Before October 18, 2009, the chemical composition control before the furnace in the foundry workshop was completed by manual testing, and the process control was mainly based on experience. Since the introduction of the spectrometer on October 18, 2009, the chemical composition adjustment before the furnace is divided into two tests: the initial sample and the duplicate sample, which adds a certain degree of controllability to the control of the chemical composition of the centrifugal roller. However, in 2010, the chemical composition was still unstable. The average pass rate of centrifugal roll composition was only 93.26%, which brought great hidden danger to the quality of the roll.
At the beginning of 2011, the technical director organized the test group to analyze the poor control of ingredients in 2010. The following problems exist:
1. Because the second test needs to wait for a certain period of time, because of the beginning of contact with the spectrometer, the operator thinks that the molten iron can be produced by one manual test in the past, not to mention the more advanced spectrometer now, waiting is a waste of time and cost. As a result, sometimes the result of the duplicate sample is not available, and the molten iron is poured, and the composition is unstable.
2. The sampling personnel did not standardize the sampling before the furnace or sampled the molten iron when the sampling was not safe and uniform.
3. After the spectrum sample is ground, if there are too shallow grinding and pores, slag inclusions are not ground or cracks, etc., it will have a certain impact on the composition.
4. The spectrometer is prone to abnormalities in the case of power failure or the process of changing argon gas, and the test is inaccurate.
5. The silicon and carbon contents of the test piece tend to be unstable during the process of controlling the composition of the centrifugal roller. When the temperature of molten iron is high, the carbon burning loss is more serious, and the silicon content of the infinite chilled roll is also unstable after inoculation, especially when the bainite and ductile centrifugal rolls are spheroidized, they should be covered with iron cutting and at high temperature, silicon and carbon more difficult to control.
After analysis and discussion and make corresponding rectification measures:
1. The technical director believes that waiting may be a waste of time and cost from an objective point of view, but the unstable use of the rolls caused by the unstable composition has a greater impact and waste. Since 2011, we must carry out 2 tests to ensure the quality of the water. At the same time, it is necessary to coordinate the connection work of various teams to minimize the waiting time.
2. Strictly operate in accordance with the spectrometer sampling standards formulated by Chief Engineer Li Jiyu.
3. The test piece worker must judge the first to second tests and the alloys added. If there is any abnormality, the third re-sample is required for confirmation.
4. The abnormality of the spectrometer has been reported to the quality control department, and its department has also made corresponding improvements, which has brought certain help to the furnace control. But the tester also needs to carefully judge each chemical spectrum sample.
5. For the control of infinite chilled centrifugal roll silicon, the test piece must not only judge the components well tested but also have a better choice for inoculating silicon. It is required to choose ferrosilicon with no impurities or less impurities as the inoculant. This improves the accuracy of the silicon after inoculation. The control of carbon means that the number of molten iron is large. For the heats where the molten iron is placed in the furnace for a long time, it is necessary to spot-check individual finished samples in the middle after pouring several tubes. If there is a problem, it can be remedied and rectified in time. For the control of silicon in bainite and ductile centrifugal rolls, the test piece worker should judge the amount and composition of the iron cut capping, and measure the final silicon content as much as possible within the range. The control of carbon is due to the serious burning loss of high-temperature spheroidized carbon, so the carbon in front of the furnace should be adjusted to the upper limit, and a certain amount of carbon loss should be given. If it is placed for a long time, it can also be sampled and analyzed before carbon supplementation.
In 2011, with the joint efforts of technicians in the foundry, the chemical composition of centrifugal rolls continuously refreshed the historical record for three consecutive months from January to March. 96.2% in January, 98.02% in February, 99.25% in March and 99.25% in March, from 93.27% in 2010 to 98.10% in November 2011, an increase of 4.83 percentage points, an increase of 5.18%, and a modest contribution to the strong brands.