阅读说明：本技术 一种球墨铸铁及其制备方法 (Nodular cast iron and preparation method thereof ) 是由 杜永红 董立社 张军 权国英 李保卫 *** 杜秋丽 于 2019-03-26 设计创作，主要内容包括：本发明涉及一种球墨铸铁及其制备方法,所述球墨铸铁的制备方法采用单线喂丝球化法制备球墨铸铁,所述球墨铸铁中各元素成分的质量百分比为C 3.4％-3.9％,Si 2.2％-2.8％,Mn 0.2％-0.8％,S＜0.035％,P＜0.05％,Cu 0.4％-0.8％,Cr＜0.1％,Mg 0.03％-0.08％,Re≤0.04％,余量为Fe；产品满足抗拉强度Rm≥600Mpa,屈服强度Rp<Sub>0.2</Sub>≥380Mpa,延伸率≥7％,布氏硬度190-270HB的性能要求。根据本发明提供的一种球墨铸铁及其制备方法,采用单线喂丝球化法制备球墨铸铁,制备高韧性、高强度产品,有利于提高产品的使用寿命,降低产品的整体重量,提高生产效率,降低生产成本,促进产品的轻量化发展。(The invention relates to nodular cast iron and a preparation method thereof, wherein the preparation method of the nodular cast iron adopts a single-line wire feeding spheroidization method to prepare the nodular cast iron, and the nodular cast iron comprises the following elements, by mass, 3.4% -3.9% of C, 2.2% -2.8% of Si, 0.2% -0.8% of Mn, less than 0.035% of S, less than 0.05% of P, 0.4% -0.8% of Cu, less than 0.1% of Cr, 0.03% -0.08% of Mg, less than or equal to 0.04% of Re, and the balance of Fe; the product meets the requirements of tensile strength Rm being more than or equal to 600Mpa and yield strength Rp 0.2 Not less than 380MPa, and elongation not less than7%, Brinell hardness 190-. According to the nodular cast iron and the preparation method thereof provided by the invention, the nodular cast iron is prepared by adopting a single-line wire feeding spheroidization method, so that a high-toughness and high-strength product is prepared, the service life of the product is favorably prolonged, the overall weight of the product is reduced, the production efficiency is improved, the production cost is reduced, and the lightweight development of the product is promoted.)

1. A method for preparing nodular cast iron,

the method is characterized in that:

preparing nodular cast iron by adopting a single-line wire feeding spheroidizing method;

the method comprises the following steps:

smelting, namely smelting raw molten iron by using pig iron, foundry returns, scrap steel and a carburant, adding ferrosilicon for increasing silicon in the final stage of smelting, heating to 1520-1550 ℃ for melting, preserving heat for 8-12 minutes, and then cutting off power for feeding and rapidly cooling to a tapping temperature (1490-1510 ℃) for normal tapping;

secondly, preprocessing, namely putting 0.4-0.8 wt% of Cu and 0.1-0.4 wt% of a preprocessing agent at the bottom of a spheroidizing ladle, and then normally tapping molten iron smelted in the first step into the spheroidizing ladle;

step three, spheroidizing, namely measuring the temperature of the spheroidizing bag filled with the molten iron before the spheroidizing bag is transferred to a spheroidizing chamber, entering the spheroidizing chamber, requiring the position of the spheroidizing bag to be over against a bag cover, steadily and slowly feeding the spheroidizing bag to a limiting beam, lifting the spheroidizing bag upwards, enabling the edge of the spheroidizing bag to be attached to the bag cover, and carrying out single-line wire feeding spheroidizing;

step four, inoculation treatment, namely transferring the spheroidized ladle out of a spheroidizing chamber after spheroidizing is finished, pouring an inoculant accounting for 0.4-0.7 wt% into the spheroidized ladle after slagging-off treatment, uniformly stirring, and pouring molten iron in the spheroidized ladle into a pouring ladle and transferring to a pouring station;

step five, pouring, wherein during pouring, the stream-following inoculant with the weight percentage of 0.05-0.15 percent is added along with molten iron to perform instantaneous inoculation;

and step six, cooling, after pouring, controlling the cooling time to be more than 120 minutes to manufacture the nodular cast iron with high strength, high toughness and uniform microstructure.

2. The method for preparing ductile iron according to claim 1, wherein the pig iron is 30-60% pig iron, the scrap returns are 20-40% scrap returns, the scrap steel is 20-50% high-quality scrap steel, and the ferrosilicon is 75 ferrosilicon.

3. The method of claim 1, wherein the Cu is provided by scrap copper and the pretreatment agent is a SiC pretreatment agent.

4. The method of claim 1, wherein the spheroidized core-spun yarn is a spheroidized core-spun yarn containing Mg 30.

5. The method as claimed in claim 1, wherein said inoculant is a Ba-containing inoculant.

6. The method of claim 1, wherein the stream inoculant is a Ca-containing stream inoculant.

7. The method as claimed in claim 6, wherein said Ca-containing stream inoculant is SiCa inoculant.

8. Nodular cast iron prepared by the method according to any one of claims 1 to 7, wherein the nodular cast iron comprises the following elements in percentage by mass: 3.4 to 3.9 percent of C, 2.2 to 2.8 percent of Si, 0.2 to 0.8 percent of Mn, less than 0.035 percent of S, less than 0.05 percent of P, 0.4 to 0.8 percent of Cu, less than 0.1 percent of Cr, 0.03 to 0.08 percent of Mg, less than or equal to 0.04 percent of Re and the balance of Fe.

9. The nodular cast iron of claim 8, wherein the nodular cast iron has a tensile strength Rm of 600MPa or more and a yield strength Rp_0.2380MPa or more, the elongation rate is 7% or more, and the Brinell hardness is 190-270 HB.

Technical Field

The invention relates to nodular cast iron and a preparation method thereof, in particular to an as-cast nodular cast iron axle housing material and a preparation method thereof, and belongs to industrial innovation.

Background

The birth of the automobile has a history of hundreds of years, is rapidly developed, is currently the most important vehicle in the world and is an important driving force for pulling economic growth, and is also an indispensable important component of human life. The casting is one of important components of automobile parts, and the application of the casting product on the automobile parts plays an important role. The main characteristics of the automobile casting are complex shape, thin wall thickness, high dimensional accuracy, large production batch, high required reliability and the like. To reduce the weight of the automobile as much as possible, the cast is required to be light and have high strength. In the past, the material for many automobile parts is gray cast iron, and nowadays, the material is mostly changed into nodular cast iron. Ductile iron has higher strength and better toughness than ordinary gray cast iron.

The ductile iron is a high-strength cast iron material developed in the 20 th century and the fifties, the comprehensive performance of the ductile iron is close to that of steel, and the ductile iron is successfully used for casting parts which are complex in stress and high in requirements on strength, toughness and wear resistance based on the excellent performance of the ductile iron. The term "iron as a substitute for steel" is used to refer to nodular cast iron. The cast iron is an iron-carbon alloy with a carbon content of more than 2.11%, and is obtained by high-temperature melting and casting of iron and steel such as industrial pig iron, scrap steel and the like and alloy materials thereof, and iron is removed, and carbon in other cast iron is precipitated in a graphite form, if the precipitated graphite is strip-shaped, the cast iron is gray cast iron or gray cast iron, the cast iron in a worm form is vermicular cast iron, the cast iron in a cluster-shaped, the cast iron in a sphere-shaped, the cast iron is white cast iron or nodular cast iron. The nodular cast iron is spheroidized and inoculated to obtain spheroidal graphite, so that the mechanical properties of the cast iron are effectively improved, and particularly, the plasticity and toughness are improved, so that the strength of the cast iron is higher than that of carbon steel.

At present, the spheroidizing method for producing the nodular cast iron material for casting the axle housing mostly adopts a punching method, and the production flow is as follows: and (3) bagging (nodulizer, inoculant and covering agent) → temperature measurement discharging → slag removal → inoculation and stirring → pouring → transferring to a pouring station → slag removal, temperature measurement → pouring. The spheroidizing method has simple treatment mode and equipment and easy operation, but has the problems of severe metallurgical reaction, low safety, large environmental pollution, poor mechanical property of castings and low qualification rate of high strength and high toughness of the nodular cast iron in the operation process.

Disclosure of Invention

The invention is provided for solving the problems in the prior art, and aims to provide nodular cast iron and a preparation method thereof, so as to achieve the purposes of improving the mechanical property and the service life of a product, reducing the overall weight of the product, reducing the manufacturing cost and promoting the lightweight development of the product.

In order to achieve the purpose, the invention provides nodular cast iron and a preparation method thereof, wherein the preparation method of the nodular cast iron adopts a single-wire feeding spheroidizing method to prepare the nodular cast iron, and comprises the following steps:

smelting, namely smelting raw molten iron by using pig iron, foundry returns, scrap steel and a carburant, adding ferrosilicon for increasing silicon in the final stage of smelting, heating to 1520-1550 ℃ for melting, preserving heat for 8-12 minutes, and then cutting off power for feeding and rapidly cooling to a tapping temperature (1490-1510 ℃) for normal tapping;

secondly, preprocessing, namely putting 0.4-0.8 wt% of Cu and 0.1-0.4 wt% of a preprocessing agent at the bottom of a spheroidizing ladle, and then normally tapping molten iron smelted in the first step into the spheroidizing ladle;

step three, spheroidizing, namely measuring the temperature of the spheroidizing bag filled with molten iron before the spheroidizing bag is transferred to a spheroidizing chamber, entering the spheroidizing chamber, requiring the position of the spheroidizing bag to be over against a bag cover, stably and slowly feeding the spheroidizing bag to a limiting beam, lifting the spheroidizing bag upwards to enable the edge of the spheroidizing bag to be tightly attached to the bag cover, determining the single-wire feeding length and the wire feeding speed according to the original molten iron component, the station entering temperature, the iron output and the spheroidizing core-spun wire parameters, and carrying out single-wire feeding spheroidizing;

step four, inoculation treatment, namely transferring the spheroidized ladle out of a spheroidizing chamber after spheroidizing is finished, pouring an inoculant accounting for 0.4-0.7 wt% into the spheroidized ladle after slagging-off treatment, uniformly stirring, and pouring molten iron in the spheroidized ladle into a pouring ladle and transferring to a pouring station;

step five, pouring, wherein during pouring, the stream-following inoculant with the weight percentage of 0.05-0.15 percent is added along with molten iron to perform instantaneous inoculation;

and step six, cooling, after pouring, controlling the cooling time to be more than 120 minutes to manufacture the nodular cast iron with high strength, high toughness and uniform microstructure.

The nodular cast iron comprises the following element components in percentage by mass: 3.4 to 3.9 percent of C, 2.2 to 2.8 percent of Si, 0.2 to 0.8 percent of Mn, less than 0.035 percent of S, less than 0.05 percent of P, 0.4 to 0.8 percent of Cu, less than 0.1 percent of Cr, 0.03 to 0.08 percent of Mg, less than or equal to 0.04 percent of Re and the balance of Fe.

Preferably, the pig iron is 30-60% of pig iron, the foundry returns are 20-40% of foundry returns, the scrap steel is 20-50% of high-quality scrap steel, and the ferrosilicon is 75 ferrosilicon.

Preferably, the Cu is provided by waste copper and the pretreating agent is a SiC pretreating agent.

Preferably, the spheroidized core-spun wire is a spheroidized core-spun wire containing Mg 30.

Preferably, the inoculant is a Ba-containing inoculant.

Preferably, the stream inoculant is a Ca-containing stream inoculant.

Preferably, the Ca-containing stream inoculant is a SiCa inoculant.

Preferably, the ductile cast iron meets the requirements that the tensile strength Rm is more than or equal to 600Mpa and the yield strength Rp_0.2380MPa or more, the elongation rate is 7% or more, and the Brinell hardness is 190-270 HB.

The nodular cast iron is prepared by adopting a single-line wire feeding spheroidizing method, and a high-toughness and high-strength product is prepared, wherein the tensile strength Rm of the product is more than or equal to 600Mpa, and the yield strength Rp of the product is higher than or equal to 600Mpa_0.2380Mpa or more, the elongation rate is 7% or more, and the performance requirement of 190-270HB of Brinell hardness is favorable for prolonging the service life of the product, reducing the overall weight of the product and promoting the development of light weight of the product; the single-wire feeding spheroidization method separates the spheroidization process and the inoculation process, saves the waiting time between the wire feeding and the inoculation of the spheroidized core-spun wires, is favorable for shortening the wire feeding time and reducing the production cost; the pretreatment process of the spheroidizing ladle is set, so that the metallurgical reaction is more sufficient, the pretreatment of the molten iron is realized, and the preparation is better for the subsequent spheroidizing treatment; the spheroidizing ladle is additionally arranged between the smelting furnace and the pouring ladle, so that the reaction is more sufficient, the components are more uniform, and the production efficiency is improved.

Detailed Description

Hereinafter, preferred embodiments of the present invention will be described in detail. In explaining the embodiments of the present invention, if a detailed description of known elements or functions obstructs the gist of the present invention, a detailed description thereof will be omitted.

A single-wire feeding spheroidizing method is used for producing the axle housing of the high-strength and high-toughness nodular cast iron QT 600-7.