Forging forming method of large marine crank

Abstract

The invention provides a forging forming method of a large marine crank. The forging forming method includes the steps of steel ingot calculating, upset forging, rough machining, compression bending, pressing and shaping after demoulding and heat treatment. When a forged piece of the crank is subjected to rough machining, the shaft part in the middle of the crank is preferably directly machined into a cylindrical shape, crank arms on two sides are machined into tabulate shapes to have machining allowance reserved according to a rough machining figure, and a transition slope is symmetrically machined between the cylindrical shaft part and the tabulate crank arms. With the method, internal crank arm drapes, unsuited complete fiber, local flaw detection defects and the like appearing in other bend forging methods are effectively reduced, utilization rate of steel ingots can be increased, and production cost is lowered.

Description

technical field [0001] The invention relates to a crank forming method, in particular to a forging and pressing forming method of a large marine crank, and belongs to the technical field of forging and forming. Background technique [0002] The crankshaft is one of the core components of the diesel engine, known as the "heart" of the engine, its manufacturing cost accounts for about 10%-20% of the total cost of the engine, and for marine crankshafts, this ratio can even reach 1 / 3 , it plays a vital role in the smooth and safe operation of the diesel engine. [0003] As we all know, the good internal organization, reasonable metal flow line and high dimensional accuracy of the marine crankshaft are inseparable from its manufacturing process. At present, among the forged crankshafts, the small crankshaft can adopt the integral forging method to finally obtain a full-fiber crankshaft. This kind of crankshaft is mainly used for small and medium-sized ships equipped with small a...

AI Technical Summary

Problems solved by technology

[0004] At present, the forging methods of large-scale marine cranks include block forging, ring forging, die forging, upsetting forging, bending forging, etc. The above-mentioned forging methods have shortcomings in actual production, for example: block forging , its disadvantages are large processing allowance, high cost, and the quality is difficult to meet the standard, and the scrap rate is relatively high; the disadvantage of ring forging method is that the process requires high operation skills of equipment and workers, which is not easy to achieve in production, and There is still the risk of air holes in the forgings; the main disadvantage of the die forging method is that different types of crankshafts need to use different molds, and the production cost will be relatively high, especially when the die forging method is used to produce large marine crankshafts. High tonnage, in addition, there are very high requirements on the strength of the mold, and the application in actual production is not easy to realize; Upsetting method, the disadvantage of this method is that the manufacturing cost in production is too high, not suitable for small batch production; Bending forging method , using upsetting forging-bending forging two-step forming, mainly including RR, TR, NTR, NRR method, although it is currently a method commonly used by Chinese marine crankshaft manufacturers to produce large marine crankshaft cranks, but this method is prone to crank arm Severe wrinkles at the bottom of the inner side, convex or concave at the outer side, severe indentation at the crank pin, etc. Some of the indentations even exceed the processed surface, and after processing, the indentation has local black skin. In order to make the above wrinkles , convex and concave removed, it is necessary to increase the machining allowance of the crank, which undoubtedly reduces the utilization rate of steel ingots (some steel ingots utilization rate is less than 25%), resulting in the waste of raw materials and increasing production costs

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