Failure Cause Analysis And Solution Of Blast-Furnace Distribution Chute

The main failure factors of SLIP tank in blast furnace include: (1) Impact damage due to high feed flow drop; ② the sliding wear of the material on the lining board; ③ shell burning and cavitation; ④ Weld cracking, bolt shearing, matrix tearing due to thermal stress.

Preventing the failure of fabric trough and ensuring the reliability and long life of fabric trough are mainly considered from two aspects: one is the internal structure and the other is the material selection.

1 Structure selection

From the structural point of view, the fabric trough has two main structural forms: one is the accumulation (abrasive) type and the other is the smooth surface type.

1) Slotted fabric trough is mainly composed of slotted plate, wear-resistant alloy block, matrix plate, heat insulation material and shell plate. The basic principle is to arrange a certain number, height and Angle of grid plates at the feed points inside the feed trough to form a small cavity that can store a certain charge. After the first blanking, a certain amount of loose charge is stored in the cavity to form a nest, which avoids the direct impact of subsequent charge on the internal shell of the slip tank. A wear-resistant alloy is surfacing on the surface of the dimpling board, and a wear-resistant alloy block is inlaid on the bottom of the dimpling board and the lower part of the distributing trough.

(1) The advantages of nesting fabric trough :① make up for the defects of high hardness and poor toughness of cemented carbide structure, which greatly extends the service life of fabric trough; (2) It avoids the direct impact of feed flow on the wear-resistant part of the slip, greatly reduces the harm of the secondary impact, and has good controllability of feed flow; (3) In the case of parallel canning bell top, the cushioning and decelerating effect of the accumulator type feed trough greatly reduces the elliptical feed phenomenon caused by misalignment of feed flow.

(2) The disadvantages of nesting fabric trough :① the structure design is difficult and the production process is complex; ② Large volume, heavy weight. It is estimated that the service life of this type of feed tank (based on 2500 BF characteristic parameters) can reach more than 36 months. This has been proved in practice.

2) Smooth fabric slip can be divided into surfacing welding type and assembly type according to the structure of the wear-resistant part.

The prefabricated fabric trough consists of a cast base and removable segmented prefabricated liners, presses, and fasteners. Under normal circumstances, the substrate can be used for a long time, only need to replace the liner. Each liner can also be interchanged according to the degree of wear to extend the service time.

The fabric slip with surfacing structure is fabricated by surfacing wear-resistant material on the surface of the casting matrix. Surfacing can be repaired according to the degree of wear. Whether it is a slotted structure or a smooth surface structure, the fabric slipway outlet must have sufficient smooth length to ensure that the charge flows out of the slipway cylindrical bus instead of moving randomly.

2. Selection of materials

1) The material selection of fabric slip is mainly considered in two parts, one is the matrix and the other is the wear-resistant part. The selection of matrix materials from the current point of view, basically there is no big problem, usually choose heat-resistant steel, whether it is cast or sheet molding, can meet the strength and stiffness and prevent the need for thermal deformation at high temperatures. The burn-through and cavitation of the matrix can be achieved by adding refractory fiber or refractory lining protection to the outside of the matrix. At present, the main problem is the selection of wear-resistant materials.

2) The long life of fabric trough requires the use of wear-resistant materials to have good wear resistance and impact toughness. These are contradictory demands. At present, hardness is generally used to measure the wear resistance index, and for the now known materials, the higher the hardness means the worse the toughness. Therefore, it is unrealistic to solve the wear-resistant problem of fabric slip by relying solely on materials. At present, the main materials used in the wear-resistant parts of the slip are cemented carbide, which are mainly cast (including surfacing) and sintered. The strength and hardness of the as-cast cemented carbide are much lower than that of the sintered type.