Anhydrous gun mud refers to gun mud which is made of corundum, bauxite, clay, silicon carbide and coke powder with tar and resin as binder. When the anhydrous carbon gun mud is made by the mud mill, the oil shall be discharged first, then the block material (clay and asphalt) shall be put, and then the powder material (coke powder and clinker powder) shall be put after being crushed. After being pressed and mixed well, the mud can be discharged when it meets the standard.
In order to maintain the taphole, according to the working conditions, the blast mud is generally required to have the following properties:
① Good workability, can be easily pushed out from the clay gun, and has a high filling density;
② The opening performance is good, and the bit of the opening machine is easy to drill in when opening;
③ Erosion and erosion of high temperature resistant iron;
④ The volume stability is good, that is, the volume change is small at high temperature;
⑤ High fire resistance, > 1580 ℃;
⑥ It has certain plasticity at room temperature.
Factors affecting the quality of gun mud:
1. Impact of raw material quality
The raw materials used for gun mud have a great influence on its quality.
(1) Influence of chemical composition
Because of the poor quality of clay, for example, Fe2O3 can not meet the three-level clay quality standard of the ministry standard, thus reducing the high temperature strength and fire resistance of gun mud. In addition, the quality of clay containing more impurities, such as small stones and sand, also affects the quality of gun mud.
The fixed carbon content of coke powder is about 3% lower than that of Angang Steel, and the ash content is about 0.5% higher. The fixed carbon of coke powder is low and the ash content is high, which will reduce the high temperature strength of the mud.
Generally, the water content of anthracene oil is about 1%, but sometimes it is as high as 8%, which mainly comes from the condensate produced by heating the oil directly with steam. Anthracene oil is added in the process of grinding gun mud ingredients by weight, so the fluctuation of water content in the oil will cause the fluctuation of gun mud quality. The higher the water content is, the more damp and soft the mud is, the worse the high temperature strength is, and the greater the color shrinkage is, which leads to the reduction of the qualified rate of the taphole.
(2) Influence of raw material size
① The influence of coke size.
② The influence of clinker size.
The requirement of clinker powder size is generally < 3mm.
(3) Impact of poor raw material management
Clay, asphalt and other raw materials are stored in the open air. When it rains or snows, the water content greatly increases, resulting in the inaccuracy of ingredients, because the above raw materials are added by weight when grinding the gun mud. In addition, the site is dusty, which pollutes the raw materials. Moreover, the raw material yard is narrow, and the mixing phenomenon sometimes occurs, such as the mixture of dry soil and asphalt. These conditions are bound to affect the performance of raw materials.
2. Influence of proportion
When the clay is dried at high temperature, it shrinks greatly and becomes dense, resulting in cracks in blast furnace slag of Jiuquan Iron and Steel Co., Ltd. when the blast furnace slag is heated and dried in the iron port, the amount of blast furnace slag is large. At about 800kg / T iron, the clay in the mud can not bear the mechanical erosion and chemical erosion of large amount of slag. The clinker powder can reduce shrinkage and dry quickly in the iron mouth mud, which is beneficial to improve the fire resistance and high temperature strength of the blast mud, and can be scoured and eroded by a large amount of slag. Therefore, the reasonable amount of dry soil and clinker powder should be considered in the proportioning.
3. effect of mud milling operation
(1) Short rolling time
After several tests, the rolling time is generally 9-10min. Due to the short rolling time, the uniformity and particle size of the mixture can not be guaranteed.
(2) Unreasonable feeding sequence
During rolling, materials are added in the following order: first, clay and asphalt are put to be pressed into powder, then coke powder and clinker powder are added to be added to be added later. This later method of adding oil can make the materials agglomerate. Some large particles may be wrapped in the aggregates, resulting in raw materials sandwiched, making the particle size of the slurry uneven and not easy to be crushed, resulting in poor plasticity of the blasting mud.
(3) The level of mud grinding equipment is not high
The level of mud grinding equipment directly affects the quality of gun mud. The main problem of the equipment of the mud mill is the poor precision, the severe wear of the surface of the roller and the plate, which causes the poor contact between the roller and the plate, and it is not easy to crush and mix the mud, so the mud quality is inevitably affected.
4. The influence of low temperature in winter
In winter, the weather is cold and the temperature is low. Due to the high softening point of anthracene oil itself and the hardening of condensation, the quality and plasticity of the clay become worse, so it is necessary to seriously solve the problem of cold and heat preservation of gun mud.
5. Weighing effect
Sometimes the weighing is not strict enough, and there is no adjustment when the weight is more or less than the specified material weight, resulting in the inaccuracy of the raw material ratio of the gun mud and the decline of the quality of the gun mud.
6. The work in front of the furnace needs to be improved
The operation in front of the furnace shall ensure that the slag iron is removed on time, which is not only beneficial to the maintenance of the iron port, but also beneficial to the smooth operation of the furnace. However, due to many accidents in front of the furnace, such as the failure of electric gun and opening machine, and the failure of iron port blocking, as well as the tension of slag iron pile from time to time, the iron tapping is not on time and the slag iron is not clean, so that the slag iron left in the hearth is floating and scattered, which makes the iron port mud bag not easy to form, This will inevitably cause the fluctuation of the depth of the iron mouth and affect the qualified rate of the iron mouth.
The effect of the amount of binder added on the performance of anhydrous gun clay:
Tar is the main binder of anhydrous gun clay and also plays a role in increasing plasticity. In use, coal tar is carbonized to form carbon bond; once the carbon bond is formed, the strength of gun mud from low temperature to high temperature can be * guaranteed. Therefore, tar can improve the slag erosion resistance and molten iron erosion resistance of anhydrous gun mud, and prolong the tapping time. However, the composition of tar is complex, the carbonization is slow, and the formation of strength takes a long time; in addition, the viscosity of tar at room temperature is large, and it is not easy to disperse evenly, which also brings difficulties to production. The problem was solved by using modified tar.
With bauxite clinker particles and coke powder as aggregate, the effect of the amount of tar added (plus) on the performance of anhydrous gun clay was studied. The amount of tar has a great influence on the performance of anhydrous gun mud. With the increase of binder content, the plasticity of anhydrous clay is better, but the bulk density is smaller, the apparent porosity is larger, the normal temperature compressive strength and flexural strength are smaller, and the linear expansion is smaller after firing. Because the anhydrous gun mud must have good plasticity when it is pressed, and it needs to have good erosion resistance and erosion resistance in the process of use, therefore, the tar in the anhydrous gun mud

Project	AL2O3, %	SiO2, %	C %	挥发分 %	灰分 %	Drying at 200 ℃		1200℃×2h
						Flexural strength, MPa	Compressive strength, MPa	Bulk strength, g / cm3	%Apparent porosity,%
Indicators	≥35	≥35	≥20	≤22	≤56	≥ 1.5	≥4	≥1.4	≤42