Our customer had used HP400 cone crusher to crush stone， our foundry supplies cone crusher replacement parts for this customer. In the process of use, due to the extremely unstable nature of the ore and the influence of the season, the water content of the ore changes greatly, which has adversely affected the normal operation of the crusher.
Problems
The fixed cone is the main component of the HP 400 cone crusher. It is a ring structure with an inner diameter of l 156 mm, an outer diameter of l 556 mm, a height of 840 mm, and a thickness of 220 mm. There are two sets of dressing plants, which are called A and B fixed cones. In use until March 2013, two sets of fixed cones had severe cracks, the cracks were located on the inner ring surface, and the auxiliary ring stabilizing nail holes were used as nodes, which were evenly distributed and cracked longitudinally. There are 8 cracks in the fixed cone of piece A, 2 of which are larger and penetrate through the thickness direction, with a length of 540 mm and a depth of 200 mm. The other 6 cracks are about 200 mm in length and range from 100 to 150 B in. Piece B also has 8 cracks, only 1 penetrating through crack, with a length of 450 mm and a depth of 200 mm. The others are non-penetrating cracks. The dimensions are basically the same as those of Part A.
Regarding the crack of the fixed cone, technicians from foreign factories clearly stated that once the fixed cone cracked, it could not be repaired by welding and could only be replaced. Domestic technical personnel also hold the same opinion, but because there is no replacement of spare parts, they have to continue to use it. Once the crack is completely cracked, it will inevitably lead to a longer stoppage accident. Even if no accident occurs, its service life is only 20 days. After research, it was decided to repair the fixed cone crack by welding.
Solderability test
The fixed cone is subjected to huge instantaneous loads during work, and its maximum value is difficult to predict. From a structural point of view, the fixed cone is a ring structure, which is cast in one shot and has a large thickness. Therefore, the weld metal of the fixed cone must have high tensile strength and good plasticity.
The solderability test is performed in two steps. First, estimate the material composition. Due to the intellectual property rights involved, the manufacturer is strictly confidential. Use gas cutting to cut the cracks and observe the cut surface carefully. It is found that the cut surface has a thicker oxide layer, more dross, and the color is bluish. The entire cut surface is not smooth. Based on empirical analysis, the material contains more sulfur and phosphorus, about 0.045%. Judging from the combustion of the metal in cutting oxygen, the manganese content should be higher than 0.8%, the carbon content should be below 0.25%, and other trace elements are unknown. It should be a low alloy high strength steel. The oxide has a lower melting point after burning, but the fluidity is average, indicating that its cutting performance is good. The second step is to perform a solderability test. Welded fixed cone base metals with electrodes such as E4303, E 5016, and A 307. We found that the first two types of electrodes had unsatisfactory welding performance and poor weldability; A 307 had better welding performance, but tensile strength could not be guaranteed. Judging from experience, the cone has poor weldability with ordinary electrodes, but good weldability with pure nickel core austenitic electrodes.
Process selection
- Welding rods. Welds must have high tensile strength, good plasticity, and weldability. After analysis of solderability test, it was decided to choose A 507 electrode. This electrode belongs to the austenitic stainless steel series and is suitable for welding low-alloy steel, medium-alloy steel and steel under strong stress. The elongation is above 30%. It can be welded in all positions. Damage, so the V-belt can be a good compressor, with a tensile strength 10 times that of the E 5016 electrode, especially with major consumables. Large plasticity, welding fixed cone is ideal.
- Welding current .A507 welding electrode requires 20% lower welding current than ordinary electrodes. Taking into account the characteristics of the thickness of the fixed cone welding piece and the rapid heat dissipation, the welding current value is 120 to 140 A, which is 10% to 15% smaller than that of ordinary electrodes.
- Weld bevel type. Weld bevel is a combination of double-sided u-shape and single-sided u-shape.
Relieve welding stress
The fixed cone is a toroidal structure with a large wall thickness, and a large welding stress will be generated during welding. Whether the welding stress can be eliminated becomes the key to the success of the welding. If measures are taken improperly, the weld seam will crack by itself during the welding process. There are several ways to eliminate welding stress:
① Heat up the weldment as a whole, keep it cool for a certain time, and then slowly cool it down;
② Vibrate with a high-frequency oscillator;
③ Hammer the weld;
④ Use the shrinkage force of the weld itself to eliminate stress.
The mine does not have the first two conditions, so the last two methods are used to eliminate welding stress. When welding each layer of welds, each weld is performed in the order of two sides and then the middle. When welding the middle bead, the shrinkage force of the middle bead can eliminate the welding stress on both sides of the bead by more than 30%. After each welding layer is welded, heat preservation is performed for 5 min, and then the weld zone is rapidly cooled with cold water. When the interlayer temperature is below 30 ° C, hammer the weld. First, hammer both sides of the weld and then the middle. Careful hammering is required. There must be no missing hammer on the surface of the weld to ensure the complete elimination of interlayer stress. Adopting the correct welding sequence and hammering method to eliminate welding stress and ensure
Weld quality.
Comments
Post a Comment