
1250 |
3.2 |
500 |
2600/3200 |
0.1~0.15 |
0.25~0.3 |
4 |
610/560 |
| 17 |
GW-5-4000/0.5J |
4400 |
950
(6 Pulse) |
2300 |
4000 |
3330 |
1250 |
5 |
500 |
3400 |
0.1~0.15 |
0.25~0.3 |
5 |
600/550 |
| 18 |
GW-6-4000/0.5J |
4400 |
950
(12 Pulse) |
2300 |
4000 |
3330 |
1250 |
5 |
500 |
3400 |
0.1~0.15 |
0.25~0.3 |
6 |
600/550 |
| 19 |
GW-8-5000/0.5J |
5000 |
950
(12 Pulse) |
3400 |
5000 |
4200 |
1250 |
7~8 |
500 |
3400 |
0.1~0.15 |
0.25~0.3 |
8 |
600/550 |
| 20 |
GW-10-6000/0.5J |
6300 |
950
(12 Pulse) |
3750 |
6000 |
4600 |
1250 |
8.5~9 |
500 |
3400 |
0.1~0.15 |
0.25~0.3 |
10 |
600/550 |
| 21 |
GW-12-8000/0.25J |
8000 |
950
(12 Pulse) |
4900 |
8000 |
6000 |
1250 |
9~10.5 |
250 |
3400 |
0.1~0.15 |
0.25~0.3 |
12 |
600-550 |
| 22 |
GW-15-8000/0.25J |
8000 |
950
(12 Pulse) |
4900 |
8000 |
6000 |
1250 |
9~10.5 |
250 |
3400 |
0.1~0.15 |
0.25~0.3 |
15 |
600-550 |
| 23 |
GW-15-10000/0.25J |
10000 |
950
(24 Pulse) |
6500 |
10000 |
8000 |
1250 |
13~15 |
250 |
3400 |
0.1~0.15 |
0.25~0.3 |
15 |
600-550 |
| 24 |
GW-18-12000/0.25J |
12000 |
950
(24 Pulse) |
8160 |
12000 |
10000 |
1200 |
15~17 |
250 |
3400 |
0.1~0.15 |
0.25~0.3 |
18 |
600-550 |
| 25 |
GW-20-12000/0.25J |
12000 |
950
(24 Pulse) |
8160 |
12000 |
10000 |
1200 |
17~19 |
250 |
3400 |
0.1~0.15 |
0.25~0.3 |
20 |
600-550 |
| 26 |
GW-25-14000/0.25J |
14000 |
950
(24 Pulse) |
9460 |
14000 |
11600 |
1200 |
19~21 |
150~200 |
3400 |
0.1~0.15 |
0.25~0.3 |
25 |
600-550 |
| 27 |
GW-30-16000/0.2J |
16000 |
950
(24 Pulse) |
10850 |
16000 |
13300 |
1200 |
21~23 |
150~200 |
3400 |
0.1~0.15 |
0.25~0.3 |
30 |
600-550 |
| 28 |
GW-40-20000/0.2J |
20000 |
950
(24 Pulse) |
13545 |
20000 |
16600 |
1200 |
25~27 |
150~200 |
3400 |
0.1~0.15 |
0.25~0.3 |
40 |
600-550 |
| 29 |
GW-50-22000/0.2J |
22000 |
950
(24 Pulse) |
14932 |
22000 |
18300 |
1200 |
25~28 |
150~200 |
3400 |
0.1~0.15 |
0.25~0.3 |
50 |
600-550 |
Note:
(1) GW - means medium frequency induction furnace, - 1 - means induction furnace capacity of 1 ton, - 500 - means furnace rated power of 500 KW, / 1 - means furnace operating frequency of 1000 Hz, / 0.5 - means melting furnace frequency of 500 Hz, - J - means hydraulic tilting furnace (furnace shell is steel shell), - JJ - means mechanical tilting furnace. (the shell of the furnace is aluminum alloy).
(2) The above quoted price is for routine configuration. Other configurations can be added, such as leak alarm, water temperature alarm, furnace switch, cover mechanism, lining ejector and transformer, cooling device (open and close cooling tower, closed cooling tower, plate heat exchanger)
3) If necessary, send technicians to carry out the commissioning: the domestic section is free; the overseas section travel expenses, accommodation and food are borne by the user and each person is subsidized 150 US dollars per day.
4) I quote EX-W at a price including simple packing, including shipping charges to Shanghai port area and all inland charges in China.
V) The above electric furnace voltage levels are 380V, 690V and 950/1000V, and the frequency is 50HZ. If the user equipment requirements are different from the above voltage levels and frequencies, each item needs to be increased by 15000USD.
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