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Yuan Lei tells you what principles should be followed in the ratio of castable aggregate, powder and binder?

Release time:

2024-01-29 09:37

 

Yuan Lei tells you what principles should be followed in the ratio of castable aggregate, powder and binder?

 

  • What are the characteristics of refractory castable compared with fired brick?

 

Answer: refractory castable is essentially refractory concrete. Compared with fired refractory bricks, refractory casting materials have the following characteristics in performance:

(1) The load softening temperature is much lower than that of homogeneous refractory bricks.

(2) The linear expansion coefficient is small, and the sintering shrinkage effect of the binder during heating can offset the expansion of a part of the aggregate during heating.

(3) The resistance to temperature changes is good, and the number of cold and heat exchanges can be more than 15 times, which is better than homogeneous refractory bricks.

(4) The reburning line is generally larger than the refractory brick.

(5) The overall performance is better than that of refractory masonry.

  • How many methods are there for building a furnace with refractory castables? What are the conditions for on-site pouring?

 

Answer: There are two construction methods of commonly used refractory castables; one is directly wound and tamped on site, and the other is prefabricated. There are three situations of direct casting and tamping on site: integral casting and tamping (such as small chamber furnace); Partial casting and tamping (such as the top of heating furnace) and partial casting and tamping or repair (such as leveling of walls and arches with difficult bricklaying operations).

  • What are the principles for the proportioning of castable aggregate, powder and binder?

 

Answer: The preparation principle of refractory castable is to reasonably select the particle gradation, ultra-fine powder and admixture varieties and their dosage.

The large amount of refractory aggregate depends on the thickness of the engineering lining, generally 10mm or 5mm, and its particle gradation is: 10~5mm is 40% ~ 50%,5~3mm is 20% ~ 30%,3~0.1mm is 20% ~ 30%; or 5~3mm is 40% ~ 60%,3~1mm is 20% ~ 30%,1~0.15mm is 15% ~ 25%. Generally, three or four gradations are used to achieve maximum bulk density. The amount of refractory aggregate is 68% ~ 72%.

The dosage of refractory powder is 18% ~ 25%, in which the dosage of high-grade material is 5% ~ 10%, the dosage of refractory ultrafine powder is 2% ~ 12%, and the total dosage of refractory powder and ultrafine material is 28% ~ 32%.

  • How to determine the plastic index in the field construction?

Answer: Small fire-resistant plastic with suitable plastic index can be kneaded into a ball by hand. No water is secreted, and it does not touch hands and is not loose.

  • How many kinds of ramming materials? How to ramming construction?

Answer: There are two kinds of ramming materials: hot ramming and cold ramming.

During construction, first remove dirt or derusting, apply binder, then lay materials in layers (100mm thick) and pound in layers. Partitions (strips or sections) shall be pounded back and forth for 2-3 times with a wind key, one hammer pressing half hammer or 1/3 hammer. When hot tamping is used, the hammer head shall be heated to dark red (the hammer head is divided into large, medium and small), and the wind pressure shall not be less than 0.5MPa. The upper and lower material layers shall be staggered at a certain angle, and the pounding shall be carried out continuously at one time to prevent delamination. The surface of each stubble shall be "chiseled" or brushed with adhesive, and then laid and pounded.

  • What method is used to identify the quality of pounding?

Answer: The compression ratio test method for sampling is used to identify the quality of tamping. The formula is

Compression ratio = press-down thickness/loose paving thickness × 100%

In the formula, the pressing thickness is the thickness of the loose laying thickness after tamping.

  • What are the construction steps and process requirements for furnace wall castable plus anti-wear boss technical measures?

Answer:(1) chisel off the castable on the heating surface of the furnace water wall and the castable at the separation of the water wall by 100mm to expose the water wall. During the chiseling process, strict attention should be paid to avoid hurting the base material of the water wall tube and chisel off the fixing pin on the water wall.

(2) Weld φ8mmlCr18Ni9Ti heat-resistant steel bars on the upper fin tube at the separation between the castable on the heating surface of the water wall around the furnace and the water wall as required. The steel bars shall be welded into horizontal and vertical steel nets, and the welding shall be firm and reliable. The current should not be too large during welding, and the water wall tube should be protected during welding.

(3) Clean up the castable on the heating surface of the water wall around the furnace and the pins welded at the separation of the water wall and the castable part chiseled off, and purge it with compressed air. Brush 2mm thick bitumen primer at the pin.

(4) The castable on the heating surface of the water wall around the furnace and the upper and lower pins at the separation of the water wall shall be poured with refractory plastic. The pouring construction shall be carried out in strict accordance with the construction process of refractory plastic. The surface of the arc surface shall be smooth and smooth, and the thickness of the castable shall exceed the pin by 2~6mm. Sufficient expansion joints shall be reserved at every 500mm.

(5) The size of the boss is 200mm high, 270mm wide, triangular, and the outermost height is 50mm.

 

 

 

 

 

Aggregate, refractory, castable, water cooling, thickness, forming, dosage, welding, pin, construction

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