Knowledge about Steel Production-I

1. What are the basic tasks of steel making? By what means?
The basic tasks of steel making are decarburization, dephosphorization, desulfurization, deoxidation, removal of harmful gases and non-metallic inclusions, increase of temperature, and adjustment of molten steel composition. 
Oxygen supply, slagging, agitation, and alloying are the means to accomplish the steel making task.
2.What’s the main role of steel making in adding dolomite in converter?
Dolomite is a slag-regulating agent, which is divided into raw dolomite and light-burned dolomite. According to the needs of slag splashing protection technology, the amount of MgO in the slag is added to maintain saturation or to reduce the erosion of the initial slag on the furnace lining, the final slag can be made sticky, and the slag splashing requirement is achieved after tapping.
3. Combine the situation before, during and after the blowing, and briefly describe the operation of the constant pressure gun.
The constant flow variable gun position operation is to keep the oxygen supply flow constant during the blowing process of a furnace steel, and control the blowing by changing the position of the oxygen flow and the molten pool by adjusting the gun position. Most manufacturers in China use a staged constant flow variable gun position operation. Oxygen lance operation is not exactly the same due to different tonnages of the converter, nozzle structure, raw material conditions and steel grades. There are currently two lance operation modes.
High-low-high-low gun position mode. The open blow gun position is higher, and the initial slag is formed early. When the second batch of rice is added, the gun is lowered at the appropriate time. When the middle slag is blown back, the gun can be added or an appropriate amount of flux can be added to adjust the slag fluidity to shorten the blowing time and the end point. Pull carbon out of steel.
High-low-low gun position mode. The open blow gun position is higher, and the initial slag is formed as soon as possible; the gun position is gradually reduced during the blowing process, and an appropriate amount of flux is added in the middle of the blowing to adjust the slag fluidity, and the carbon steel is extracted at the end point.
4. Write the carbon oxidation reaction formula of the converter steelmaking, and indicate the carbon-oxygen reaction generated by the spray.
[C]+1⁄2{O2}={CO} [C]+(FeO)={CO}+[Fe] (carbon-oxygen reaction by splash)[C]+[O]={CO}
5. What is a non-metallic inclusion? What is the main source?
Non-metallic phases that are produced or mixed during smelting, casting, and solidification of molten steel are referred to as non-metallic inclusions. Non-metal phases are compounds in which some metal elements and Si are combined with non-metal elements, such as oxides, nitrides, sulfides, and the like. Due to the presence of inclusions, the continuity of the steel matrix is destroyed, resulting in unevenness of the steel structure, affecting the mechanical properties and processing properties of the steel. However, non-metallic inclusions also have a favorable effect on steel, such as controlling the fine grain size, precipitation hardening, promoting grain orientation, and improving the cutting performance of steel.

6. How to classify according to room temperature and carbon content steel?
(1) Eutectic steel: 0.0218<C<0.77%;
(2) Eutectoid steel: C = 0.77%;
(3) Hypereutectoid steel: 0.77% < C < 2.11%.
7. Say 10 common hot rolled strip quality defects?
Crusting, bubbles, surface inclusions, delamination, cracks, scales, roll marks, indentations, scratches, waves, edge cracks, pitting.
8. What are the advantages of ferritic rolling technology?
(1) Reduce heating energy consumption;
(2) Increase the metal yield;
(3) Reducing the consumption of steel rolls per ton;
(4) Improve the surface quality of the strip;
(5) After the subsequent processing, it may not be cold rolled;
(6) Reduce the cold rolling rolling force.
9. What is the significance of quality management?
(1) Improve product quality;
(2) Improve product design;
(3) speed up the production process;
(4) Improve employees' work enthusiasm and enhance quality awareness;
(5) Improve product after-sales service&acceptance of the market;
(6) Reduce the cost of operating quality & operating losses&on-site maintenance costs;
(7) Reduce liability accidents.
10. How does the iron-carbon equilibrium phase diagram be applied in the rolling process?
According to the iron-carbon equilibrium phase diagram, the heating temperature range, the rolling temperature range and the finishing rolling temperature range of each steel type can be determined. This is the relationship between the temperature and the structure of the iron-carbon equilibrium phase diagram, which provides a reference for people to ensure that Each steel grade is processed in a reliable state and ultimately achieves the desired texture and properties.