CN106994496B - A kind of forging method of steel bimetallic cracking connecting-rod - Google Patents

Abstract

The invention provides a method for forging a steel bimetal cracking connecting rod, which includes the following steps: S1: preparing a casting slab for a steel bimetallic cracking connecting rod through a casting process, the casting slab is composed of a connecting rod body, a cracking zone and a connecting rod Cover composition; S2: Normalizing the billet to eliminate the cracked material and reticular cementite in the interface area, and promote the formation of a continuous diffusion layer at the bimetallic interface; S3: Forging the billet, through forging mold to control the flow direction of the cracked material; S4: Clean the surface burr of the forging and perform shot blasting; S5: Quench and temper the forging to make the mechanical properties of the connecting rod meet the requirements and ensure the cracking brittleness of the cracked material; S6: Set up cracking Grooving, cracking, and reassembly, and finally the finished steel bimetallic cracking connecting rod is obtained. The invention can break through the material limitation of the cracking connecting rod, and solve the problem that the alloy steel cannot be used in the production and manufacture of the cracking connecting rod.

Description

A kind of forging method of steel bimetal cracking connecting rod

technical field

The invention belongs to the field of forging research of transmission power component materials, and in particular relates to a forging method of a steel bimetal cracking connecting rod.

Background technique

The connecting rod, as a key component for power transmission inside the engine, not only bears the air pressure generated by the combustion chamber, but also needs to bear the constantly changing load, which requires the connecting rod to have high strength, high hardness, and good comprehensive mechanical properties. The traditional connecting rod manufacturing is first through integral forging, then sawing, milling, and grinding the main body of the connecting rod and the end face of the connecting rod cover, and finally process the bolt holes on the connecting rod body and the connecting rod cover, and realize the combination of the two through connecting bolts. Pack. The processing technology of the traditional connecting rod is too cumbersome, the efficiency is low, the quality is poor, and the bearing capacity is weak. Therefore, the new cracking connecting rod processing technology has gradually replaced the traditional connecting rod processing technology and become the mainstream of connecting rod production.

The complexity of the working environment of connecting rods determines that ordinary single materials are difficult to meet the quality requirements of cracked connecting rods. At present, the main materials for foreign cracked connecting rods are C70S6 high-carbon non-quenched and tempered steel from Germany, and the SPLITASCO series high-quality steel developed in France. Carbon steel, this type of material has good brittle fracture, but its hardness is relatively high, the processing tool wears quickly, and the manufacturing cost is high. Domestic non-quenched and tempered steels for connecting rods mainly include 38MnVS, 40MnV, 48MnV and other vanadium series and manganese vanadium series. However, these materials still have defects such as cracking deformation, slag falling off the cross section, and low assembly accuracy in the actual processing of connecting rods. The existence of these problems seriously hinders the production and development of high-quality connecting rods in China.

In order to improve the cracking quality and assembly of steel cracking connecting rods, the current research on steel cracking connecting rods mainly focuses on two aspects: (1) Research on cracking materials. The research on the cracked material is mainly to increase the strength of the material and realize the brittle fracture of the material by adding trace alloy elements Mn, S, V, Cr, P, etc.; (2) Change the cracking mode of the cracked connecting rod. According to the different driving methods of the cracking equipment, there are currently three types of cracking processing equipment, which are wedge-shaped block cracking processing equipment, hydraulic piston direct push cracking processing equipment, and horizontal force acting cracking processing equipment. None of the above methods and technologies can fundamentally break through the material limitations of cracked connecting rods, and ordinary medium-carbon steel and medium-carbon alloy steel are still unable to be used in the production and manufacture of cracked connecting rods.

The application number is 201210586143.6, and the patent titled "a manufacturing method of cracked steel connecting rod" proposes to insert preheated gray cast iron into the gap between the main body of the connecting rod and the big end of the connecting rod when casting the cracked connecting rod, so as to realize the bimetallic Metallurgical bonding at the interface. This steel cracking connecting rod manufacturing method has the following disadvantages: gray cast iron has a low melting point, and when the casting temperature of the main body material is high, the cracking material is easily over-melted, resulting in the failure to open the cracking tank and the cracking process of the connecting rod.

The application number is 201210111190.5, and the patent titled "a method for manufacturing a composite bimetal cracking connecting rod" proposes to cast the connecting rod body and the connecting rod cover in the connecting rod mold, and then pull out the isolation plate when it is half-solidified, and cast and crack material, this process can realize the manufacture of bimetallic composite cracking connecting rod. The manufacturing method of this bimetal cracking connecting rod has the following disadvantages. When the separating plate is pulled out, the separating plate is easy to stick to the main material, and it is difficult to pull it out smoothly. At the same time, it is difficult to accurately control the casting time of the cracking material, and the bimetallic interface cannot form a stable Combine interface.

The application number is 201510660790.0, and the patent titled "Investment Casting Method for Bimetal Composite Cracking Connecting Rod" proposes to prepare bimetallic cracking connecting rod by investment casting process. The cracked connecting rod formed by this bimetal cracking connecting rod manufacturing method has not been forged, and the casting has many casting defects, poor interface bonding quality, weak mechanical properties, and low fatigue strength, so it cannot be directly used in engines.

In order to solve the problems of the above-mentioned patented technology, the forging method of the steel bimetal cracking connecting rod proposed by the present invention realizes the fusion and bonding of the connecting rod billet at the bimetal interface through the investment casting process, and the heat treatment before forging can increase the bimetal The diffusion of interface elements forms a stable and continuous diffusion layer and enhances the bonding strength of the interface; after forging, the comprehensive mechanical properties of the connecting rod can be improved, and the defects of the forging casting can be combined; the quenching and tempering treatment after forging can make the main material structure of the connecting rod as Quenched and tempered structure, the pyrolysis material is tempered martensite structure, which is beneficial to the subsequent pyrolysis processing of the connecting rod.

Contents of the invention

The object of the present invention is to provide a forging method for steel bimetal cracking connecting rods in view of the above problems, which can solve the problem that ordinary medium carbon steel and medium carbon alloy steel cannot be used for the production and manufacture of cracking connecting rods.

The technical solution of the present invention is: a forging method of a steel bimetal cracking connecting rod, characterized in that it comprises the following steps:

S1: Prepare the casting slab of steel bimetal cracking connecting rod by casting process, the casting slab is composed of connecting rod body, cracking zone and connecting rod cover, wherein the material of the cracking zone is set as cracking material, and the casting blank of the connecting rod body and between the connecting rod cover; the material of the connecting rod body and the connecting rod cover is set as the main material;

S2: Normalizing the slab to eliminate cracked materials and reticular cementite in the interface area, and promote the formation of a continuous diffusion layer at the bimetallic interface;

S3: Forging the slab, and controlling the flow of the cracked material through a bridge on the forging die;

S4: Clean the surface burrs of forgings and perform shot blasting;

S5: Quenching and tempering treatment of forgings, so that the mechanical properties of the connecting rod meet the requirements, and ensure the cracking brittleness of the cracked material;

S6: Set up a cracking tank, crack and reinstall, and finally get the finished steel bimetallic cracking connecting rod.

Further, the main material described in step S1 is medium-carbon steel or medium-carbon alloy steel; the cracked material is a high-carbon alloy steel with a carbon content of 0.7% to 1.2%, and its metallographic structure is spherical in an annealed state Pearlite structure; the thickness of the cracked material is 2mm-3mm.

Further, the step S1 is specifically as follows:

S11: manufacturing sand mold shells;

S12: After the preheating temperature of the pyrolysis material is 500°C, insert it into the pyrolysis zone in the sand mold shell;

S13: casting the main material.

Further, the normalizing treatment described in step S2 is specifically as follows:

S21: heating the billet to 800°C-820°C;

S22: heat preservation for 6-10 hours, to promote the interdiffusion of elements between the main material and the pyrolysis material at the interface between the connecting rod body and the pyrolysis area, and at the interface between the pyrolysis area and the connecting rod cover, to form a continuous diffusion layer and enhance the bonding performance of the interface , to prevent subsequent forging cracking;

S23: Air cooling treatment.

Further, the forging conditions described in step S3 are as follows: the initial forging temperature is 1100°C, the final forging temperature is 800°C; the total forging ratio of the height before and after forging of the slab is 1.5 to 3.0; the forging process is divided into billet making, pre-forging and final forging, in which the forging ratio of the billet pre-forging height accounts for 60% to 80% of the total forging ratio.

Further, the forging die in the final forging process is provided with cracking zone bridge openings and connecting rod zone bridge openings around the forging, wherein the cracking zone bridge openings are on both sides of the cracking zone centerline; the cracking zone bridge opening height It is 2 to 3 times the height of the bridge in the connecting rod area. It is used to reduce the metal flow resistance, guide the metal to flow to the bins on both sides of the middle cracking zone during final forging, control the position of the cracking material, and prevent the forging from causing The interface is cracked.

Further, the quenching and tempering treatment in step S5 is metastable quenching plus high temperature tempering.

Compared with prior art, the beneficial effect of the present invention is:

1. The forging method of the steel bimetal cracking connecting rod according to the present invention fundamentally breaks through the limitation of the material of the cracking connecting rod, and solves the problem that ordinary medium carbon steel and medium carbon alloy steel cannot be used for the production and manufacture of cracking connecting rods question.

2. The forging method of the steel bimetal cracking connecting rod of the present invention solves the problems of the bonding quality of the bimetal interface, the easy cracking of the forging interface, and the easy forging and breaking of the cracking material, and creates a good process for forging the bimetal cracking connecting rod condition.

3. The forging method of the steel bimetal cracking connecting rod of the present invention not only ensures the overall mechanical properties of the forging, but also ensures the cracking brittleness of the cracking material, creating conditions for cracking and reassembling.

4. The forging method of the steel bimetal cracking connecting rod according to the present invention, the process method reduces the problems of cracking deformation, slag falling off the cross section, low assembly accuracy and the like in the process of connecting rod processing, improves the quality of the cracking connecting rod, and promotes Production and development of cracking connecting rod.

Description of drawings

Fig. 1 is the schematic diagram of the connecting rod casting wax mold group of the forging method of the steel bimetal cracking connecting rod according to the present invention.

Fig. 2 is a schematic diagram of the structure of the bimetal composite cracking connecting rod according to the present invention.

Fig. 3 is a schematic diagram of a final forging die according to the present invention.

Fig. 4 is a B-B sectional view of Fig. 3 .

FIG. 5 is a cross-sectional view along line A-A of FIG. 3 .

In the picture:

1-connecting rod body, 2-cracking area, 3-connecting rod cover, 4-casting system, 5-cracking tank, 6-connecting bolts, 7-cracking interface, 8-cracking area bridge mouth, 9-connecting rod area bridge mouth.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited thereto.

A method for forging a steel bimetal cracking connecting rod specifically follows the steps:

S1: The casting slab of steel bimetal cracking connecting rod is prepared by casting process, and the casting slab is composed of connecting rod body 1, cracking zone 2 and connecting rod cover 3, as shown in Figure 1 and Figure 2, wherein the cracking zone 2 The material is set as cracking material, between the connecting rod body 1 and the connecting rod cover 3; the material of the connecting rod body 1 and the connecting rod cover 3 is set as the main material; the main material is medium carbon steel or medium Carbon alloy steel; the cracked material is a high-carbon alloy steel with a carbon content of 0.7% to 1.2%, and its metallographic structure is a spherical pearlite structure in an annealed state; the thickness of the cracked material is 2 mm to 3 mm, ensuring that the forging The cracking zone 2 will not crack due to the thicker cracking material, and ensures brittle cracking. The present invention selects connecting rod main body material to be 25 steel, and its chemical composition mass percentage is with reference to GB/T699-1999 " high-quality carbon structural steel "; Cracking material is the W18Cr4V of the spherical pearlite structure that matrix structure is annealed state after heat treatment, its The mass percentage of chemical composition refers to GB/T 9943-2008 "High Speed Tool Steel". The step S1 is specifically as follows:

S11: manufacturing sand mold shells;

S12: After the preheating temperature of the pyrolysis material is 500°C, insert it into the cracking zone 2 in the sand mold shell;

S13: casting the main material. The pouring temperature is 1600°C, and after cooling, a bimetallic billet is obtained.

S2: Perform normalizing treatment on the billet to eliminate the cracked material and reticular cementite in the interface area, and promote the formation of a continuous diffusion layer at the bimetallic interface; the specific normalizing treatment is as follows:

S21: heating the billet to 800°C-820°C;

S22: heat preservation for 6-10 hours, to promote mutual diffusion of the main material and cracked material at the interface between connecting rod body 1 and cracking zone 2 and at the interface between cracking zone 2 and connecting rod cover 3, forming a continuous diffusion layer, strengthening The bonding performance of the interface prevents subsequent forging cracking;

S23: Air cooling treatment.

S3: The billet is forged, and the flow of the cracked material is controlled by setting a bridge on the forging die; the forging conditions are: the initial forging temperature is 1100°C, and the final forging temperature is 800°C; the total forging ratio of the height of the billet before and after forging is 1.5～3.0, the calculation of forging ratio is the height before forging divided by the height after forging; %. As shown in Figure 3, Figure 4 and Figure 5, the forging die in the final forging process is provided with a cracking zone bridge 8 and a connecting rod zone bridge 9 around the forging, wherein the cracking zone bridge 8 is in the cracking zone 2. Both sides of the center line; the height of the bridge opening 8 in the cracking zone is 2 to 3 times the height of the bridge opening 9 in the connecting rod zone, which is used to reduce the metal flow resistance and guide the metal to the middle cracking zone 2 during final forging. The flow of the side bins controls the position of the cracked material and prevents interface cracking during forging.

S4: Clean the burrs on the surface of the forging and perform shot blasting; use the waste heat after forging to remove the flash, and then cool it with strong wind; use a grinder to clean the surface burrs of the bimetal cracking connecting rod forgings, and then use a shot blasting machine to treat the processed cracking. Rod forgings are shot blasted.

S5: Quenching and tempering treatment of forgings, so that the mechanical properties of the connecting rod meet the requirements, and ensure the cracking brittleness of the cracked material; carry out quenching and tempering treatment of metastable quenching and high temperature tempering on the forgings; specifically, heat the forgings to 760～800℃, hold for a certain period of time, and then quench the workpiece in a low temperature salt bath or alkali bath furnace. The temperature of the salt bath or alkali bath is around 340℃. This cooling method can make the internal and external temperature of the workpiece more uniform, and at the same time carry out martensitic transformation, which can greatly reduce the quenching stress and prevent deformation and cracking; high temperature tempering heats the quenched forging to 500-600°C to ensure that the main material is quenched and tempered Microstructure, the cracked material is tempered martensite structure; quenching and tempering treatment can improve the strength, plasticity and toughness of the main material, so that the forging has good comprehensive mechanical properties, and prevents cracks or deformation in subsequent cracking processing;

S6: Set up a cracking tank, crack and reinstall, and finally get the finished steel bimetallic cracking connecting rod. Carry out the cracking test, open the V-shaped cracking groove 5 symmetrically by laser along the central line at the big end of the connecting rod, use cracking equipment, and crack in the cracking area 2; The body 1 and the connecting rod cover 3 are reassembled through the connecting bolt 6, and finally the length of the hardcover bimetal cracking connecting rod is increased by 0.26mm compared with the forging, which is less than the error requirement of 0.5mm required by the cracking, which proves that the forging process is reasonable sex.

It should be understood that although this description is described according to various embodiments, not each embodiment only includes an independent technical solution, and this description of the description is only for clarity, and those skilled in the art should take the description as a whole , the technical solutions in the various embodiments can also be properly combined to form other implementations that can be understood by those skilled in the art.

The series of detailed descriptions listed above are only specific descriptions for feasible embodiments of the present invention, and they are not intended to limit the protection scope of the present invention. Any equivalent embodiment or All changes should be included within the protection scope of the present invention.

Claims (7)

1. a kind of forging method of steel bimetallic cracking connecting-rod, which comprises the steps of:

S1: preparing the slab of steel bimetallic cracking connecting-rod by casting technique, slab by gonnecting rod body (1), cracking zone (2) and Connecting rod cap (3) composition, wherein the cracking zone (2) material is set as cracking material, the gonnecting rod body (1) and connecting rod cap (3) it Between；The gonnecting rod body (1) and connecting rod cap (3) material are set as material of main part；The material of main part is medium carbon steel or medium carbon alloy steel； The cracking material is high-carbon alloy steel of the phosphorus content 0.7% ~ 1.2%, and metallographic structure is the spherical pearly-lustre of annealed condition Body tissue；

S2: carrying out normalized treatment to slab, for eliminating the network cementite in cracking material and interface zone, and promotes double gold Belong to interface and forms continuous diffusion layer；

S3: slab is forged, and the flowing of cracking material is controlled by setting bridge mouth on forging die；

S4: cleaning forging surface spikes, and Shot Blasting；

S5: to forging modifier treatment, the mechanical property of connecting rod is made to reach requirement, and guarantees the cracking brittleness of cracking material；

S6: opening up splitter, cracking, refitting, finally obtains steel bimetallic cracking connecting-rod finished product.

2. the forging method of steel bimetallic cracking connecting-rod according to claim 1, which is characterized in that described in step S1 Cracking material with a thickness of 2mm ~ 3mm.

3. the forging method of steel bimetallic cracking connecting-rod according to claim 1, which is characterized in that the step S1 tool Body is as follows:

S11: manufacture sand mold formwork；

S12: after being 500 DEG C by the preheating temperature of cracking material, it is inserted into cracking zone (2) position in sand mold formwork；

S13: casting material of main part.

4. the forging method of steel bimetallic cracking connecting-rod according to claim 1, which is characterized in that described in step S2 Normalized treatment is specific as follows:

S21: slab is heated to 800 DEG C ~ 820 DEG C；

S22: heat preservation 6 ~ 10 hours, to promote material of main part and cracking material at the interface of gonnecting rod body (1) and cracking zone (2) And the interface element phase counterdiffusion of cracking zone (2) and connecting rod cap (3), continuous diffusion layer is formed, the combination at interface is enhanced Performance prevents subsequent forging crack；

S23: air-cooled processing.

5. the forging method of steel bimetallic cracking connecting-rod according to claim 1, which is characterized in that described in step S3 Forging condition are as follows: initial forging temperature be 1100 DEG C, final forging temperature be 800 DEG C；Total forging ratio of height of slab forging front and back is 1.5~3.0；Forging process is divided into base, blocking and finish-forging, wherein the forging ratio of slab blocking height account for total forging ratio 60% ~ 80%。

6. the forging method of steel bimetallic cracking connecting-rod according to claim 5, which is characterized in that the finish-forging process Forging die be surrounded by cracking zone Qiao Kou (8) and connecting rod area Qiao Kou (9) in forging, wherein the cracking zone Qiao Kou (8) is being split The two sides of Xie Qu (2) center line；Cracking zone Qiao Kou (8) height is 2 ~ 3 times of connecting rod area Qiao Kou (9) height, for subtract Small metal flow resistance guides metal to flow in finish-forging to the storehouse portion of intermediate cracking zone (2) two sides, controls the position of cracking material It sets, and prevents from causing Interface Cracking when forging.

7. the forging method of steel bimetallic cracking connecting-rod according to claim 1, which is characterized in that the step S5's Modifier treatment is that metastable quenching increases temperature tempering.