阅读说明：本技术 一种厚大件用固溶强化铁素体球墨铸铁的制备方法 (Preparation method of solid solution strengthened ferritic nodular cast iron for thick and large parts ) 是由 王小磊 程淦昌 陈思 杨正银 贺献峰 于 2018-07-26 设计创作，主要内容包括：一种厚大件用固溶强化铁素体球墨铸铁的制备方法,包括如下步骤：(1)生铁与废钢加热至1460～1520℃熔化,并通过添加增碳剂调整C元素含量至3.0～4.0％,(2)选用盖包球化法对铁液进行球化,球化剂加入量为原铁液重量的1.0～2.0％,球化的同时加入Ce和Sb金属元素；(3)球化孕育包制备时球化剂紧时,在球化剂的上方均匀覆盖粒径为3～8mm的75SiFe孕育剂；(4)加入0.04～0.1％的TiC和TiN混合纳米粉末,并加入原铁液重量0.004-0.008％的Bi合金；(5)浇注时随流孕育；(6)铁液冷却后即得强化铁素体球墨铸铁。本发明孕育结束后,添加TiC、TiN的纳米粉末和Bi元素,使得球墨铸铁的抗拉强度和延伸率增加；本发明的制备工艺简单、可以降低厚大件的整体质量,成本低、易于实现工业化生产。(A preparation method of solid solution strengthened ferritic nodular cast iron for thick and large parts comprises the following steps: (1) heating pig iron and scrap steel to 1460-1520 ℃ for melting, and adjusting the content of C element to 3.0-4.0% by adding carburant, (2) spheroidizing the molten iron by a covering spheroidizing method, wherein the adding amount of the spheroidizing agent is 1.0-2.0% of the weight of the original molten iron, and Ce and Sb metal elements are added during spheroidizing; (3) when a nodulizer is tight during preparation of the spheroidized inoculant ladle, uniformly covering 75SiFe inoculant with the grain diameter of 3-8 mm above the nodulizer; (4) adding 0.04-0.1% of TiC and TiN mixed nano powder, and adding Bi alloy accounting for 0.004-0.008% of the weight of the original molten iron; (5) stream inoculation is carried out during pouring; (6) and cooling the molten iron to obtain the strengthened ferrite nodular cast iron. After inoculation is finished, nano powder of TiC and TiN and Bi elements are added, so that the tensile strength and the elongation of the nodular cast iron are increased; the preparation method has the advantages of simple preparation process, low cost and easy realization of industrial production, and can reduce the overall quality of thick and large parts.)

1. A preparation method of solid solution strengthened ferritic nodular cast iron for thick and large parts is characterized by comprising the following steps:

(1) adding pig iron and scrap steel into a medium-frequency induction furnace, heating to 1460-1520 ℃ for melting, detecting the content of carbon in molten iron after all the molten iron is melted, adding a carburant to adjust the content of C to 3.0-4.0% to form raw molten iron, and controlling the tapping temperature of the molten iron to 1520 +/-10 ℃;

(2) spheroidizing inoculation is carried out on the molten iron by a covering spheroidizing method, the adding amount of a spheroidizing agent is 1.0-2.0% of the weight of the original molten iron, and Ce and Sb metal elements are added during spheroidizing;

(3) when the nodulizer is tight during preparation of the spheroidized inoculant packet, uniformly covering the nodulizer with a grain size of 3-8 mm;

(4) adding TiC and TiN mixed nano powder accounting for 0.04-0.1% of the weight of the original molten iron into a spheroidizing inoculation ladle, and adding Bi alloy accounting for 0.004-0.008% of the weight of the original molten iron;

(5) stream inoculation is carried out during pouring, and the pouring temperature is 1400-1420 ℃;

(6) cooling the molten iron to obtain the strengthened ferrite nodular cast iron;

the inoculant is 75 SiFe;

the total addition amount of the inoculant is 1.0-2.0% of the weight of the original iron liquid;

the nodulizer is rare earth magnesium.

2. The method for preparing the solid solution strengthened ferritic spheroidal graphite cast iron for the thick and large parts according to the claim 1, characterized in that the mass ratio of the pig iron to the scrap iron is 0.75: 0.25; the carbon content of the pig iron is 4.2 percent, and the carbon content of the waste iron is 0.2 percent.

3. The method for preparing the solid solution strengthened ferritic spheroidal graphite cast iron for the thick and large parts according to claim 1, characterized in that the carbon content of the carburant is 96%, and the Mn content is 0.28%.

4. The method for preparing the solid solution strengthened ferritic spheroidal graphite cast iron for the thick and large parts according to claim 1, characterized in that the Si content of 75SiFe is 75-77%, and the Ca content is 0.6-0.8%.

5. The method of claim 1, wherein the rare earth magnesium has a Si content of 46%, a Mg content of 6%, and an Sb content of 0.1%.

6. The method for preparing the solid solution strengthened ferritic nodular cast iron for thick and large parts according to claim 1, wherein the mixing ratio of TiC to TiN is 3:1 by mass, and the grain size of the nano powder is 100-150 nm.

7. The method for preparing the solid solution strengthened ferritic spheroidal graphite cast iron for the thick and large parts according to claim 1, characterized in that the inoculant added in the step (3) accounts for 20-30% of the total amount; and (5) adding the rest of inoculant during stream inoculation.

8. The method for preparing the solid solution strengthened ferritic nodular cast iron for thick and large parts according to claim 1, characterized in that the amount of the Ce and Sb metal elements added in the step (2) is 0.008-0.012% and 0.006-0.010% of the mass of the original molten iron respectively.

Technical Field

The invention relates to the field of preparation of ferritic nodular cast iron, in particular to a preparation method of solid solution strengthened ferritic nodular cast iron for thick and large parts.

Background

With the development of wind power generator projects around the world, the wind power generator project is taken as a core component in the wind power project: the parts such as the hub, the base, the shaft and the like are made of ferrite nodular cast iron materials which are selected along with the severe geographical conditions, and the performance requirements are higher.

Many wind power ferrite nodular cast iron parts are thick and large parts (the wall thickness is larger than 60mm), however, the thick and large parts of nodular cast iron are easy to produce broken graphite in the cooling process due to slow cooling speed and long eutectic solidification time, and the performances of tensile strength, elongation and the like of the nodular cast iron can be obviously reduced.

The general cast nodular cast iron such as QT400-18, QT450-10, QT500-7, QT600-3, QT700-2 and other brands can not meet the requirements of thick large parts in comprehensive properties such as tensile strength, elongation and the like, and the QT600-10 has better tensile strength and extensibility.

The invention patent CN 103710612A discloses a production method of an as-cast ferrite-based nodular cast iron QT600-10, and the invention patent CN104120332A discloses a high-strength high-toughness nodular cast iron 600-10 and a production process thereof, the nodular cast iron produced by the technical schemes of the two patents has lower tensile strength or elongation, and the technical scheme does not provide a solution aiming at the strength and the elongation of a heavy nodular cast iron casting.

Disclosure of Invention

In view of the problems in the prior art, the invention aims to provide a preparation method of solid solution strengthened ferritic nodular cast iron for thick and large parts, which can improve the strength and the elongation of the prepared thick and large parts ferritic nodular cast iron.

In order to achieve the purpose, the invention is realized by the following technical scheme:

a preparation method of solid solution strengthened ferritic nodular cast iron for thick and large parts comprises the following steps:

(1) adding pig iron and scrap steel into a medium-frequency induction furnace, heating to 1460-1520 ℃ for melting, detecting the content of carbon in molten iron after all the molten iron is melted, adding a carburant to adjust the content of C to 3.0-4.0% to form raw molten iron, and controlling the tapping temperature of the molten iron to 1520 +/-10 ℃;

(2) spheroidizing inoculation is carried out on the molten iron by a covering spheroidizing method, the adding amount of a spheroidizing agent is 1.0-2.0% of the weight of the original molten iron, and Ce and Sb metal elements are added during spheroidizing;

(3) when the nodulizer is tight during preparation of the spheroidized inoculant packet, uniformly covering the nodulizer with a grain size of 3-8 mm;

(4) adding TiC and TiN mixed nano powder accounting for 0.04-0.1% of the weight of the original molten iron into a spheroidizing inoculation ladle, and adding Bi alloy accounting for 0.004-0.008% of the weight of the original molten iron;

(5) stream inoculation is carried out during pouring, and the pouring temperature is 1400-1420 ℃;

(6) and cooling the molten iron to obtain the strengthened ferrite nodular cast iron.

The inoculant is 75 SiFe;

the total addition amount of the inoculant is 1.0-2.0% of the weight of the original iron liquid;

the nodulizer is rare earth magnesium.

Further, the adding mass ratio of the pig iron to the scrap iron is 0.75: 0.25; the carbon content of the pig iron is 4.2 percent, and the carbon content of the waste iron is 0.2 percent.

Further, the carbon content in the recarburizing agent is 96%, and the Mn content is 0.28%.

Furthermore, the Si content of the 75SiFe is 75-77%, and the Ca content is 0.6-0.8%.

Further, the rare earth magnesium has a Si content of 46%, a magnesium content of 6%, and an Sb content of 0.1%.

Further, the mass mixing ratio of TiC to TiN is 3:1, and the particle size of the nano powder is 100-150 nm.

Further, the inoculant added in the step (3) accounts for 20-30% of the total amount; and (5) adding the rest of inoculant during stream inoculation.

Furthermore, the amount of Ce and Sb added in the step (2) is 0.008-0.012% and 0.006-0.010% of the mass of the original molten iron respectively.

The beneficial effects of the invention include:

sb is rare earth which interferes graphite spheroidization, when rare earth magnesium is selected as a spheroidizing agent, and the content of Sb is 0.007-0.012%, the nodular cast iron has a certain spheroidization effect, so that the number of graphite spheres is increased, Sb and added Ce can easily form a high-melting-point stable compound which is used as a heterogeneous core of the nodular cast iron, the number of the graphite spheres is increased, the content of the pearlite of the nodular cast iron is favorably improved, and the tensile strength of a matrix is improved.

After inoculation is finished, the nano particles of TiC and TiN with the mass ratio of 3:1 and the particle size of 100-150nm are added, the nano TiC and TiN can promote continuous dendritic crystals of austenite, the size of graphite nodules is reduced by adding Bi, and the system is easy to form austenite grains with stable structure and uniform density, so that the tensile strength and the elongation of the nodular cast iron are increased.

The preparation method has the advantages of simple preparation process, low cost and easy realization of industrial production, and can reduce the overall quality of thick and large parts.

Detailed Description

The present invention will be further described with reference to examples, but the present invention is not limited to these examples.