CN103966384A - Tufftride-matched low-alloy high-strength gray cast iron smelting method - Google Patents

Abstract

The invention discloses a tufftride-matched low-alloy high-strength gray cast iron smelting method which comprises the following steps: 1) electric furnace smelting: sequentially adding 15-25 parts by weight of pig iron, 40-60 parts by weight of scrap steel and 20-40 parts by weight of foundry return into an electric furnace, and melting; 2) adding 20-30 parts of chromium iron into the electric furnace, wherein the chromium accounts for 0.2-0.3% of the chromium iron; 3) continuing adding 0.5-0.6 part of copper; and 4) carrying out inoculation three times, wherein 0.3 part of silicon-barium inoculator is added into the iron ladle in the first tapping process, 0.2 part of silicon-barium inoculator is added in the second ladle-to-ladle process, and 0.1 part of silicon-strontium inoculator is used for metal-stream inoculation in the third process. By combining small amounts of alloy elements and inoculation, the matrix structure is reinforced, the graphite is refined, and the pearlite is properly increased and stabilized to form carbide, thereby enhancing the mechanical properties of the cast iron, preventing the phenomenon of chilling and ensuring not to influence the processing; and the surface tufftride HV is 950-1000.

Description

The end alloy high strength gray cast iron smelting method of coupling tufftride

Technical field

The present invention relates to melting technology, specifically mate the end alloy high strength gray cast iron smelting method of tufftride.

Background technology

The development of graphitic cast iron is to obtain 100% pearlite matrix to be organized as target all the time, and for this reason, many iron-founder authors are working hard always.From early stage employing, reduce carbon silicone content to improve the method for strength of gray cast iron, adopt finally nucleating agent to carry out inoculation, the mechanical performance index of graphitic cast iron is constantly being improved.At some special dimension graphitic cast iron, require to have very high wear resistance, hardness, thermostability and erosion resistance, need to carry out special processing to graphitic cast iron, tufftride is processed can improve cast iron surface hardness and wear resistance, the foundry goods that traditional technology is produced, although the trade mark also reaches HT300, surperficial tufftride can only HV550-600, major cause is that the inner ferrite of foundry goods is more, pearlite fraction is few, and graphite is thick, is difficult to form enough carbon nitrogen hardening layers after surperficial tufftride.And our product requirement HV950-1000.

Summary of the invention

The object of the present invention is to provide the end alloy high strength gray cast iron smelting method of coupling tufftride, the method that a small amount of alloying element and inoculation combine, so that its matrix is strengthened, refinement graphite also suitably increases and stabilizing pearlite, form carbide to improve the mechanical property of its cast iron, also prevent the generation of " spoken parts in traditional operas " phenomenon, guarantee not affect processing, surperficial tufftride HV950-1000.

In order to reach above-mentioned purpose, the present invention has adopted following technical scheme, the end alloy high strength gray cast iron smelting method of coupling tufftride, and its step comprises:

1) adopt electrosmelting, add successively by weight pig iron 15-25 part in electric furnace, steel scrap adds 40-60 part, and foundry returns 20-40 part, melts;

2) after fusing, add 20-30 part ferrochrome in electric furnace, that wherein chromium content accounts for ferrochrome total amount is 0.2%-0.3% again;

3) then continue to add 0.5-0.6 part copper;

4) then divide and carry out inoculation three times, while tapping a blast furnace for the first time, in hot metal ladle, add the silicon titanate innoculant of 0.3 part, when ladle-to-ladle for the second time, add the silicon titanate innoculant of 0.2 part, use for the third time 0.1 part of current-following inoculation of silicon strontium nucleating agent.

Compared to prior art, the present invention has following beneficial effect:

In order to obtain high-intensity graphitic cast iron, guarantee that the tissue of its foundry goods can meet the processing requirement of postorder, its method has two kinds.Method one: change the composition of furnace charge, increase the add-on of steel scrap, thereby reduce carbon equivalent and wrap interior inoculation.Method two: add a small amount of alloying element and breed the measure combining.Method one is owing to having reduced carbon, silicone content, its carbon equivalent is lower, reduced graphite, refinement graphite, thereby improved the intensity of cast iron, but the reduction of carbon equivalent simultaneously can cause the reduction of cast properties, casting section susceptibility increases, foundry goods internal stress increases, and hardness rises, the problems such as processing difficulties.Method two utilization adds a small amount of alloying element in stokehold, can suitably promote and strongly stablize the inner pearlitic formation of foundry goods, and part refine pearlite, reinforced ferrite, form appropriate carbide, should make original iron melt keep higher carbon equivalent simultaneously, its chilling tendency is reduced, good casting property, is difficult for producing shrinkage cavity and porosity phenomenon.Through relatively, then according to the feature of casting structure, adopts two kinds of methods in conjunction with and use, through analysis and comparison repeatedly, determine to select the method that copper, chromium two clock alloys are used simultaneously and inoculation combines to carry out the trial production of low alloying high-strength gray cast iron.

The present invention makes foundry goods possess suitable metallographic structure composition, when guaranteeing processing characteristics, comprehensive mechanical property, after surperficial tufftride, can generate enough carbon nitrogen hardening layers, reach HV900-950, aspect the production of high-strength gray cast iron, started a kind of novel process.

Embodiment

Embodiment 1:

The end alloy high strength gray cast iron smelting method of coupling tufftride, its step comprises:

1) adopt electrosmelting, add successively by weight 15 parts of the pig iron in electric furnace, steel scrap adds 40 parts, and 20 parts of foundry returns, melt;

2) after fusing, temperature is elevated to 1400 ℃, then in electric furnace, adds 30 parts of ferrochrome, and what wherein chromium content accounted for ferrochrome total amount is 0.3%;

3) then continue to add 0.5 part of copper (electrolytic copper));

4) then divide and carry out inoculation three times, for the first time, while tapping a blast furnace, the silicon titanate innoculant (Ba7-8%, Ca1.5-2%, the Si70-72% that in hot metal ladle, add 0.3 part, Al1-1.5%), for the second time, when ladle-to-ladle, the silicon titanate innoculant ((Ba7-8% that adds 0.2 part, Ca1.5-2%, Si70-72%, Al1-1.5%), for the third time, use 0.1 part of current-following inoculation of silicon strontium nucleating agent (containing Si70%).Then melting finishes, and forms finished product graphitic cast iron.

The carbon nitrogen hardening layer thickness 0.008-0.015mm of the graphitic cast iron after embodiment, more than reaching HV950.

Embodiment 2:

1) adopt electrosmelting, add successively by weight 25 parts of the pig iron in electric furnace, steel scrap adds 60 parts, and 40 parts of foundry returns, melt;

2) after fusing, temperature is elevated to 1450 ℃, then in electric furnace, adds 20 parts of ferrochrome, and what wherein chromium content accounted for ferrochrome total amount is 0.2%;

3) then continue to add 0.6 part of copper (electrolytic copper);

4) then divide and carry out inoculation three times, for the first time, while tapping a blast furnace, the silicon titanate innoculant (Ba7-8%, Ca1.5-2%, the Si70-72% that in hot metal ladle, add 0.3 part, Al1-1.5%), for the second time, when ladle-to-ladle, silicon titanate innoculant (the Ba7-8% that adds 0.2 part, Ca1.5-2%, Si70-72%, Al1-1.5%), for the third time, use 0.1 part of current-following inoculation of silicon strontium nucleating agent (containing Si70%).Then melting finishes, and forms finished product graphitic cast iron.

The carbon nitrogen hardening layer thickness of the graphitic cast iron after embodiment is 0.008-0.015mm, reaches HV950.

Embodiment 3:

1) adopt electrosmelting, add successively by weight 20 parts of the pig iron in electric furnace, steel scrap adds 50 parts, and 30 parts of foundry returns, melt;

2) after fusing, temperature is elevated to 1430 ℃, then in electric furnace, adds 25 parts of ferrochrome, and what wherein chromium content accounted for ferrochrome total amount is 0.25%;

3) then continue to add 0.55 part of copper (electrolytic copper);

4) then divide and carry out inoculation three times, for the first time, while tapping a blast furnace, the silicon titanate innoculant (Ba7-8%, Ca1.5-2%, the Si70-72% that in hot metal ladle, add 0.3 part, Al1-1.5%), for the second time, when ladle-to-ladle, silicon titanate innoculant (the Ba7-8% that adds 0.2 part, Ca1.5-2%, Si70-72%, Al1-1.5%), for the third time, use 0.1 part of current-following inoculation of silicon strontium nucleating agent (containing Si70%).Then melting finishes, and forms finished product graphitic cast iron.

The carbon nitrogen hardening layer thickness of the graphitic cast iron after embodiment is 0.008-0.015mm, more than reaching HV950.

The foregoing is only preferred embodiment of the present invention, non-in order to limit the scope of the claims of the present invention, other use the equivalence of patent spirit of the present invention to change, and all should all belong to the scope of the claims of the present invention.

Claims (1)

1. mate the end alloy high strength gray cast iron smelting method of tufftride, its step comprises:

1) adopt electrosmelting, add successively by weight pig iron 15-25 part in electric furnace, steel scrap adds 40-60 part, and foundry returns 20-40 part, melts;

2) after fusing, add 20-30 part ferrochrome in electric furnace, that wherein chromium content accounts for ferrochrome total amount is 0.2%-0.3% again;

3) then continue to add 0.5-0.6 part copper;

4) then divide and carry out inoculation three times, while tapping a blast furnace for the first time, in hot metal ladle, add the silicon titanate innoculant of 0.3 part, when ladle-to-ladle for the second time, add the silicon titanate innoculant of 0.2 part, use for the third time 0.1 part of current-following inoculation of silicon strontium nucleating agent.