1. A high-strength gray cast iron multi-element low-alloying treatment method is characterized by comprising the following steps:

determining the components and proportion of furnace burden in the high-strength gray iron casting, the matching method and content range of various alloy elements and the content range of conventional chemical elements according to the requirements of the casting to be produced;

b, determining a melting process procedure of the high-strength gray iron casting;

preparing materials, charging materials and heating for melting according to the requirements of the cast iron melting and proportioning process sheet;

d, sampling and analyzing the chemical components of the molten iron in the furnace, and adjusting the chemical components of the molten iron in the furnace;

e, treating molten iron and discharging and casting;

and F, detecting the material performance of the high-strength gray iron casting.

2. The multi-element low-alloying treatment method for high-strength gray cast iron as claimed in claim 1, wherein: the process procedure in step B comprises:

a, determining a cast iron melting and batching process sheet and a charging material adding sequence;

b, determining the requirements of sampling temperature, tapping temperature, processing temperature and pouring temperature;

c, determining a method for inoculation treatment in the molten iron furnace and during tapping.

3. The multi-element low-alloying treatment method for high-strength gray cast iron as claimed in claim 1, wherein: the matching method for the alloys normally used in the high-strength gray cast iron in step A is determined according to the following table.

4. The multi-element low-alloying treatment method for high-strength gray cast iron as claimed in claim 1, wherein: the content of the alloying elements in the high-strength gray iron casting in step a was determined according to the following table.

5. A high strength gray cast iron multi-element low alloying treatment method according to any one of claims 3 or 4, characterized in that: the bearing is large, the strength is high: the high-strength gray iron casting is a high-strength gray iron casting with a single-casting standard sample tensile strength requirement of more than 275MPa and a body tensile strength requirement of more than 260 MPa;

good wear resistance and high hardness: the high-strength gray iron casting is a high-strength gray iron casting with the Brinell hardness requirement of a single-casting standard sample of more than 230HB and the Brinell hardness requirement of a body of more than 220 HB;

large bearing capacity and good wear resistance: the high-strength gray iron casting has the two characteristic requirements.

6. The multi-element low-alloying treatment method for high-strength gray cast iron as claimed in claim 1, wherein: the conventional chemical elements comprise C, Si, Mn, P and S, and the content range of the conventional chemical elements is determined according to the following table.

7. The multi-element low-alloying treatment method for high-strength gray cast iron as claimed in claim 4, wherein: when the wall thickness of the casting is increased, C, Si takes a lower limit, Mn takes an upper limit, and the content is not more than 1% when Mn is taken as a common chemical element.

8. The multi-element low-alloying treatment method for high-strength gray cast iron as claimed in claim 1, wherein: the furnace burden in the step A comprises pig iron, scrap steel and foundry returns, the surface of the furnace burden is clean, oil-free and rust-free, and when the chemical components are sampled and analyzed in the step D, all the furnace burden is completely melted and homogenized, and the sampling temperature range is 1350-1450 ℃.

9. The multi-element low-alloying treatment method for high-strength gray cast iron as claimed in claim 1, wherein: and D, adjusting the chemical components of the molten iron in the furnace by adopting one or more methods of a similar alloy supplementing method, a pig iron or carburant supplementing method, a scrap steel supplementing method, a tapping reassortment method and a time-delay burning loss method for joint treatment.

10. The multi-element low-alloying treatment method for high-strength gray cast iron as claimed in claim 1, wherein: and E, the molten iron treatment method comprises one or more of high-temperature standing of molten iron, purification and deslagging of the molten iron and deoxidation and desulfurization of the molten iron.

Background

As a traditional casting metal material, gray cast iron occupies a considerable position in casting production, and under the background of light weight, energy conservation and consumption reduction of automobiles, the gray cast iron material is increasingly widely applied due to the advantages of low cost, good shock absorption, good casting formability and the like. However, with the rapid development of the modern mechanical industry, the requirements for the quality and production technology of gray cast iron products are more and more strict, and the requirements of high strength, thin wall, low cost and the like are provided.

The alloying of cast iron is one of the main technological approaches for improving the structure and mechanical property of cast iron and producing high-strength gray cast iron, and the multi-element low alloying is the most common and efficient technological method for improving the mechanical property and service property of cast iron in the alloying treatment method of cast iron. "Multi-element" means that a plurality of alloying elements are added simultaneously to the cast iron melt. "Low alloying" means that the content of the alloying elements added to the molten cast iron is relatively low, and the total content of the alloying elements is generally less than 3%. The addition of a small amount of alloying elements to gray cast iron not only improves the tensile strength but also enlarges the area where high strength is obtained.

Generally, high strength gray cast iron refers to gray cast iron having a cast body tensile strength of 250MPa or more. High strength gray cast iron material grades generally include: HT275, HT300, HT350, etc. In the aspect of the existing medium-frequency electric furnace cast iron smelting technology, researches on the aspect of multi-element low-alloying treatment of high-strength and high-grade gray cast iron are rare, systematic and comprehensive high-strength gray cast iron alloy element matching methods and melting and batching process technologies are not available, and cast iron smelting practitioners generally only rely on production practice experience to grope and control, can not ensure accurate, rapid and low-cost cast iron alloying treatment, control of cast iron chemical components and smelting production processes, and can not ensure that the quality of cast iron and the internal quality of castings meet requirements stably.

Therefore, an instruction method is urgently needed at present, the cast iron smelting process can be effectively controlled, the casting quality is kept stable, and the casting production cost is reduced.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a simple and easy high-strength (high-grade) gray cast iron multi-element low-alloying treatment technical method, so that operators in a foundry can know how to carry out melting ingredient design, melting operation and casting quality control when meeting the problem of producing high-strength (high-grade) gray cast iron by melting in the cast iron melting process.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows:

a high-strength gray cast iron multi-element low-alloying treatment method comprises the following steps:

determining the components and proportion of furnace burden in the high-strength gray iron casting, the matching method and content range of various alloy elements and the content range of conventional chemical elements according to the requirements of the casting to be produced;

b, determining a melting process procedure of the high-strength gray iron casting;

preparing materials, charging materials and heating for melting according to the requirements of the cast iron melting and proportioning process sheet;

d, sampling and analyzing the chemical components of the molten iron in the furnace, and adjusting the chemical components of the molten iron in the furnace;

e, treating molten iron and discharging and casting;

and F, detecting the material performance of the high-strength gray iron casting.

The technical scheme of the invention is further improved as follows: the process procedure in step B comprises:

a, determining a cast iron melting and batching process sheet and a charging material adding sequence;

b, determining the requirements of sampling temperature, tapping temperature, processing temperature and pouring temperature;

c, determining a method for inoculation treatment in the molten iron furnace and during tapping.

The technical scheme of the invention is further improved as follows: the matching method for the alloys normally used in the high-strength gray cast iron in step A is determined according to the following table.

The technical scheme of the invention is further improved as follows: the content of the alloying elements in the high-strength gray iron casting in step a was determined according to the following table.

The technical scheme of the invention is further improved as follows: the bearing is large, the strength is high: the high-strength gray iron casting is a high-strength gray iron casting with a single-casting standard sample tensile strength requirement of more than 275MPa and a body tensile strength requirement of more than 260 MPa;

good wear resistance and high hardness: the high-strength gray iron casting is a high-strength gray iron casting with the Brinell hardness requirement of a single-casting standard sample of more than 230HB and the Brinell hardness requirement of a body of more than 220 HB;

large bearing capacity and good wear resistance: the high-strength gray iron casting has the two characteristic requirements.

The technical scheme of the invention is further improved as follows: the conventional chemical elements comprise C, Si, Mn, P and S, and the content range of the conventional chemical elements is determined according to the following table.

The technical scheme of the invention is further improved as follows: when the wall thickness of the casting is increased, C, Si takes a lower limit, Mn takes an upper limit, and the content is not more than 1% when Mn is taken as a common chemical element.

The technical scheme of the invention is further improved as follows: the furnace burden in the step A comprises pig iron, scrap steel and foundry returns, the surface of the furnace burden is clean, oil-free and rust-free, and when the chemical components are sampled and analyzed in the step D, all the furnace burden is completely melted and homogenized, and the sampling temperature range is 1350-1450 ℃.

The technical scheme of the invention is further improved as follows: and D, adjusting the chemical components of the molten iron in the furnace by adopting one or more methods of a similar alloy supplementing method, a pig iron or carburant supplementing method, a scrap steel supplementing method, a tapping reassortment method and a time-delay burning loss method for joint treatment.

The technical scheme of the invention is further improved as follows: and E, the molten iron treatment method comprises one or more of high-temperature standing of molten iron, purification and deslagging of the molten iron and deoxidation and desulfurization of the molten iron.

Due to the adoption of the technical scheme, the invention has the technical progress that:

the application provides a set of systematically complete high-strength gray cast iron multi-element low-alloying element matching, alloy liquid smelting and processing technology and an operation control method, changes the traditional experience groping mode, and provides a set of simple and easy chemical component determination, melting and batching and alloy liquid processing technical method, so that the alloy element matching, cast iron melting and batching and alloying processing of the high-strength gray cast iron are more accurate and convenient, and the cast iron melting operation control is more reasonable and feasible. The method makes up the blank that no high-strength gray cast iron alloying treatment technical method exists, and solves the technical problems of alloy element matching, determination of the content of the adopted alloy elements, and smelting and treatment of the alloy iron liquid in the high-strength gray cast iron. By the method, smooth operation of high-strength gray cast iron alloying treatment and stable control of alloy melting quality are realized, and stable casting material quality and internal quality are ensured.

Detailed Description

The present invention will be described in further detail with reference to the following examples:

example 1

S1 production technical conditions

S1.1 production of castings and technical requirements

The production of the casting takes the high-strength gray iron casting No. 3 transmission case on a diesel engine as an example. The casting material of the No. 3 transmission case is HT350, belongs to a case shell type thin-wall high-strength gray iron casting, the main wall thickness is about 10-15mm, the external dimension of a casting blank is about 700X500X170mm, and the weight of the casting is about 60 Kg. The mechanical property requirements of the casting are as follows: the tensile strength of the single-cast sample is not lower than 350MPa, and the hardness is required to be 210-240 HB. The casting does not allow for casting defects that affect the strength and appearance quality of the casting.

S1.2 raw materials and smelting equipment

A1.5 t intermediate frequency electric furnace is selected as smelting equipment for producing the high-strength gray iron casting of the No. 3 transmission case. The furnace burden for melting the cast iron is as follows: wuan Z14 cast iron is selected, low-carbon steel leftovers of a steel rolling mill are selected as waste steel, and various ferroalloys are purchased according to the international standard requirements. (the chemical compositions of the various conventional metal charges are shown in Table S1.3). According to the technical requirements of the acceptance of the castings and the combination of production practice, the production processes of the various castings are compiled, and various casting molds are manufactured. Adopts the craft of making mould and core with furan resin self-hardening sand.

S1.3 chemical composition of various conventional Metal furnace charges

TABLE S1.3 general chemical composition (%) of various conventional metal charges

S2 Main production process

(1) Method for determining matching of multiple alloys in high-strength gray cast iron

The method is characterized in that a proper common alloy matching method in the high-strength gray cast iron is determined by combining the specific conditions of the high-strength gray cast iron transmission case to be produced, including the specific conditions of material grade of the transmission case casting, use requirements, casting wall thickness, structure size, weight, working environment conditions and the like. The transmission case belongs to case shell class thin wall ironcasting, and the foundry goods material is HT350, and transmission case operating mode condition requires that the foundry goods bears greatly, and the intensity requires highly, so the alloy matching method adopts: cu + Ni.

(2) Determining the content range of conventional chemical elements in high-strength gray cast iron

According to the technical requirements of the transmission case casting material, factors of wall thickness, weight, size and the like of the transmission case casting are comprehensively considered, so that the suitable chemical composition control range of various transmission case castings is determined. The specific situation is as follows: c%: 3.0-3.3, Si%: 1.1-1.4 (in furnace), 1.5-1.9 (casting), Mn%: 0.9-1.0 percent, less than or equal to 0.05 percent of P percent and less than or equal to 0.05 percent of S percent.

(3) Determining the content range of various alloy elements in the high-strength gray cast iron

Considering the specific conditions of the high-strength gray iron casting transmission case to be produced, including the specific conditions of the transmission case casting material grade (HT350), the use requirement, the casting wall thickness (thin-wall part), the structure size, the weight, the working environment condition, the use requirement (large bearing strength and high strength) and the like, the content of common alloy elements in the suitable high-strength gray iron is determined, and the specific selection is as follows: 0.7-1.2% of Cu and 0.5-1.0% of Ni.

(4) Determining melting process rules of high-strength gray iron casting transmission case

Firstly, determining a melting and batching process sheet of a high-strength gray iron casting transmission case

According to the control range requirements of alloy elements and chemical components of conventional elements of castings, the chemical components and the storage conditions of various metal furnace charges in actual production are combined, the oxidation burning loss of various chemical elements is considered, and a melting and batching process sheet of a high-strength gray iron casting transmission case can be compiled through calculation, wherein the specific conditions are as follows:

secondly, determining the technological parameters of the transmission box cast iron melting and pouring:

the process parameter contents to be determined generally include: sampling temperature, overheating temperature, standing time, tapping temperature, inoculation temperature, pouring time and the like, wherein the concrete conditions are as follows:

sampling temperature of the transmission case: 1350-: 1510 ℃ and 1530 ℃, and the high-temperature standing time: 3-8min, tapping temperature: 1490 ℃ and 1510 ℃, and the inoculation temperature is as follows: 1450 ℃ and 1500 ℃, and the pouring temperature is as follows: 1360-: 15-30S. And (3) adopting an in-ladle flushing method to perform inoculation treatment while tapping molten iron.

(5) Preparing materials, charging materials and heating for melting according to the requirements of cast iron melting and proportioning process sheet

According to the requirements of a transmission case 'cast iron melting and batching process sheet', various furnace materials such as pig iron, scrap steel, scrap iron, ferroalloy and the like required by the melting operation of the transmission case are accurately weighed, are positioned and placed orderly in a partition mode according to the melting operation sequence, and are marked to prevent misuse or confusion. Then according to the technological requirements, various furnace charges such as pig iron, scrap steel, ferroalloy and the like are sequentially added into the furnace, and the furnace charge is opened to heat the furnace charge so as to continuously melt the furnace charge.

(6) Sampling and analyzing chemical composition of iron liquid in furnace

According to the technological specification requirements, all the furnace charges are added into the furnace in sequence, completely melted and homogenized, and then the chemical components of the molten iron are sampled and detected, wherein the sampling temperature range is preferably 1350-1450 ℃. Usually, a direct-reading spectrometer is adopted to quickly and accurately detect the chemical components of the molten iron in the furnace and provide a stokehole chemical component analysis report. According to the process specification requirements, the analysis result of the chemical components in front of the furnace is checked to meet the requirements of various process parameters, and whether the detection result of the chemical components in the molten iron is qualified or not is judged.

(7) Adjusting the chemical composition of molten iron in the furnace

If the chemical composition of the molten iron in the furnace does not meet the process requirements, the chemical composition adjustment is carried out until the chemical composition of the molten iron in the furnace is qualified, and then the subsequent operation can be carried out.

The common methods for adjusting the chemical components in the furnace comprise a method for supplementing the similar alloy, a method for supplementing pig iron or carburant, a method for supplementing scrap steel, a method for reassembling iron tapping, a time-delay burning loss method and the like, and one or more appropriate adjusting methods can be selected and adopted according to the specific situation that the chemical components in the furnace exceed the standard.

In general, when the content of one or more alloy elements in the molten iron is lower than the process requirement, a method for supplementing the same type of alloy is suitable; when the content of carbon element in the molten iron is lower than the process requirement, a method of supplementing pig iron or carburant is suitable for being adopted; when the content of the carbon element in the molten iron is higher than the process requirement, a scrap steel supplementing method is suitable for being adopted; when the contents of various chemical elements in the molten iron do not meet the process requirements and the overproof degree is larger, the method is suitable for adopting an iron tapping reconfiguration method; when the content of one or more chemical elements in the molten iron is higher than the process requirement and the exceeding degree is smaller, the method is suitable for adopting a time-delay burning loss method.

And (3) selecting an optimum method to adjust by referring to the common method for adjusting the chemical components in front of the furnace, calculating the weight of the burden to be supplemented, weighing, and supplementing the burden into the furnace. After the furnace burden which is added continuously is completely melted and homogenized, the chemical components of the iron liquid in the furnace are sampled and detected again, and the subsequent operation can not be carried out until the contents of various elements are qualified.

(8) Molten iron treatment and tapping and pouring

When the molten iron of the transmission box is discharged from the furnace, the molten iron inoculation treatment is carried out by adopting an in-package flushing method according to the process requirements. When tapping, adding an inoculant (calcium barium ferrosilicon alloy) into a casting ladle along with the flow, flushing and melting the inoculant by using high-temperature iron liquid, stirring the iron liquid in the ladle to uniformly melt the inoculant, detecting the temperature of the iron liquid in the ladle, and pouring a casting after the temperature meets the pouring process requirement.

And pouring a group of (3) standard single-casting mechanical property samples while pouring the casting by using molten iron in each furnace. The mold material of the samples generally corresponds to the casting molding material.

(9) Quality of high-strength gray cast iron transmission case casting is detected comprehensively

After the casting is fully cooled in the casting mould, performing shakeout cleaning, performing shot blasting and finishing treatment, and performing comprehensive casting quality, wherein the inspection items comprise: appearance of the blank, size of the casting, chemical composition, mechanical property and other inspection items required by acceptance conditions. After all the checks are qualified, the product can be delivered or circulated.

(10) Effect of the experiment

After the produced transmission case casting is subjected to proper alloying treatment, the tensile strength of a single-cast sample reaches more than 350MPa, and the Brinell hardness is within the range of 210 plus 240 HB. The tensile strength of the casting body reaches more than 300MPa, the hardness of the casting body is within the range of 200-230HB, the quality of the casting is stable, and all inspection items meet the technical requirements of acceptance and acceptance. And on the basis of ensuring the quality, the consumption of alloy materials is reduced, and the production cost of the casting is favorably reduced.

Example 2

S1 production technical conditions

S1.1 production of castings and technical requirements

The production of the casting takes the high-strength gray iron casting No. 2 transmission connecting disc on a diesel engine as an example. The casting material of the No. 2 transmission connecting disc is HT275, belongs to a wheel disc type thick-wall high-strength gray iron casting, the main wall thickness is about 50-55mm, the external dimension of a casting blank is about phi 180X60mm, and the weight of the casting is about 13 Kg. The mechanical property requirements of the casting are as follows: the tensile strength is not lower than 275MPa, and the hardness is required to be 230HB and 250 HB. The casting does not allow for casting defects that affect the strength and appearance quality of the casting.

S1.2 raw materials and smelting equipment

A0.5 t intermediate frequency electric furnace is selected as smelting equipment for producing the high-strength gray iron casting of the No. 2 transmission connecting disc. The furnace burden for melting the cast iron is as follows: wuan Z14 cast iron is selected, low-carbon steel leftovers of a steel rolling mill are selected as waste steel, and various ferroalloys are purchased according to the international standard requirements. According to the technical requirements of the acceptance of the castings and the combination of production practice, the production processes of the various castings are compiled, and various casting molds are manufactured. Manually molding and making cores by using furan resin self-hardening sand.

S2 Main production process

(1) Method for determining matching of multiple alloys in high-strength gray cast iron

The method is characterized in that a proper common alloy matching method in the high-strength gray cast iron is determined by combining the specific conditions of the high-strength gray cast iron transmission case to be produced, including the specific conditions of material grade of the transmission case casting, use requirements, casting wall thickness, structure size, weight, working environment conditions and the like. The No. 2 transmission connecting disc belongs to a wheel disc type thick-wall high-strength gray iron casting, the material of the casting is HT275, the working condition of the casting requires good wear resistance and high hardness (the hardness requires 230HB and 250HB), so the alloy matching method adopts the following steps: cu + Cr.

(2) Determining the content range of conventional elements in high-strength gray cast iron

According to the technical requirements of the materials of the transmission connecting disc castings, factors such as wall thickness, weight, size and the like of the castings are comprehensively considered, and the appropriate chemical component control range of the castings is determined by combining the previous successful experience. The specific situation is as follows: c%: 3.2-3.5, Si%: 1.3-1.6 (in furnace), 1.7-2.0 (casting), Mn%: 0.8 to 1.0 percent, less than or equal to 0.08 percent of P percent and less than or equal to 0.08 percent of S percent.

(3) Determining the content range of various alloy elements in the high-strength gray cast iron

The content of common alloy elements in the high-strength gray cast iron is determined by considering the specific conditions of the high-strength gray cast iron transmission connecting disc to be produced, including the specific conditions of the transmission connecting disc casting material grade (HT275), use requirements, casting wall thickness, structural size, weight, working environment conditions (good wear resistance and high hardness) and the like. The specific situation is as follows: 0.6-0.9% of Cu and 0.2-0.5% of Cr.

(4) Determining melting process schedule of high-strength gray iron casting transmission connecting disc

Firstly, determining a melting and batching process sheet of a high-strength gray iron casting transmission connecting disc

According to the control range requirements of alloy elements and chemical components of conventional elements of castings, the chemical components and the storage conditions of various metal furnace charges in actual production are combined, the oxidation burning loss of various chemical elements is considered, and a melting and batching process sheet of a high-strength gray iron casting transmission case can be compiled through calculation, wherein the specific conditions are as follows:

secondly, determining the technological parameters of the transmission box cast iron melting and pouring:

the process parameter contents to be determined generally include: sampling temperature, overheating temperature, standing time, tapping temperature, inoculation temperature, pouring time and the like, wherein the concrete conditions are as follows:

sampling temperature of a transmission connecting disc: 1350-: 1500-: 3-6min, tapping temperature: 1480 + 1500 ℃, inoculation temperature: 1450 ℃ and 1500 ℃, and the pouring temperature is as follows: 1330 ℃ 1370 ℃, single casting time: 10-15S. And (3) adopting an in-ladle flushing method to perform inoculation treatment while tapping molten iron.

(5) Preparing materials, charging materials and heating for melting according to the requirements of cast iron melting and proportioning process sheet

Same as example 1

(6) Sampling and analyzing chemical composition of iron liquid in furnace

Same as example 1

(7) Adjusting the chemical composition of molten iron in the furnace

Same as example 1

(8) Molten iron treatment and tapping and pouring

Same as example 1

(9) Quality of high-strength gray cast iron transmission case casting is detected comprehensively

Same as example 1

(10) Effect of the experiment

After proper alloying treatment, the cast iron produced by the technical method has tensile strength of more than 275MPa, hardness within the range of 230-250HB, stable casting quality and all inspection items meeting the technical requirements of acceptance and acceptance. On the basis of ensuring the quality, the consumption of alloy materials is reduced, and the production cost of the casting is favorably reduced

Example 3

S1 production technical conditions

S1.1 production of castings and technical requirements

The casting is produced by taking the cylinder liner No. 5 of the high-strength gray iron casting on the diesel engine as an example. The casting material of the No. 5 cylinder liner is alloy gray cast iron, the material is equivalent to HT300, the casting belongs to a sleeve type thin-wall high-strength gray cast iron part, the main wall thickness is about 15-20mm, the external dimension of a casting blank is about phi 210X320mm, and the weight of the casting is about 15 Kg. The mechanical property requirements of the casting are as follows: the tensile strength of the body is not lower than 280MPa, and the hardness of the body is required to be 250HB and 280 HB. The casting does not allow for casting defects that affect the strength and appearance quality of the casting.

S1.2 raw materials and smelting equipment

The smelting equipment for producing the No. 5 cylinder liner high-strength gray iron casting selects a 1.5t intermediate frequency electric furnace. The furnace burden for melting the cast iron is as follows: wuan Z14 cast iron is selected, low-carbon steel leftovers of a steel rolling mill are selected as waste steel, and various ferroalloys are purchased according to the international standard requirements. According to the technical requirements of the acceptance of the castings and the combination of production practice, the production processes of the various castings are compiled, and various casting molds are manufactured. And (4) adopting a centrifugal casting process method.

S2 Main production process

(1) Method for determining matching of multiple alloys in high-strength gray cast iron

The method is characterized in that a proper common alloy matching method in the high-strength gray cast iron is determined by combining the specific conditions of the high-strength gray cast iron transmission case to be produced, including the specific conditions of material grade of a cylinder liner casting, use requirements, casting wall thickness, structural size, weight, working environment conditions and the like. No. 5 cylinder liner belongs to sleeve class thin wall high strength grey iron casting, and the foundry goods material is equivalent to HT300, and the foundry goods operating mode condition requires that the wearability is good, and bears the weight of greatly, so the alloy matching method adopts: cu + Cr + Ni.

(2) Determining the content range of conventional elements in high-strength gray cast iron

According to the technical requirements of the materials of the cylinder liner castings, factors of wall thickness, weight, size and the like of the castings are comprehensively considered, so that the proper chemical composition control range of the castings is determined. The specific situation is as follows: c%: 3.1-3.3, Si%: 1.2-1.5 (in furnace), 1.6-1.9 (casting), Mn%: 0.9-1.0 percent, less than or equal to 0.06 percent of P percent and less than or equal to 0.06 percent of S percent.

(3) Determining the content range of various alloy elements in the high-strength gray cast iron

According to the influence of the common alloy elements on the structure and the performance of the cast iron summarized in the table 1, the successful production practice experience in the past is summarized, and the appropriate content of the common alloy elements in the high-strength gray cast iron is determined by considering the specific conditions of the high-strength gray cast iron cylinder liner to be produced, including the specific conditions of the material grade of the cylinder liner casting, the use requirement, the casting wall thickness, the structure size, the weight, the working environment condition and the like. The specific situation is as follows: 0.6-0.9% of Cu, 0.6-0.9% of Ni and 0.2-0.4% of Cr.

(4) Determining melting process schedule of high-strength gray iron casting cylinder liner

Firstly, determining the melting and batching process list of the cylinder liner of the high-strength gray iron casting

According to the control range requirements of alloy elements and chemical components of conventional elements of castings, the chemical components and the storage conditions of various metal furnace charges in actual production are combined, the oxidation burning loss of various chemical elements is considered, and a melting and batching process sheet of a high-strength gray iron casting cylinder liner can be compiled through calculation, wherein the specific conditions are as follows:

secondly, determining the cylinder liner cast iron melting and pouring technological parameters:

the process parameter contents to be determined generally include: sampling temperature, overheating temperature, standing time, tapping temperature, inoculation temperature, pouring time and the like, wherein the concrete conditions are as follows:

sampling temperature of a cylinder liner: 1360-1460 ℃, superheat temperature: 1510 ℃ and 1530 ℃, and the high-temperature standing time: 3-8min, tapping temperature: 1490 ℃ and 1510 ℃, and the inoculation temperature is as follows: 1450 and 1510 ℃ and the pouring temperature: 1400 ℃ and 1430 ℃ and the single-piece pouring time: 10-15S. And (3) adopting an in-ladle flushing method to perform inoculation treatment while tapping molten iron.

(5) Preparing materials, charging materials and heating for melting according to the requirements of cast iron melting and proportioning process sheet

Same as example 1

(6) Sampling and analyzing chemical composition of iron liquid in furnace

Same as example 1

(7) Adjusting the chemical composition of molten iron in the furnace

Same as example 1

(8) Molten iron treatment and tapping and pouring

Same as example 1

(9) Casting quality for comprehensively detecting high-strength gray cast iron cylinder liner

Same as example 1

(10) Effect of the experiment

After proper alloying treatment, the tensile strength of the casting body can reach more than 280MPa, the Brinell hardness of the casting body is kept within the range of 250-280HB, the casting quality is stable, and all inspection items meet the technical requirements of acceptance inspection. And on the basis of ensuring the quality, the consumption of alloy materials is reduced, and the production cost of the casting is favorably reduced.