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Graphite Electrode Machining Services

Release time:2019-11-14 From: Zhengnai Industry in China

What is graphite electrode machining

After calcination and graphitization, the size of the formed blank varies, sometimes bending and deforming to a certain extent, bumping or falling, and the surface is rough and uneven because of some fillers or other impurities. It must be properly machined to cut off a layer of skin, and achieve the required external diameter size and surface light. Cleanness. Because graphite electrodes are continuously used in electric arc furnace, it is necessary to cut both ends flat, then process the nipple holes with nut threads on both ends, and process the nipples with corresponding size and outer common threads with specially prepared nipple blanks for connection.

graphite electrode machining services

The purpose of machining graphite materials is to achieve the required size, shape, precision, etc. by cutting, and to make electrode body and joint meeting the use requirements
  • 1 the processing of graphite electrode is divided into two independent processes: electrode body and joint
  •    1.1 The main body boring and rough flat end, turning outer circle and fine flat end and milling process. The processing of conical joint can be divided into three processes: cutting, flat end, turning cone, milling thread, drilling bolt and slotting.
  •    1.2 Connection mode of electrode joint: conical joint and one inch four button connection, connection due to column joint (male female connection)
  • 2 taper deviation, thread pitch, major diameter deviation of joint (hole), coaxiality of joint hole, perpendicularity of joint, flatness of electric extreme drawing, four point deviation of joint, etc. of machining accuracy. Check the finished electrode with special ring gauge and plate gauge: accuracy, weight, length, diameter, bulk density, resistivity, pre assembly and matching accuracy, etc
 

Pore formation in graphite electrode machining

The raw material of the graphite product is petroleum coke or pitch coke. During the roasting process, due to the decomposition, polycondensation and carbonization of the coal tar pitch, the carbon residue rate of the formed pitch coke is generally only about 50%. The volume of coal tar pitch forming pitch coke is smaller than the volume occupied by coal tar pitch in the green body. Although the green body shrinks slightly during calcination, many different sized pores are left in the calcined product.

Effect of Porosity on Physicochemical Properties of Graphite Products

For the graphite electrode, as the porosity of the finished product increases, the density decreases, the electrical resistivity increases, and the mechanical strength decreases. Graphite products with a large porosity have a faster oxidation rate at a certain temperature, a lower corrosion resistance, and a gas or liquid is more easily penetrated.
 

Graphitization consumption

The graphitization consumes the average energization time (in min) per ton of roasting product in a graphitization furnace.

The cause of "flatness" in the graphitization process

Although the "flat" in the graphitization process is mainly related to the sulfur content, some researchers believe that "flat" has a certain relationship with the amount of nitrogen in the coke.
 

graphite electrode supplier  in China

Our company also began to produce needle coke after efforts to solve the problem of raw materials needed for the production of high and ultra-high power graphite electrodes. A great deal of research work has been done on the production of high and ultra-high power graphite electrode by several universities, scientific research institutes and factory research institutes , and fruitful results have been achieved, laying a technical foundation for the further development of graphite electrode industry.
 

Parameter and Size of graphite electrode

Item Unit UHP HP RP
300-600mm 650-800mm 300-800mm 300-800mm
Electric resistivity Electrode μΩm 4.8-5.8 4.6-5.8 5.8-6.6 7.8-8.8
Nipple 3.8-4.5 3.8-4.5 4.2-5.0 5.0-6.5
Flexural strength Electrode Mpa 10.0-14.0 10.0-14.0 10.0-13.0 7.0-12.0
Nipple 20.0-26.0 22.0-26.0 18.0-22.0 15.0-20.0
Elastic modulus Electrode Gpa 9.0-13.0 10.0-14.0 8.0-12.0 7.1-9.3
Nipple 15.0-18.0 15.0-18.0 14.0-16.0 12.0-14.0
Bulk density Electrode ≥g/cm3 1.68-1.74 1.70-1.74 1.62-1.66 1.53-1.56
Nipple 1.77-1.82 1.78-1.84 1.74-1.80 1.70-1.74
CTE(100-600℃) Electrode x10-6/℃ 1.1-1.4 1.1-1.4 1.6-1.9 2.2-2.6
Nipple 0.9-1.2 0.9-1.2 1.1-1.4 2.0-2.5
Ash   0.3 0.3 0.3 0.5

Issues to improve the quality of graphite electrodes

Improving the quality of graphite electrodes mainly grasps two problems, stabilizes physical and chemical indicators at a high level, and seriously improves the quality of product processing. The main physical and chemical indicators such as resistivity, flexural strength, linear expansion coefficient, ash, density and elastic modulus are controlled within a certain range. It is not the higher the higher the better, and the stability is more important in a certain sense. Modification of ordinary machine tools or purchase of combined machine tools with guaranteed machining accuracy to improve product quality.
 
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