CN1075350A - Valve with hard-facing - Google Patents

Abstract

A kind of nickel-base alloy that is used for the seat material on the exhaust valve for internal combustion engine, it contains chromium, 0～8% tungsten, 4～7% aluminium, 0.2～0.55% carbon, 0～2% hafnium, 0.1～1.5% niobium, 0～8% molybdenum, 0～1.2% silicon and 0～15% the iron of (representing with weight percentage) 20～24%, and wherein the total content of tungsten and molybdenum must not surpass 10%.When 500 ℃ of operating temperatures and be in the sulfur environment that severe corrosive is arranged very much, its alloy have good anti-corrosion and with alloy 50 corresponding ductility.

Description

Valve with hard-facing

The present invention relates to a kind of valve, particularly a kind of outlet valve that is used for internal-combustion engine, it comprises a movably valve member, this valve member has the valve seat section of a nickel based metal alloy.

For many years, in the outlet valve of internal-combustion engine, the metal ingredient of selected valve seat section is to the life-span of internal-combustion engine functional reliability and outlet valve, and necessary maintenance work aspect has played very big effect.

In internal-combustion engine, the burning in the clutch release slave cylinder produces the coking residue of being made up of grit, and these residues are discharged from by outlet valve.But these residues can be stuck between the closed valve seat sometimes, thereby may produce indenture on valve base surface.Described indenture can cause local leakage at first in a well-known manner, just can cause that then large size burns out, and valve base surface is subjected to corrosion and damage.

Desirable seat material preferably has enough hardness to reduce or to hinder the formation of indenture.In recent years, in the diesel engine of great majority use Heavy diesel oil, did many trials, make this valve seat surface with Ni-based hard-facing metal alloy 50.Most important alloying element comprises about 12% and chromium (Cr), 3.9% silicon (Si), 2.9% iron, 2.25% boron (B) and 0.5% carbon (C) in this metal alloy.Except that desired hardness, alloy 50 has high temperature corrosion-resisting under very strong corrosive environment, outlet valve in the diesel engine of use Heavy diesel oil can use in this strong corrosive environment, for example in the motor of 600～900 millimeters big cylinders, except having excellent corrosion resisting performance, to the mechanical strength of employing material, also has the requirement of strictness.Use the result to show that under a stable condition, radial crack occurs on the hard material alloy 50, thereby cause that the whole of valve seat burn out, or the danger of using the limit to damage strengthens.In order to eliminate this danger, ductile hard material stellite 6 can be used for such motor, as cobalt base alloy, in actual environment, the high temperature corrosion-resisting of this cobalt base alloy is less than the high temperature corrosion-resisting of alloy 50, thereby shortened the use blanking time of each test valve situation.

As everyone knows, when temperature raise, the hardness of hard material descended.Like this, stellite 6 at room temperature hardness is about 370HB, and hardness is about 298HB when temperature is 500 ℃, and alloy 50 is when corresponding temperature, and hardness is about 530HB to 420HB respectively.

Up to now, everybody is also clear, and it is very poor or do not have an extensibility to have the general ductility of Ni-based hard material of high hardness.Therefore its fatigue strength is on duty mutually.

Up to now in the nickel-base alloy known to, preferably obtain required hardness by adding boron, silicon and carbon component.Particularly the metal boride in described alloy structure owing to their size and dimension, in welding process or after shortening or prolonging the operation cycle, makes this stiff dough have poor ductility, and produces the danger of breaking.

Boron content in reducing alloy or remove fully under the situation of boron in order to improve hardness of alloy, just must increase the content of carbon by the method for a large amount of deposition carbide.Thereby produce the deposition carbide network, also greatly reduce ductility.

A universal feature in the nickel-base alloy of described prior art is, in order to obtain high hardness when about 500 ℃ operating temperature, just must provide such alloy, and this alloy has suitable hardness and brittleness at normal temperatures.

Japan Patent Jp-A-59-9146(is open) relate to a kind of valve of nickel-base alloy, be lower than 4.5% at the content of this Aluminum in Alloy, be convenient to the welding of alloy.Being higher than 0.55% carbon by the deposition of carbide, titanium, tungsten and molybdenum and content with in the alloy just combines and can improve hardness of alloy.Disclosed boron up to 2% can further make alloy rigidity increase greatly.But, will change aspect the micro-penetration hardness of alloy, this is because stone carbide is deposited on the reason that its ductility gone up and also can reduce owing to above-mentioned carbide network mutually by softer base with boride.

US Patent specification US-A-3795,510 relate to a kind of nickel-base alloy, and it contains 20% chromium, 5.5% aluminium, 2.5% titanium, 7.5% iron and 0.15% carbon.This valve is to be welded on the operating valve parts of being made up of carbon steel by the nickel alloy blank that friction welding will be made in advance.This alloy can not weld with general method, and its hardness is significantly less than the hardness that the present invention will reach.

The purpose of this invention is to provide a kind of valve with hard material, this valve can be used on the motor of any specification, the high temperature corrosion of the high hardness when it has more than 500 ℃ simultaneously, good anti-combustible substance and enough ductility are so that it is used in the periodic duty valve of high mechanical load.

For this purpose, the valve that the present invention's beginning is mentioned is characterised in that described nickel-base alloy, represent recently and except that all impurity that with weight percent it contains aluminium, 0.2%～0.55% carbon, 0～1.8% hafnium, 0～1.5% niobium, 0～8.0% molybdenum, 0～1.2% silicon and 0～15% the iron of 20～24% chromium, 0～8% tungsten, 4-7%.Wherein the content summation of tungsten and molybdenum is no more than 10%.

Be surprised to find this alloy and had required characteristic.People always thought in the multi-layer welding termination process in the past, have the high welding nickel alloy of aluminum content and have sizable hot tearing trend when weld metal is combined with the parting structure that is influenced by heat.Thereby the described in the literature nichrome with the aluminium more than 3～4% is considered to not have the possibility of welding.

The weldability of the nichrome with above-mentioned aluminium content that proposes according to the present invention has been utilized the PH process in this alloy, thus intermetallic phase Ni ₃Al(γ ') is deposited and is called relevant hardness, increased the phase in ductile Ni-based (γ).γ ' can deposit in structure and reach 45%, be preferably in the basic γ structure and deposit 20% at least, so that the material that acquisition has required high strength and high hardness, therefore, in general when common work outlet valve is put into 20 °～600 ℃ temperature environment its intensity and hardness can not change.

Chromium content in the alloy is to the great help that met the demands.This requirement is that its alloy must have quite high corrosion resistance in working environment.Sulfur compound has played basic role in this working environment.Aluminium content makes and form an Al on valve seat ₂O ₃And Cr ₂O ₃The combination meter surface layer, thereby improved corrosion resistance, particularly improved corrosion resistances 750 ℃ and its above temperature.Thereby under the situation that leakage formation indenture takes place on the valve seat, the described corrosion resistance that is enhanced can prevent that especially valve seat is damaged very soon, and above-mentioned leakage can cause the local surfaces temperature to be higher than the normal working temperature of valve.

In addition, the content of chromium has the dissolving humidification, and it helps to improve the intensity of alloy, and its dissolving humidification can further add molybdenum by conversion and tungsten improves.The total content of molybdenum and tungsten must not surpass 10%, otherwise the carbide structure of alloy can produce opposite effect.

The last definite of alloy rigidity be can influence by the content of adjusting carbon, thereby the quantity and the structure of carbonaceous deposits influenced.If the content of carbon is lower than 0.2%, just can not obtain required hardness.If the content of carbon surpasses 0.55%, just is difficult to obtain required ductility.Certified is that the alloy that contains 0.3%～0.55% carbon provides hardness and the ductility that is best suited for the valve material.

Opposite with the commercial nickel that is easy to obtain, chromium, boron with the silicon hard facing alloy, alloy of the present invention also can be used for making hot isostatic pressing power (HIP) mixing exhaust valve, because the solidus temperature of this alloy is near the solidus temperature of valve body material, this is the necessary condition of hot isostatic pressing power technology.

The ductility of alloy is subject to the influence of carbide structure, particularly needle-like, and the carbonaceous deposits of sheet shape plays opposite effect to ductility.For existing alloy, having determined to produce this trend that is unfavorable for carbide structure of being made " Chinese test result " (" Chinese scri Pt ") type increases along with the increase of Kohlenstoffgehalt, for this reason, the content of carbon must not surpass 0.6%.

Have been found that the hafnium of adding 1～2%, carbide structure is had active influence, owing to increased hafnium, carbide structure is by needle-like, and sheet shape carbide becomes more circular carbide, and its circular carbide can not reduce the ductility of alloy on same degree.Yet, beat allly be, by adding hafnium, carbide only to be had to a certain degree influence just in case Kohlenstoffgehalt surpasses 5%.And in this case, Kohlenstoffgehalt is adjusted at 0.35～0.50%, easy.

Yet, proof in surprise, its alloy structure, especially slow already solidified melt adds and is no more than 1.5% niobium (Nb) and has high hardness, and this may be because the component that niobium has increased the amount of carbon precipitates and/or changed carbide.Find out simultaneously, add niobium in alloy, the carbide after the change occurs with the form of segmentation metal carbide, and this kind carbide has active influence to the ductility of alloy.

When valve seat area is soldered, can add silicon (Si) to improve welding performance, this is because the deoxidation of silicon.The content of silicon approximately is controlled at 0.8～1.2%.Yet, be surprisingly found out that when aluminium content surpassed 5～5.5%, described silicone content had caused aluminium, silicon, chromium and the formation of the rich eutectic of the chances are carbon.Because the corrosion-resistant corrosivity of the relict structure element of surprisingly described eutectic ratio alloy is low, be limited in described eutectic phasor about below 5% because wish.

Valve member with suitable valve seat area is generally made by austenitic stainless steel alloy.When the valve seat district was soldered, a small amount of alloyed steel was blended in the Ni-based filler, therefore added by mixing ground, and when particularly welding first layer, the amount of iron is no more than 15%.

γ mutually in, being less than 20% iron content has a kind of enhancement effect, still, its corrosion resistance has also reduced simultaneously.At iron content is 5% o'clock, the danger that exists corrosivity to reduce.Therefore purpose is that last weld layer becomes the iron content of valve district near surface not to be higher than 10%, is preferably lower than 5%.

In the zone on proximate valves surface, its alloy should preferably comprise 55% nickel at least, because low nickel content can reduce sedimentary hardness, thereby reduces this hardness of alloy.

As mentioned above, this hardness of alloy is to obtain by adding hard sludge, the high aluminium content of the alloy in its sludge increases the hardness of nickel-base material (Ni-matrix) itself, and its hardness is at high temperature constant, and the sedimentary hardness of the carbonization in its stock also has this characteristic.In order to preserve useful carbide structure, the carbide that its alloy should contain minimum definite amount forms thing, except the chromium content of regulation.Therefore, to be at least 5% be favourable to the content of hafnium, niobium, tungsten and molybdenum.

Referring now to chart each embodiment of the present invention is described in detail, Fig. 1 to Fig. 4 has amplified 320 times photo, is the grinding of 4 kinds of different-alloys and the photo of polishing sample according to the present invention.

Example 1

For alloy of the present invention and known valve seat alloy are done a basic comparison, make 4 valve rod blanks that geometrical shape is identical, be the shape of Austenitic Stainless Steel valve head, its diameter D=250mm.After its rod member preheated, by the plasma welding of conversion electric arc, 4 kinds of different-alloys are welded to respectively on separately the blank, welding parameter is as follows:

The grade of welding powder: 50～150 μ m

Deposition: 1.7 kilograms/hour

Welding current: 120A

Welding speed: be about 60 millimeters/hour

Its soldered is three layers, and its degree of depth is 8mm, and width is 25mm, and the tape edge angle is 60 °.

Table 1 is listed in the proximate analysis of the alloy that is made of, and wherein stellite 6 and alloy 50 mentioned in the above that mark alloy B W1-50 also was a kind of nickel alloy that economic implications is arranged, and mark alloy I-1 is a kind of alloy of the present invention.

Table 1

The weight percentage component

C Si B Cr Fe Ni W Mo Al other

Tungsten chromium cobalt 6 1.14 1.06-28.5 0.43-4.65--all the other Co

Alloy 50 0.46 3.9 2.25 10.78 2.88 all the other----

BW1-50 0.49 6.99 0.92 19.30 3.5 all the other 1.75---

I-1 0.51 1.02-23.05 0.23 all the other 7.1-5.63 0.43Y

With the face of weld upset, check defective after the welding through capillary detection.

Then blank is placed on and is heated to 250 ℃ in the stove, then they are put into an about pond of 40 ℃.By visual inspection and capillary detection blank, on seat material, do not find any crack.

All blanks are put into stove once more be heated to 350 ℃, then they are put into about 70 ℃ pond earlier, with the naked eye reach capillary detection afterwards, in alloy 50, find three radial cracks and some crackles, and other three do not have defective.

Three intact blanks that are heated to 450 ℃ are carried out the temperature blockage test again, put into 70 ℃ water afterwards, in the BW1-50 alloy, find the fractue spacing of coarse-grain lattice crackle form, and other valve seat district of two is not damaged.

Then this two blank is heated to 520 ℃, and puts into about 70 ℃ water, show that through naked eyes and capillary detection a large amount of radial cracks are arranged, and itself there is a radial crack in the valve seat district of I-1 alloy in stellite 6.Opposite with other three kinds of alloys, the crack in the I-1 alloy has clearly illustrated the plastic deformation feature that is limit, round crack shape.

Nickel-base alloy of the present invention has weldability and ductility preferably, and its resistance to cracking is fully identical with stellite 6, and is better than nickel-base alloy 50 and BW1-50.

A radial opening is offered in seat zone at each valve rod, carries out hardness test (HV20) when welding on its opening, and this test is to carry out apart from the different distance of seat surface at normal temperatures, and test result is as shown in table 2.

Table 2

Alloyed tungsten chrome-cobalt alloy 6 alloys 50 BW1-50 I-1

Throat depth (mm) 8.8 9.5 8.0 8.5

Seating face is measured hardness (HV20) down

The position (mm) of amount point

0.5 426 473 490 457

1.5 441 473 509 412

2.5 441 473 509 426

3.5 426 490 509 426

4.5 386 473 374 441

5.5 412 374 412 362

6.5 412 374 374 374

7.5 399 386 278 286

8.5 412 271 232 303

9.5 257 271 - 226

10.5 - 232 - -

As can be seen, the hardness of nickel-base alloy is responsive to the mixing of the stem material in the seat material, and the hardness of the outer part of seat material owing to reason is rapidly solidified in the molten bath, thereby has stoped the complete equilibrium of alloy compositions in the expection lit range.

Example 2

In order when heating up, to test this hardness of alloy, by a kind of so-called hot isostatic pressing method (HIP-Process), produce bar-shaped blank with powdery starting material, the diameter of this kind blank is 30mm, long 160mm therefrom downcuts the thick sheet of 8mm and carries out hardness measurement.Stellite 6 and nickel-base alloy that this kind blank is analyzed with table 1 are made, the hardness that records (HB10/3000/15) is listed in table 3, as can be seen, high temperature hardness obviously descended (28%) when stellite 6 was 500 ℃ in temperature, and alloy rigidity of the present invention decline very little (3%).

Table 3

Temperature stellite 6 I-1

Hardness HB

20℃ 415 406

500℃ 298 393

By with the hardness ratio of table 2, hardness measurement (HV20) result of following three stellites 6 of room temperature and I-1 is as follows:

Table 4

Stellite 6 I-1

a b c a b c

HV(20) 441 441 438 426 426 426

The hardness that records alloy 50 seat materials in the table 2 about 20 ℃ is 473HV, and the hardness of this seat material has reduced approximately 20% when operating temperature, and hardness becomes 378HV, and that the I-1 hardness of alloy only reduces when operating temperature is about 3%, is 413HV.

Example 3

By artificial TIG welding, be 80mm at diameter, thickness is welding various alloys of the present invention on the valve rod blank of Austenitic Stainless Steel of 20mm, the initial analysis result of these alloys is referring to table 5.

Be included in 20 ℃ and the 500 ℃ various hardness of alloy of measuring (HB10/3000/15).

Table 5

C Si Cr W Nb Mo Al Ni 20℃ 500℃

I-2 0.55 1.14 23.3 6.53--6.04 all the other 438 429

I-3 0.5 1.05 23 5.88 0.35 0.9 5.44 all the other 435 415

I-4 0.44 0.95 23 5.22 0.7 1.8 4.83 all the other 420 388

I-5 0.4 0.86 23 4.57 1.05 2.7 4.22 all the other 415 385

As can be seen, from room temperature to 500 ℃, the hardness downward trend increases, from about 7% of about 2% to I-5 alloy of I-2 alloy.

Every kind of alloy is further made grinding and polishing sample, and Fig. 1 to 4 is alloy I-2 photos to alloy I-5 sample.

In Fig. 1, visible spherical dark sludge may contain Al from alloy I-2, Si, and Cr and C eutectic perovskite do not have the sludge of aluminum metal carbide with elongated light color, can make alloy that higher ductility is arranged by reducing carbide precipitation.

I-3 alloy among Fig. 2 demonstrates a kind of clearly dendritic lattice structure, and wherein material has a kind of uniform crystal lattice orientation.Some perovskite sludges and metal carbide sludge are arranged in dendritic morphology.This alloy may have ductility and higher high temperature hardness preferably.

Alloy I-4 among Fig. 3 has a pine-tree structure, and some is inhomogeneous slightly for this structure, and only presents few perovskite deposition.In the alloy I-5 of Fig. 4, the perovskite deposition can not appear in general.

Example 4

On nickel-base alloy, do and example 2 described the same experiment of hardness, the analysis of its experiment is consistent with the I-1 in table 1 and the table 3, but before measuring its hardness, this blank is heat-treated, heat treatment is included in the solution treatment of carrying out under 1150 ℃ of high temperature 2 hours, then carries out 2 hours precipitation hardening under 750 ℃ temperature at least.Measured hardness (HB10/3000/15) is listed in the table 6, and measured hardness (HV20) is listed in the table 7.

Table 6

I-1

Temperature hardness HB

20℃ 496

500℃ 462

Table 7

I-1

a b c

HV(20) 502 509 506

Though high temperature hardness slightly descends (7%), the last hardness in the time of 500 ℃ is about 460HB, than much higher by the obtainable hardness of existing hard facing alloy institute.

If the content of chromium is less than 20% in the alloy, it is meaningless that its corrosion resistance will become when high temperature.If the content of chromium surpasses 24%, the strength characteristics of this alloy will be adversely affected, and in addition, its welding performance be descended.

As if when aluminium content was less than 4%, high temperature hardness was too low, aluminium content is higher than at 7% o'clock, and the perovskite deposition is unfavorable for the corrosion resistance and the ductility of alloy.

This alloy both can be used for valve seat is welded on the valve member, and this alloy will comprise silicon in this case, and the amount of yttrium oxidation will be lacked as much as possible.This alloy also can be used for the HIP method and makes this valve member.

Prove that nickel alloy comprises aluminium, 0～5% iron, 0.3～0.5% carbon and 5～7.5% tungsten and/or the molybdenum of 20～23% chromium, 4-5.5%, its alloy has high hardness and good ductility.If valve seat is welded, can suitably play effect by adding nickel-base filling material so.This packing material comprises 20～23% chromium, 4～5.5% aluminium, 0.3～0.5% carbon, 0.8～1.2% silicon and 5～7.5% tungsten and/or molybdenum.

As if the alloy that contains 22.5～23.5% chromium, 4.0～5.0% aluminium, 0.40～0.45% carbon, 1.0～1.5% hafnium and 5.5%～6% tungsten and/or molybdenum can be applied in has very high requiring under the situation to hot-cracking resistance.

If make this alloy with the HIP method, that may comprise yttrium when analyzing, and therefore aspect high temperature resistant positive effect is arranged.

Should see that according to circumstances the various compositions of its alloy are all recently represented with weight percent.

Claims (12)

1, a kind of valve, outlet valve especially for internal-combustion engine, it comprises a movably valve member that has a nickel based metal alloy valve seat end face, it is characterized in that nickel-base alloy, represent with weight percentage, except that the impurity of general existence, contain 20～24% chromium, 0～8% tungsten, 4～7% aluminium, 0.2～0.55% carbon, 0～2% hafnium, 0～1.5% niobium, 0～8.0% molybdenum, 0～1.2% silicon and 0～15% iron, wherein the content sum of tungsten and molybdenum must not surpass 10%.

2, valve according to claim 1 is characterized in that this alloy has 20～23% chromium, 4～5.5% aluminium, 0～5% iron, 0.3～0.5% carbon and 5～7.5% tungsten and/or molybdenum.

3, valve according to claim 1 is characterized in that this alloy contains the hafnium of 22.5～23.5% chromium, 4～5% aluminium, 0.40～0.45% carbon and 1～1.5% and 5.5～6% tungsten and/or molybdenum.

4,, it is characterized in that this alloy has 1～2% hafnium and 0.35～0.5% carbon according to arbitrary described valve in the claim 1 to 3.

5,, it is characterized in that this alloy contains 0.3～1.5% niobium, is preferably 0.5～1.4% niobium according to the arbitrary described valve of claim 1～4.

6,, it is characterized in that this alloy contains 0.6～4.0% molybdenum and tungsten according to the arbitrary described valve of claim 1-5.

According to the arbitrary described valve of claim 1～6, it is characterized in that 7, a kind of alloy content in hafnium, niobium and the molybdenum is 0% at least.

8,, it is characterized in that this alloy contains 0.6～1.2% silicon, preferably contains 0.8～1.2% silicon according to the arbitrary described valve of claim 1～6.

9,, it is characterized in that near the described valve base surface alloy contains to be no more than 5% iron according to the arbitrary described valve of claim 1～6.

According to the arbitrary described valve of claim 1～9, it is characterized in that 10, the total alloy amount of hafnium, niobium, tungsten and molybdenum is at least 5%.

11,, it is characterized in that near the alloy valve surface contains 55% nickel at least according to the arbitrary described valve of claim 1～10.

12, the manufacture method of the arbitrary described valve of a kind of claim 1～11, wherein the valve seat end face is with welding manner it to be welded on the valve member, it is characterized in that, when welding, the condensation material of filling out that adds nickel alloy, except that the general impurity that exists, its nickel alloy contains the chromium of 20-23%, the aluminium of 4-5.5%, the carbon of 0.3-0.5%, the silicon of 0.8-1.2%, the hafnium of 0-2%, tungsten and/or the molybdenum of 5-7.5%, remaining nickel.

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