CN101560665A - Fillet rolling and reinforcing technology of normalized nodular cast iron crankshaft - Google Patents

Abstract

The invention provides a nitridized fillet rolling and reinforcing technology of a normalized nodular cast iron crankshaft. The technology comprises the following steps: firstly, nitriding is performed, nitriding layers are formed on the surfaces of a crankshaft journal and a fillet by contolling an atmosphere of a nitriding furnace and a rolling wheel is utilized to roll the fillet; during rolling, the rolling angle alpha is from 30 degrees to 45 degrees, the rolling pressure P is from 8000N to 15000N, the rolling radius R is from 1.5mm to 2.5mm, and the rolling depth h is from 0.1mm to 0.2mm. The reinforcing technology can effectively improve the fatigue bending moment of a crankshaft and the wear resistance of the crankshaft journal, can improve the fatigue bending moment by more than 99.4 percent and the surface hardness HV0.1 to be between 500 and 620 and satisfies the use requirements of a supercharged mid-cooling engine with high explosion pressure so that the nodular cast iron crankshaft can also be used in the supercharged mid-cooling engine with the explosion pressure of 12MPa to 14MPa or even higher, and the manufacture cost of the crankshaft is greatly decreased. The invention optimizes and combines various nitridized fillet rolling parameters and avoids the bearing edge load phenomenon caused by rolling protrusions.

Description

A kind of nitrogenize of normalized nodular cast iron crankshaft, fillet rolling and reinforcing technology

Technical field

The present invention relates to a kind of complete processing of engine crankshaft, especially a kind of engine for automobile Strengthen Techniques of Crankshaft.

Background technology

Spheroidal graphite cast iron has obtained using widely in the manufacturing of automobile engine crankshaft owing to have high strength, high-ductility, high-wearing feature, high damping property and good processing characteristics and lower production cost.Particularly in being the natural aspiration type automobile engine crankshaft of 7-9MPa, explosion pressure is in absolute predominance.Yet in recent years along with the raising to the motor car engine emission request, supercharging technology has obtained increasing application in motor car engine.To explosion pressure 12-14MPa even higher charge inter cooling engine, performances such as the tired moment of flexure of the engine crankshaft that existing complete processing is produced and neck of bent axle wear resistance can not satisfy the requirement of service condition.

Summary of the invention

Technical problem to be solved by this invention is, a kind of nitrogenize, fillet rolling and reinforcing technology of normalized nodular cast iron crankshaft are provided, it can effectively improve the tired moment of flexure and the neck of bent axle wear resistance of bent axle, with the service requirements of the charge inter cooling engine that adapts to high explosion pressure.

The present invention realizes like this, a kind of nitrogenize of normalized nodular cast iron crankshaft, fillet rolling and reinforcing technology, described technology is, carry out nitrogenize earlier, by control to nitriding furnace atmosphere, make neck of bent axle and radiused surface form nitrided case, wherein white brightening is closed layer at the following 0.002-0.007mm of outside surface, diffusion layer is at the following 0.08-0.12mm of outside surface, surface hardness HV _0.1Be 500-620, utilize rolling wheel to carry out roll extrusion to fillet then, during roll extrusion, the roll extrusion angle [alpha] is 30-45 °, and roll extrusion power P is 8000-15000N, and the roll extrusion radius R is 1.5-2.5mm, and roll extrusion degree of depth h is 0.1-0.2mm.

This nitrogenize, fillet rolling and reinforcing technology can effectively improve the tired moment of flexure and the neck of bent axle wear resistance of bent axle, and tired moment of flexure can improve more than 99.4%, surface hardness HV _0.1At 500-620, adapted to the service requirements of the charge inter cooling engine of high explosion pressure, make ductile iron crankshaft also can be used for explosion pressure 12-14MPa even higher charge inter cooling engine, thereby reduced the manufacturing cost of bent axle significantly.By to nitrogenize and each Parameter Optimization combination of fillet rolling, avoided the bearing shell edge load phenomenon that causes because of the roll extrusion projection.

Description of drawings

Fig. 1 is the synoptic diagram of fillet rolling.

Fig. 2 is the synoptic diagram at the crankshaft fillet place after the roll extrusion.

Fig. 3 is the synoptic diagram that bent axle cooperates with bearing shell.

Among the figure, the 1-rolling wheel, 2-roll extrusion bull wheel, 3-treats rolling crankshafts, the 4-bearing shell.

Embodiment

Further specify the present invention below.

By control to nitriding furnace atmosphere, make neck of bent axle and radiused surface form nitrided case, wherein white brightening is closed layer at the following 0.002-0.007mm of outside surface, and diffusion layer is at the following 0.08-0.12mm of outside surface, surface hardness HV _0.1During for 500-620, the control method of nitriding furnace atmosphere is a prior art, no longer describes in detail.

Described nitrogenize is that the mechanical workout before roll extrusion is carried out afterwards.Nitrogenize is made the bent axle finished product through after the roll extrusion again.Obviously, described fillet is a bullnose.

The used rolling device of the present invention is identical with existing rolling device, and roll extrusion bull wheel 2, rolling wheel 1 are arranged above it.During roll extrusion, rolling wheel is at the roll extrusion bull wheel and treat between the fillet of rolling crankshafts 3.

As shown in Figure 1, when carrying out fillet rolling, can be according to the design of concrete automobile engine crankshaft, parameters such as tired moment of flexure value, bearing shell tolerance clearance, explosion pressure are determined roll extrusion parameters such as roll extrusion power P, roll extrusion angle [alpha], roll extrusion degree of depth h, roll extrusion radius R.

Maximum roll extrusion projection τ is the function of roll extrusion power P, roll extrusion fillet R, bent axle matrix hardness H.

Calculating maximum roll extrusion projection apart from the formula of bent axle shelves lateral distance L is:

$L\≈R+\sqrt{R^2-{(R-h)}^2}$

As shown in Figure 2, make L≤[(B by choosing parameters such as P, α, R, h ₁-B ₂)/2+1.25], and make bearing shell 4 edge (B ₁-B ₂The projection τ of place)/2 _bBe no more than 0.003mm, bearing shell edge load phenomenon then can not take place.

Embodiment 1

To be strengthened is that model is the ductile iron crankshaft of Y4105, and material is QT800-3.

A kind of nitrogenize of normalized nodular cast iron crankshaft, fillet rolling and reinforcing technology, described technology is, carry out nitrogenize earlier, by control to nitriding furnace atmosphere, make neck of bent axle and radiused surface form nitrided case, wherein white brightening is closed layer at the following 0.002-0.007mm of outside surface, and diffusion layer is at the following 0.08-0.12mm of outside surface, surface hardness HV _0.1Be 556, utilize rolling wheel to carry out direct roll extrusion to fillet then, during roll extrusion, the roll extrusion angle [alpha] is 40 °, and roll extrusion power P is 9800N, and the roll extrusion radius R is 2.0mm, and roll extrusion degree of depth h is 0.15mm.Control roll extrusion projection: τ _b≤ 0.003mm.

After the roll extrusion, strengthening effect is: the tired moment M behind the nitrogenize of normalizing attitude, the fillet rolling _-1=2285N.m, and the tired moment M of not roll extrusion of normalizing attitude _-1=1146N.m, tired moment of flexure increase rate is 99.4%.

The technique effect of above-mentioned processing satisfies the tired moment of flexure design of boosting type engine service condition: M _-1〉=2100N.m, and axle journal wear resistance design requirements: 〉=HV _0.1500.

Claims (1)

1, a kind of nitrogenize of normalized nodular cast iron crankshaft, fillet rolling and reinforcing technology, it is characterized in that, described technology is, carry out nitrogenize earlier, by control to nitriding furnace atmosphere, make neck of bent axle and radiused surface form nitrided case, wherein white brightening is closed layer at the following 0.002-0.007mm of outside surface, diffusion layer is at the following 0.08-0.12mm of outside surface, surface hardness HV _0.1Be 500-620, utilize rolling wheel to carry out roll extrusion to fillet then, during roll extrusion, the roll extrusion angle [alpha] is 30-45 °, and roll extrusion power P is 8000-15000N, and the roll extrusion radius R is 1.5-2.5mm, and roll extrusion degree of depth h is 0.1-0.2mm.

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