Uzbekistan’s state-owned enterprise, located in Bekabad, built a large steel production enterprise in the Soviet Union in 1944, and now it produce steel, building insulation materials, daily enamel consumer goods. The annual output of steel is 700,000 tons with 2 production lines for bars and 1 high-line production line.
Our company designed pre-cut composite rolls (19&20&21 stand) for the No. 1 and No. 2 bar production lines, and provided five set of composite rolls, which have been used well. In April, the customer suddenly reported that there was a horizontal cross crack in the roller ring, and provided the rolling record and photos. Our engineers immediately conducted a seminar and get a preliminarily judge that the temperature of the composite roller roller was too high, causing the roller ring burst ,and the same time,require customer provided a photo of the water pressure gauge at the time of production running. It has not been provided all the time and customer invited our engineers to discuss with the steel mill engineer at site,and hope to negotiate on problems and avoid in the future.
In order to solve problems quickly for steel enterprises and avoid similar problems happen again, our company decided to arrange engineers to go to Uzbekistan immediately. After confirming the itinerary with customer, we arrived in Uzbekistan in May and immediately inspected the site once we arrived. Rolling mill stand,rolled material, production specifications, production process and so on,on-site viewing of the customer’s process of replacing the cooling water pipe and the bearing. The exclusion method was used to judge the possible causes:
1> bearing installation, the bearing has a temperature warning system, exclude bearing causes the roller to heat up.
2> cooling water pipe, on-site inspection of pipe diameter, nozzle diameter and number,no problem
3> When start the production line, open the cooling water firstly ,then start to mill.no problem.
4> At site,we found that the water pressure was 0.38Mpa in the main pipe,when the cooling water comes to the rolling mill pipe,it must be less than 0.4Mpa, and the standard requirement was 0.4-0.6Mpa.
5>composite roller repair modulus requires more than 2mm, but according to customer use record table, the last two repair modulus is only 1.7mm
Combined with the transverse cracks appearing in the roller ring, and the experience of domestic and foreign use, the reason we confirmed is that the water pressure is insufficient, the cooling effect is not good, the heat generated by the rolling is not dissipated in time, the thermal expansion coefficient of the roller is higher than the roller ring,thermal expansion causes the roller ring to cross crack.
After discussions with the chief engineer and technical leader of the Uzbekistan rolling mill, the idea was finally unified as below:
1> Install a water pressure gauge at the mill location to monitor water pressure in real time
2>Improve water pressure and strive to meet water pressure requirements of 0.4-0.6Mpa
3>Due to the special position of the use position, the repair amount is guaranteed 3-4mm
4>repair damaged composite roller
Since the customer did not have the disassembly ability, the final agreement was reached to transport the composite roller to our factory for maintenance and replacement.
It is the first time for our company to return the repair of the composite roller of foreign customers, which lays a foundation for providing faster and more efficient services to foreign customers in the future. At the same time, it also solves the hidden dangers of the composite roller for oversea small steel enterprises.
We once again remind our customer that the importance of water pressure and water volume ,it not only avoid this problem, but also keep a high-quality use environment for composite rolls ,and will bring benefits to steel enterprises. We are always striving for excellence and quality. LMM hope that we could make more contributions to Uzbekistan steel companies with our joint efforts.