The treatment process is analyzed
2020年3月11日The treatment process is analyzed. In terms of chemical composition, the chemical composition of the broken shovel tooth body is analyzed respectively. The composition of high manganese steel shovel teeth required for castings is based on the composition of standard ordinary high manganese steel. In order to improve the strength of high manganese steel, especially the yield strength, Cr, Mo and other alloying elements were added in the alloying design, and the chemical composition of the broken residual teeth wt%) was used to detect the fracture of the shovel teeth of Knot 4 excavator, and the casting process of the shovel teeth was analyzed, which is a schematic diagram of the casting process for producing the shovel teeth. It can be seen that during casting, the riser is located above the broken part of the shovel tooth, i.e. The working surface of the shovel tooth. According to the analysis, The riser is not in the right position, On the one hand, the riser on the working surface is easy to produce casting defects, which has a great influence on the use. On the other hand, the riser on the working surface is difficult to locate during casting, which is easy to cause the riser position deviation. If it is close to the positioning rib, the feeding during the solidification process after pouring will cause large stress between the riser and the positioning rib, which is easy to produce cracks. In terms of heat treatment process,
As that alloy content of high manganese steel is high, Due to poor thermal conductivity and large linear shrinkage, large thermal stress will be generated during heat treatment and heating. At the same time, carbide formed in as-cast structure significantly reduces the plasticity and toughness of steel due to low strength and large brittleness, which is easy to crack the shovel tooth and shovel lip castings. Therefore, strict requirements should be imposed on heating speed during water toughening treatment of high manganese steel. Observing the fracture morphology and shovel lip crack morphology of shovel tooth castings, it is found that the fracture and crack have oxidation color, which indicates that too fast heating speed during heat treatment is the main cause of casting cracks. It is a place for shovel tooth castings of a shovel loader to break residual bodies
The metallographic structure of the impact specimen is taken, There is no massive or reticular carbide phase in the metallographic structure of the spade tooth, only a small amount of carbide with fine dispersion distribution, but the grain size is large. The impact energy Ak) absorbed with the furnace sample is 216,202,183, Brinell hardness 205HB, which has high impact toughness and hardness. The impact toughness and hardness meet the requirements of the national standard for high manganese steel shaft factory https://www.bronzecast.net/product/transmission-parts-series/worm-shafts/ steel (GB/T5680-1998). 3 Process Improvement in view of the fact that the chemical composition meets the requirements, the improvement is mainly made in terms of casting process and heat treatment. In terms of casting technology, As for that shovel tooth castings of WK-4 excavator, Change the riser position as shown). Compared with the original process, the riser position changes and the parting surface also changes. The riser is placed at the hot pitch circle, which is beneficial to feeding and riser placement. Sawdust sand is avoided for the core in the working surface and shovel tooth cavity, thus increasing the concession of the core. Open the box 10 hours after pouring to reduce the thermal stress during casting solidification. In terms of heat treatment process, As that high manganese steel has poor thermal conductivity, The requirements for heating speed are relatively strict during heat treatment, but the heating speed cannot be controlled for the heat treatment furnace in actual production.
Therefore, the heat treatment process is changed from 650C-times of heat preservation in the original heating process to a stepped heating curve, with heat preservation for 2 hours every 100C gap, so as to increase the temperature uniformity inside and outside the casting and reduce the thermal stress. The microstructure of high manganese steel treated by water toughening should be single-phase austenite microstructure and non-magnetic, but the core of fracture surface of residual tooth casting was found to be absent by inspection of fractured shovel tooth residual body.
As that alloy content of high manganese steel is high, Due to poor thermal conductivity and large linear shrinkage, large thermal stress will be generated during heat treatment and heating. At the same time, carbide formed in as-cast structure significantly reduces the plasticity and toughness of steel due to low strength and large brittleness, which is easy to crack the shovel tooth and shovel lip castings. Therefore, strict requirements should be imposed on heating speed during water toughening treatment of high manganese steel. Observing the fracture morphology and shovel lip crack morphology of shovel tooth castings, it is found that the fracture and crack have oxidation color, which indicates that too fast heating speed during heat treatment is the main cause of casting cracks. It is a place for shovel tooth castings of a shovel loader to break residual bodies
The metallographic structure of the impact specimen is taken, There is no massive or reticular carbide phase in the metallographic structure of the spade tooth, only a small amount of carbide with fine dispersion distribution, but the grain size is large. The impact energy Ak) absorbed with the furnace sample is 216,202,183, Brinell hardness 205HB, which has high impact toughness and hardness. The impact toughness and hardness meet the requirements of the national standard for high manganese steel shaft factory https://www.bronzecast.net/product/transmission-parts-series/worm-shafts/ steel (GB/T5680-1998). 3 Process Improvement in view of the fact that the chemical composition meets the requirements, the improvement is mainly made in terms of casting process and heat treatment. In terms of casting technology, As for that shovel tooth castings of WK-4 excavator, Change the riser position as shown). Compared with the original process, the riser position changes and the parting surface also changes. The riser is placed at the hot pitch circle, which is beneficial to feeding and riser placement. Sawdust sand is avoided for the core in the working surface and shovel tooth cavity, thus increasing the concession of the core. Open the box 10 hours after pouring to reduce the thermal stress during casting solidification. In terms of heat treatment process, As that high manganese steel has poor thermal conductivity, The requirements for heating speed are relatively strict during heat treatment, but the heating speed cannot be controlled for the heat treatment furnace in actual production.
Therefore, the heat treatment process is changed from 650C-times of heat preservation in the original heating process to a stepped heating curve, with heat preservation for 2 hours every 100C gap, so as to increase the temperature uniformity inside and outside the casting and reduce the thermal stress. The microstructure of high manganese steel treated by water toughening should be single-phase austenite microstructure and non-magnetic, but the core of fracture surface of residual tooth casting was found to be absent by inspection of fractured shovel tooth residual body.
Unknown coatings can be determined by chemical analysis. In fact, a systematic exclusion method is used. The specific method is described below. First use magnesium oxide powder and water degreased mud to scrub the surface to be tested to remove the oil on the surface, rinse it with water, and soak it in a 1: 1 nitric acid solution for 2 minutes. (1) The plating layer is dissolved by nitric acid.
If the plating layer is dissolved and the following phenomena occur, it can be judged according to the phenomena that occur. ① Blue or green solution appears a. Blue appears Blue may be copper or copper alloy plating. To confirm, the following operations can be performed: the blue solution is evaporated to dryness, and the residue is dissolved in 1 ml of a 20% (volume ratio) sulfuric acid solution and diluted to 100 ml. Put a small iron nail in this diluted solution to remove oil and rust and clean it. After a certain period of time, if a red metal replacement film appears on the surface of the nail, it can be determined that the coating is copper or a copper alloy. b. Green appears Green may be nickel plating. However, to confirm that you also need to do the following tests: make the solution alkaline with concentrated ammonia, add litmus indicator, and then add lmll% butanedione oxime ethanol solution. If there are red or pink flocculent precipitates, the coating is nickel. ② White turbid solution may appear tin, and tin coating can be proved by another corroboration rule: dissolve the plating of the sample with the same coating in concentrated hydrochloric acid, and add solid carboxicillin.
If purple red appears It turns out to be tin. ③Colorless solution If the coating is a colorless solution after dissolution, it may be zinc, silver, lead or cadmium. a. Determination of zinc Add concentrated ammonia and litmus indicator, make the test solution appear 10% sodium sulfide under alkaline conditions, if there is white flocculent precipitation, it can be determined to be zinc coating. b. The determination of cadmium is the same as that of zinc. After adding 10% sodium sulfide, if a yellow flocculent precipitate appears, it is a cadmium coating. C. Confirmation of silver Add 10% sodium hydroxide solution, and use litmus indicator to steel shaft factory determine that the test solution is alkaline. At this time, if a black precipitate appears, it indicates that it is a silver coating. d. Determination of lead After determining that it is not zinc and cadmium, if a white flocculent precipitate appears in the same way as the test silver, then this coating is lead. (2) The coating is not dissolved by nitric acid If the tested coating is not dissolved by nitric acid, this indicates that the coating may be aluminum, chromium, gold or a platinum group (palladium, platinum, rhodium) metal. ① Determination of gold When the coating has color without being dissolved by nitric acid, it can be determined that this coating is gold. Copper and its alloys will not be colored without being dissolved by nitric acid. The non-ferrous metals that are insoluble in nitric acid can only be gold. It should be noted that the gold plating is not always yellow-gold, but also purple-gold, red-gold, rose-gold, etc., which can easily cause illusion. ② Determination of aluminum Treat the coating with 10% sodium hydroxide solution. If it is corroded, it indicates that it is aluminum. Aluminum is passivated in nitric acid and is therefore insoluble. The surface aluminum layer may be vacuum-plated or hot-dip. However, the aluminum coating is easily removed in the lye. ③ Determination of chromium Treat the coating with concentrated hydrochloric acid. If a green solution appears, it is a chromium coating. ④ Determination of platinum group metals If it is neither soluble in nitric acid, hydrochloric acid, or alkali, and it is a white coating https://www.bronzecast.net/product/transmission-parts-series/worm-shafts/ , it is a platinum group metal. To identify the coating using the above method, it is necessary to determine that the corrosion is not the base metal . This is very important, otherwise, the correct conclusion will not be obtained due to the interference of the base metal. The correct analysis method is to remove the plating layer from the substrate and identify it, which is more accurate.
If the plating layer is dissolved and the following phenomena occur, it can be judged according to the phenomena that occur. ① Blue or green solution appears a. Blue appears Blue may be copper or copper alloy plating. To confirm, the following operations can be performed: the blue solution is evaporated to dryness, and the residue is dissolved in 1 ml of a 20% (volume ratio) sulfuric acid solution and diluted to 100 ml. Put a small iron nail in this diluted solution to remove oil and rust and clean it. After a certain period of time, if a red metal replacement film appears on the surface of the nail, it can be determined that the coating is copper or a copper alloy. b. Green appears Green may be nickel plating. However, to confirm that you also need to do the following tests: make the solution alkaline with concentrated ammonia, add litmus indicator, and then add lmll% butanedione oxime ethanol solution. If there are red or pink flocculent precipitates, the coating is nickel. ② White turbid solution may appear tin, and tin coating can be proved by another corroboration rule: dissolve the plating of the sample with the same coating in concentrated hydrochloric acid, and add solid carboxicillin.
If purple red appears It turns out to be tin. ③Colorless solution If the coating is a colorless solution after dissolution, it may be zinc, silver, lead or cadmium. a. Determination of zinc Add concentrated ammonia and litmus indicator, make the test solution appear 10% sodium sulfide under alkaline conditions, if there is white flocculent precipitation, it can be determined to be zinc coating. b. The determination of cadmium is the same as that of zinc. After adding 10% sodium sulfide, if a yellow flocculent precipitate appears, it is a cadmium coating. C. Confirmation of silver Add 10% sodium hydroxide solution, and use litmus indicator to steel shaft factory determine that the test solution is alkaline. At this time, if a black precipitate appears, it indicates that it is a silver coating. d. Determination of lead After determining that it is not zinc and cadmium, if a white flocculent precipitate appears in the same way as the test silver, then this coating is lead. (2) The coating is not dissolved by nitric acid If the tested coating is not dissolved by nitric acid, this indicates that the coating may be aluminum, chromium, gold or a platinum group (palladium, platinum, rhodium) metal. ① Determination of gold When the coating has color without being dissolved by nitric acid, it can be determined that this coating is gold. Copper and its alloys will not be colored without being dissolved by nitric acid. The non-ferrous metals that are insoluble in nitric acid can only be gold. It should be noted that the gold plating is not always yellow-gold, but also purple-gold, red-gold, rose-gold, etc., which can easily cause illusion. ② Determination of aluminum Treat the coating with 10% sodium hydroxide solution. If it is corroded, it indicates that it is aluminum. Aluminum is passivated in nitric acid and is therefore insoluble. The surface aluminum layer may be vacuum-plated or hot-dip. However, the aluminum coating is easily removed in the lye. ③ Determination of chromium Treat the coating with concentrated hydrochloric acid. If a green solution appears, it is a chromium coating. ④ Determination of platinum group metals If it is neither soluble in nitric acid, hydrochloric acid, or alkali, and it is a white coating https://www.bronzecast.net/product/transmission-parts-series/worm-shafts/ , it is a platinum group metal. To identify the coating using the above method, it is necessary to determine that the corrosion is not the base metal . This is very important, otherwise, the correct conclusion will not be obtained due to the interference of the base metal. The correct analysis method is to remove the plating layer from the substrate and identify it, which is more accurate.
