Design & Process of Steel Bloom

Introduction

Steel is an alloy made by combining iron and other elements, the most common of these being carbon. When carbon is used, its content in the steel is between 0.2% and 2.1% by weight, depending on the grade. Other elements used are manganese, chromium  vanadium, tungsten. Carbon and other elements act as a hardening agent, preventing dislocation in the iron atom crystal lattice from sliding past one another. Varying the amount of alloying elements and the form of their presence in the steel (solute elements, precipitated phase) controls qualities such as the hardness,ductility and tensile strength of the resulting steel. Steel with increased carbon content can be made harder and stronger than iron, but such steel is also less ductile than iron.

When iron is smelted from its ore by commercial processes, it contains more carbon than is desirable. To become steel, it must be melted and reprocessed to reduce the carbon to the correct amount, at which point other elements can be added. This liquid is then continuously cast into long slabs or cast into ingots. Approximately 96% of steel is continuously cast, while only 4% is produced as cast steel ingots. The ingots are then heated in a soaking pit and hot rolled into slabs, blooms, or billets. Slabs are hot or cold rolled into sheet metal or plates. Billets are hot or cold rolled into bars, rods, and wire. Blooms are hot or cold rolled into structure steel, such as I-beam and rails. In modern foundries these processes often occur in one assembly line, with ore coming in and finished steel coming out.

Design of Bloom

Different design principles are used for casting strands of different cross sections. Bloom casters solidify sections of 300 by 400 millimeters.

Steel Bloom dependable Semi-finished product for steel plant. The Steel Bloom is widely demanded in different size and dimension with different quality.

Sizes:
Different Sizes of Steel bloom like 200x200 Mm, 260x260 Mm, 260x340 Mm, 265x335 Mm.

Length:
Specifiable Up to 12 M

Chemical Composition of Bloom

Grade	C	Mn	Si	S(Max)	P(Max)	Al(Max)	Mo(Max)	Cr	V(Max)
880	0.60-0.80	0.80-1.30	0.10-0.50	0.030*	0.030*	0.015	-	-	-
1080 Cr	0.60-0.80	0.80-1.20	0.50-1.10	0.025	0.025	0.004	0.20	0.80-1.20	0.20
VANADIUM (VN)	0.60-0.80	0.80-1.30	0.10-0.50	0.025*	0.030*	0.015	-	-	0.20
Copper-Molybdenum (CM) 0.35	0.60-0.80	0.80-1.30	0.10-0.50	0.030*	0.030*	0.015	0.2-0.3	-	0.25

Mechanical properties of Bloom Steel

UTS(MPa)(min)	Yield Strength***(MPa)(min)	Elongation% om Gauge Length-5.65 So(min)
880	460	10.0
1080	560	9.0
880	540	10.0
880	460	10.0

Uses of Steel Bloom

Wire rod

Railways Rail

TMT rod etc

Process of Steel Making

1.   Molten pig iron (sometimes referred to as "hot metal") from a blast furnace is poured into a large refractory-lined container called a ladle;

2.   The metal in the ladle is sent directly for basic oxygen steel making or to a pretreatment stage. Pretreatment of the blast furnace metal is used to reduce the refining load of sulfure, Silicon and phosphorus. In desulfurising pretreatment, a lance is lowered into the molten iron in the ladle. The decision to pretreat depends on the quality of the blast furnace metal and the required final quality of the BOS steel

3.   Filling the furnace with the ingredients is called charging. The BOS process is autogenous: the required thermal energy is produced during the process.

4.   The vessel is then set upright and a water-cooled lance is lowered down into it. The lance blows 99% pure oxygen onto the steel and iron, igniting the carbon dissolved in the steel and burning it to form carbon monoxide and carbon dioxide, causing the temperature to rise to about 1700°C.

5.   Fluxes (burnt lime or dolomite) are fed into the vessel to form slag, which absorbs impurities of the steelmaking process. During blowing the metal in the vessel forms an emulsion with the slag, facilitating the refining process.

6.   The BOS vessel is tilted again and the steel is poured into a giant ladle. This process is called tapping the steel. The steel is further refined in the ladle furnace, by adding alloying materials to give the steel special properties.

                                        Flow diagram of Steel Making

Process of Steel Bloom

Molten steel is cast into large blocks called "blooms". During the casting process various methods are used, such as addition of aluminum, so that impurities in the steel float to the surface where they can be cut off the finished bloom.

Because of the energy cost and structural stress associated with heating and cooling a blast furnace, typically these primary steelmaking vessels will operate on a continuous production campaign of several years duration. Even during periods of low steel demand, it may not be feasible to let the blast furnace grow cold, though some adjustment of the production rate is possible.

Integrated mills are large facilities that are typically only economical to build in 2,000,000 ton per year annual capacity and up. Final products made by an integrated plant are usually large structural sections, heavy plate, strip, wire rod, railways rail, and occasionally long product such as bars and pipe.

Steel Bloom produce by Continuous Casting

In this process, molten steel flows from a ladle, through a tundish into the mold. The tundish holds enough metal to provide a continuous flow to the mold, even during an exchange of ladles, which are supplied periodically from the steelmaking process. The tundish can also serve as a refining vessel to float out detrimental inclusions into the slag layer.

Once in the mold, the molten steel freezes against the water-cooled walls of a bottomless copper mold to form a solid shell. The mold is oscillated vertically in order to discourage sticking of the shell to the mold walls. Drive rolls lower in the machine continuously withdraw the shell from the mold at a rate or “casting speed” that matches the flow of incoming metal, so the process ideally runs in steady state. The liquid flow rate is controlled by restricting the opening in the nozzle according to the signal fed back from a level sensor in the mold.

                                      Continuous Casting of Bloom

Test of Steel Bloom

Non-destructive testing (NDT) is a wide group of analysis techniques used in science and industry to evaluate the properties of a material, component or system without causing damage. The terms Nondestructive examination (NDE) , Nondestructive inspection (NDI), and Nondestructive evaluation (NDE) are also commonly used to describe this technology. Because NDT does not permanently alter the article being inspected, it is a highly-valuable technique that can save both money and time in product evaluation, troubleshooting, and research. Common NDT methods include Ultrasonic, magnetic particle, liquid penetrate, radiographic, remote visual inspection (RVI), Eddy current testing.

In ultrasonic testing (UT), very short ultrasonic pulse-waves with center frequencies ranging from 0.1-15 MHz and occasionally up to 50 MHz are launched into materials to detect internal flaws or to characterize materials. In ultrasonic testing, an ultrasound transducer connected to a diagnostic machine is passed over the object being inspected. The transducer is typically separated from the test object by a couplant (such as oil) or by water, as in immersion testing.

Advantages

1.   High penetrating power, which allows the detection of flaws deep in the part.

2.   High sensitivity, permitting the detection of extremely small flaws.

3.   Only one surface need be accessible.

4.   Greater accuracy than other nondestructive methods in determining the depth of internal flaws and the thickness of parts with parallel surfaces.

5.   Some capability of estimating the size, orientation, shape and nature of defects.

6.   Nonhazardous to operations or to nearby personnel and has no effect on equipment and materials in the vicinity.

7.   Capable of portable or highly automated operation