CN104988269A

CN104988269A - High-strength gray iron casting smelting method

Info

Publication number: CN104988269A
Application number: CN201510318712.2A
Authority: CN
Inventors: 刘飞
Original assignee: Individual
Current assignee: Individual
Priority date: 2015-06-06
Filing date: 2015-06-06
Publication date: 2015-10-21

Abstract

The invention discloses a high-strength gray iron casting smelting method. Gray iron casting smelting is performed with scrap steel, pig iron and foundary returns as raw materials. The smelting method includes the specific steps that ferromanganese and the 10% pig iron are added into a medium-frequency induction electric furnace; then, carbon agents and the scrap steel are added at the same time; smelting is performed till the size of molten iron in the induction electric furnace is reduced by 3/4 through smelting; smelting is performed while silicon carbide is added, so that base iron is formed; the base iron is heated so that temperature can be raised; the induction electric furnace is adjusted to be in a heat-preservation state, and standing lasts for 5-10 minutes; and silicon and zirconium inoculant and final molten iron are punched into iron discharging ladles, and then the silicon and zirconium inoculant and the final molten iron are punched into a cast cavity so that casting can be performed. The method replaces a traditional method that alloyed elements such as copper or tin need to be added, manufacturing cost is reduced, and the foundary returns can be conveniently managed. The method that the silicon carbide and furnace burden are smelted at the same time is adopted for pre-processing the molten iron, and the pre-processing effect is guaranteed. The efficient silicon and zirconium inoculant is adopted so that the inoculation effect is guaranteed, and more than 80% of A-type graphite is obtained from the casting body metallographic phase.

Description

The melting method of high-strength gray cast iron part

Technical field

The present invention relates to a kind of melting method of gray iron casting, particularly relate to the melting method of high-strength gray cast iron part, belong to chemical melting field.

Background technology

The cocrystallizing type alloy that graphitic cast iron is made up of iron, carbon and silicon substantially, wherein, carbon mainly exists with the form of graphite.Produce premium casting, form and the matrix metal tissue of the graphite formed when controlling cast iron solidified are vital.Inoculation is one of most important link in production technique.Good inoculation can make graphitic cast iron have satisfactory microstructure, thus ensures mechanical property and the processing characteristics of foundry goods.In liquid cast, add nucleating agent, a large amount of sub-micro-core can be formed, impel eutectic cell to generate in the liquid phase.During close to eutectic solidification temperature, first raw core place forms tiny graphite flake, and grows into eutectic cell thus.The formation of each eutectic cell, all peripherad liquid phase can discharge a small amount of heat, the eutectic cell of formation is more, and the solidification rate of cast iron is lower.The reduction of solidification rate, just contributes to solidifying by iron-graphite stable system, and can obtain A type graphite tissue.

General, good inoculation has following effect: (1) is eliminated or alleviated chilling tendency; (2) avoid occurring over-cooling structure; (3) alleviate the sectional sensitivity of ironcasting, make the difference of thin, the thick section microstructure of foundry goods little, difference in hardness is also little; (4) be conducive to the raw core of eutectic cell, Eutectic Cell Number is increased; (5) make the form of Graphite in Cast Iron mainly tiny and equally distributed A type graphite, thus improve the mechanical property of cast iron.Breed good cast iron mobility better, the contraction minimizing of foundry goods, processing characteristics improvement, residual stress reduce.

Alloy element copper or tin must be added during traditional medium-frequency induction furnace melting height trade mark gray iron casting, add manufacturing cost.

Summary of the invention

The object of this invention is to provide the melting method of high-strength gray cast iron part, to solve the high difficult problem of above-mentioned manufacturing cost, and the A type graphite of higher yields can be obtained.

The technical solution used in the present invention is: the melting method of high-strength gray cast iron part, is characterized in that: the pig iron that the steel scrap being with trade mark Q235, the trade mark are Q10 and foundry returns carry out the melting of gray iron casting for raw material; Described melting concrete steps are:

(1) pig iron being first Q10 by ferromanganese and 10% trade mark together adds in medium-frequency induction furnace, then the carburelant and 60% trade mark that add 2% are the steel scrap of Q235 simultaneously, melting until in induction furnace the melting of molten iron volume to 3/4 of original volume, regulate temperature of fusion to be 1444 ~ 1456 DEG C, fusing time is 1 ~ 3h;

(2) at molten iron volume be 3/4 induction furnace in add 0.5% silicon carbide carry out melting simultaneously and form base iron, regulate temperature of fusion to be 1444 ~ 1456 DEG C, fusing time is 1 ~ 3h;

(3) after the base iron in step 2 being heated to 1502 ~ 1518 DEG C, induction furnace is adjusted to keeping warm mode, molten iron leaves standstill and forms whole molten iron in 5 ~ 10 minutes;

(4), in the silicon zirconium nucleating agent of 0.8% and whole molten iron together being poured and tapping a blast furnace and wrap, pour in casting mold die cavity more subsequently simultaneously and cast, arranging pouring temperature is 1378-1408 DEG C, and pouring time is 1 ~ 3h.

Further, in described step 1, the trade mark is that the massfraction of each moiety in the pig iron of Q10 is respectively C:4.45 ~ 4.50%, Si:0.75 ~ 0.80%, Mn:0.12 ~ 0.15%, P:0.024 ~ 0.027%, S:0.01 ~ 0.015%, Cr:0.033 ~ 0.040%, Ti:0.02 ~ 0.030%, V:0.010 ~ 0.020%, surplus is Fe.

Further, in described step 1, the trade mark is that the massfraction of each moiety in the steel scrap of Q235 is respectively C:0.23 ~ 0.30%, Si:0.15 ~ 0.18%, Mn 0.43 ~ 0.55%, P 0.019 ~ 0.022%, S, 0.021 ~ 0.030%Cr, 0.017 ~ 0.020%Ti, 0.001 ~ 0.003%, V 0.001 ~ 0.004%, surplus is Fe.

Further, in described step 1, each constituent mass mark of carburelant is respectively nitrogen :≤0.02%, carbon: 98 ~ 100%.

Further, in described step 2, the massfraction of silicon carbide is 88 ~ 90%, wherein silicon: 60 ~ 63%, carbon: 27%, impurity 10 ~ 13%; Granularity 1 ~ the 4mm of described silicon carbide.

Further, in described step 4, each constituent mass mark of silicon zirconium nucleating agent is respectively Si:73.1%, Zr:2.42%, impurity 24.48%.

Further, in described step 4, the granularity of silicon zirconium nucleating agent is 0.2 ~ 0.5mm.

Beneficial effect: alloy element copper or tin must be added when method of the present invention instead of traditional medium-frequency induction furnace melting height trade mark gray iron casting, reduce manufacturing cost, and be convenient to the management of foundry returns; Present method adopts the method for silicon carbide and furnace charge melting simultaneously to carry out pre-treatment to molten iron, ensure that pretreated effect; Adopt effective inoculation agent silicon zirconium nucleating agent to ensure that the effect bred, make the A type graphite obtaining more than 80% in foundry goods body metallographic, foundry goods body tensile strength reaches between 270 ~ 300, body surface E type graphite≤20%, centre≤5%.

Embodiment

Implementation column below can make those skilled in the art more fully understand the present invention, but does not therefore limit the present invention among described scope of embodiments.

Embodiment 1

The melting method of high-strength gray cast iron part: the pig iron that the steel scrap being with trade mark Q235, the trade mark are Q10 and foundry returns carry out the melting of gray iron casting for raw material; Melting concrete steps are:

According to the melting method of the present embodiment, assay is that tensile strength reaches 276, and surface hardness reaches 220, and content of pearlite in alloy is 98%.

Embodiment 2

Be 2.5% by the carbon increasing amount added, Silicon carbide addition is 0.7%, and silicon zirconium innoculant adding quantity is 0.9%, carries out melting according to the melting method described in embodiment 1.

According to the melting method of the present embodiment, assay is that tensile strength reaches 281, and surface hardness reaches 228, and content of pearlite in alloy is 98.5%.

Embodiment 3

Be 3% by the carbon increasing amount added, Silicon carbide addition is 0.8%, and silicon zirconium innoculant adding quantity is 1%, carries out melting according to the melting method described in embodiment 1.

According to the melting method of the present embodiment, assay is that tensile strength reaches 277, and surface hardness reaches 236, and content of pearlite in alloy is 98.9%.

Claims

1. the melting method of high-strength gray cast iron part, is characterized in that: the pig iron that the steel scrap being with trade mark Q235, the trade mark are Q10 and foundry returns carry out the melting of gray iron casting for raw material; Described melting concrete steps are:

(1) pig iron being first Q10 by ferromanganese and 10% trade mark together adds in medium-frequency induction furnace, then the carburelant and 60% trade mark that add 2 ~ 3% are the steel scrap of Q235 simultaneously, melting until in induction furnace the melting of molten iron volume to 3/4 of original volume, regulate temperature of fusion to be 1444 ~ 1456 DEG C, fusing time is 1 ~ 3h;

(2) at molten iron volume be 3/4 induction furnace in add 0.5 ~ 0.8% silicon carbide carry out melting simultaneously and form base iron, regulate temperature of fusion to be 1444 ~ 1456 DEG C, fusing time is 1 ~ 3h;

(4), in the silicon zirconium nucleating agent of 0.8 ~ 1% and whole molten iron together being poured and tapping a blast furnace and wrap, pour in casting mold die cavity more subsequently simultaneously and cast, arranging pouring temperature is 1378 ~ 1408 DEG C, and pouring time is 1 ~ 3h;

In described step 1, the trade mark is that the massfraction of each moiety in the pig iron of Q10 is respectively C:4.45 ~ 4.50%, Si:0.75 ~ 0.80%, Mn:0.12 ~ 0.15%, P:0.024 ~ 0.027%, S:0.01 ~ 0.015%, Cr:0.033 ~ 0.040%, Ti:0.02 ~ 0.030%, V:0.010 ~ 0.020%, surplus is Fe;

In described step 1, the trade mark is that the massfraction of each moiety in the steel scrap of Q235 is respectively C:0.23 ~ 0.30%, Si:0.15 ~ 0.18%, Mn 0.43 ~ 0.55%, P 0.019 ~ 0.022%, S, 0.021 ~ 0.030%Cr, 0.017 ~ 0.020%Ti, 0.001 ~ 0.003%, V 0.001 ~ 0.004%, surplus is Fe.

2. the melting method of high-strength gray cast iron part according to claim 1, is characterized in that: in described step 1, each constituent mass mark of carburelant is respectively nitrogen :≤0.02%, carbon: 98 ~ 100%.

3. the melting method of high-strength gray cast iron part according to claim 1, is characterized in that: in described step 2, the massfraction of silicon carbide is 88 ~ 90%, wherein silicon: 60 ~ 63%, carbon: 27%, impurity 10 ~ 13%; Granularity 1 ~ the 4mm of described silicon carbide.

4. the melting method of high-strength gray cast iron part according to claim 1, is characterized in that: in described step 4, each constituent mass mark of silicon zirconium nucleating agent is respectively Si:73.1%, Zr:2.42%, impurity 24.48%.

5. the melting method of high-strength gray cast iron part according to claim 1, is characterized in that: in described step 4, the granularity of silicon zirconium nucleating agent is 0.2 ~ 0.5mm.