Method for manufacturing composite double-metal fracture splitting connecting rod

Abstract

The present invention provides a method for manufacturing a composite double-metal fracture splitting connecting rod, comprising the steps of: providing a moveable spacer at a large end of a mold cavity of a connecting rod, to divide the mold cavity into two separate parts; casting a connecting rod body and a connecting rod cap with material for the main body of the connecting rod; removing the spacer from the mold cavity when the majority of the material is solidified, then injecting material for a fracture splitting region into an empty mold cavity obtained after the removal of the spacer, and metallurgically bonding the two types of material to form a composite double-metal casting; then, separating the connecting rod body from the connecting rod cap by a fracture splitting apparatus along preset fracture surfaces; and positioning and accurately assembling through engaged staggered structures on the two fracture surfaces.

Claims

1. A method for manufacturing a composite bimetallic fracture splitting connecting rod, wherein the connecting rod comprises a connecting rod body, a connecting rod cap, and a fracture splitting layer disposed between the connecting rod body and the connecting rod cap, wherein the connecting rod body and the connecting rod cap comprises a first material, the fracture splitting layer comprises a second material, the method comprising: (A) providing a spacer inside a mold of the connecting rod at a position where the connecting rod body and the connecting rod cap are adjacent to each other, wherein the spacer is a corrugated sheet; (B) casting the first material into the mold to form the connecting rod having the spacer disposed therein; (C) removing the spacer from the connecting rod when a majority of the first material solidifies, creating a cavity inside the connecting rod, wherein a shape of the cavity corresponds to the shape of the spacer; (D) injecting the second material into the cavity, wherein the second material forms the fracture splitting material layer inside the cavity, the fracture splitting material layer bonds to the connecting rod; (E) forging the connecting rod having the fracture splitting material layer; (F) forming a fracture splitting notch in the fracture splitting layer; (G) fracture-splitting the connecting rod to separate the connecting rod body from the connecting rod cap at the fracture splitting layer, wherein the resulting connecting rod body has a first jagged surface and the resulting connecting rod cap has a second jagged surface; and (H) assembling the connecting rod body and the connecting rod cap by mating together the first jagged surface and the second jagged surface, wherein a joint between the first jagged surface and the second jagged surface is in a shape corresponding to the shape of the spacer.

2. The method according to claim 1, further comprising, between Step (C) and Step (D), adjusting a thickness of the cavity created by the removal of the spacer to a predetermined value.

3. The method according to claim 1, furthering comprising, between Step (D) and (E), compressing the fracture splitting material layer so that a thickness of the fracture splitting material layer reaches a predetermined value.

4. The method according to claim 1, wherein the fracture splitting material layer has a thickness ranging from 1 mm to 20 mm.

5. The method according to claim 1, wherein the injection of the second cavity is carried out by gravity or by applying a pressure.

6. The method according to claim 1, wherein the first material is an aluminum alloy, a titanium alloy, or an alloy steel.

7. The method according to claim 6, wherein the aluminum alloy is LD10 aluminum alloy and the alloy steel is Cr40.

8. The method according to claim 1, wherein the second material is a brittle material.

9. The method according to claim 8, wherein the second material is A390 high-silicon aluminum alloy.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a structural diagram of a double-metal fracture splitting connecting rod;

(2) FIG. 2 is a schematic diagram of a connecting rod using a jagged spacer; and

(3) FIG. 3 is a flowchart of casting a composite double-metal fracture splitting connecting rod;

(4) In the figures: 1Connecting rod body; 2Fracture splitting interface; 3Connecting rod cap; 4Connecting bolt; 5Fracture splitting layer; 6Second casting system; 7Separating plate; 8First casting system; 9Fracture splitting notch; and, 30Jagged spacer.

DETAILED DESCRIPTION OF THE INVENTION

(5) The present invention will be further described as below with reference to accompanying drawings by embodiments.

(6) As shown in FIG. 1, a connecting rod in this embodiment consists of a connecting rod body 1 and a connecting rod cap 3, which are positioned and engaged by staggered structures on fracture splitting interfaces 2. The connecting rod body 1 and the connecting rod cap 3 are integrally connected by bolts 4.

(7) As shown in FIG. 1 and FIG. 3, the present invention employs the following technical solution. When a blank of a fracture splitting connecting rod is to be manufactured, a fracture splitting layer 5 is formed in a fracture splitting region and filled with material different from that for the main body of the connecting rod, and then fracture splitting machining is performed at the position of the fracture splitting layer 5. The specific method is as follows: the coordination of components of the material for the connecting rod is designed first; then, two independent casting systems are used, that is, the material for the main body of the connecting rod, having high-strength, high-toughness and anti-fatigue performance, is injected into the connecting rod body 1 and the connecting rod cap 3 by a first casting system 8, and then the fracture splitting material is injected into an empty mold cavity in the fracture splitting region by a second casting system 6. The two metals are metallurgically bonded. The resulting integral composite connecting rod has excellent comprehensive performance. Furthermore, the fracture splitting layer 5 at the large end portion of the connecting rod becomes brittle due to an external force, so that the connecting rod meets the technical requirements of the fracture splitting machining.

(8) The material selection in this embodiment is as follows: the material for the main body of the connecting rod: LD10 aluminum alloy; the brittle material for the fracture splitting region: A 390 high-silicon aluminum alloy; and the interface contact area: 5080 mm.sup.2.

Composition of Alloy

(9) TABLE-US-00001 Content of Elements (percentage by nominal weight, %) Aluminum Magnesium Zinc Manganese Silicon Copper No. (Al) (Mg) (Zn) (Mn) (Si) (Cu) LD10 Remaining 0.4-0.8 0.3 0.4-1 0.6-1.sup. 3.9-4.8 A390 Remaining 0.45-0.65 >0.1 <0.1 16-18 4-5

(10) The following shows key process steps of manufacturing a composite connecting rod by the above mold device:

(11) 1) two metals to be compounded are smelted, respectively, refined, and then degassed and purified;

(12) 2) the surface of the spacer 7 to come into contact with molten metal is pretreated: greasy dirt, impurities and other deposits on the surface, which are disadvantageous for metal compounding, are removed by means of liquid immersion (such as, with acid, alkali or alcohol), and the surface is then preheated at 100-300 C.; and the mold is preheated to 240-280 C. and a release agent is spray-coated inside the mold cavity;

(13) 4) the molten LD10 alloy is injected into the mold cavity of the connecting rod body 1 and the connecting rod cap 3, the spacer 7 is driven by a transmission mechanism to exit the mold cavity along a concave cavity after the majority of molten LD10 alloy is solidified, and the molten A390 alloy is then injected into the empty mold cavity, where the casting temperature of the LD10 aluminum alloy is 730-760 C. and the casting temperature of the A390 high-silicon aluminum alloy is 690-710 C.;

(14) 6) after the casting is cleaned, heat treatment is performed for the composite casting according to specific conditions; by further heat treatment, diffusion between atoms at the interface or further metallurgical reaction may be facilitated, or, the interface structure may be adjusted, so that the bonding strength of the two metal layers is improved, where the temperature of the heat treatment is preferably 475-490 C. and the heat preservation time is preferably 12-14 hrs; and

(15) 7) the large end hole of the composite connecting rod is machined coarsely: a fracture splitting notch is formed at a position close to an intermediate plane of the fracture splitting layer at the large end portion of the composite connecting rod; then, by means of fracture splitting, the connecting rod body is completely separated from the connecting rod cap in the fracture splitting material region by a fracture splitting apparatus; positioning is performed by the engaged staggered structures on the two fracture surfaces; and, the connecting rod body 1 and the connecting rod cap 3 are integrally connected by bolts to form a finely finished product.

(16) Upon analysis by experiments, it can be seen from a microstructure at the bonding interface that, an obvious metallurgical reaction occurs at the interface, the material on two sides is connected by the intermediate transition layer, and the bonding at the interface is tight without obvious cracks and pores. During fracture splitting, by applying an external load, the connecting rod has obvious crackability in its fracture splitting layer, and the fracture surfaces are controlled within the region of the fracture splitting layer, thereby effectively reducing the problems such as torn single-side, fracture splitting insufficiency, deformed large-end hole. Analysis on the quality of the fracture surfaces indicates that the fracture surfaces are flat from a macroscopic perspective, and the two fracture surfaces have naturally staggered structures from a macroscopic perspective, so that the connecting rod body and the connecting rod cap may be positioned and accurately assembled.

(17) The method in the present invention for providing a fracture splitting layer in a blank of a part with composite double-metals is also suitable for machining parts having structures and process flows similar to connecting rod holes, for example, the fracture splitting machining of bearing seats for engine crankcases. Various deductions and replacements, which may be made without departing from the idea of the present invention, shall be regarded as falling into the patent protection scope defined by the submitted claims of the present invention.