The Study On Machinability Of Casting Cold Work Die Steel

Domestic casting cold work die steel is the common material of the car covermold. It is formed by the method of casting instead of forging. Compared withforging, casting die steel costs lower, has short production period and can processmore complex shape of the mold. But it also has the characters of irregular shape,hardworking, and update fast so that the actual production process is put forwardhigher requirements.The studies on cutting properties and cutting mechanisms of the casting coldwork die steel were systematically carried out in this paper. The main properties ofthis material in the annealed condition were deeply discussed in turning and milling.Its aim is to reveal the influence of factors such as cutting force, tool wear, surfaceroughness and chips and analyze its experimental results. Suitable cuttingparameters can be obtained to improve the cutting mechanisms of the domesticcasting steel. At the same time, the simulation cutting process was done by usingABAQUS software to verify the correctness of the experimental results. This papermainly does the following work.1. The test specimens of cold work die steel were casted by the method ofmold casting. And they were annealed, quenched and tempered to survey themicrostructure, properties and hardness. The study found that the casting structure ofthis material is martensitic, retained austenite and inclusions and its hardness is57HRC. The organization of fine spherical carbides and granular secondary carbidesis obtained after annealing at760°C whose hardness is223HB. It was quenched at1040°C to get quenched martensitic. After tempering at500°C, the structure oftempered martensitic was acquired.2. Through single factor experiment, the experimental annealed specimenswere machined by turning to explore the influence of cutting parameters on cuttingforce, tool wear, surface roughness and chips. The study found that cutting depth isthe main factors to influent cutting force. Among three component of cutting force, the main cutting force is maximum, and back force is minimum. The style of toolwear is mainly abrasive wear on the back. On the one hand, the tool wear increaseswith the increase of cutting depth and feed, but they have little effect. On the otherhand, the tool wear sharply increases when the spindle speed is increased. Cuttingspeed is the major influential factor to tool wear, feed is the minor factor and cuttingdepth is the least one. The surface roughness increases with the increase of cuttingdepth and feed while it decreases with the increase of spindle speed. Chipdeformation coefficient deceases with the increase of cutting depth and spindlespeed but increases with the increase of speed. And spindle speed among the impactfactor is the smallest.3. Material specimens were machined by milling machine after annealing. Thestudy found that the surface finish deteriorates with the increase of cutting depth andfeed while it improves with the increase of spindle speed. Chips will become biggerwhen the cutting depth increases. While the feed increases, cutting force andtemperature both increases. Nominal thickness of cut also increases so roll chips areformed. Chip breaking becomes increasingly difficult because shear stress of thefirst deformation zone decreases with increase of spindle speed.4. The cutting model was established through the finite element modelsoftware named ABAQUS. The cutting force and chips were obtained when thecutting parameters were spindle speed710r/min, feed0.1mm/r and cutting depth0.3mm. The simulation result found that compared with experiment the cutting forceis relatively small because the simulation cutting condition is ideal. And thedifference is little. The result is continuous chips and it is identical in shape betweenexperiment and simulation.This paper studies on the machinability of casting cold word die steel and itprovides the theoretical basis for the die steel on the car cover mold.