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Nodular Cast Iron Support Roller For Sinopec Successfully Manufactured

Support Roller is a key part of rotary kiln, which is widely used in cement and metallurgical mining machinery. Due to the huge alternating compressive stress and hundreds of tons of load, the working environment is very bad, so its quality requirements are very strict. At present, cast steel is usually used for support wheel at home and abroad. Compared with ductile iron, cast steel has higher strength and better impact toughness, but its shock absorption, wear resistance, notch sensitivity and other properties are poor. Because the properties of nodular cast iron are close to that of cast steel, it has good castability, low cost and excellent shock absorption and wear resistance.
In October 2020, Sinopec commissioned us to transform its Φ7.2m large rotary kiln support roller from the original cast steel to ductile iron, so as to reduce the weight of supporting roller, enhance its shock absorption and wear resistance, and improve the operation stability and efficiency of the whole rotary kiln. The first batch of trial production of 2 pieces, if the quality inspection meets the standard, Sinopec will change all the supporting wheels of rotary kiln equipment to ductile iron.
Substituting iron for steel has the advantages of low cost and short production cycle, which has become an important development direction of manufacturing roller. As early as the 1970s, the International Foundry Technology Committee has listed heavy section ductile iron as one of the key casting technology problems at that time. After decades of development, although many important progresses have been made in the basic practice of heavy section ductile iron, the control of its microstructure and properties is still the key problem in the research and production of heavy section ductile iron.
The maximum wall thickness of the support roller with large section is 415mm. It is difficult for the roller to have complete shape, accurate size, no casting defects inside, compact structure, up to standard graphite spheroidization rate and excellent mechanical properties. Therefore, we carefully design the manufacturing process and organize the production.

1.Basic Information Of Support Roller

the maximum outer diameter is 1300 mm, the height is 760 mm, the maximum wall thickness is 415 mm, the gross weight is 7.5 T, and the material grade is QT700-2.

2.The Mechanical Properties Of The Cast Sample Are As Follows

HB280-320,Rm≥650MPa,Rp0.2≥380MPa,A≥1%.

3.Testing Standard For Support Roller

the casting quality is accepted according to GB/T1348-2009, and the spheroidization grade of the casting is up to grade 3 according to GB/T 9441-2009;

4.Casting Process Design Of Support Roller

Casting process design is very important. To obtain high quality supporting wheel, the first step is to ensure the complete stamping die, then to ensure that there are no surface and internal casting defects, and to achieve no micro casting defects, compact structure and good performance.

5. The Rationality Of ProCAST Simulation Process

The results show that the cross-section of supporting roller is thick, the solidification time is long, the graphite morphology in the center of wall thickness and hot spot is easy to deteriorate, and the defects of shrinkage cavity and porosity are easy to occur. Manufacturing is very difficult. In order to produce qualified castings, ProCAST simulation software was used to simulate the solidification process and temperature field of nodular cast iron supporting roller, predict the possible defects and take corresponding improvement measures.

6.Casting Process Of Nodular Cast Iron Support Roller

The casting process of nodular cast iron roller includes resin sand mold making, smelting, pouring and nodularizing treatment. Each step must be strictly controlled according to the process parameters, especially the nodularizing treatment must be strictly controlled. Only time and temperature can guarantee the shape and quantity of nodular cast iron.

7. Support Roller Casting

After careful process design, accurate process parameter control and rich production organization experience, the shape of the supporting roller casting is complete, there is no casting defects, and rough machining and NDT are needed to detect the internal quality.

8.Suport Roller Inspection

the casting needs UT, and the UT is up to grade 3 according to en12680-3-2011; the coloring testing is up to grade 3 according to en1371-1-2011. The flaw detection parts are all machined surfaces.

9.Metallographic Analysis Of Nodular Cast Iron Spport Roller

Metallography is based on the test results of cast samples attached to the body of spport roller.


Distribution of graphite spheres in low power optical microscope	Normalize P-base + G-ball	Annealed F + G spheres	As cast (P + F) base + G ball ox eye shape

Three dimensional morphology of spheroidal graphite

10. Finished Products Of Support Roller After Machining

Through the correct process design and strict production control of the roller products.The results show that the hardness, yield strength and elongation are up to the standard; the spheroidization rate is 85%, and the shape distribution of graphite spheres reaches grade 3; the P content is 90%, and the amount of phosphorus eutectic is 0.5,After machining, the finished product quality of supporting roller is excellent, which has accumulated important process parameters for Sinopec to replace supporting roller of cast steel rotary kiln in batches.