DE3111097A1 - "METHOD FOR IMPROVING THE METALLURGICAL CONNECTION BETWEEN AN IRON METAL INSERT AND AN ALUMINUM MOLDED BODY" - Google Patents

Description

PATENT LAWYERS

DR.-ING. R. DOERING - 3 - DIPL.-PHYS. DR. J. FRICKE

BRAUNSCHWEIG -. MUNICH

DANA CORPORATION

P.O.Box 1000

Toledo, Ohio 43 697 / USA

"Method for improving the metallurgical bond between a ferrous metal insert and an aluminum casting"

The invention relates to a method for improving the metallurgical Connection between a ferrous metal insert and an aluminum cast body,

This is mainly about the production of a piston for heavy internal combustion engines, for example engines for trucks, regardless of whether the engines are based on the Otto principle or the diesel principle.

Liquid metal forging is also known as die casting or extrusion casting. It is a hybrid process _} in which the advantages of both forging and casting are combined. Workpieces of greater strength are obtained than in the pure casting process. On the other hand, much less energy is required than for pure forging.

^L 130063/0732 ^J

; The main advantages of using liquid metal forging compared to the constant production of molds for pistons

j in higher production speeds and the elimination of m & t * eriai wasting sprues and risers like them _; be} · the previous casting practices occur. It is also with

'' Aluminum casting required nitrogen-

j degassing obsolete because of gas porosities or shrinkage holes can be eliminated by the pressures applied.

It also igt common experience that a sufficient piston ring seal in the region of the head end is just the piston of particular importance, both in terms of the life of the piston and in terms of effectiveness During operation, if there is no proper sealing ^": it is not iqöglich to enable the combustion gases to a satisfactory ■ alternate combustion under sufficient pressure. This results in §rh_ält an incomplete combustion of the fuel with the result that carbon deposits may occur at. piston head and the cylinder walls. the sealing problem becomes greater, depending On heavy machines it is practical to use a piston ring insert made of a harder material, which is inserted into the piston ring area of the piston heads made in the conventional manner by casting constant Tilting of the piston ring under the pressures occurs at the start of combustion. ''

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So far, the process of liquid metal cutting has been used in the manufacture of pistons for lighter machines which inserts in the piston head were not required.

; Ea is the object of the invention to connect inserts and

ί - to improve aluminum, tfG.ußkkörern significantly and in particular, the • manufacture of pistons for heavy internal combustion engines with ί iron metal inserts in the main sealing area of the piston heads > to simplify and cheaper.

'

This object is achieved according to the invention in that the insert made of ferrous metal is inserted into a recess in the form and ■ then this is poured out with molten aluminum that - then the melt is subjected to increased pressure and the Pressure is maintained until the melt solidifies, whereupon the cast body is removed from the mold recess.

With this method, a significantly better metallurgical connection between the piston inserts is obtained Ferrous metal and the aluminum alloy from which the piston is made. So you get pistons especially for heavy Internal combustion engines with a much longer service life and better sealing. At the same time, the cast aluminum body Provided with better strength properties than with the pure casting process.

Ί ■ '

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As a ring insert, cast iron inserts with a high

Nickel content can be produced. Appropriately, the

, Einsat? before inserting into the mold recess by sand [

j radiate Qthe like. pretreated. After this pre-treatment

The insert

'Preferably with a thin composite layer'

j are coated with an iron / aluminum alloy,

! When compacting the aluminum in the mold recess

\ the pressure exerted on the melt is applied with a pusher

; are brought,., up to pressure values in the range of

j 200 kg / cm ² to 1750 kg / cm ² .

; The invention is explained below with reference to schematic drawings

ί on a device used to carry out the procedure

! explained in more detail.

Show it;

Figure 1 is a vertical section through a pouring device in the closed position, using the new procedure works and

Figure 2 is a vertical section through an internal combustion engine piston, which has been produced by the method according to the invention. , "'·' ·.

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In Fig. 1 a molding device is shown. This can be used for ■ lead the method according to the invention are used,

; A mold recess 10 used for casting a piston is . formed between upper and lower mold halves 12 and 14. The upper half of the mold is used to shape the piston head, while the lower mold half is used to form the piston skirt 20. An inner core 16 extends through a Bore 15 in the bottom of the lower mold half 14 upwards into the mold recess 10 in order to be in the finished piston according to FIG To form recess 18 under the piston skirt 20. The upper mold half 12 includes a bore 17 extending therethrough There is a pressure tappet 22. With this, the molten metal in the mold is subjected to increased pressure.

The preferred embodiment of the method according to the invention is described below. One made of ferrous metal Piston ring insert 24 is first pretreated by sandblasting or the like. Instead of sandblasting, a shotblast treatment can also be used are provided. In both cases the oxides should be removed from the surface of the insert. at The insert is preferably cast iron with a high nickel content. After sandblasting or the like. The use coated with a thin layer of an iron / aluminum alloy. An aluminizing process is preferably used for this purpose applied as it is known to those skilled in the art. The pre-coated annular insert 24 is then or the like by means of pliers several small ^ integrally molded support tabs (not shown) placed, extending from a countersunk hole 26 in the top

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ι the lower half 14 from extending upwards. The upper

■ Mold half 12 is then lowered onto the lower mold half 14,

: to close the mold recess 10. It is melted

'Aluminum alloy in the recess 10 through the hole

; 17 poured, up to a carefully monitored one

\ Elevation level · The melt is poured in briefly

: stood after inserting the ring. It should just be a very

• short delay time of 5 to 20 seconds between the onset ·

! the use and pouring of the aluminum melt

- Swipe to create a new formation of oxides on the insert ring to be avoided or kept to a minimum. Next, the pressure ram 22 is lowered through the bore 17 into the mold cavity 10. The ram 22 is connected to a hydraulic press (not shown) through which a required pressure is exerted can be. Pressure on the molten aluminum should be preferred

lie.

2 2

preferably in the range between 100 kg / cm and 1750 kg / cm

The pressure from the ram is maintained until the cast body has solidified. The time required for this is 3 to 5 minutes, depending on the size of the cavity. The mold is then opened and the piston produced by forge casting is ejected. In a preferred embodiment of the method, a temperature of the mold of 260 to 316 ^° C. should be maintained. The temperature depends on the size of the casting and the shape of the mold cavity. The mold must be hot enough that the molten metal can be pressurized before solidification begins. However, it should not be so hot that it cracks

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of the piston through the mold when removing the piston from the Form takes place.

FIG. 2 shows the finished piston 40 after subsequent machining. The grooves 42, 44 and 46 are in the outer periphery have been cut and are used to insert the piston rings. The upper piston ring is inserted into a groove 42 which is cut into the annular insert 4 made of ferrous metal. This significantly reduces the rate of wear and tear, which is favored by the constant tilting of the upper ring in the manner described above.

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Claims (2)

DR.-ING. R. DÖRING DIPL.-PHYS. DR. J. FRICKE BRAUNSCHWEIG MUNICH claims 1. Method of improving the metallurgical bond between a ferrous metal insert and a cast aluminum body, / ■. characterized by the steps that the insert inserted into a mold recess and this then with melted Aluminum is poured out so that the melt is then subjected to increased pressure and the pressure until it solidifies the melt is maintained, whereupon the cast body is removed from the mold cavity. ·, · 2. The method according to claim 1, characterized in that that the cast aluminum body is shaped as a piston of an internal combustion engine and the annular insert in the Sealing area is used at the piston end, 3. The method according to claim 2, characterized in that that üer ring insert is made of a cast iron with a high nickel content. H. Method according to Claim 3, characterized in that the insert is pretreated by sandblasting or the like before it is inserted into the mold recess. ^L 130063/0732 5. The method according to claim 4, characterized I · ' net that the use after sandblasting and before inserting into the mold recess with a thin dpi composite layer of an iron-aluminum alloy is coated. 6. The method according to one or more of claims 1 to 5, characterized in that the pressure on the melt with a ram up to pressure values in the loading 2 2 rich γοη 200 kg / cm to 1750 kg / cm is applied. 130063/0732