Analysis of New Standard for Ultra High Power Graphite Electrode

Analysis of New Standard for Ultra High Power Graphite Electrode
1 Job profile

1.1 Task source

According to the requirements of the Ministry of Industry and Information Technology Department of Industry and Information Technology [2009] No. 260 document, Jilin Carbon Co., Ltd. and other units are responsible for revising the People's Republic of China ferrous metallurgy industry standard "Ultra High Power Graphite Electrodes", plan number: 2009-1976T-YB .

1.2 Working situation

After receiving the task, Jilin Carbon Co., Ltd., China Pingmei Shenma Group Kaifeng Carbon Co., Ltd., and Metallurgical Industry Information Standards Research Institute jointly formed a standard drafting and revision group. Through investigation, research and data collection, the standard writing team completed the draft for comments and preparation instructions of this standard in April 2014 based on the actual production and use of ultra-high-power graphite electrodes in the past few years, and sent it to relevant manufacturers and user units for review. Solicit opinions, and form a standard draft for review on the basis of soliciting opinions.

In December 2014, the Carbon Materials Sub-Technical Committee of the National Steel Standardization Technical Committee organized a standard approval meeting in Beijing. According to the approval meeting, the content was revised and the draft of the standard was completed.

In July 2015, the Ministry of Industry and Information Technology issued Announcement No. 49 of 2015, which approved the release of the "YB/T 4090-2015 Ultra High Power Graphite Electrode" standard, which was implemented on January 1, 2016.
2 Determination of main technical indicators

2.1 Standard scope

With the advancement of carbon technology, the raw materials for the production of ultra-high-power graphite electrodes have been greatly changed. Therefore, "this standard applies to high-quality needle coke as the main raw material" was revised to "this standard applies to needle coke and coal tar pitch as the main raw materials.”

2.2 Reference Standards

(1) Since most electrode manufacturers have not carried out the elastic modulus test of the whole graphite electrode and have not measured the sound velocity on site, the reference standard "GB/T 24210 Test of the elastic modulus of the whole graphite electrode - sound velocity method" is deleted.

(2) The reference standard is revised to the latest test item standard.

2.3 Appearance, dimension and allowable deviation

(1) Amend "Length" in Table 1 to "Nominal Length".
(2) Due to the continuous increase of the capacity of the electric furnace used by users, this standard adds the relevant requirements for the external dimensions of Φ750 mm and Φ800 mm electrodes and joints according to IEC 60239-2005 and SGL's corporate standards.

(3) In order to be in line with the IEC60239-2005 international standard and improve the versatility of the product, the maximum actual diameter of the electrode with a nominal diameter of 350 mm was revised from 357 mm in the original standard to 358 mm; the minimum actual diameter of the electrode with a nominal diameter of 700 mm was changed from The original standard 708 mm was revised to 710 mm, and the minimum actual diameter of the black skin part was revised from the original standard 705 mm to 707 mm.

(4) Since the market of Φ550 mm electrodes has a demand of 2 700 mm in length, the nominal length of 2 700 mm has been increased; and 2 standard nominal lengths of 2 000 mm and 2 200 mm have been added for electrodes with specifications of Φ650 mm and above. ;The standard nominal length of 3 000 mm is added for electrodes of Φ600 mm and above.

(5) For the convenience of users, the maximum standard length deviation of the nominal length of 2 700 mm is increased from the original standard +150 mm to +200 mm; the allowable deviation of the standard nominal length of 3 000 mm is determined as the nominal length of 2 700 mm. consistent.
(6) For the convenience of users, the allowable short-length electrodes for each batch in the supply are revised to 5%. See clause 3.3 in the standard.

(7) In order to improve the quality of the electrode connection and improve the performance of the product, the end face gap at the connection of the two electrodes is not greater than 0.4 mm, and is revised to 0.05 mm. See clause 3.5 in the standard.

(8) Item 3.6 "If there are special requirements for electrode specifications, it shall be negotiated by both the supplier and the buyer".

2.4 Physical and chemical indicators

(1) Due to the continuous improvement of user requirements, the quality of ultra-high-power graphite electrode products is also constantly improving. In order to improve the user's performance of the product, improve product quality, and better meet user requirements, the ultra-high-power graphite electrode of Φ300~500 mm is revised. Electrode part indicators.

Φ300~400 mm: The electrode bulk density is revised from 1.65 g/cm3 to 1.67 g/cm3; the joint is revised from 1.72 g/cm3 to 1.74 g/cm3. Φ450~500 mm: The electrode bulk density is revised from 1.64 g/cm3 to 1.66 g/cm3; the electrode flexural strength is revised from 10.0 MPa to 10.5 MPa; the electrode resistivity is revised from 6.5 μΩ·m to 6.3 μΩ·m; the joint bulk density Revised from 1.70 g/cm3 to 1.75 g/cm3; joint flexural strength revised from 16.0 MPa to 20.0 MPa.

The resistivity of the connector of Φ500 mm and below is revised from 5.5 μΩ·m to 5.3 μΩ·m.

Ash was revised from 0.3% to 0.5% due to the use of additives.

(2) Due to the continuous increase in the market share of large-scale ultra-high-power graphite electrodes, in order to promote the development of production enterprises, the index requirements for large-scale ultra-high-power graphite electrodes of Φ550~800 mm have been increased.

The revised technical indicators are shown in Table 1 (see Table 4 in the standard).
2.5 Surface Quality

(1) The requirements for dropped blocks or holes on the surface of the electrode are revised to "there are no more than two spots or holes on the surface of the electrode, and the diameter of the defect is 10-20 mm, and those smaller than 10 mm are not counted, and the depth is 5-10 mm, less than 5 mm. Excluding". See clause 4.2.1 in the standard.

(2) Transverse cracks are not allowed on the electrode surface; longitudinal cracks with a width of 0.3~1.0 mm shall be no more than 80 mm in length and no more than two

and longitudinal cracks less than 0.3 mm in width" shall be revised as "Cracks are not permitted on the electrode surface". See clause 4.2.4 in the standard.

(3) Add "electrodes with a diameter of 550~800 mm are not allowed to have black skin". See clause 4.2.5 in the standard.
2.6 Other amendments

(1) Due to the continuous revision and improvement of the testing method standards, the serial numbers of the chapters will be changed. Therefore, "Determination of resistivity shall be carried out in accordance with the provisions of Section 5 (On-site measurement of graphite electrode products) in GB/T 24525" is revised to " The determination of resistivity shall be carried out in accordance with the provisions of GB/T 24525". See clause 5.1 in the standard.

(2) The inspection rules for batches of thermal expansion coefficient of joints and the number of samples to be sampled in each batch have been revised. Since the materials, formulations and process control of joints of the same variety and specification are basically stable, and the thermal expansion coefficient index is relatively stable, the " Electrodes of the same variety and specifications shall be measured at least once a month; joints shall be measured once per furnace" was revised to "electrodes and joints of the same variety and specifications shall be measured at least once a month". See clause 6.3.1 in the standard.

3) The suggested allowable current load for ultra-high power graphite electrodes of Φ550~700 mm is provided. See Appendix A in the standard.
3 Comparison with international indicators

In order to improve the level, scientificity and rationality of the standard and ensure the universality of the products, the standard writing team systematically collected IEC 60239-2005 international standards, UCAR Company of the United States, SGL Company of Germany, Tokai Carbon Company of Japan, Showa Denko and HEG of India The standards or product samples of internationally renowned carbon companies such as the company have determined the electrode and joint dimensions and tolerance requirements of the ultra-high power graphite electrode industry standard through research. The IEC 60239-2005 international standard is equivalent, and some tolerance requirements are higher than IEC 60239. -2005 standard requirements. Physical and chemical indicators and other technical requirements are comprehensively determined according to domestic and foreign enterprise standards and user usage.

4 Conclusion

(1) This revised standard improves the flexural strength, bulk density and other indicators of joints, determines the indicators of large-scale ultra-high power graphite electrodes, and proposes the size and tolerance requirements of Φ750~800 mm electrodes, which are produced for carbon enterprises. It provides technical support and quality assurance for use with users, drives the quality improvement and development of ultra-high-power graphite electrode products, increases the market share of domestic products, and improves the economic benefits of enterprises.

(2) According to the actual situation of production and users, the size and tolerance requirements are equivalent to the IEC 60239-2005 international standard, and some tolerance requirements are higher than the IEC standard, and the standard is more scientific and reasonable.