GB2253213A

GB2253213A - Injection part for die-casting machines

Info

Publication number: GB2253213A
Application number: GB9201411A
Authority: GB
Inventors: Soeda Tomomi
Original assignee: TYK Corp
Current assignee: TYK Corp
Priority date: 1991-01-24
Filing date: 1992-01-23
Publication date: 1992-09-02
Anticipated expiration: 2012-01-23
Also published as: DE4201781C2; KR960006046B1; CA2060028C; CA2060028A1; FR2672056A1; FR2672056B1; DE4201781A1; KR920014946A; GB2253213B; GB9201411D0

Description

225, - 4_ 32 1 IN3ECTION PART FOR DIE-CASTING MACHINES

BACKGROUND OF THE INVENTION

This invention relates to an injection part for die-casting machines, which is to be in contact with molten metal or alloy such as injection nozzles for diecasting machines. More particularly this invention relates to the injection part for die-casting machines, which.is excellent in resistance to melt-erosion, impact resistance, and suitable for casting of non-ferrous metals (including alloys thereof) such as aluminum, zinc, tin and lead.

Recently, the die-casting which enables non-ferrous metals such as aluminum and the like to cast with high precision at a high speed, has become an important process of casting various kinds of parts in the fields of manufacturing automobiles, industrial equipments, household electrical appliances and the like.

Conventionally there has been used hot die steel of JIS SKD61 and the like for injection parts of diecasting machines. In recent years, there have been used injection parts for die-casting machines of such as sleeves, plungers and the like, wherein ceramic members are provided on the portion in contact with the melt by shrinkage fitting or inserting.

However, the conventional injection parts for die-casting machines stated above have problems as follows.

Firstly, in relation to the injection parts made of die steel, the portion in contact with the melt used in die-casting machines is strikingly eroded by the melt, because non-ferrous metals generally have a character tending to readily react with iron,. Consequently the injection part has only a short life, bringing about necessity for frequent exchanges thereof. Moreover steel has a high thermal conductivity, so that the temperature of the melt injected into an injection part is likely to fall down, thus markedly deteriorating production yield of casts.

On the other hand, certainly it is true that the injection parts in which a ceramic is disposed to the portion in contact with the melt, is excellent in resistance to melt-erosion, but the impact or shock exerted on the injection part at the moment when the die-casting machine injects the melt is so strong that the portion made of ceramic, which is brittle in itself, is liable to break down. If it happens, operation has to be stopped, resulting in inefficiency.

SUMMARY OF THE INVENTION

It is therefore an object of the present inventio to provide an injection part for die-casting machines which is excellent in melt-erosion resistance against melts of non-ferrous metals, impact resistance, heat retainability and wear resistance, having a long life and good works efficiency.

In the injection part for die-casting machines of the present invention, at least a part of a portion in contact with melt is formed of a composite material obtained by sintering a mixture of:

a first powder of a metal or alloy selected from a group consisting of Mo, Mo alloy, Nb, Nb alloy, Ta, Ta alloys, V and V alloys; second powder of Ti or a Ti alloy; third powder of ceramic.

Here, the first powder of the metal or alloy such as Mo, Mo alloy or the like, is compounded in an amount of 0.1 to 50 by volume.

The third powder is preferably compounded in an amount of 0.1 to 50 by volume.

Since in the injection part for die-casting machines according to the present invention, at least a part of the portion in contact with the melt Is formed of a composite material consisting essentially of predetermined amount of a first powder of such as Mo or Mo alloy, a second powder of such as Ti, or Ti alloy and a third powder of ceramic, it is possible to suppress erosion by melts and wear of the injection part for diecasting machines to a great extent. Moreover, since it is excellent in impact resistance to avoid cracks occurring in the part during the operation of injection, it is. possible to operate the machine continuously, thus providing excellent work efficiency. The same effects can be obtained other than Mo or Mo alloy by using Nb or Nb alloy, Ta or Ta alloy or V or V alloy.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

According to the present invention, at least a part of the portion in contact with the melt is formed of a composite material of mixture which contains predetermined amount of an Mo (molybdenum) or Mo alloy powder, a Ti (titanium) or Ti alloy powder and a ceramic powder. The composite material is prepared in such a manner that a titanium or titanium alloy powder having not only an excellent erosion resistance against melts of non-ferrous metals but also a good impact resistance, is added with ceramic particles which have high strength and hardness, further being mixed with Mo or Mo alloy particles in order to enhance the wettability between the former and the latter, so that the prepared material is made to be improved in binding performance and to be excellent in any of melt-erosion resistance, impact resistance, and wear resistance.

Moreover, the composite material is low in thermal conductivity as compared to steel, thereby exhibiting excellence in heat retainability for melts.

Accordingly, formation of this composite material into the portion in contact with melt enables the injection part for die-casting machines to have a long life excellent work efficiency.

Now, explanation will be made on reasons why each component of this composite material is to be added and why there are limitations to the compositions. Mo Mo has an effect to better wettability between matrices consisting of metallic titanium or titanium alloy and ceramic particles to improve the binding performance therebetween, so that addition of Mo to the composite material makes improvement in impact resistance of the composite material. The Mo component can be added as Mo powder to the powder ingredients of the composite material or may be mixed as Ti-Mo alloy powder into the composite material. In the case where the Mo component is added as Ti-Mo alloy powder, three modes are possible as follows:

1. Ti-Mo alloy powder + Mo powder + ceramic powder 2. Ti-Mo alloy powder + ceramic powder 3. Ti-Mo alloy powder + Ti powder + ceramic powder In any case of 1. to 3, the Mo content in the composite material is required to be more than 0.1 by volume on the basis of the Mo or Mo alloy powder compounded ratio. If the Mo content is less than 0.1 by volume, the above-stated effect of improvement in wettability cannot be obtained. This failure to improve the wettability cause the imperfection of the sintering of the material powder in production, thus deteriorating the hardness and the elongation performance. on the 1 other hand, when the Mo content is more than 50 by volume, the inter- metallic compound is generated between Mo and Ti In greater amount than is required, only to make the composite material brittle. Consequently the Mo content in the composite material is restricted to be 0.1 to 50 by volume on the basis of the Mo or Mo alloy powder compounded ratio.

In place of the Mo or Mo alloy powder, the same effect is obtainable in use of Nb or Nb alloy, Ta or Ta alloy, and V or V alloy. In these cases, the content of Nb or Nb alloy, Ta or Ta alloy, or V or V alloy is restricted to the same manner.

It should be noted that there may be existing impurity component that is not removable in Mo or Mo alloy powder and in Ti or Ti alloy powder, but the present invention, needless to say, does not exclude these cases. Ceramic Powder In a case where the content of ceramic powder in the composite material is less than 0.1 by volume, the hardness and the wear resistance of the composite material are low. On the other hand, when the content of ceramic powder in the composite material is more than 50 by volume, the composite material is made to be brittle, lowering the impact resistance to thereby be broken easily. Therefore, the content of ceramic powder in the composite material is preferably 0.1 to 50 by volume.

The present invention will be explained in more detail showing examples of the injection parts for diecasting machines produced in practice according to the present invention with reference to their comparative examples.

In the first example, a Titanium (Ti) powder having an average particle diameter of 20 11A m and a silicon carbide (SiC) powder having an average particle diameter of 5)-11 m were mixed in a ratio of 5: 1 by volume. Then this powder mixture was added and mixed uniformly with an Mo powder having an average diameter of 15 Am in the proportions as shown below in Table 1.

Thus prepared mixtures were used for the starting materials.

- 8 Table. 1

Composition ( by volume) 1 1 Ti powder + Mo powder SiC powder i 1 i i i M1 99.9 Example M2 70

M3 50 0.1 30 50 i 1 1 Comparative 1 M1 1 100 1 0 Example M2 48 52 M3 45 55 Each of these stating materials was sealed up in a rubber-made pattern and was subjected to the cold isostatic pressing (CIP) process under the pressure of 1 2 ton/cm ' to form a cylinder of the pressurized powder. Then the cylinder was sintered in a vacuum furnace at a temperature of 1,350 C a pressure of 10-5 Torr.. The sintered body was processed by the lathe to be formed Into a sleeve for cold-chamber consisting of the composite material. Thus prepared sleeves were adopted as examples M1 to M3 and comparative examples M1 to M3 respectively.

Next to this, a titanium alloy powder of 45 rm in average diameter comprising Mo in an amount of 15 by volume and titanium and inevitable impurity for the rest, and tungsten carbide (WC) of 10xm in average diameter were mixed uniformly in the compositions as shown below in Table.2 into starting materials. Table.2 1 Example

1 comparative 1 1 Example 1

1 Composition (% by volume) i Ti alloy WC powder powder i i i i i M4 99.9 M5 90 M6 70 M7 50 M4 100 M5 48 M6 45 0.1 1 30 50 0 52 55 9 1 1 1 Each of these starting materials was, as the same manner in the examples M1 to M3 and the comparative examples M1 to M3, p rocessed by the cold isostatic pressing, and sintered in the vacuum, and thereafter the sintered body was machined by the lathe to be formed into a cylindrical composite material. By shrinking the obtained composite material into the conventional sleeve (made of SKD61) for cold-chamber so as to form the inner surf ace, a sleeve of cold-chamber was prepared to which sleeve the composite material is disposed in the portion in contact with the melt. These sleeves were adopted as examples M4 to M7 and comparative examples M4 to M6 respectively.

The sleeve of cold chamber consisting of the hot die steel (M61) conventionally used was adopted as conventional example 1, and the sleeve of cold-chamber with a ceramic (silicon nitride) being shrunk thereinside was adopted as Conventional example 2.

Each sleeve for examples, comparative examples, and conventional examples was examined in its performance by the tests shown as follows.

1. Hardness test Micro-Vickers hardness of the inner surface of sleeve was measured for each specimen.

2. Tensile test The elongation of the portion of the inner surface was measured for each specimen.

3. Operational suitability test Engine covers for automobile were cast in practice with aluminum alloy (ADC12) by attaching each of the sleeves to a die-casting machine for cold-chamber (capacity; 250 tons). After 10,000 shots, the sleeve was removed and examined in the melt- erosion state 2Q thereof.

The result of this test was shown below in Table.3. Here, the melterosion state is represented by "ExcellenC for the case where the maximum melt-eroded loss was 0.1 mm or less, by "GooW for the case of more than 0. 1 mm to 0.3 mm, and by "little bad" for the case of more than 0.3mm.

Table. 3

Micro-Vickers Elongation State of hardness(HMV) () melt-erosion 400 580 630 410 500 590 640 280 710 780 350 700 730 M1 M2 M3 1Example 1 M4 1 1 1 M5 1 1 1 M6 1 1 1 M7 1 i i i i i i 1 1 M1 1 lcompara-1 M2 1 1 Itive 1 M3 1 1 lexample 1 M4 1 1 M5 1 1 M6 1 1 1 1 1 12 1 8 1 2 1 16 8 7 3 1 17 1 0.6 0.4 1 18 0.9 0.8 Excellent Excellent Excellent Excellent Excellent Excellent Excellent 1 Little bad Icracks arouse lafter 900 shotsi Icracks arouse 1 lafter 200 shotsi Little bad Good Icracks arouse lafter 500 shotsi 1Conven- 1 1 1 600 1.8 1 Little bad 1 Itional 1 2 1700 0.1 Icracks arouse 1 lexample 1 lafter 200 shotsi As is apparent from Table.3, any of sleeves in the examples M1 to M7 was excellent not only in wear resistance as having a high hardness in the inner surface, but also in impact resistance as having a large elongation. Moreover the sleeves tested in the examples M1 to M7 were little eroded by melt and had no crack caused after 10,000 shots.

On the other hand, the sleeves in comparative examples M2, M3, M6 and conventional example 2 exhibited as extremely low elongations as 0.8t or less, and were found to have cracked. All the remaining sleeves, that is, sleeves in comparative examples Ml, M4, M5 and conventional example 1 had melt-eroded loss of more than 0.1mm, exhibiting poor resistance to melt-erosion.

Now, explanation will be made on the production test result using Nb powder in place of Mo powder. Each specimen of Nb powder for examples Nl to N7 and comparative examples N1 to N6 was prepared in the same condition and manner as in examples Ml to M7 and comparative example Ml to M6 for Mo powder except that Nb powder was used in place of Mo, powder. The examples Nl to N7 and comparative examples Nl to N6 correspond examples Ml to M7 and comparative examples Ml to M6 respectively. Compositions of examples and comparative examples are shown below in Tables.4 and 5.

Hardness test, tensile test, and operational suitability test for each examples and comparative examples was made under the same condition as in the examples and comparative examples for Mo. The result is shown below in Table.6. Here, the same conventional examples in Table.3 are shown in Table.6.

- 14 Table. 4

1 Composition ( by volume) Ti powder + Nb powder SiC powder N1 99 Example N2 70

N3 50 comparative N1 100 Example N2 48

N3 45 0.1 30 50 0 52 55 1 1 1 1 1 Table. 5

1 Composition ( by volume) Ti alloy WC powder powder N4 99.9 N5 90 Example N6 70

N7 50 Comparative N4 Example N5 N6 48 45 1 1 1 0.1 50 0 52 55 - 15 Table. 6

1 1 1 1 1 1 Micro-Vickers Elongation State of hardness(HMV) (%) melt-erosion i 1 i N1 420 13 Excellent N2 600 8 Excellent N3 640 2 Excellent 1Example 1 N4 430 15 Excellent N5 520 9 Excellent N6 580 6 Excellent N7 650 3 Excellent N1 290 18 Little bad 1Compara-1 N2 720 0.7 1Cracks arouse1 1 1 lafter 800 shotsi Itive 1 N3 1 790 0.4 1Cracks arouse 1 1 1 1 lafter 250 shotsi lexample 1 N4 1 360 19 1 Little bad 1 N5 700 0.9 1 Good N6 720 0.8]Cracks arouse lafter 400 shotsi i i i i i i 1Conven- 1 1 1 600 1 1.8 1 Little bad Itional 1 2 1 1700 0.1 1Cracks arouse 1 lexample 1 1 lafter 200 shotsi 1 1 1 j As is apparent from Table.6, any of sleeves in the examples M1 to M7 was excellent not only in wear resistance as having a high hardness in the inner surface, but also in impact resistance as having a large elongation. Moreover the sleeves tested in the examples N1 to N7 were little eroded by melt and had no crack - 16 caused after 10,000 shots.

On the other hand, the sleeves in comparative examples N2, N3, N6 and conventional example 2 exhibited as extremely low elongations as 0.8 or less, and were found to have cracked. All the remaining sleeves, that is, sleeves in comparative examples N1, N4, N5 and conventional example 1 had melt-eroded loss of more than O.lmm, exhibiting poor resistance to melt erosion.

Next, explanation will be made on the test result using Ta powder in place of Mo powder. Also in this case each specimen of Ta powder for examples Tl to T7 and comparative examples Tl to T6 was prepared in the same composition, preparing condition and testing condition as in examples for Mo powder except that Ta powder was used in place of Mo powder. Compositions of examples and comparative examples are shown below in Tables.7 and 8, and the test result is shown in Table.9.

1 1 1 1 i 1 1 Example

Table. 7

Composition (% by volume) Ta powder i 1 Ti powder + SiC powder Tl T2 T3 99.9 1 1 1 0.1 30 50 1 i i i i i Comparative Tl 100 0 Example T2 48 52 T3 45 55 Table. 8

1 Composition (% by volume) Ti alloy WC powder powder T4 99.9 0.1 T5 90 10 Example T6 70 30 T7 50 50 i i i i i comparative T4 Example T5 T6 1 0 48 1 52 1 55 - is Table. 9

Micro-Vickers Elongation state of hardness(Hmv) (%) melt-erosion Tl 410 12 Excellent T2 630 6 Excellent T3 650 2 Excellent 1Example 1 T4 1 580 13 E;Kcellent T5 530 8 Excellent T6 570 6 Excellent T7 660 3 Excellent I I Tl 1 290 16 1 Little bad I lCompara-I T2 1 750 0.6 lCracks arouse I I I I I lafter 900 shotsl Itive I T3 1 780 1 0.3 Icracks arouse I I I I I lafter 350 shotsl lexample I T4 1 350 17 Little bad T5 720 0.8 Good I T6 -730 0.7 lCracks arouse I I lafter 450 shotsl lConven- 1 1 1 600 1.8 Little bad I Itional 1 2 1 1700 1 0.1 Icracks arouse I lexample I I I lafter 200 shotsl 1 1 1 1 1 As is apparent from Table.9, any of sleeves in the examples Tl to T7 was excellent not only in wear resistance as having a high hardness in the inner surface, but also in impact resistance as having a large elongation. Moreover the sleeves tested in the examples Tl to"T7 were little eroded by melt and had no crack 1 caused after 10,000 shots.

On the other hand, the sleeves in comparative examples T2, T3, T6 and conventional example 2 exhibited as extremely low elongations as 0.8% or less, and were found to have cracked. All the remaining sleeves, that is, sleeves in comparative examples Tl, T4, T5 and conventional example 1 had melt-eroded loss of more than O.1mm, exhibiting poor resistance to melterosion.

Next, explanation will be made on the test result of examples Vl to V7 and comparative examples Vl to V6 using V powder in place of Mo powder. The compositions, production conditions and testing conditions for each specimen were the same as in the examples and comparative examples for Mo powder. Compositions of examples and comparative examples are shown below in Tables.10 and 11, and the test result is shown in Table.12.

- 20 Table. 10

1 Composition ( by volume) i 1 i 1 Ti powder + 1 SiC powder V powder 1 A i i i V1 99.9 0.1 Example V2 70 30 V3 50 50 1 comparative 1 V1 1 100 1 0 Example V2 48 52 V3 45 55 Table. 11

Composition (% by volume) 1 i 1 1 Ti alloy 1 WC powder powder 1 A i i i V4 99.9 0.1 V5 90 10 Example V6 70 30 V7 50 50 comparative V4 100 Example V5 48

V6 45 0 52 55 1 1 1 1 1 41 Table. 12

Micro-Vickers Elongation State of hardness(HMV) () melt-erosion V1 425 12 Excellent V2 610 6 Excellent V3 630 2 Excellent 1Example 1 V4 1 550 13 Excellent V5 520 8 Excellent V6 560 6 Excellent V7 650 3 Excellent 1 V1 285 17 1 Little bad 1 1Compara-1 V2 1 755 0.6 Icracks arouse 1 1 1 1 lafter 700 shotsi Itive 1 V3 1 770 0.4 icracks arouse 1 1 1 1 lafter 380 shotsi lexample 1 V4 1 360 17 Little bad V5 730 0.9 Good V6 740 0.6 Icracks arouse 1 lafter 500 shotsi 1Conven- 1 1 600 1.8 Little bad Itional 1 2 1 1700 0.1 Icracks arouse lexample, 1 lafter 200 shotsI 1 1 1 As is apparent from Table.12, any of sleeves in the examples V1 to V7 was excellent not only in wear resistance as having a high hardness in the inner surface, but also in impact resistance as having a large elongation. Moreover the sleeves tested in the examples V1 to V7 were little eroded by melt and had no crack -ir Yk caused after 10,000 shots.

On the other hand, the sleeves in comparative examples V2, V3, V6 and conventional example 2 exhibited as extremely low elongations as 0.8% or less, and were found to have cracked. All the remaining sleeves, that is, sleeves in comparative examples Vl, V4, V5 and conventional example 1 had melt-eroded loss of more than O.lmm, exhibiting poor resistance to melt-erosion.

It should be noted that the ceramics applicable to the present invention are not limited to SiC and WC stated above, but various kinds of ceramics can be used including oxide ceramics such as Cr203, Ti02, Zr02, M90, Y203 and the like; nitride ceramics such as Si3N4, TiN, BN, AlN and the like; carbide ceramics such as TiC, B4C, CrC2 and the like; boride ceramics such as ZrB2, TiB2 and the likes; and SIALON and etc.. It is also possible to use more than two kinds of ceramics in combination.

The above detailed explanation of examples are made as to sleeves for cold-chamber, but it is possible to form the composite material comprising Mo or Mo alloy powder and the like, titanium or titanium alloy powder and ceramic powder into these injection parts for diecasting machines such as plunger tip and sleeve bush for cold-chamber, and sleeve, plunger ring, plunger tip and nozzle for hot-chamber as well as melt transport pipe and the like.

1 k

Claims

What is claimed is;

1. An injection part for die-casting machines characterized in that at least a part of a portion which is to be in contact with melt is formed of a composite material obtained by sintering a mixture of:

a first powder of a metal or alloy selected from a group consisting of Mo, Mo alloy, Nb, - Nb alloy, Ta, Ta alloy, V and V alloy; a second powder of Ti or Ti alloy; a third powder of ceramic, wherein said first powder is compounded in an amount of 0.1 to 50 by volume based on the total amount of said mixture.

2. An injection part according to claim 1, wherein said third powder is compounded in an amount of 0.1 to 50 by volume based on the total amount of said mixture.

3. An injection part for die-casting machines, substantially as hereinbefore described with reference to any of the Examples.