SU1368746A1 - Method of checking pig iron castings for quality - Google Patents

Abstract

The invention relates to physicochemical methods for controlling the quality of alloys and can be used to control the quality of products under factory conditions. The purpose of the invention is to increase the control performance by optimizing the interval of permissible values of the control parameters. From a material of controlled castings make a calibration sample in the form of a wedge-shaped casting. Then, one of the faces of the wedge-shaped casting is x-rayed at points located at predetermined distances from the point of the wedge or with a certain pitch. Radiography of cast iron should be carried out in cobalt radiation, registering closely located lines of FejC carbide in radiation and iron in K Co. The carbide content at these points is determined from the ratio of line intensities, and then the thermopower is determined at the same points relative to its value at the base of the wedge and the thermopower is plotted against the carbide content. After that, a batch of specimens is made for mechanical tests, and the carbide content is determined therein by X-ray diffraction and thermopower. Samples are subjected to tests for machinability, setting permissible limits for the content of carbide in them, and according to the calibration schedule, permissible values of thermoEMF. In the subsequent control of castings for sorting, it is sufficient to measure only the thermoEMF and. compare the obtained value with the valid one. 2 Il. S (L 00 O) 00 4 O

Description

The invention relates to physicochemical methods for controlling the quality of alloys and can be used to control the quality of products under factory conditions.

The purpose of the invention is to increase the performance of the control by optimizing the interval of permissible values of the parameters of the control.

Figure 1 shows the dependence of the intensity ratio of the carbide () and / 4-line of iron I -pc / I on the amount of carbide in the material; in Fig.2, the change in thermoEMF depending on the amount of iron carbide.

The essence of the method consists in the fact that a calibration sample is made of the material to be tested, is cast in the form of a wedge, with a variable carbide content along its length. In the calibration sample, the amount of iron carbide is determined by X-ray, the wire is taken from the diffraction lines of carbide in K-radiation, and the base line of the alloy in K-radiation and compared their intensity. Then, a measurement of thermopower between the point with the minimum number of carbides is compared. and points with a known, measured radiographic amount of carbide. According to the measurement results, the dependences of the intensity ratio

tei diffraction lines I p, c - Red and differences. thermopower from carbide content.

Having made test specimens, they determine the quantitative content of carbide and the difference in thermoEMF, then mechanically treat them, determine the workability of the material, and determine the limits of allowable values of the difference in thermoelectric power for the material being tested according to the allowable limits of workability. Thereafter, the thermopower difference for the controlled castings is measured and the measured values are compared with the allowable interval.

Example. Since thermoEMF is a function of the concentration of silicon, carbon, and manganese in the cast iron and the phase composition of the casting, it is necessary to exclude the influence of the chemical composition of the cast iron on the thermoelectric power. For the convenience of monitoring and ensuring its automation, it is advisable to choose the area for monitoring as a reference.

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casting, on which, according to the technological conditions of production, waste is always absent. ThermoEMF difference, i.e. The difference in thermoelectric power between the surface to be tested and the one chosen as a reference depends only on the structure of the casting — the concentration of carbides at the control point.

The method was used to control local bleaching on castings of the axle shaft gland sleeves to the car, made of gray cast iron of grade SCH-18. A wedge-shaped casting with a variable carbide content was made of cast iron of grade SCH-18. On one of the faces of the wedge, starting with the tips, with an interval of 2 mm, X-ray diffraction was performed. The survey was carried out in the angular, in the range of 26–43–50 °, registering the (021) (112) line in the K and (110) Fe radiation in K / iCo. Then, the integrated intensity is determined over the areas of the corresponding lines.

The ratio of the intensities of cementite and iron on the calibration curve found the amount of cementite in the studied points on the wedge.

The dependence of the ratio Ipg / I rev on the amount of carbide in the sample (Fig. 1) is linear. Further, at a point with a known amount of carbide, the difference in thermoEMF was measured using a thermoEMF sensor, which contains a hot electrode (160 C) of L62 brass, between the point with a known carbide content and the wedge butt, where the carbide content is minimal. The dependence of the thermopower difference on the amount of carbide in the wedge (figure 2) also has a linear character.

Full-scale samples, i.e., are used to select the limit value of the carbide content in the gland sleeve castings. casting sleeve gland. The carbide content in them is determined by X-ray. Castings are tested on a lathe and the machinability of the castings is determined by the intensity of wear of the tool. With a cutter wear intensity of 20 µm / min, it is considered that the casting contains a valid carbide content. According to the technological instructions for the processing of castings from cast iron, cutting on metal-cutting automatic machines should be done.

The wear rate of the pick is no more than 20 µm / min. Increased wear of the incisors is not allowed, since this leads to premature stopping of the automata and reconfiguring them.

The allowable carbide content is 3%. According to the calibration dependence of the thermopower difference on the carbide content (Fig. 2), the allowable value of the thermopower difference is set to 34 mV.

To control local bleaching in castings, a five-electrode thermopower sensor is used. Four electrodes heated to 413 K made of brass grade L62 are installed at the outer edge of the casting, and a fifth electrode of the same material, heated to the same temperature, is located near the inner edge where there is no chill. The difference in thermopower is measured alternately between the fifth electrode and the electrodes located at the outer edge of the casting.

Claims (1)

In the controlled batch, 4% of castings with local bleaching were found. When machining a batch of castings with a thermal thermopower difference less than the allowable value, no castings with bleaching were detected. Invention Formula The method of quality control of iron castings, including manufacturing 68746 sample, X-ray irradiation of the sample, obtaining a diffraction pattern of reflections from the sample, comparing the intensities of diffraction lines of carbides in K-radiation with the diffraction lines of the base alloy in K -radiation and radiographic determination of the number of carbides, Q characterized in that, in order to increase the productivity of the control by optimizing the interval. the permissible values of the control parameters, a sample with a variable amount of carbides in the form of a wedge-shaped casting is made from a controlled gog iron, the distribution of carbides along the casting length at fixed points is determined by X-ray diffraction, the thermopower difference is determined in the same points, a calibration dependence of thermoEMF on the amount of carbides found by X-ray diffraction is made; samples of known carbide content are made of the same grade of cast iron, specimens are tested for machinability, the interval of acceptable values of carbides and the interval are determined Q admissible values of the thermopower difference, measure the thermopower difference in controlled castings and compare it with the allowable interval. The concentration of Fe C / Phage. hell 60 80 t 204060 80 Fe C concentration 2