Nodular cast iron section bar capable of improving fracture toughness and technology

A ductile iron and fracture toughness technology, which is applied in the process field of ductile iron profiles, can solve the problems of poor fracture toughness and other problems, and achieve the effects of avoiding crack initiation, high roundness and large quantity.

Inactive Publication Date: 2019-10-18
HANDAN HENGGONG METALLURGICAL MACHINERY CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The presence of graphite is easy to initiate cracks in the structure of cast iron profiles, and the fracture toughness is poor

Method used

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  • Nodular cast iron section bar capable of improving fracture toughness and technology
  • Nodular cast iron section bar capable of improving fracture toughness and technology
  • Nodular cast iron section bar capable of improving fracture toughness and technology

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0045] Example 1: A ductile iron profile with improved fracture toughness, the mass percentage ranges of carbon, silicon, manganese, sulfur, phosphorus and bismuth in the ductile iron profile are: carbon: 3.45%-3.55%; silicon: 2.55%-2.65 %; Manganese: 0.15%-0.25%; Sulfur: 0.009%-0.011%; Phosphorus: 0.030%-0.034%; Bismuth: 0.009%-0.0011%; the rest is iron. The graphite balls in the structure of the ductile iron profile are small and numerous, and have high roundness. The round and fine graphite balls have relaxation stress, which can delay the expansion of cracks and achieve the effect of avoiding crack initiation.

[0046] Based on the above components and mass percentage ranges, a ductile iron profile with improved fracture toughness is selected and produced, wherein the mass percentages of carbon, silicon, manganese, sulfur, phosphorus and bismuth are respectively: carbon: 3.50%; silicon: 2.60; manganese: 0.22%; Sulfur: 0.010%; Phosphorus: 0.032%; Bismuth: 0.01%; the rest is...

Embodiment 2

[0047] Example 2: Select and produce a ductile iron profile (QT400 material) that improves fracture toughness. Choose to produce on the No. 3 line of Hebei Henggong Machinery Equipment Technology Co., Ltd., three production lines are produced at the same time, and a trace amount of metal bismuth is added in the spheroidization process to refine the shape of graphite, increase the number of graphite balls, and reduce the diameter of graphite. Include the following steps:

[0048] (1) For the smelting of molten iron, a 6-ton and a 10-ton intermediate frequency induction furnace is used to smelt the molten iron. The weight of the molten iron is 1.6-1.7 tons / bag, according to the mass ratio of pig iron Q10: scrap steel: returned rod / The iron filings are weighed at 20:65:15 and the ingredients after the furnace are weighed. The molten iron formed after smelting the ingredients after the furnace contains less sulfur. Due to the ductile iron containing sulfur, it is easy to make th...

Embodiment 3

[0056] Intercept the QT400 material produced in Example 2 Nodular cast iron section, observe the metallographic structure of the section under a microscope of 100 times, and obtain the metallographic structure image 3 , and the microstructure of the fractured ductile iron without adding pure metal bismuth figure 2 contrast, from figure 2 and 3 The comparison shows: figure 2 The number of graphite balls is small, the graphite balls are larger, and the graphite grade is grade 5, that is, the diameter of the graphite balls is about 6-12mm. and image 3 The number of graphite balls increased significantly, the graphite balls are smaller, the graphite grade is 7, that is, the diameter of the graphite balls is about 1.5-3mm, the matrix structure is uniformly refined, and the graphite grade is significantly improved. Therefore, the matrix structure of the ductile iron profile added with pure metal bismuth has a better stress relaxation effect, which slows down the propagati...

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Abstract

The invention discloses a nodular cast iron section bar capable of improving the fracture toughness. The nodular cast iron section bar comprises, by mass, 3.45%-3.55% of carbon, 2.55%-2.65% of silicon, 0.15%-0.25% of manganese, 0.009%-0.011% of sulphur, 0.030%-0.034% of phosphorus, 0.009%-0.0011% of bismuth and the balance iron. Graphite nodules in the section bar structure are small, large in quantity and high in roundness, the round and small graphite nodules have the relaxation stress and have the effect of delaying crack propagation, and the effect of preventing cracks from being generatedis achieved. The invention further discloses a technology for the nodular cast iron section bar capable of improving the fracture toughness. The metal bismuth is added into iron liquid, therefore, the quantity of the graphite nodules is increased, the declination speed in the inoculation process is decreased, abnormal graphite generated in the quick cooling process is eliminated, and the roundness of the graphite nodules can be improved. Meanwhile, size grading of the graphite nodules is improved, the plasticity of the nodular cast iron is obviously improved on the condition that the strengthof the nodular cast iron is invariable, and then the nodular cast iron has the good fracture toughness.

Description

technical field [0001] The invention belongs to the technical field of cast iron materials and casting metallurgy, in particular to a ductile iron profile with improved fracture toughness, and also relates to a process for a ductile iron profile with improved fracture toughness. Background technique [0002] Compared with sand casting, horizontal continuous casting has faster cooling rate and finer grains. Graphite has the characteristics of small diameter, large quantity and higher roundness. The graphite balls in cast iron are like cavities, and the damage to the material is mainly manifested in the splitting of the matrix, resulting in stress concentration and crack sources. The existence of graphite is easy to initiate cracks in the structure of cast iron profiles, and the fracture toughness is poor. [0003] However, because the microcracks in the preamble of crack propagation have the effect of evacuating energy during the expansion process, there are many microcrack...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C37/10C22C37/04C22C33/08C21C1/10
CPCC21C1/105C22C33/08C22C37/04C22C37/10Y02P10/20
Inventor 魏志勇王敬民孔令伟
Owner HANDAN HENGGONG METALLURGICAL MACHINERY CO LTD
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