TPT July 2011

A rticle

The content of high-price alloy elements are raised in new composition design, but the cost increased by the above mentioned reason is significantly lower when compared to a cheap casting process with an expensive forging process. The price of high chromium alloy cast straightening pipe roll, HFW/ ERW welding pipe roll and cold roll forming steel roll are only 1 / 3 – 1 / 2 of price of D2, X155CrVMo121 and SKD11 forging steel roll. The price is lower than Cr12MoV forging steel roll produced at home and is equal with ordinary forging alloy steel roll produced at home. The successful research and development of high chromium alloy casting formed process can decrease energy consumption, increase utilisation factor of raw material, simplify production process, reduce production period and save production cost. High chromium alloy steel pipe straightening roll, HFW/ERW welding pipe roll and cold roll forming steel roll have been used in more than ten advanced production lines of steel pipe and cold roll forming steel at home and abroad over the last ten years. The result has proved that the service life is up to the level of D2, X155CrVMo121 and SKD11 forging steel roll and is two times as long as X165CrMoV12KU and 9Cr2MoV forging steel roll, is three times as long as 3Cr2W8V, Cr12 and GCr15 forging steel roll. Now high chromium alloy roll has been the first selected roll for steel pipe straightening, and has achieved good feedback after being used in the mills of HFW/ERW welding pipe and cold roll forming steel in China and abroad. The high chromium alloy roll used in the biggest production line of stainless steel welding pipe in China can overcome the defects of stick steel and scratching on steel pipe face, which is presented in traditional forging steel roll producd at home. The high chromium alloy roll used in 500×500×20mm square steel pipe mills, which is in biggest demand in China, can effectively ensure the product’s quality of rolled steel pipe, and the rolls have been used more than five years and still continuous now. 3.2 Compared with sample property Separate sampling from X155CrVMo121 finished steel pipe straightening roll, D2 finished steel pipe straightening roll, SKD11 finished welding pipe roll, high chromium alloy steel pipe straightening roll (casting state, eliminated stress temper), high chromium alloy welding pipe roll (quenching and temper state), sliced along roll face to inside hole. The serial number is A. B. C. D. E. See figure 4. 3.2.1 Compared with hardness and quenching degree To do hardness test to sliced sample along outside to inside, the results are as follows. 3. Compared with properties 3.1 Compared with utilisation properties

Figure 3: Welding pipe roll exported to Oman and India

The successful research and development of special sand mould can raise casting quality. On the basis of some questions of complex shape, more size and small batch of roll and poor cast properties of high chromium alloy material Shandong have explored and innovated new cast processes and it can achieve high quality forming of complex shape roll. From the outside feature of welding pipe roll exported to Oman and India we can see that the roll possessed of big differential size section and special-shaped section is difficult to cast by traditional cast methods. 2.2.3 Researching and developing of heat treatment and machining process According to differential working condition and differential composition high chromium alloy has designed a different heat treatment process. Through practice and continuous revision over many years, the heat treatment system in series has been formed, they can guarantee the good property of roll. High chromium alloy has excellent quenching degree and the quenching depth as air quenching is 300mm. No ready-made production line can be introduced for machining high chromium roll, so machining process, drilling holes process, screwing process and devices are all designed by Shandong. 2.3 Compared with manufacturing processes Casting formed or forging formed roll block are two different manufacturing methods. The casting block compared with forging block is still close to a product’s shape, so it can effectively increase the utilisation factor of raw material, greatly decreasing energy consumption. The high chromium alloy casting formed process is simple compared to forging tool steel formed process, which is traditional process at home and abroad. This process can save the forging process and reduce the manufacturing period. Compared with the forging process of low alloy tool steel at home, every ton of finished roll can save 1.4 ton standard coal and 350 kilowatt-hour power.

Figure 4: Five kinds of rolls after sampling

128

J uly 2011

www.read-tpt.com

›