阅读说明：本技术 一种铸态全铁素体球墨铸铁材料生产工艺 (Production process of as-cast full-ferrite nodular cast iron material ) 是由 苗昕旺 马宇 臧玉郡 刘希德 李常金 李金红 王丹丹 宋佳健 孙明 于 2019-10-19 设计创作，主要内容包括：一种铸态全铁素体球墨铸铁的生产工艺,以生铁、废钢、硅铁、增碳剂、球化剂、孕育剂和随流孕育剂做为铁水冶炼原料,放入在中频炉进行熔化,获得前样铁水；对球化处理包进行烤包作业,装入球化剂、孕育剂和铁屑,保温,将铁水冲入球化处理包中；铁水完全冲入球化处理包后,扒渣,然后进行浇注,在浇注的同时加入随流孕育剂进行随流孕育,得到铸态全铁素体球墨铸铁。优点：工艺简单,操作方便；通过增加球墨铸铁中硅元素的含量,进行固溶处理,铸态得到100％铁素体基体金相组织和超高的韧塑性。(A production process of as-cast full-ferrite nodular cast iron comprises taking pig iron, scrap steel, ferrosilicon, a carburant, a nodulizer, an inoculant and a stream inoculant as molten iron smelting raw materials, and putting the molten iron smelting raw materials into an intermediate frequency furnace for melting to obtain a sample molten iron; carrying out ladle baking operation on the spheroidizing ladle, loading a nodulizer, an inoculant and scrap iron, preserving heat, and pouring molten iron into the spheroidizing ladle; and after the molten iron is completely flushed into the spheroidizing ladle, slagging off, then pouring, and adding a stream inoculant for stream inoculation while pouring to obtain the as-cast full-ferrite nodular cast iron. The advantages are that: the process is simple and the operation is convenient; by increasing the content of silicon element in the nodular cast iron and carrying out solid solution treatment, the metallographic structure of a 100% ferrite matrix and ultrahigh toughness and plasticity are obtained in an as-cast state.)

1. A production process of as-cast full-ferrite nodular cast iron is characterized by comprising the following steps:

The method comprises the following specific steps:

(1) ingredients

The molten iron smelting raw materials comprise the following components in percentage by weight: 58 to 65 percent of pig iron, 29 to 36 percent of scrap steel, 2.5 to 3.35 percent of ferrosilicon, 0.4 to 0.5 percent of carburant, 1.15 percent of nodulizer, 1.0 percent of inoculant and 0.1 percent of stream-following inoculant;

(2) molten iron

Smelting the molten iron smelting raw materials in an intermediate frequency furnace, sampling and detecting molten iron components obtained by smelting when the smelting temperature reaches 1510-1530 ℃ for 10 minutes, so that the mass content of C in the molten iron is 3.3%, the mass content of Si in the molten iron is 2.6%, and obtaining the former molten iron;

(3) baking bag treatment

before packaging, baking the spheroidized processing bag at the temperature of 400-450 ℃;

(4) Inoculation treatment

before packaging, baking nodulizer, inoculant and scrap iron at 400 ℃ and keeping the temperature for 1 hour; putting a nodulizer accounting for 1.15 percent of the total mass of the molten iron, an inoculant accounting for 1.0 percent of the total mass of the molten iron and scrap iron accounting for 0.65 percent of the total mass of the molten iron after baking into a casting ladle, paving and tamping the mixture, and then pouring the front sample molten iron in the step (2) into the casting ladle;

(5) pouring treatment

controlling the temperature of molten iron to be 1380-1440 ℃ for pouring, after the molten iron is completely poured into a casting ladle, slagging off the ladle, removing all slag, covering a deslagging agent, starting pouring, adding 0.1% stream-following inoculant during pouring, and finishing pouring to obtain the as-cast full-ferrite nodular cast iron.

2. the process for producing as-cast full-ferritic spheroidal graphite cast iron according to claim 1, characterized by: the pig iron component C is more than or equal to 4.0 percent by mass, the S content i is less than or equal to 0.4 percent by mass, the Mn content is less than or equal to 0.10 percent by mass, the P content is less than or equal to 0.025 percent by mass, the S content is less than or equal to 0.02 percent by mass, the Ti content is less than or equal to 0.03 percent by mass, and the balance is Fe.

3. The process for producing as-cast full-ferritic spheroidal graphite cast iron according to claim 1, characterized by: the mass content of C in the scrap steel component is less than or equal to 0.6 percent, the mass content of Si is less than or equal to 0.4 percent, the mass content of Mn is less than or equal to 0.3 percent, the mass content of P is less than or equal to 0.02 percent, the mass content of S is less than or equal to 0.015 percent, and the balance is Fe.

4. The process for producing as-cast full-ferritic spheroidal graphite cast iron according to claim 1, characterized by: the ferrosilicon is available in the grades of FeSi75-B and FeSi 75-C.

5. The process for producing as-cast full-ferritic spheroidal graphite cast iron according to claim 1, characterized by: the nodulizer is an Eken 5800 nodulizer; the mass content of the carburant C is more than or equal to 99.5 percent, and the mass content of N and S is less than or equal to 0.05 percent in total.

6. the process for producing as-cast full-ferritic spheroidal graphite cast iron according to claim 1, characterized by: the inoculant is an Angen calcium barium inoculant with the granularity of 3-8 mm; the stream inoculant is an Ekenan oxysulfide inoculant with the granularity of 0.2mm-0.7 mm.

7. the process for producing as-cast full-ferritic spheroidal graphite cast iron according to claim 1, characterized by: the mass content of Mn in the components in the molten iron sample before the step (2) is less than or equal to 0.15 percent, the mass content of S is 0.006-0.018 percent, and the mass content of p is less than or equal to 0.03 percent.

8. the process for producing as-cast full-ferritic spheroidal graphite cast iron according to claim 1, characterized by: the cast full-ferrite nodular cast iron in the step (5) comprises 3.0-3.2% by mass of C, 3.6-3.8% by mass of Si, less than or equal to 0.15% by mass of Mn, 0.006-0.018% by mass of S, less than or equal to 0.03% by mass of p, 0.03-0.055% by mass of Mg and less than or equal to 0.02% by mass of Re.

9. the process for producing as-cast full-ferritic spheroidal graphite cast iron according to claim 1, characterized by: the whole pouring completion time in the step (5) is less than 10 min.

10. the process for producing as-cast full-ferritic spheroidal graphite cast iron according to claim 1, characterized by: the base structure of the as-cast full-ferrite nodular cast iron is 100% ferrite.

Technical Field

the invention relates to a production process of as-cast full-ferrite nodular cast iron.

Background

The QT500-7 nodular cast iron has good strength and toughness and good machinability, and is mostly used for key parts such as axle boxes of rail transit parts. At present, the strength required by the performance index of the domestic QT500-7 nodular cast iron is not less than 500MPa, the yield is not less than 320MPa, the elongation is not less than 7 percent, and the metallographic structure is ferrite and pearlite. The performance of the traditional rail transit part material is improved, the material is more suitable for the high-speed development of rail transit in China, and the toughness and plasticity are very important while the strength is considered.

disclosure of Invention

The invention aims to solve the technical problem of providing a production process of as-cast full-ferrite nodular cast iron, wherein the nodular cast iron does not need heat treatment, the metallographic structure of the as-cast nodular cast iron obtained after solid solution solidification is full-ferrite, the elongation after fracture is mostly improved while the normal strength is ensured, and the elongation after fracture can reach between 20 and 20.5 percent.

the technical solution of the invention is as follows:

A production process of as-cast full-ferrite nodular cast iron comprises the following specific steps:

(1) ingredients

The molten iron smelting raw materials comprise the following components in percentage by weight: 58 to 65 percent of pig iron, 29 to 36 percent of scrap steel, 2.5 to 3.35 percent of ferrosilicon, 0.4 to 0.5 percent of carburant, 1.15 percent of nodulizer, 1.0 percent of inoculant and 0.1 percent of stream-following inoculant;

(2) molten iron

smelting the molten iron smelting raw materials in an intermediate frequency furnace, sampling and detecting molten iron components obtained by smelting when the smelting temperature reaches 1510-1530 ℃ for 10 minutes, so that the mass content of C in the molten iron is 3.3 percent and the mass content of Si in the molten iron is 2.6 percent, and obtaining the former sample molten iron;

(3) Baking bag treatment

before packaging, baking the spheroidized processing bag at the temperature of 400-450 ℃;

(4) Inoculation treatment

Before packaging, baking nodulizer, inoculant and scrap iron at 400 ℃ and keeping the temperature for 1 hour; putting a nodulizer accounting for 1.15 percent of the total mass of the molten iron, an inoculant accounting for 1.0 percent of the total mass of the molten iron and scrap iron accounting for 0.65 percent of the total mass of the molten iron after baking into a casting ladle, paving and tamping the mixture, and then pouring the front sample molten iron in the step (2) into the casting ladle;

(5) Pouring treatment

Controlling the temperature of molten iron to be 1380-1440 ℃ for pouring, after the molten iron is completely poured into a casting ladle, slagging off the ladle, removing all slag, covering a deslagging agent, starting pouring, adding 0.1% stream-following inoculant during pouring, and finishing pouring to obtain the as-cast full-ferrite nodular cast iron.

Furthermore, the pig iron component C is more than or equal to 4.0 percent, Si is less than or equal to 0.4 percent, Mn is less than or equal to 0.10 percent, P is less than or equal to 0.025 percent, S is less than or equal to 0.02 percent, Ti is less than or equal to 0.03 percent, and the balance is Fe.

Furthermore, the scrap steel component C is less than or equal to 0.6 percent, Si is less than or equal to 0.4 percent, Mn is less than or equal to 0.3 percent, P is less than or equal to 0.02 percent, S is less than or equal to 0.015 percent, and the balance is Fe.

Further, the grade of the ferrosilicon is FeSi75-B and FeSi75-C according to GB2272-87 standard.

further, the nodulizer is an Angen 5800 nodulizer, Si is 44-48%, Mg is 5.55-6.15%, Re is 0.85-1.15%, Ca is 0.80-1.20%, and Al is 1.0% max; the carburant brand SQ-ZT-09 has a C content of more than or equal to 99.5 percent and a total mass content of N and S of less than or equal to 0.05 percent.

Further, the inoculant is an Eken calcium barium inoculant with the granularity of 3-8 mm; the stream inoculant is an Ekenan oxysulfide inoculant with the granularity of 0.2mm-0.7 mm.

Furthermore, the former sample molten iron contains 3.3 percent of C, 2.6 percent of Si, less than or equal to 0.15 percent of Mn, 0.006-0.018 percent of S and less than or equal to 0.03 percent of p.

Further, the components of the as-cast full-ferrite nodular cast iron in the step (5) are 3.0-3.2 percent of C, 3.6-3.8 percent of Si, less than or equal to 0.15 percent of Mn, 0.006-0.018 percent of S, less than or equal to 0.03 percent of p, 0.03-0.055 percent of Mg and less than or equal to 0.02 percent of Re.

Further, the base structure of the as-cast full-ferrite nodular cast iron is 100% ferrite.

Further, the whole pouring completion time in the step (5) is less than 10 min.

The invention has the beneficial effects that:

simple process and convenient operation. The nodular cast iron is subjected to solid solution solidification by increasing the content of silicon element in the nodular cast iron without heat treatment, and the metallographic structure and ultrahigh toughness and plasticity of a 100% ferrite matrix are obtained in an as-cast state; the obtained elongation after fracture is mostly improved while the normal strength is ensured, and the elongation after fracture can reach between 20 and 20.5 percent.

drawings

FIG. 1 is a 100-fold gold phase diagram after etching in example 1 of the present invention;

FIG. 2 is a 100-fold gold phase diagram after etching in example 2 of the present invention;

FIG. 3 is a 100-fold gold phase diagram after etching in example 4 of the present invention;

FIG. 4 is a 100-fold gold phase diagram after etching in example 3 of the present invention;

FIG. 5 is a 100-fold gold phase diagram after etching in example 5 of the present invention;

FIG. 6 is a 100-fold gold phase diagram after etching in example 6 of the present invention;

FIG. 7 is a tensile force deformation curve of example 1 of the present invention;

FIG. 8 is a tensile force deformation curve of example 2 of the present invention;

FIG. 9 is a tensile force deformation curve of example 3 of the present invention.

Detailed Description

the standard requirements of the pre-sample molten iron and the index ranges of the full-ferrite nodular cast iron products in the embodiments 1 to 6 of the invention are implemented according to the following table:

TABLE 1 Standard requirements for forebody iron

Composition (I)

C％

Si％

Mn％

P％

S％

Mg% (the remainder)

RE% (for the remainder)

Range of

3.3

2.6

≤0.15

≤0.003

0.006-0.018

0.03-0.055

＜0.02

TABLE 2 index ranges for full ferritic spheroidal graphite cast iron products

Composition (I)

C％

Si％

Mn％

P％

S％

Mg% (the remainder)

RE% (for the remainder)

range of

3.0-3.2

3.6-3.8

≤0.15

≤0.003

0.006-0.018

0.03-0.055

＜0.02

。