Production process for preventing waists and deformation of sintering machine trolley

Abstract

A production process for preventing waist collapse and deformation of a sintering machine trolley is characterized in that a ferritic nodular cast iron trolley is produced by adopting a silicon solid solution strengthening method, and cast iron comprises the following chemical components in percentage by weight: 3.55-4.0% of Si, 4.35-4.75% of CE, less than or equal to 0.3% of Mn, less than or equal to 0.07% of P, less than or equal to 0.02% of S, 0.045-0.065% of Mg and the balance of Fe and inevitable impurities; wherein CE = C + (Si + P) / 3, and C + 1 / 7Si is greater than or equal to 3.9%. The method is used for solving the problems of waisted deformation and fracture of a large trolley under the conditions of large sintering scale and thick material layer technology. The tensile strength can reach 550 N / mm < 2 > or above, the elongation can reach 12% or above, compared with an original design material QT500-7, the tensile strength is obviously improved by one mark, and the yield ratio can be improved by 20% from 0.6 to 0.75 or above. Theoretically, the trolley can resist collapse deformation and fracture under the condition of bearing high load.

Description

Technical Field

[0001] This invention relates to the field of sintering trolley technology, and in particular to a production process for preventing sintering machine trolleys from collapsing or deforming. Background Technology

[0002] The sintering machine trolley is a key component in the operation of the sintering machine. It has a complex structure and operates under harsh conditions. It must not only bear its own weight, but also the weight of the grate bars and materials, and is also subjected to the negative pressure load of the exhaust fan and the thermal load of alternating hot and cold temperatures. During use, it is prone to waist collapse deformation and even breakage. In particular, in recent years, with the increase in the scale of sintering and the development of thick-layer sintering technology, the load on the trolley has become increasingly greater. Due to the limitations of the original trolley size and structural design by the original plant structure, there is no way to significantly improve the strength of the trolley body and its resistance to deformation. The original material (QT500-7 ferritic-pearlitic mixed matrix ductile iron) is no longer able to meet the needs of the large-scale sintering and thick-layer technology development, and the problems of waist collapse deformation and breakage of the trolley have become more and more prominent. Summary of the Invention

[0003] This invention provides a production process to prevent sintering machine trolleys from collapsing and deforming, in order to solve the problem of collapse, deformation and breakage of large-scale sintering machine trolleys under large-scale sintering and thick material layer processes.

[0004] To achieve the above objectives, the present invention employs the following technical solution:

[0005] A production process to prevent sintering machine trolley collapse and deformation involves producing ferritic ductile iron trolleys using a silicon solid solution strengthening method. The chemical composition of the cast iron, by weight percentage, is: Si: 3.55%–4.0%, CE: 4.35%–4.75%, Mn≤0.3%, P≤0.07%, S≤0.02%, Mg: 0.045%–0.065%, with the remainder being Fe and unavoidable impurities; wherein CE = C + (Si + P) / 3, and the requirement is: C + 1 / 7Si ≥ 3.9%.

[0006] Due to the complex structure and uneven wall thickness of the trolley, worm-like graphite is easily generated in the thick-walled parts of the casting after the silicon content is increased. Therefore, a silicon-barium alloy inoculant is used to ensure that all parts of the trolley casting are spherical or nodular graphite with a ferrite content of ≥95%.

[0007] Three inoculation processes were employed: in-ladle inoculation, in-flow inoculation during tapping, and in-flow inoculation during casting.

[0008] Simultaneously, yttrium-based heavy rare earth spheroidizing agents are used for spheroidization treatment to prevent spheroidization decay, and the ductile iron chips are covered to control the spheroidization initiation effect, ensuring that the spheroidization rate of the internal structure of the trolley casting is ≥85%.

[0009] The tensile strength of the cast iron specimen is ≥550 N / mm². 2 The elongation is ≥12%, and the yield strength ratio is ≥0.75. The spheroidization rate of the internal structure of the trolley casting is ≥85%.

[0010] This invention breaks through the limitations of the original sintering machine design material (QT500-7) and selects a new material to replace it, so that the sintering trolley can be used under harsh conditions of high load, negative pressure, and alternating hot and cold.

[0011] The design principle of this invention is as follows:

[0012] Generally, material deformation and fracture failure occur because the force the material bears exceeds its yield strength limit. Therefore, increasing tensile strength, especially yield strength, is more beneficial for trolleys to resist waist deformation and fracture under high load conditions. Silicon plays a multifaceted role in cast iron. Firstly, it promotes graphitization and solid solution strengthening. Secondly, when the silicon content is above 3.5%, the oxidation resistance and thermal growth resistance of cast iron are greatly improved. Silicon's solid solution strengthening effect in cast iron can replace alloying elements such as copper that improve strength. For a long time, there was a misconception that high silicon content would reduce ductility and toughness. In reality, some experiments only considered changes in silicon content, ignoring the influence of other factors and unintentionally exaggerating the "brittleness" of silicon while neglecting its solid solution strengthening and other benefits. For a long time, the foundry industry has not fully utilized this potential of silicon. Silicon-enhanced solid solution strengthening can achieve high strength while ensuring high elongation after fracture. Silicon-enhanced ferritic ductile iron has a better fatigue limit than conventional ductile iron. Silicon-solution-strengthened ferritic ductile iron exhibits superior impact toughness compared to conventional ductile iron. Based on the above analysis, this invention ultimately determines to use silicon-solution strengthening to replace pearlitic alloying elements such as Cu and Sn, thereby obtaining ferritic ductile iron with superior comprehensive mechanical properties, including high strength and high elongation.

[0013] Compared with the prior art, the beneficial effects of the present invention are:

[0014] Ferritic ductile iron produced using the silicon solution strengthening method showed a tensile strength of 550 N / mm² in the attached casting samples. 2 The elongation can reach ≥12%, which is a significant improvement over the original material QT500-7, and the yield strength ratio can be increased by 20%, from 0.6 to over 0.75. Theoretically, this is more beneficial for the trolley to resist waist deformation and fracture under high load conditions. Detailed Implementation

[0015] The specific embodiments of the present invention will be further described below with reference to examples:

[0016] The chemical composition of the embodiments of the present invention is shown in Table 1; the internal structure and mechanical properties of the products of the embodiments are shown in Table 2.

[0017] Table 1 Chemical composition (wt%) of the examples

[0018]

[0019]

[0020] The inoculant used is a barium silicon alloy to ensure that all parts of the trolley casting are composed of spheroidal or nodular graphite. A three-stage inoculant process is employed: in-ladle inoculant, in-flow inoculant during tapping, and in-flow inoculant during pouring. Simultaneously, a yttrium-based heavy rare earth spheroidizing agent is used for spheroidization treatment to prevent spheroidization fading and to cover ductile iron chips to control the spheroidization initiation effect.

[0021] Table 2 Internal structure and mechanical properties of the products in the examples

[0022]

[0023] As can be seen from the data in the table, the tensile strength of the cast iron specimens in the embodiments of the present invention is ≥550 N / mm². 2 The elongation is ≥12%, and the yield strength ratio is ≥0.75. The spheroidization rate of the internal structure of the trolley casting is ≥85%. Currently, this invention has demonstrated good resistance to deformation and cracking on several large-scale and thick-layer sintering production lines in China.

Claims

1. A production process for preventing sintering machine trolley collapse and deformation, characterized in that, The ferritic ductile iron casting trolley is produced using a silicon solid solution strengthening method. The chemical composition of the cast iron, by weight percentage, is: Si: 3.55%–4.0%, CE: 4.35%–4.75%, Mn≤0.3%, P≤0.07%, S≤0.02%, Mg: 0.045%–0.065%, with the remainder being Fe and unavoidable impurities; wherein CE = C + (Si + P) / 3, and the requirement is: C + 1 / 7Si ≥ 3.9%.

2. The production process for preventing sintering machine trolley collapse and deformation according to claim 1, characterized in that, The inoculant used is a barium-silicon alloy inoculant.

3. The production process for preventing sintering machine trolley collapse and deformation according to claim 2, characterized in that, Three inoculation processes were employed: in-ladle inoculation, in-flow inoculation during tapping, and in-flow inoculation during casting.

4. A production process for preventing sintering machine trolley collapse and deformation according to any one of claims 1-3, characterized in that, Spheroidizing was performed using a yttrium-based heavy rare earth spheroidizing agent.

5. The production process for preventing sintering machine trolley collapse and deformation according to claim 1, characterized in that, The tensile strength of the cast iron specimen is ≥550 N / mm². 2 The elongation is ≥12% and the yield strength ratio is ≥0.

75.

6. The production process for preventing sintering machine trolley collapse and deformation according to claim 1, characterized in that, All parts of the trolley casting are composed of spheroidal or nodular graphite with a ferrite content of ≥95%.

7. The production process for preventing sintering machine trolley collapse and deformation according to claim 1, characterized in that, The spheroidization rate of the internal structure of the trolley casting is ≥85%.

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