The Study of Inner Surface Crack Formation of Seamless Modified 9Cr-1Mo Tube Rolled on Mandrel Mill and Its Application

The hot workability of modified 9Cr-1Mo, as a grade of heat resistant steels, is inferior to that of low-alloy steel, so the inner surface crack (ISC) easily occurs in seamless boiler tubes produced by the Mandrel Mill under improper rolling conditions. With the aid of FEM, the metal flow status during the rolling process was analyzed in 140mm 8-stand mandrel mill of Bao Steel. Both the metallographic shape and size of the ISC together with the result from the simulation show that the ISC of seamless tube forms at the elongation stage of shell. The mechanism of the ISC was discussed. With its initiation in stand No.1 and No.2 due to poor hot workability of modified 9Cr-1Mo steel, the ISC develops in subsequent passes. Based upon the mechanism devised was a special roll pass system which substantially upgraded the yield of qualified products.

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Mechanical Analysis on the Inner Surface Crack of Modified 9Cr-1Mo Seamless Steel Tubes Rolled by Mandrel Mill

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.97-101.3070 ◽

2010 ◽

Vol 97-101 ◽

pp. 3070-3074

Author(s):

Sheng Zhi Li ◽

Jie Xu ◽

Yuan De Yin ◽

Hui Chao Su

Keyword(s):

Surface Crack ◽

Production Efficiency ◽

Circumferential Stress ◽

Rolling Process ◽

Mechanical Analysis ◽

Steel Tube ◽

Roll Pass ◽

Steel Tubes ◽

Inner Surface ◽

Seamless Steel

The inner surface crack (ISC) defect easily occurs in seamless modified 9Cr-1Mo steel tubes rolled by the mandrel mill with high production efficiency. The reason for the formation of the ISC lies in both the properties of deformed material and rolling conditions. With the aid of commercial FE code MSC.SuperForm, the rolling process of modified 9Cr-1Mo seamless steel tube produced by the Mandrel Mill of Bao Steel in China was simulated, focusing on mechanical analysis of deformed metal. It was found from the simulation that the metal on the inner surface of the tube, in the position of 0 or 90 of the roll pass, experiences strong tensile stresses, especially the circumferential stress, which is closely related .to the strain behavior governed by the two-high pass caliber of the mandrel mill. Therefore an optimal design of the roll pass can be realized to decrease the tensile stress so as to relax the tendency to the ISC, which has been confirmed by the tests in Steel Tube & Pipe Company of Bao Steel.

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Research on Design Method of Polygonal Roll Pass for Stretch Reduced Seamless Tubes

Materials Science Forum ◽

10.4028/www.scientific.net/msf.654-656.1614 ◽

2010 ◽

Vol 654-656 ◽

pp. 1614-1617 ◽

Cited By ~ 2

Author(s):

Sheng Zhi Li ◽

Hai Yan Bao ◽

Zhi Chao Zhang ◽

Yang Hua Li ◽

Gong Ming Long

Keyword(s):

Wall Thickness ◽

Design Method ◽

Element Model ◽

Rolling Process ◽

Contact Length ◽

Transverse Wall ◽

Roll Pass ◽

Steel Tubes ◽

Pass System ◽

Lateral Curvature

the aid of commercially available software MSC.SuperForm, a 3-D finite element model has been established to simulate the rolling process of steel tubes on the stretch reducing mill (SRM) with group centralized differential drive in certain factories. A special effort was made to analyze the fluctuation of transverse wall thickness uniformity. It was found that the wall thickness of each stand was accumulated in the original pass 50°~60° along the circumferential direction, which caused the formation of the inner hexagon defects and worsen. In view of this, this paper proposes a modified roll pass design method which uses the interactive technology of CAD graph curve and MATLAB equation. By means of decreasing the lateral curvature of roll pass contour curve to enlarge the contact length between the tube and groove, also the rolling process using the new pass system were simulated and analyzed. The results indicate that the design of such polygonal roll pass can be effective in improving the inner hexagon defects.

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Increasing the Durability of Separating Rolls During Rolling Ribbed Bars in the Three-Strand Technology

Archives of Metallurgy and Materials ◽

10.1515/amm-2017-0236 ◽

2017 ◽

Vol 62 (3) ◽

pp. 1535-1540 ◽

Cited By ~ 1

Author(s):

D. Strycharska ◽

P. Szota ◽

S. Mróz

Keyword(s):

Numerical Modelling ◽

Experimental Tests ◽

Rolling Process ◽

Production Volume ◽

Roll Pass Design ◽

Pass Design ◽

Roll Pass ◽

Band Shape ◽

Groove Surface ◽

Pass System

Abstract The paper presents the results of investigations aimed at enhancing the durability of slitting passes in the process of three-strand rolling of 16 mm-diameter ribbed bars. Using the Forge2011® computer program, numerical modelling of the rolling process was carried out in order to examine the variations in band shape in individual rolling passes, to verify the correctness of the designed new slitting pass system, to determine the local strains in the rolled band, and then to determine the distribution of unit friction force work on the roll groove surface. From the obtained investigation results it was found that the application of the new roll pass design in stands 13-16 increased their durability in the rolling process by approx. 30%. The wear of the roll sets for the stands under examination after rolling out the annual 16 mm-diameter bar production volume was determined in the study. The obtained numerical modelling results were verified in experimental tests.

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The Study of Inner Surface Crack Formation of Seamless Modified 9Cr-1Mo Tube Rolled on Mandrel Mill and Its Application

Materials Science Forum - PRICM 6 ◽

10.4028/0-87849-462-6.61 ◽

2007 ◽

pp. 61-64 ◽

Cited By ~ 1

Author(s):

S.Z. Li ◽

Jie Xu ◽

Y.D. Yin ◽

J.G. Xue ◽

Y. Feng

Keyword(s):

Surface Crack ◽

Crack Formation ◽

Inner Surface

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The Chosen Aspects of Skew Rolling of Hollow Stepped Shafts

Materials ◽

10.3390/ma14040764 ◽

2021 ◽

Vol 14 (4) ◽

pp. 764

Author(s):

Jarosław Bartnicki ◽

Yingxiang Xia ◽

Xuedao Shu

Keyword(s):

Cross Section ◽

Rolling Mill ◽

Metal Flow ◽

Experimental Tests ◽

Rolling Process ◽

Numerical Control ◽

Technological Parameters ◽

Flow Mechanisms ◽

The Individual ◽

Skew Rolling

The paper presents chosen aspects of the skew rolling process of hollow stepped products with the use of a skew rolling mill designed and manufactured at the Lublin University of Technology. This machine is characterized by the numerical control of spacing between the working rolls and the sequence of the gripper axial movement, which allows for the individual programming of the obtained shapes of parts such as stepped axles and shafts. The length of these zones and the values of possibly realizable cross-section reduction and obtained outlines are the subject of this research paper. The chosen results regarding the influence of the technological parameters used on the course of the process are shown in the present study. Numerical modelling using the finite element method in Simufact Forming, as well as the results of experimental tests performed in a skew rolling mill, were applied in the conducted research. The work takes into account the influence of cross-section reduction of the hollow parts and the feed rate per rotation on the metal flow mechanisms in the skew rolling process. The presented results concern the obtained dimensional deviations and changes in the wall thickness determining the proper choice of technological parameters for hollow parts formed by the skew rolling method. Knowledge about the cause of the occurrence of these limitations is very important for the development of this technology and the choice of the process parameters.

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The Effect of Process Parameters in Helical Rolling of Balls on the Quality of Products and the Forming Process

Materials ◽

10.3390/ma11112125 ◽

2018 ◽

Vol 11 (11) ◽

pp. 2125 ◽

Cited By ~ 4

Author(s):

Janusz Tomczak ◽

Zbigniew Pater ◽

Tomasz Bulzak

Keyword(s):

Metal Flow ◽

Experimental Tests ◽

Rolling Process ◽

Helical Rolling ◽

Forming Process ◽

University Of Technology ◽

Quality Of Products ◽

Skew Rolling

This paper presents selected numerical and experimental results of a skew rolling process for producing balls using helical tools. The study investigates the effect of the billet’s initial temperature on the quality of produced balls and the rolling process itself. In addition, the effect of billet diameter on the quality of produced balls is investigated. Experimental tests were performed using a helical rolling mill available at the Lublin University of Technology. The experiments consisted of rolling 40 mm diameter balls with the use of two helical tools. To determine optimal rolling parameters ensuring the highest quality of produced balls, numerical modelling was performed using the finite element method in the Forge software. The numerical analysis involved the determination of metal flow kinematics, temperature and damage criterion distributions, as well as the measurement of variations in the force parameters. The results demonstrate that the highest quality balls are produced from billet preheated to approximately 1000 °C.

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