CN1165870A

CN1165870A - Rare-earth vanadium titanium synthetic cast iron for engine cylinder and its prodn. method

Info

Publication number: CN1165870A
Application number: CN 96117562
Authority: CN
Inventors: 邱代荣
Original assignee: Sichuan Union University
Current assignee: Sichuan Union University
Priority date: 1996-05-21
Filing date: 1996-05-21
Publication date: 1997-11-26

Abstract

A composite V-Ti cast iron used for manufacturing cylinder body of engine contains C (3.2-3.6%), Si (1.70-2.25%), Mn (0.6-0.8%), P (0.01-0.10%), S (0.02-0.08%), V (0.10-0.20%), Ti (0.06-0.12%), Cu (0.50-0.70%), RE (0.01-0.03%) and Fe (the rest). Its production method is composite casting. Its raw materials consist of waste steel (40-50%), recirculated iron (20-30%), V-Ti pig iron (30-40%), C, Si, Mn, Cu and RE. Said cylinder body made of the V-Ti cast iron has long service life, high rate of finished product after honed (up to 90%) and low cost.

Description

Rare-earth vanadium titanium synthetic cast iron for engine cylinder and production method thereof

The invention belongs to the synthetic cast iron field, particularly a kind of rare-earth vanadium titanium synthetic cast iron of engine cylinder body and function and production method thereof.

Automobile engine cylinder-body (having another name called crankcase) occupy first of the big vital part of five on the engine, performance fine or not most important, correspondingly also high to the requirement of material, but because its shape structure is very complicated and wall thin, from manufacturability, countries in the world generally are material with the grey cast iron, adopt castmethod production.The cylinder body that grey cast iron is made, thick because of the graphite length of a film, cause tensile strength on the low side, cylinder barrel hardness is inhomogeneous, and particularly the biased difference in cylinder barrel top and the bottom is big, and the mill back graphite that spreads out comes off, loosens, and easy oil leakage is leaked during pressure testing, and scrap rate is up to 40～50% in the production.After automobile was exercised 3～50,000 kilometers, the gap between cylinder barrel and the piston was big, easy oil mixed, and over-emitting black exhaust reduces automobile horsepower and contaminate environment, makes major repair of vehicle frequent.

The objective of the invention is to overcome the deficiencies in the prior art, a kind of rare-earth vanadium titanium synthetic cast iron for engine cylinder and production method thereof are provided, this kind synthetic cast iron can not only be eliminated the slag inclusion, pore of cylinder body, defective such as loose effectively, improve the tensile strength and the hardness of cylinder body, thereby prolong the work-ing life of cylinder body, and castibility and machinability are good.

The object of the present invention is achieved like this:

1. add RE (rare earth), to change the form and the purifying molten iron of graphite.

Rare earth, particularly contain the form that cerium mischmetal can change graphite, make graphite change into tubbiness sheet or silkworm chrysalis shape by thick lengthy motion picture shape, thereby reduce destruction to matrix, improve the tensile strength of cast iron, and make graphite difficult drop-off when cylinder barrel spreads out mill, and help eliminating rarefaction defect, solve the leakage of oil seepy question of pressure testing.Rare earth can not only change the form of graphite, and because of the avidity of itself and oxygen, sulphur is strong, can also purifying molten iron, eliminate the slag inclusion and the gas hole defect of cylinder body.

2. add V, Ti, to strengthen matrix.

Vanadium (V), titanium (Ti) element can solid solution in matrix can form vanadium carbide (VC) again, titanium carbide (TiC) polygon solia particle is deposited on the matrix, thereby strengthened matrix, increased the wear resistance of matrix, improved the work-ing life of cylinder body.

3. add Cu, to guarantee that as-cast pearlitic stably reaches more than 90% in matrix.

The Cu element is to promote the perlite element, and its adding can guarantee either pearlite occurred required in the matrix.

4. adopt synthetic casting.

During production, adopt a small amount of pig iron, a large amount of steel scrap to add graphite carbon and synthesize, overcome the heredity of the various places pig iron, be convenient to adjust and the control chemical ingredients.According to above mechanism, the chemical ingredients of synthetic cast iron provided by the invention is (by weight percentage): C 3.2～3.6%, Si 1.70～2.25%, Mn 0.6～0.8%, P 0.01～0.10%, S 0.02～0.08%, V 0.10～0.20%, Ti 0.06～0.12%, Cu 0.50～0.70%, RE 0.01～0.03%, all the other Fe.

Production method provided by the invention is operated according to the following steps:

1. prepare burden

Batching mode is: steel scrap 40～50%, and foundry return 20～30%, vanadium titanium iron 30～40%, C, Si, Mn, Cu, RE element add according to calculating aequum, and the V in the chemical ingredients, Ti element need not add, and are provided by vanadium titanium iron.

2. reinforced

Order of addition(of ingredients) is: steel scrap → graphite carbon → vanadium titanium iron → foundry return.

3. melting

(1) fusing molten iron

Add start fusing behind the vanadium titanium iron by above-mentioned order of addition(of ingredients), wait to begin to add foundry return successively after the fusing, join foundry return until adding and also be fused into molten iron fully.

(2) adjust C, Si, Mn amount

The molten iron of fusing is warming up to 1500-1550 ℃ of sampling, and rapid determination C, Si content are also adjusted in the desired amount, add institute then and join the ferromanganese fusing.

(3) compound inoculated

The impouring of fused high temperature liquid iron is installed in advance in the casting ladle of rare earth, ferrosilicon and copper they impulsive motions, carry out inoculation.

(4) molten iron is mediated

Molten iron after the inoculation in the casting ladle returned mix and be warming up to 1500-1550 ℃ in the stove thoroughly and come out of the stove, the teeming temperature of molten iron is controlled at 1400～1420 ℃.

4. cast

The molten iron of mediating is poured into casting mold.

Method provided by the invention adopts electric furnace or cupola furnace to add the electric furnace double melting when melting.

Synthetic cast iron provided by the invention, its as-cast structure and mechanical property are as follows:

Graphite form short-movie shape+silkworm chrysalis shape+cotton-shaped (on a small quantity)

Matrix pearly-lustre shape (＞90%)+ferrite (on a small quantity)+granular vanadium titanium carbide

Tensile strength sigma _b=280～350MPa

Hardness (Bu Shi) HB=170～240

The present invention has the following advantages:

1. the selection of chemical ingredients and supporting production method make the tissue of cast iron and the requirement that castability satisfies cylinder body, thereby can eliminate slag inclusion, pore, defective such as loose effectively, improve its mechanical property, make the cylinder body strand spare of the being produced mill back yield rate of spreading out reach 90%.

2. steel scrap is many when preparing burden, the pig iron is few, has both utilized refuse, has reduced cost again, and is convenient to adjust chemical ingredients.

3. the pig iron adopts the vanadium ferrotianium, has both satisfied the vanadium titanium content in the chemical ingredients, and (climbing steel vanadium ferrotianium than Benxi, northeast iron price low 20%) can reduce cost again.

4. order of addition(of ingredients) makes and adds graphite carbon and can be fused in the molten iron fully.

5. compound inoculatedly can reduce inoculation fade, guarantee pregnant effect.

Embodiment:

Cylinder body model: JL462Q

Starting material:

Steel scrap, its composition are C 0.1275%, Si 0.136%, Mn 0.753%, all the other Fe;

Vanadium titanium iron, its composition are C 4.1%, Si 0.14%, Mn 0.23%, P 0.017%, S 0.054%, V0.35%, Ti 0.23%, all the other Fe;

Foundry return, its composition are C 3.45%, Si 1.95%, Mn 0.7%, Cu 0.6%, all the other Fe;

Contain cerium mischmetal, its composition is Si 40.15%, rare earth 29%, Mn 0.3%, all the other Fe;

Ferrosilicon, its composition are Si 76.4%, all the other Fe;

Copper contains Cu 99.9%; Ferromanganese, its composition are Mn 79.6%, all the other Fe.

Batching (500 kilograms of total amounts):

50% → 250 kilogram of steel scrap; 30% → 150 kilogram of vanadium titanium iron; 20% → 100 kilogram of foundry return; 0.5% → 2.5 kilogram of rare earth; 1.86% → 9.3 kilogram of ferrosilicon; 0.3% → 1.5 kilogram in ferromanganese; 0.37% → 1.8 kilogram of copper; 0.35% → 1.74 kilogram of graphite carbon.

Melting: use 0.5 ton of intermediate frequency furnace

Order of addition(of ingredients) steel scrap → graphite carbon → vanadium titanium iron → foundry return

(1) fusing molten iron

(2) adjust carbon, silicon, manganese amount

The molten iron of fusing is warming up to 1500 ℃ of samplings, and rapid determination C, Si content are also adjusted in the desired amount, add the ferromanganese fusing then.

(3) compound inoculated

The impouring of fused high temperature liquid iron is installed in advance inoculation in the casting ladle of rare earth, ferrosilicon and copper.

(4) molten iron is mediated

Molten iron after the inoculation in the casting ladle returned mix and be warming up to 1500 ℃ in the stove thoroughly and come out of the stove, the teeming temperature of molten iron is controlled at 1410 ℃.

Cast:

The molten iron of mediating is poured into cylinder body casting mold.

Sample on coupon: coupon is 30 millimeters.

(1) chemical ingredients

C 3.35%, Si 2.2%, Mn 0.63%, P 0.015%, S 0.051%, Cu 0.56%, RE0.021%, V 0.112%, Ti 0.091%, all the other Fe.

(2) mechanical property

Tensile strength sigma _b=286MPa, Brinell hardness HB=218

(3) metallographic structure

Graphite form: short-movie shape+silkworm chrysalis shape+cotton-shaped (on a small quantity), 4～5 grades of graphite length.

Matrix: perlite＞90%, a little ferrite, a small amount of VC and TiC particle.

Claims

1. rare-earth vanadium titanium synthetic cast iron for engine cylinder, the chemical ingredients (by weight percentage) that it is characterized in that it is: C 3.2～3.6%, Si 1.70～2.25%, Mn 0.6～0.8%, P 0.01～0.10%, S 0.02～0.08%, V 0.10～0.20%, Ti 0.06～0.12%, Cu 0.50～0.70%, RE 0.01～0.03%, all the other Fe.

2. the production method of a rare-earth vanadium titanium synthetic cast iron for engine cylinder is characterized in that this method for synthetic casting, promptly adopts a small amount of pig iron, and a large amount of steel scraps add graphite carbon and synthesize,

Batching mode is as follows:

Steel scrap 40～50%, foundry return 20～30%, vanadium titanium iron 30～40%, C, Si, Mn, Cu, RE element add according to calculating aequum,

Order of addition(of ingredients) is as follows:

Steel scrap → graphite carbon → vanadium titanium iron → foundry return

Melting technology is as follows:

(1). the fusing molten iron

Add start fusing behind the vanadium titanium iron by above-mentioned order of addition(of ingredients), wait to begin to add foundry return successively after the fusing, join foundry return until adding and also be fused into molten iron fully,

(2). adjust C, Si, Mn amount

The molten iron of fusing is warming up to 1500～1550 ℃ of samplings, and rapid determination C, Si content are also adjusted in the desired amount, and add institute then and join the ferromanganese fusing,

(3). compound inoculated

The impouring of fused high temperature liquid iron is installed in advance inoculation in the casting ladle of rare earth, ferrosilicon and copper,

(4). molten iron is mediated

Molten iron after the inoculation in the casting ladle returned mix and be warming up to 1500～1550 ℃ in the stove thoroughly and come out of the stove, the teeming temperature of molten iron is controlled at 1400～1420 ℃.

3. rare-earth vanadium titanium synthetic cast iron according to claim 1 is characterized in that RE is for containing cerium mischmetal.