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Pressing mechanism: mainly through worm gear, worm, gear, drive rod rotation to achieve synchronous adjustment of roll seam up and down. Both the operating side and the transmission side can be adjusted at the same time, or the connecting shaft can be disconnected for unilateral adjustment. Under the joint action of machinery, hydraulic pressure and electric apparatus, the roller gap can be accurately adjusted remotely.
Box (roll assembly) : the rolling mill can be divided into two parts, the transmission side and the fixed side, each of which is composed of two boxes. The four boxes bear the radial force and axial force transmitted by the rolling mill bearing, and pass it to the tie rod to form the stress loop. The box and rod of the mill are the main working parts of the mill. The box of the driving side of the mill is free end, which only bears radial force; The operating side box is equipped with four rows of bearings to bear radial force and a thrust bearing to bear axial force; The upper box of the operating side is equipped with worm gear and worm mechanism for axial adjustment, and the adjustment amount is mostly ±3mm; The lower roller can not be adjusted axially (see the lower pull rod assembly for this part). The four rows of short cylindrical bearings in the box mainly bear radial forces.
Pull rod and box assembly: pull rod and copper nut are the main working part of the mill force, the condition of this part of the equipment will directly affect the quality of the product and the control of the production process. The rolling mill moves the upper and lower boxes symmetrically through the rotation of the copper nut installed on the tie rod, so as to realize the symmetric adjustment of the rolling roll gap. The biggest advantage of this adjustment method is that the rolling line is stable and unchanged, which can avoid the rolling and quality accidents caused by the misalignment of the rolling line and the pass center line, greatly reduce the dependence on the technical level of the rolling mill adjuster, and simplify the rolling process. Thus, the purpose of reducing rolling accidents and improving product accuracy is achieved. The elastic deformation caused by the copper nut, press ring, ring and the clearance of the whole box installed on the tie rod and the tension rod is the main reason for the rolling mill to produce "bounce". Eliminating "bounce" is the main measure to improve the rolling stability, and also an important means to improve the utilization rate of rolling groove and product quality. The elimination of "bounce" is mostly achieved by disc spring, hydraulic pressure and damping body. "Bounce" is an important index to evaluate the working performance of short stress line rolling mill. The size and control level of the bounce will directly reflect whether the mill can meet the quality requirements of high-end products.
Mill Base: The rod of the rolling mill is fixed on the base through the middle frame. The main job is to fix the mill base to the rolling line by four locking cylinders fixed on the foundation. The base of the mill is not subjected to rolling force, but only to tipping force. The working media such as oil, water and gas required in rolling production are provided to each part of the rolling mill through the water, oil and gas interfaces on the quick connecting plate. The base of the rolling mill is shown in Figure 6. In this part of the mill base, there are two aspects that need special attention, the first is the pin hole. The pin hole is not only the connection between the mill and the output shaft of the reducer, but also a safety part that must be checked and maintained regularly. The second is the fast connection board. The joints on the quick connection plate must be checked frequently and replaced in time to avoid water, oil and gas leakage, which will cause serious consequences.
Fault analysis:
There are many reasons for bearing damage, such as:
incorrect installation; Bearing force is too large;
Insufficient lubricating oil; Seal failure; Spare parts processing error;
The "bounce" of the rolling mill body is large, and the impact force is too large when the rolling piece bites.
Roll neck size machining error, resulting in inner sleeve cracking or "playing circle";
Bearing performance can not meet the requirements of use.
How to avoid bearing burn? Here is just to discuss the sealing failure, the biggest consequence of sealing failure is the leakge of bearing lubrication oil, pollutants into the bearing, aggravate bearing wear, and then bearing "burn". So what are the causes of seal failure?
The first is the sealing selection. Since the mill is often disassembled, the seal must be sealed with a secondary lip, and the direction cannot be reversed to ensure that the lubricating oil or lubricating oil is sealed well;
Secondly, when assembling the rolling mill, it is necessary to adjust or observe the height of the roll before assembling, so as to avoid damage to the seal; The third is to replace regularly, damaged at any time. The use time of the seal is too long, the seal lip and the dynamic maze joint form a gap, the oil leaks when using oil and gas lubrication (grease is relatively better), and the pollutants such as water and oxide sheet enter the bearing, damaging the bearing, making the bearing life shorten or "burn".
The main problems of Pull rod and roll assembly In addition to the above mill bearing "burn", there are some common accidents (accident causes do not include process aspects) :
1: Axial channeling. Cause: tie rod positioning device failure; Thrust bearing gland and bearing clearance greater than 0.2 mm; Thrust bearing wear greater than 0.2 mm; Single equipment gap or momentum of no more than 0.2 mm to meet the GB/T702-2008 in the two groups of standards.
2: Rolling mill "bounce" large. Cause: hydraulic balance cylinder failure (or balance failure); Ring, pressure ring, end cap wear, break; Copper nut wear, bearing clearance is too large.
3: Abnormal rotation of the tie rod. Cause: the rack copper sleeve falls off; Copper nut position change; The axis of the upper roll and the lower roll have included angles; The tie rod seal fails and the oxide sheet enters; The copper nut screw buckle is damaged.
4: The frame copper sleeve falls off: the output shaft of the reducer is affected; Copper sleeve wear; The relative position of tie rod, box and frame is changed; The fastening bolt is loose.