Graphite Electrode URP

Graphite Electrode URP Definition

Ultra high power graphite electrodes (EHSP-UHP) are manufactured for operation at currents with a density of more than 25A / cm2

Graphite Electrode URP Application

1.URP graphite electrode used in steel making electric arc furnaces, refining furnaces, as conductive electrodes.

2.Graphite electrode URP used in industrial silicon furnaces, yellow phosphorus furnaces, corundum furnaces. As conductive electrodes for graphite electrode URP.

Graphite Electrode UHP Specification
 

Name	Unit	diameter of electrode 300mm-600mm
		standard		Actual measurement
		Electrode	Nipple	Electrode	Nipple
Specific electrical resistivity	μOhm • m	6.2-6.5	5.5	5.0-6.5	4.5
Limit of mechanical resistance to bending	MPa	10.5	16	14-16	18-20
Elastic modulus	GPa	14	18	12	14
Ash content, not more than	%	0.5	0.5	0.5	0.5
Bulk density, not less than	g / cm3	1.64-1.65	1.70-1.72	1.72-1.75	1.78
Thermal coefficient of linear expansion (100-600 ° C)	× 10-6 / ℃	1.5	1.4	1.3	1.2

 
The Length & Diameter & Permissible Deviation of the Graphite Electrode UHP
 

Diameter				Length
Nominal diameter		Actual diameter		Nominal length	tolerance
Millimeters (mm)	Inch (inch)	Max. (Max.)	Min (min)	mm	Length	the maximum
300	12	307	302	1600 1800	± 100	-100	-275
350	14	357	352
400	16	409	403
450	18	460	454
500	20	511	505	1600/1800/2000/2200	± 100	-100	-275
550	22	556	553
600	24	613	607

 
Graphite Electrode UHP Current Capacity
 

Nominal diameter		Current throughput (A)	The current density (A / cm2)
Millimeters (mm)	Inch (inch)
250	10	9200-15100	21-30
300	12	13000-22000	20-30
350	14	20000-30000	20-30
400	16	25000-40000	19-30
450	18	32000-45000	19-27
500	20	38000-55000	18-27
550		48000-60000	18-24
600	24	52000-72000	18-24
700	27th	62000-95000	18-24

Graphite Electrode URP Manufacturer in RS Refractory Factory Advantages

1.High quality graphite electrodes products.

2.Graphite electrode URP manufacturer from China

3.Profitable price for high quality graphite electrodes.

4.RS refractory factory can produce various specifications in accordance with customer requirements.
 
Graphite Electrode URP Using Precautions 

1.In actual use the graphite electrode URP, specifications and grades of the graphite electrode should be selected according to the specific furnace conditions.

2.Primary factor is the maximum current intensity, but also consider the influence of other factors, such as the characteristics of the Arc electric furnace itself, the type of charge, the smelting time, the oxygen blowing amount, the mechanical requirements, the steel making process.

3. Normally, specification of most grades of graphite electrodes have been standardized. But in the process of use, sometimes also consider the temperature to some impacts of these indicators.

4. Select the grade and diameter of the electrode according to the furnace capacity and transformer load.

5. When charging the electric furnace, refractory material should be installed at the bottom of  furnace to prevent furnace refractory material from collapsing and breaking the electrode. In the smelting process, lime, it should be avoided.

6. A large amount of objects are concentrated directly under the electrodes, otherwise it will affect the energization of the electrodes and may even cause the electrodes to break.

7. Pay attention to the position of the furnace cover. If the furnace cover is misaligned, the furnace cover will be scratched when the electrode is lifted, resulting in damage to the electrode.

8. If the connector plug is found to be missing when connecting the electrode, replace it and connect it.

9. After the electrodes are connected, if there is a gap on the connection surface, be sure to find out the cause. It can be used after the gap is eliminated.

10. Graphite electrode holder should be sandwiched between the upper and lower guard lines of the topmost electrode. It is forbidden to be caught in the warning line (the joint hole) and the middle electrode, otherwise the electrode column may be broken.

11.Since raw refractory materials and production processes of different manufacturers may be different, the physical and chemical properties of the electrodes are also different. It is recommended that the joints and electrodes produced by different manufacturers should not be used interchangeably during use.

Refractory Materials fo Hot Metal Pretreatment Effect

1.Strong scouring and wear of high temperature molten iron and slag. Since the temperature of molten iron is as high as 1400 ℃or higher, industrial refractory material for furnace lining and the stirring and blowing equipment will be strongly washed by the high temperature iron during the pre-existing process of molten iron, industrial refractory material is required to be used in the hot metal pretreatment process. The refractory material has high temperature strength and is resistant to wear.

2.Chemical attack of various pretreatment agents. Since various desulfurizing agents react with the kiln lining and the refractory materials for the stirring and blowing devices during use, and can generate some low-melting substances, dissolved in molten iron, especially for some low-melting soda and other fluxes, They make the refractory erosion of various pretreatment agents particularly severe, so the refractory materials used in the pre-existing process of molten iron are resistant to various pretreatment agents.

3.Permeation and erosion of furnce slag. In the hot metal pretreatment process, both CaO and FeO will form a low melting point with SiO 2 and Al 203 in the refractory material, which will cause erosion and melt damage to the refractory material. Therefore, it is required that the refractory material used in the hot metal pretreatment process is good. Resistance to slag erosion.

4.The temperature drastic effect caused by intermittent operation, because the molten iron pretreatment device will undergo the process of charging molten iron, hot metal treatment and pouring molten iron and empty bag between each hot metal pretreatment process, so the molten iron pretreatment. The device will be subjected to a certain temperature change, which requires the hot metal pretreatment device to have good thermal shock stability with the furnace refractory materials.

In addition, the refractory materials in furnace used are also required to facilitate on-site construction and have less environmental pollution.

Steelmaking Electric Arc Furnace with Graphite Electrode

The configuration of the graphite electrode for steelmaking electric arc furnace should follow the basic principle of "common power electric furnace with ordinary power graphite electrode, high power electric furnace with high power graphite electrode, ultra high power electric furnace with ultra high power graphite electrode".

AC Steelmaking Electric Arc Furnace with Graphite Electrode Configuration Plan

For AC steelmaking electric arc furnace, 10~30t electric furnace is equipped with graphite electrode with diameter of 300~400mm, 30~50t electric furnace is equipped with graphite electrode with diameter of 450mm, 60~80t electric furnace is equipped with graphite electrode with diameter of 500mm, electric furnace with diameter of 100~170t is equipped with diameter of 550~600mm graphite electrode, 200t electric furnace with 600~700mm diameter graphite electrode, 250~300t electric furnace with 700mm diameter graphite electrode.

Configuration Scheme of DC Steelmaking Electric Arc Furnace

For the DC steelmaking electric arc furnace, the 30t electric furnace is equipped with a 450mm diameter graphite electrode, the 60t electric furnace is equipped with a 500mm diameter graphite electrode, the 70~80t electric furnace is equipped with a 600mm diameter electric furnace arc graphite electrode, the 100~130t electric furnace is equipped with a 700mm diameter graphite electrode, and the 150t electric furnace is equipped with a 150t electric furnace. A 750 mm diameter graphite electrode was used.

Improve Thermal Shock Resistance of Refractories Material Method?

In the course of use, refractory materials are often subjected to abrupt changes in the ambient temperature, causing cracks in the product, eventually peeling off or even collapsing. This destructive effect not only limits the heating and cooling rate of the refractory product and refractory material for klin, but also limits the strengthening of the kiln operation, which is one of the main reasons for the rapid damage of the refractory product and the kiln.

The property of a refractory material against rapid changes in temperature without being destroyed is called thermal shock stability, and this property is also called thermal shock resistance or temperature sharpness.

Due to the intermittent operation characteristics of the converter, strict requirements are imposed on the thermal shock stability of the magnesia chrome refractory. Increasing the thermal shock resistance of the refractory material can be achieved by preventing crack propagation, consuming crack propagation power, increasing material fracture surface energy, increasing plasticity, reducing linear expansion coefficient, and increasing thermal conductivity.

1. Appropriate porosity of refractory brick. Surface cracks do not immediately cause cracking, and severely are spalling and fracture caused by internal thermal stress. When the porosity of fire brick is appropriately increased, the crack length of the refractory product becomes shorter and the number increases with the thermal shock. The cracks are interlaced and the degree of mesh formation is enhanced. Therefore, the fracture energy required for the product to break is increased, which can be effectively improved. Thermal shock stability of the refractory product. The optimum porosity of refractory products is usually controlled at 13% to 20%.

(2) Control the particle gradation of refractory raw materials and select low expansion, high thermal conductivity materials. In order to obtain a magnesia chrome refractory with good thermal shock resistance, which is required to increase the critical particle size and reduce the fine powder content in the chrome ore particles. Refractory raw material having a small coefficient of linear expansion and a raw refractory material having a high thermal conductivity such as Cu2O are used.

(3) Adding fine cracks and forming a network structure. By utilizing the inconsistent characteristics of the refractory product particles and the linear expansion coefficient of the matrix and the volume effect of the phase change, fine cracks are generated in the product, which has a significant effect on resisting catastrophic damage (hot peeling or fracture) of the product. Tests have shown that increasing the A1203 content in the refractory material or adding the most suitable ZrO2 to the magnesia-chromium refractory material can significantly improve the thermal shock stability of the magnesium-chromium material. Compared with the sample incision, the sample with ZrO2 has a large number of fine cracks inside. It is because of the existence of these fine cracks that the energy of crack propagation is absorbed, which enhances the thermal shock stability of the sample. The amount added should not exceed 5%.

Analysis of Damage Causes of Refractory material in Ladle lining

Steel Ladle is an important thermal equipment for steel mills. ladle is mainly composed of cladding, refractory lining and SN mechanism. The metallurgical technology continues to develop, the smelting temperature increases and the continuous casting ratio increases, and the residence time of the molten steel in the ladle is prolonged. The use condition of refractories in ladle lining directly affects the case production and logistics of steelmaking. Therefore, it is considered that Rongsheng refractory material factory pursues the continuous improvement of the life of ladle under the premise of ensuring safe use, reducing the consumption and cost of refractory tons of steel, and improving the thermal turnover rate.

Ladle Lining Refractory Combination Design

The ladle lining refractory can be divided into a working layer and a permanent layer, and different refractory material systems and construction methods are adopted depending on the difference between the bottom and the wall erosion mechanism.

When selecting the permanent layer refractory materials, it is necessary to consider the factors of heat preservation and anti-steel water penetration. The high aluminum castable is used as a permanent layer, high alumina castable has high temperature strength, good thermal stability, strong resistance to molten steel penetration and moderate heat preservation. In order to enhance its thermal insulation performance, a layer of 18mm mullite insulation brick is built between the high aluminum castable and the steel shell, and the temperature of the outer casing during the turnaround of the ladle is between 220 and 400℃. This not only reduces the probability of steel leakage, but also reduces the heat loss of the molten steel during the entire refining and pouring process, which is beneficial to low temperature tapping and energy consumption.

The refractory materials in various parts of the bottom working layer have different damage mechanisms. The bottom of the bag is subjected to molten steel impact and large static pressure, and a refractory material for ladle lining with high softness, low creep and good thermal stability is required, and corundum castable is selected. In order to improve the anti-scour performance, a large precast block is placed in the impact zone, in order to facilitate the repair and reserve a certain expansion joint, the magnesia carbon brick is built around the gas permeable brick and the water block brick.

The wall working layer is subjected to carbon absorption by steel and scouring and slag during refining. The refractory material for ladle in this part should have good erosion resistance, erosion resistance and oxidation resistance, and the thermal expansion rate is required to keep the wall without cracks. Use corundum castable (integral cast ladle) or precast block (brick ladle). The slag line part of the slag line is eroded by the slag and the arc is burned and decarburized. The ladle refractory material is required to have strong anti-oxidation and anti-erosion ability.

Damage Mechanism of Ladle Lining

1.Steel Ladle Permanent Layer Damage

Taking Baosteel ladle as an example, the service life of Baosteel ladle permanent layer is generally 600~800 heats, that is, four overhaul cycles.

During the overhaul, it was found that there were many criss-cross cracks in the permanent layer of the wall, and the cracks widened and deepened with the increase of the number of overhauls. Sometimes the cold steel that poured into the working layer would also penetrate into the cracks of the permanent layer, which would affect the safety of the ladle. Common causes of cracks include: the low strength fiberboard is compressed by the volume to create a condition for the expansion of the permanent layer, the permanent layer castable refractory has a certain shrinkage during use, and the thickness of the permanent layer of the cladding is thin and the thickness is uneven. The ladle cladding is deformed at a high temperature, and the mechanical vibration during the removal of the slag line magnesia carbon bricks also accelerates the development of cracks in the permanent layer.

2.Steel Ladle Working Layer Damage

In the refining process, desulfurization, deoxidation, decarburization, degassing, fine adjustment of alloy composition, removal of non metallic impurities, inclusion denaturation treatment, and molten steel temperature control are required in the ladle. Different refining methods for the ladle working layer are not the same. The main forms of damage are as follows:

1. Slag line: erosion (primary), flaking, erosion, hydration (secondary cause)

2. Wall: erosion (primary), erosion, hydration (secondary cause)

3. Bottom: Scour (main reason), erosion, hydration (secondary cause)

4. Nozzle system: scouring (primary), spalling, erosion (secondary cause)

5.Argon blowing system: peeling (primary), flushing (secondary cause)

1) Erosion

There are two main types of erosion for the lining of the ladle working layer: chemical attack and oxidative attack.

Chemical attack: the acidic substances (such as silica) in iron oxide or slag react with the lining of refractory materials. There are chemical reactions between iron oxide, silica, calcium oxide and magnesium oxide. These reactions make the ladle lining. The change to slag causes damage to the refractory material.

FeO+MgO=FeOMgO

SiO2+2MgO=2MgOSiO2

CaO+SiO2+MgO=CaOMgOSiO2

Oxidation reaction: Oxidation erosion is a special form of refractory lining of ladle, generally refers to the erosion caused by the reaction of carbon in refractory bricks with iron oxide or oxygen in the air. The iron oxide in the slag reacts with the graphite or resin of the hot surface of the brick, and the oxygen erodes the graphite or carbon binder on the surface of the brick lining. In both cases, the internal structure of the refractory brick is loose and the strength is lowered. And eventually the refractory brick lining is washed away by slag or molten steel. This erosion occurs in all parts of the refractory in the ladle, with the most severe slag line.

FeO+C=Fe+CO

O2+2C=2CO

2) Scour

Scouring is the physical wear or scouring of the lining caused by the flow of molten steel or slag through the surface of the refractory. For the ladle used in the eccentric bottom tapping, the molten steel has a great influence on the impact zone of the bottom steel, the nozzle of the nozzle and the permeable brick above the bottom of the package. The ladle treated by LF and CAS, due to the strong agitation of the argon blowing process at the bottom of the ladle, aggravates the scouring effect of the molten steel on the local part of the ladle wall.

3) Peeling off

Peeling is caused by the stress on the refractory lining caused by the rapid chilling of the refractory lining. When the stress exceeds the strength of the refractory material, cracks are generated inside the refractory material. As these cracks expand, intersect and penetrate, the fragments of the refractory material will partially or completely peel off, which is often the case on the nozzle block and the permeable block.

4) Hydration

The ladle work lining adopts the fire mud wet-laying process in the masonry, and the permanent lining is knotted with the refractory castable. The moisture or water vapor reacts with the MgO in the magnesia carbon brick before and during the baking to hydrate. The hydrated refractory is resistant to steel slag and molten steel with poor permeability, reduced physical and chemical properties, and will accelerate the erosion rate of the ladle lining.

MgO+H2O=Mg(OH)2

Through the above analysis of the damage mechanism of the ladle lining, it is not difficult to find that the mechanism of refractory damage in various parts of the ladle working layer is different. Therefore, the whole process of ladle lining needs to be managed, from material selection, masonry construction and baking. Bake, run, and detect, repair, etc. after problems are discovered. When the ladle is used for a certain number of times and needs to be repaired, carefully check the residual thickness of each part of the lining, analyze the damage, and carefully analyze the data in the use of the lining to grasp the damage law of the refractory materials in the lining of the ladle.