CN1493781A - Manufacturing method of cast acicular constiteont alloy ash cast iron cylinder jacket - Google Patents

Abstract

A technology for manufacturing the cast bainite alloy-gray cast iron cylinder sleeve includes using pig iron No.18 and high-grade waste steel to smelt molten iron containing C (2.6-3.3%), Si (1.7-2.5), S (0-0.1) and P (0-0.15), adding alloy elements: Mn (0-0.8%), Ni (0.8-1.5) and Mo (0.6-1.0), centrifugal casting, cooling to 400-500 deg.C for 3-6 min, slow cooling, tempering at 500+/-20 deg.C, holding the temp for 1.5-3 hr, and cooling at 40-120 deg.c/hr.

Description

The manufacture method of as-cast bainite alloy gray cast-iron cylinder liner

Technical field

The present invention relates to a kind of manufacture method of as-cast bainite alloy gray cast-iron cylinder sleeve.

Background technique

Along with science and technology development, requirement to automobile and engineering machinery engine is more and more higher, cylinder liner is as the heart of motor, its material is had higher requirement, traditional phosphorus alloy Cast iron liner, the boron alloy cast iron cylinder sleeve, molybdenum chrome copper cylinder sleeve, molybdenum monel cylinder sleeve etc. more and more can not satisfy high-power, the usage requirement of high-performance enginer, as comings C Engine Series is that China east wind group company and Cummins Corp are joint from having of Cummins Corp's introduction is world-class, heavy-duty engine has advanced design, and power character is big, oil consumption is few, the efficient height, noise is low, reaches characteristics such as Europe II emission standard, it is exactly the as-cast bainite alloy gray cast-iron to the material requirement of C Engine Series cylinder sleeve, and the as-cast bainite alloy gray cast-iron does not still have producer's development and production in China.In order to give comings C Engine Series supporting, thereby the material that can make cylinder liner attains a new height and significantly improves the working life of homemade motor, catch first chance, dominate the market, my company has dropped into lot of manpower and material resources, and as-cast bainite alloy gray cast-iron cylinder liner is developed.Because cylinder liner employing as-cast bainite material internal-combustion engine industry at home still belongs to blank.At present, this kind material has only by austempering and just can obtain, and it is very big to obtain the bainite difficulty under as cast condition.For developing new product, my company has set up foundry engieering tackling key problem group, with technique center 250Kg middle frequency furnace is experiment fusing means, with the centrifugal casting machine of PLC machine control as the cast means, self-control cooling control apparatus, with Switzerland ARL3460 metal photo-electric direct reading spectrometer is the both analysis means, carries out metallographic test with the Japanese Olympus metallurgical microscope.Adopt the WE-30 universal material experimental machine in Jinan to carry out the mechanical property analysis.Through studying assiduously of time more than 2 years, summing up experience in failure has many times finally been manufactured experimently out the as-cast bainite cylinder sleeve that metallographic, mechanical property all meet the demands, and has been dropped into batch process.

Summary of the invention

The manufacture method that the purpose of this invention is to provide a kind of as-cast bainite alloy gray cast-iron cylinder liner.

Technological scheme of the present invention: a kind of manufacture method of as-cast bainite alloy gray cast-iron cylinder liner, processing according to the following steps:

(1), select for use 18# pig iron 65-75% and high-quality steel scrap 20-30% to cast iron melting, chemical Composition Control is at C 2.6～3.3%, Si 1.7～2.5%, S≤0.1%, P≤0.15% or C 2.8～3.3%, Si 1.7～2.5%, S≤0.1%, P≤0.15%.

(2), add alloying element, control its composition and be, Mn≤0.8%, Ni 0.8～1.5%, Mo 0.6～1.0% or Ni 0.3～0.5%, Mo 0.6～1.0%Cu+Ni 〉=1.0%

(3) cooling: the high temperature blank of centrifugal pressure casting depanning is placed on the cooler, and air cooling or made the blank temperature reduce to 400～500 ℃ in air-cooled 3～6 minutes will be put into slow cooling box through air cooling or air-cooled blank, make its slow cooling.

(4) with the tempering in heat treatment furnace of semi-finished product cylinder sleeve, when tempering temperature is 500 ℃ ± 20 ℃, be incubated 1.5～3 hours, cool off with 40～120 ℃/h then.

The advance of as-cast bainite alloy gray cast-iron cylinder liner:

1, succeeding in developing of as-cast bainite alloy gray cast-iron cylinder liner filled up a domestic blank, for the production domesticization of east wind comings C Engine Series contributes, reduced cost of production, reduced the foreign exchange expenditure.

2, this kind material can be used for domestic other motors, and it is high-power that homemade motor is realized, low oil consumption, low emission (Europe II standard), long lifetime.The life-span of cylinder sleeve compares with original material and has improved 3～5 times, promptly reaches 50～700,000 kilometers, and social benefit is considerable.

3, domestic still do not have adopt this kind explained hereafter cylinder liner, compare with the cylinder liner that Britain Sheepbridge company produces, the metallographic of material, mechanical property detect the cylinder jacket material mechanical property that all is not less than in Britain Sheepbridge company through Dong Feng Auto Corporation's technical study.

Embodiment

One, manufacturing process

1, batching, chemical Composition Control is at C 2.6～3.3%, and Si 1.7～2.5%, S≤0.1%, P≤0.15%, Mn≤0.8%Ni 0.8～1.5%, Mo 0.6～1.0% (intensity is higher than the high-strength gray cast iron bainite of 380Mpa) or C 2.8～3.3%, Si 1.7～2.5%, S≤0.1%, P≤0.15%, 0.5≤Mn≤0.9%, Ni 0.3～0.5%, Mo 0.6～1.0%Cu+Ni 〉=1.0% (intensity is higher than the gray cast iron bainite of 350Mpa)

2, fire and breed: breed with silicon titanate innoculant in going out the process of molten iron, pregnant amount is 0.4～0.9%.

3, an amount of molten iron is poured in the centrifugal pressure casting machine casting mold.After 10～30 seconds, casting mold was swashed water 30～70 seconds, make the cylinder sleeve cooling, wait the blank temperature to reduce to below 850 ℃ blank is released mold.

4, cooling: blank is placed on the cooler, air cooling or made the blank temperature reduce to 400～500 ℃ of low-alloy in air-cooled 3～6 minutes must be air-cooled), will carry out roughing through air cooling or air-cooled blank, obtain semi-finished product.

5, with the tempering in heat treatment furnace of semi-finished product cylinder sleeve, tempering intensification degree is 500 ± 20 ℃ (Mo, Ni, the high capping of Cu, the low limits of taking off), is incubated 1.5～3 hours, cools off with 40～120 ℃/h then.

Through machining further rest and reorganize processing, check complete qualified finished product cylinder sleeve.

Two, as-cast bainite alloy gray cast-iron cylinder liner the key technical indexes

1, metallographic structure: graphite is based on A type and E type, and B type graphite is not more than 25%, and D type graphite is not more than 10%.Graphite length is 20～160 microns, 4～6 grades qualified (U.S. ASTM standard).

2, mechanical property: (1) hardness: 270～330HBS (2) intensity: tensile strength 〉=379Mpa (or tensile strength 〉=350Mpa)

Bending fatigue strength 〉=152Mpa Young's modulus 140000～180000Mpa

3, the selection of chemical composition

(1) C, Si content are to the influence of quality of product:

Because cylinder sleeve cools off under the state of centrifugal pressure casting comparatively fast, super cooling tendency is big, and C content is low, D, E type graphite very easily occur, and hardness is higher, and C content height, it is too much to occur graphite quantity again, and matrix is isolated seriously, and intensity hardness is on the low side.So the control carbon content also is the key of producing,, adjusts C and be controlled at optimum range (2.6-3.3) according to the situation that my company produces.

As you know, silicon is to promote graphite element strongly, it can make the eutectic point of Fe-C alloy move to left, eutectic temperature raises, and helps diffusion, the gathering of C atom in molten metal, and graphite is grown up, thereby make graphite flake thick, therefore should be low as far as possible under the prerequisite that can guarantee the metallographic requirement, this helps strengthening pregnant effect, improves the tensile strength of cast iron.According to my company's knowhow, suitable selection control range (1.8-2.5) can guarantee metallographic, can guarantee the comprehensive mechanical performance of cylinder sleeve again.

(2) Mn and Cr are to the influence of cylinder sleeve

Mn is weak carbide former, Cr is the strong carbide forming element, they promote that within the specific limits C curve moves to right, and improve intensity and hardness, but improve thereupon, cylinder sleeve hardness increases, fragility increases, and obdurability reduces, and worsens machinability, so suitable Mn:0.3-0.9, Cr:0.1-0.3 are wanted in Mn, Cr control.

(3) effect of Cu

Cu can promote the cast iron graphitizing in the eutectic stage, promotes the C line to move to right in the cylinder sleeve cooling procedure, improves the effect of the effect of intensity and fatigue strength, thus can suitably increase, but the Cu price is more expensive comparatively speaking, and must strict control (0.3-1.0).

(4) control of S and P

We think that S not only can reduce the intensity of cast iron, and can reduce the flowability of iron liquid, and easily producing slag inclusion, casting defects such as pore are so S＜0.12 is more suitable, though P can produce iron phosphide eutectic, reduce matrix strength, but it can increase the flowability of iron liquid, reduce casting defect, therefore, under the situation that guarantees iron phosphide eutectic quantity and form, must strictly control content, P is advisable to be no more than 0.2%.

(5) control of Mo and Ni

Mo and Ni are the elements that promotes that strongly bainite forms, and suitably improve the content of Mo, Ni, more help obtaining bainite under as cast condition.But the more expensive impossible addition of price is very big.

Three, technological equipment:

1, smelting electrical furnace

2, PLC centrifugal casting machine

3, cooling control apparatus

4, car type furnace or electric furnace of resistance type

5, metal photo-electric direct reading spectrometer

6, metallurgical microscope

7,30T universal material experimental machine

8, Brinell hardness tester

9, fatigue bending machine.

Claims (1)

1, a kind of manufacture method of as-cast bainite alloy gray cast-iron cylinder liner is characterized in that: processing according to the following steps:

(1), select for use 18# pig iron 65-75% and high-quality steel scrap 20-30% to cast iron melting, chemical Composition Control is at C 2.6～3.3%, Si 1.7～2.5%, S≤0.1%, P≤0.15% or C 2.8～3.3%, Si 1.7～2.5%, S≤0.1%, P≤0.15%.

(2), add alloying element, control its composition and be, Mn≤0.8%, Ni 0.8～1.5%, Mo 0.6～1.0% or Ni 0.3～0.5%, Mo 0.6～1.0% Cu+Ni 〉=1.0%

(3) cooling: the high temperature blank of centrifugal pressure casting depanning is placed on the cooler, and air cooling or made the blank temperature reduce to 400～500 ℃ in air-cooled 3～6 minutes will be put into slow cooling box through air cooling or air-cooled blank, make its slow cooling.

(4) with the tempering in heat treatment furnace of semi-finished product cylinder sleeve, when tempering temperature is 500 ℃ ± 20 ℃, be incubated 1.5～3 hours, cool off with 40～120 ℃/h then.