TPT May 2021

AR T I C L E

Shandong Province Sifang Technical Development Group

Fourthly, new type sizing roll has exceptional wear resistance and, at the same time, it has high alloying that prevents the C, Fe galvanic cell from come into being. Therefore the new type sizing roll has better corrosion resistance, so its pass surface is very bright after being machined or used, which is good to help improve the surface quality and precision of steel tubes. Fifthly, the price of new type sizing rolls is not much higher than that of traditional sizing rolls, which brings better price ratio because its service life is longer. Sixthly, taking environment protection into consideration the delivery time of new type sizing rolls is more secure. In China the government makes increased efforts to protect the environment and presents more and more strict requirements to foundry plants, thus many foundry processes are not permitted, therefore some foundry plants have been shut down and some are facing the risk of being shut down at any time. The new Sifang Group foundry processes avoid pollution factors such as smoke and dust during spheroidising of nodular cast iron and, at the same time, with necessary dust removal, noise reduction and other environment protection, facilities can ensure that the foundry process is favorable for the environment and that the foundry production is proceeding normally as well as meeting high customer demands for rolls. Since the advent of the new type sizing roll more than two years ago, it has been adopted by BAOSTEEL, TPCO, Yantai Lubao Steel Pipe Co Ltd, Hengyang Valin Steel Tube Co Ltd, Jiangsu Changbao, Boly Pipe Co Ltd, API Engineering Ltd and many others. Sifang Group also co-operates with the research institute of BAOSTEEL, working on solving technical issues relevant to the application of new type sizing roll and doing further promotion of the rolls. Internationally renowned steel pipe and tube manufacturers such as Tenaris and TMK have also expressed their interests based on general knowledge of new type sizing rolls. Hauffe & Kamper from Germany has already purchased a batch of sizing rolls for trial use. Sifang Group is confident that it will be able to popularise the new type high chromium semi-steel sizing rolls for steel pipe and tube manufacturers worldwide in a short period. As well as high chromium alloy straightening rolls and rolls for welding steel pipe high chromium semi-steel sizing, the rolls will be another high quality product. Sifang Group aims to create a national brand that produces competitive products with proprietary intellectual property rights and will continue to work hard and to innovate in order to provide better quality products and services to steel pipe and tube manufacturers in the world.

Shandong Province Sifang Technical Development Group

Bright working surface of new type sizing roll & reducing roll after use

on the working stand and finished stand were significantly improved according to the statistics collected, which showed an improvement ranged from 30 per cent to three times. Roll hardness is between 38HRC and 52HRC, the specific hardness of rolls will be controlled according to roll size and usage requirements, σb is 400-550MPa and αk is 4.5-6.0J/cm 2 . The hardness of new type sizing roll is not much higher than nodular cast iron roll, but its wear resistance is enhanced because its structure improved via high alloying and heat treatment. Its carbide content is 20-25 per cent, which is M7C3 type with micro hardness 1500-1800HV. Its matrix structure is tempering martensite and a small amount of residual austenite, which has micro hardness 500-600HV. Since the material is high alloying the new type sizing roll’s matrix and M7C3 carbide have good red hardness so it keeps good high temperature wear resistance. With the varieties of steel pipes developed from single carbon steel to alloy steel, stainless steel and special alloy steel the requirements for tools and moulds are getting higher and higher. More and more steel pipe manufacturers can fully benefit from the outstanding wear resistance of the new type sizing rolls. Secondly, new type sizing rolls have only a very slight hardness drop and ensure the same quality from working surface to core area. Today many steel tube manufacturers still use traditional rolls like chilled cast iron roll and chilled nodular cast iron roll. Normally the white chill emerges with roll surface chilling. The chill zone has high hardness and good wear resistance, but its thickness is small. Considering that the sizing roll will be machined many times in use, as for large size rolls it will be cutting 100mm to 200mm on the surface during machining thus the hardness will drop a lot. Consequently the wear resistance and service life will decrease remarkably. The new type sizing roll adopts whole body heat treatment and the hardness drop is small, which ensures that the roll performance is stable. Commonly the hardness drop is between 1HRC and 2HRC (4-6 HSD). Thirdly, it has good machining performance to meet the high requirements of the production site. Since the hardness of new type sizing rolls is not much higher than that of traditional sizing rolls, its machining performance is not too bad compared to nodular cast iron rolls, therefore the problem regarding machining efficiency can be fully resolved. The problem of difficulty in machining and low turning efficiency faced in processing high speed steel, hard alloy and high chromium will not emerge again.

Shandong Province Sifang Technical Development Group – China sdsf@vip.163.com www.cnsdsf.com

71

www.read-tpt.com

MAY 2021