Draft : Chen Zhiqiang Gao Jianping Xu Daxiong

Along with the development of steel industry and aluminum industry development, inevitable drives ferrosilicon and silicon metal industry development. Ferrosilicon and silicon metal development, and will have more, better silica source. Silicone development, also strongly promoted chemical grade silicon smelting. As the state environmental protection departments of ferrosilicon and silicon metal industry flue gas emissions, increasing the ferrosilicon and silicon metal smelting factory manufacturers will be installed to collect fine silica powder equipment and powder processing equipment. It can be used for unshaped refractory silica powder will be more and more, more and more better.

" The people's Republic of China ferrous metallurgy industry standards - Unshaped refractories with silica powder" YB / T115 - 1997 (YB / T 115--1997 ) at the end of the last century to our country unshaped refractories with silica powder played a certain role. But in executive process, also encountered a few problems. As standard of certain items did not applicable inspection method, actually cannot perform; standard in some test methods applicable scope is wrong, actually is also unable to perform; standard certain items of apply mechanically abroad enterprise standard, is not completely suitable for Chinese actual. As a result of YB / T115---1997 in some projects can not be implemented, the market there have been some pass off the sham as the genuine phenomena, such as some manufacturers will be labeled as super fine silica powder, level 91, level 92, some manufacturers even SiO2 is greater than or equal to 90% on calibration for 94, SiO2 > 85% the calibration for grade 92. Some manufacturers even double standards, the same level of silica powder with different specifications. Although silica powder to manufacturers use the application principle of good, but also must have a unified standard; otherwise, no rules is not Cheng Fangyuan. To sum up, the revised YB / T115 - 1997 standard to be imperative.

After inspection, the current international has no special refractories silicon powder industry standard. We collected some foreign industry standards, in Table 1 below its standard is the construction of concrete with silica powder industry standards.

Table 1 the United States and Canada silica powder industry standards

Index

American Standard ASTMC1240 Canadian standard CSA standard A23.5

SiO2 > = 85% > 85%

H2O = 3% = 3%

Burning salty = 6% = 6%

Particle size ( sieve residue of 45um ) = 10% = 10%

A large American companies of silicon powder are divided into metal silicon production of silicon powder and silicon alloy production of silicon powder. The index in Table 2 below can be understood as the silicon powder in refractory and requirements in the construction of the requirements are different.

Table 2 the United States of America a large company of silicon powder

SiO2 Cl equivalent basicity igloss 325 mesh sieve residue specific surface area ( nitrogen adsorption method )

Silicon metal produced by the 93-98% 0.09-0.2% 0.5-1.0% 1.5-3.5% 0.4-2.5% silicon powder 15-28 square meters / g

Ferrosilicon produced by 78-85% 0.09-0.2% 0.51.5% 1.5-3.5% 0.4-2.5% silicon powder 15-28 square meters / g

A German company silicon powder is divided into class SiO297% and class SiO290%. The high-end product with very high ratio of performance to price, in refractory material has a very good market. A Scandinavian companies will also have their high-end silicon micro powder for SiO2 > 96%.

The YB / T115-2004 standard drafting had to Sichuan, Guizhou, Hubei, Shanxi, Ningxia and Gansu and other major domestic silicon micropowder manufacturers, as well as the main production of refractory materials, research units were contacted and interviewed. On the products they have done a lot of testing, the YB / T115-1997 standard is used in the problem of existence undertook an analysis, accumulated a certain amount of data.

The standard YB / T115-2004 in YB / T115-1997 basis, revision of the project:

Enhanced definition. Emphasizing the" smelting iron alloy or industrial silicon, through the hood collection of silicon containing flue gas, oxidation and coagulation after dry dust collection device for collecting fine silica powder". The powder is silicon containing flue gas by oxidation of condensed, in mineral composition and hydration polymerization properties and other silicon dioxide powder is different in nature.

The YB / T115-1997 quality level adjustments. The main reason: YB / T 115-1997 in the" 1" and "2 grade" difference is too big. Because the standard product level is too large, the market has pass off the sham as the genuine phenomenon. According to rectify, normative silica fume market requirements, thereby guaranteeing product quality, achieve high quality. According to the actual condition of our country, advanced equipment, strict management and silica levels can reach 93% and 96% above. This will be on silica micropowder grade differentiates afresh, divided into SF96, SF93, SF90 and SF88. SF from silica Silica fume English acronyms. The number after the SF is a silicon oxide content. At the same time the standard to the development of science and technology with space, such as the need for the development of SF98 or SF85, then can be arbitrarily inserted.

The original standard references are adjusted. YB / T115-1997 determination of carbon content in GB / T13245-91 provisions, its measuring range is 5-40%, unable to determination of silica content of carbon; specific surface area by Brabender test method, the measurement range is typically less than 1 square metres / g, also cannot the determination of silicon dioxide powder. The determination of specific surface area of powder is commonly used method of nitrogen adsorption. YB / T115-2004 in determination of the specific surface area using GB / T13390 nitrogen adsorption method.

Increase "pH determination method" for the normative appendix. YB / T115-1997 determination of pH in the powder and water 1: 1 diluted, often caused by slurry cannot disperse. YB / T115-2004 determination of pH in the powder and water 1: 10 diluted, and then press GB / T9724 regulations for detection. The unshaped refractory materials, silica specific surface area will be accounted for more than 80% of all materials, therefore silica pH of unshaped refractories solidification time is very important. Silica powder, slightly acidic to neutral pH as well. Alkali metal, alkaline earth metal, usually the higher content, pH value more.

The original standard indicators were adjusted, the adjusted specific indicators are shown in Table 3, the impurity content is more more strict control. Calcium and magnesium, potassium and sodium and ignition loss index adjustment, but also conducive to the control of pH value. Specific surface area and more than 15 square meters / g unity.

Table 3 silica physicochemical index

Finger mark

A SF96 SF93 SF90 SF88

Si2O, % = 96 93 90 88

AL2O3, % = 1 1 1.5

Fe2O3, % = 1 1 2

CaO+MgO, % = 1 1.5 2

K2O+Na2O, % = 1 1.5 2

C, % = 1 2 2 2.5

Loss on ignition, % = 1 3 3 4

PH value, % = 4.5 ~ 6.5, 4.5 ~ 7.5, 4.5 ~ 7.5 and 4.5 ~ 8.5

Particle size ( sieve residue, % 45um ) less than or equal to 3 3 5 8

The specific surface area, more than 15 square meters / g%

Moisture, % = 1 2 2.5 3

The original standard group by "each 10t" to " 20t per batch"; so that the production and delivery.

The original standard routine inspection items from the six to the five. They are silica, ignition loss, particle size, moisture, pH value. If we change the production of raw materials, production processes or user needs, according to table 2 of the full project inspection.

" The people's Republic of China ferrous metallurgy industry standards - Unshaped refractories with silica powder" YB / T115 - 2004 (YB / T115-2004 ) in 2004 June 17, the people's Republic of China Development and Reform Commission issued, November 1, 2004 formally implemented.

Along with the YB / T115-2004 implementation, I believe more and more silica micropowder manufacturers, the use of manufacturers will use the standard, follow this standard. As in the actual production, the use of the process, find some shortcomings and problems, please contact with the drafting of the standard. The drafting of the standard of people welcome criticism.