Summary of the invention
The purpose of this utility model is to provide a kind of and is suitable for the bent axle spheroidal graphite cast iron manufacturing, that have specified structure.
The utility model provides a kind of new type crank, it is characterized in that this bent axle makes with spheroidal graphite cast iron; Compare with the forged steel crankshaft of same model, the diameter that the diameter of its free-ended front end diameter of axle neck increases 7%-12%, its inner end diameter of axle increases 4%-8%.
The crankweb of above-mentioned ductile iron crankshaft is symmetrically overhanging to the left and right biconvex ear shape, compares with the forged steel crankshaft corresponding site of same model, and the width of its widest position increases 20%-24%.
The knuckle radius of the free end of above-mentioned ductile iron crankshaft and main journal joint is compared with the forged steel crankshaft of same model, increase 40%-60%, and this fillet place handles through roll extrusion preferably.
Same model bent axle described in the utility model means the bent axle that meets same technical standard, and described technical standard comprises all technical standards such as NBS, industry standard and company standard.
Specifically, the WD615 Series Crankshaft of new structure of the present utility model is characterised in that, this bent axle is made with spheroidal graphite cast iron, compares with the forged steel WD615 Series Crankshaft of same model, and the diameter of its free end front end diameter of axle and the diameter of the inner end diameter of axle increase 2-5mm respectively.
The feature of this WD615 series ductile iron crankshaft also is, its crankweb is symmetrically overhanging to the left and right biconvex ear shape, the Extreme breadth at the biconvex ear place of this crankweb is compared with the Extreme breadth of the corresponding site of the forged steel WD615 Series Crankshaft of same model, has increased 25-35mm.
The feature of this WD615 series ductile iron crankshaft also is, compare with the forged steel WD615 Series Crankshaft of same model, the knuckle radius of its free end and main journal joint increases 2-5mm, and the knuckle place at main journal and connecting rod neck place also handles through roll extrusion.
New type crank of the present utility model adopts the reason of spheroidal graphite cast iron manufacturing to be that spheroidal graphite cast iron has the favorable mechanical performance, and good wear resistance is especially arranged, and itself contained graphite just has good lubricity.After graphite split away off from the matrix of foundry goods, the hole that it stays also stored lubricant oil.But compare with forged steel, the ability of its counter-bending fatigue is slightly poor.Therefore, have the mechanical property identical, then must do following improvement at the weakness of its structure with forged steel crankshaft for guaranteeing ductile iron crankshaft:
1. the free end of bent axle withstands shocks and stress alternation, and it still is a cantilever structure simultaneously.For strengthening the ability that it resists flexural fatigue, the utility model people with the diameter of the free-ended front end diameter of axle of this ductile iron crankshaft than and this diameter of the forged steel crankshaft of same model increase 7%-12%, with the diameter of the free-ended inner end of this ductile iron crankshaft diameter of axle than and this diameter of the forged steel crankshaft of same model increase 4%-8%.
2. with the free end of novel ductile iron crankshaft of the present utility model and the knuckle radius at main journal place, knuckle radius than this place of the forged steel crankshaft of same model increases 40%-60%, concentrate susceptibility with the stress that reduces this place, and then strengthen the ability of the counter-bending fatigue at this place.For further strengthening the ability of the counter-bending fatigue at this knuckle place and main journal, connecting rod neck knuckle place, also can do to surpass the roll extrusion processing of crankshaft material yield limit to this place, make the metal at this position produce compressive residual stress by top layer to deep layer, to produce the compensation stress of low value in the depths, thereby can partly offset bent axle suffered tensile stress of when work, further improve the fatigue strength at this place of bent axle.
3. the crankweb position with the utility model ductile iron crankshaft is designed to the overhanging biconvex ear shape in the left and right sides symmetrically, so that the Extreme breadth of this biconvex ear position is than the Extreme breadth increase 20%-24% of the corresponding site of the forged steel crankshaft of same model.By strengthening this size, can make the corresponding within the specific limits increasing of module of anti-bending section at this place of bent axle, the result also strengthens its resistance to flexure within the specific limits, and the bending resistance at this position is strengthened.
Ductile iron crankshaft of the present utility model makes that because of the improvement on said structure and the size weak part of this bent axle is strengthened, and its performance can be compared favourably with the forged steel crankshaft of same model.
In addition, also can make ionic nitrizing treatment, make its surface form wear-resisting, the anticorrosion layer that one deck is made up of nitrided iron and cementite, with the comprehensive mechanical performance of further this ductile iron crankshaft of raising to the surface of this ductile iron crankshaft.The conventional spheroidal graphite cast iron that can be used for making bent axle all is suitable for making new type crank of the present utility model.The utility model recommends to adopt the following spheroidal graphite cast iron of chemical composition:
C:3.8%-3.99%, Si:2.0%-2.4%, Mn:0.4%-0.5%, P: be less than or equal to 0.07%, S: be less than or equal to: Cu:0.5-0.6% 0.035%.
The spheroidal graphite cast iron of mentioned component carries out spheroidizing with Re:Mg>1 rare earth magnesium; Foundry goods is done normalizing stage by stage, can reach the performance that is higher than QT800-3 spheroidal graphite cast iron.
Embodiment
Embodiment 1
Use induction furnace melting cast iron, this cast iron chemical composition after the rare earth magnesium spheroidizing of Re:Mg>1 is as follows:
C:3.91%、Si:2.3%、Mn:0.48%、P:0.03%、S:2%、Cu:0.55%。
To cast the WD615 crank shaft blank through the spheroidal graphite cast iron of above-mentioned processing, its nodulizing grade is that 2 grades, 6 grades of sphere diameters, content of pearlite in alloy are 91%.
Above-mentioned blank carries out normalizing stage by stage: 910-920 ℃ of insulation 30 minutes after machining; Stove is chilled to 820 ℃, is incubated 1 hour; Air-cooled after coming out of the stove.
The size of bent axle after the machining, the diameter d 1 of the preceding end journal 11 of its free end 1 and the diameter d 2 of inner end axle journal 12 are respectively 52.4mm and 53mm, compare with the forged steel crankshaft of same model, the diameter of preceding end journal 11 increases 9.2%, and the diameter of inner end axle journal 12 increases 6%; Its crankweb 4 has symmetrically overhanging to the left and right biconvex ear 41, and the Extreme breadth L of the biconvex ear 41 of crankweb 4 is 159mm, and the Extreme breadth L between this biconvex ear increases 22% than the Extreme breadth of the forged steel crankshaft crankweb corresponding site of same model; Through the free end 1 of roll extrusion processing and the knuckle radius of main journal 2 joints is 6mm, compares with the forged steel crankshaft of same model, increases 50%; All the other sizes and WD615 series forged steel crankshaft measure-alike.
Can make nitrogen ion aura to this bent axle surface at last handles.
Ductile iron crankshaft of the present utility model has strengthened weak part owing to improved structure and size, the ability of its counter-bending fatigue is improved, thereby has satisfied user's technical requirements comprehensively.The operating life of the operating life that practice shows ductile iron crankshaft of the present utility model and the 45# steel of same model or 42CrMo forging steel crank shaft is identical or than its height slightly.