APPLICATION OF TECHNOLOGY IN THE PRODUCTION OF «CORTICAL» METHOD OF FORMING INSERTS FOR DIE CASTING COPPER ALLOYS

Abstract

In the present work for the creation of manufacturing technology forming statok higher heat resistance used the "cortical" method with the use of thermal spraying (TS). The essence of the method is as follows: on the model, which is a mirror copy of the forming surface of the insert, a working layer up to 3 mm thick of wear-resistant powder materials is applied by plasma spraying, and then a structural layer 10...20 mm thick of more plastic and cheap materials. The dusty "crust" process from which it will be established in a form holder, and separate from model. Working surface FV after separation from the model in size, shape and roughness fully complies with the requirements of the drawing, ie it is not subjected to additional processing. For reasons of availability and relatively low cost for the working layers forming inserts made of "cortical" method with the use of GTN, the most often used powders camofluage chromium-Nickel alloy ПН77Х15С3Р2 or metalloids brands ПН70Ю30 and ПН85Ю15. Research into the optimal composition of the mixture of powders ПН70Ю30 and ПН77Х15С3Р2 conducted on special samples of steel 45, which is a plate with dimensions 5050 mm around the perimeter with ribs protruding above the work surface to a height of 1 mm. working surface is chrome-plated and termoobrabotki to earn a guaranteed layer of Cr2O3, which provides the adhesive connection of the coating and the substrate at the level of 5 MPa. During the experiments, the composition of the mixture of powders ranged from 95% PN70YU30 + 5% PN77H15S3R2 to 70% PN70YU30 + 30% PN77H15S3R2 in steps of 5%. The coating produced according to the following mode: the current is 500 A, voltage - 60 V; the total consumption of powder - 1.5 kg/h; the sample temperature is 650 ℃; coating thickness - 0.5 mm. Deposited samples were placed in a muffle furnace and heated to a temperature of 1300 C, where they were kept for 1 hour. After cooling to room temperature, together with the furnace, the coatings were carefully separated from the samples and subjected to permeability tests for which they were placed in special containers smearing around the perimeter with special mastic. Then the coatings on the outside were covered with a layer of thick chalk, and kerosene was poured into the vessels. It is established that dusty coatings from a mixture of powders with a content of 20% or more of pn77h15s3r2 alloy practically do not have pores (kerosene within 24 hours did not penetrate the chalk-coated surface).