研究 & 高強度・高靭性ダクタイル鋳鉄素材の風力発電用鋳物材料への応用

In order to obtain low-temperature ductile iron materials with higher strength and toughness, alloying elements Ni and Nb were added to the QT400-18AL material for alloying. Through the tests of the mechanical properties, metallographic structure, low-temperature impact energy and fatigue performance of the samples, it can be known that Ni and Nb alloying can significantly improve the mechanical properties of QT400-18AL material. その間, by using this alloyed QT400-18AL material, the dual goals of improving the quality of castings and reducing costs have been achieved.

Advantages of Nodular cast iron

Nodular cast iron,with wear resistance shock absorption, is not sensitive to gaps, and the characteristics of the casting performance, and lower production cost, short production cycle, it is an ideal material for wind castings. 現在のところ, the dimensions of wind power castings are increasing as wind turbine units continue to become larger and heavier. The cross-sectional thickness of some parts has exceeded 200 mm. The solidification and cooling rate of thick and large-section castings is slow, which easily leads to poor shape and a small quantity of spherical graphite and even causes problems of fragmented graphite. The matrix structure will also form severe composition segregation, resulting in the generation of a large number of carbides that are difficult to eliminate even through long-term heat treatment. さらに, the castings have coarse grains and are more prone to defects such as black spots and shrinkage porosity.

近年では, generally adoption the strict control of chemical composition, improving the casting process after heat treatment, especially the forced cooling measures, such as to improve the organization, has had a good effect. しかし, it is almost impossible to enhance the quality of wind power ductile iron parts merely by improving processes and equipment, especially without increasing costs. 現在のところ, domestic wind power uses ductile iron casting materials mainly for qt400-18 al; its mechanical performance is the tensile strength of 360 MPa, yield strength of 220 MPa or greater, or more break elongation 12.5% 以上, そして 30 ℃ minimum impact absorbing energy of: 10 J (on average) そして 7 J (single). The materials of high-strength ductile iron castings applied abroad are solid-solution strengthened ferrite materials EN-GJS-500-14 and EN-GJS-600-10, and their mechanical properties are much higher than those of QT400-18AL. しかし, this material has no requirements for low-temperature impact energy, and its application in the wind power field poses risks. したがって, it is necessary to develop a high-strength, high-toughness and low-temperature ductile iron material for wind power castings.

The technicians try to improve the wind power by using the method of alloying with the strength and toughness of ductile iron castings to reduce the casting size and thick solution caused by the slow cooling rate of castings and the thick casting quality problem. 1, the alloying materials formula nodular cast iron is of great help to improve the mechanical properties of, however, wind power castings for low-temperature impact energy requirements. したがって, the added alloying elements need to be comprehensively considered.

Mainly in qt400-18 al material, on the basis of adding alloy elements of Ni, Nb, and Zr three elements; they basically have the following advantages: (1) Ni can reduce nodular cast iron brittle transition temperature, adding a certain amount of can improve the low-temperature performance of nodular cast iron. (2) the Nb is widely used in metallurgical industry, to increase the Nb can improve the mechanical properties of nodular cast iron, and does not affect its performance in low temperature. (3) Increasing a small amount of Zr can have the effect of DNA, purifying and refining grain, and is advantageous to the low-temperature performance of nodular cast iron.

1.The specific formula is shown in Table 1

Table 1 Material Formula (Mass Fraction, %)

2.Material trial production

2.1 material preparation

(1) adding iron, back to the furnace charge and scrap steel furnace for iron smelting.

(2) to increase carbon of liquid iron, the carbon content of control satisfies the requirement of table 1.

(3) after carburization of the liquid iron spheroidization and inoculation and alloying processing: according to table 1 quality percentage of Nb and Ni; Zr was added through silicon-zirconium inoculants.

(4) the ball, inoculation and alloying processing of iron liquid after pouring, wind power castings with high strength and high toughness ductile iron material.

2.2 try block test block size: 300 mm * 300 mm * 300 mm, と 70 mm thick test block. The pouring and unboxing conditions are shown in Figures 1 そして 2.

3. Test results

3.1 機械的性質

The test was conducted in accordance with “GB/T 228-2002 Test Method for Tensile Testing of Metallic Materials at Room Temperature”, and the results are shown in Table 2.

Table 2 機械的性質

サプライヤー

洛陽豊洋重工業株式会社, 株式会社,1998年に設立された鉄道鋳造部品のメーカーです。当社の工場面積は72,600㎡です。, 以上の 300 従業員, 32 技術者, 含む 5 シニアエンジニア, 11 アシスタントエンジニア, そして 16 技術者.

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