Naips carries a large selection of Emergency Exit Sign Light for your option. Patterns can be customized and replace.
Emergency Exit Light,Led Exit Signs,Neon Exit Sign,Emergency Exit Sign Light Foshan Nai An Lighting Electric Co.,ltd , https://www.twinspotlights.com
How to solve the top hole of 2K cylinder
　　 In the process of producing 2K cylinders in FAW Foundry No.1 , the top surface often has porosity defects. After processing, it can be seen that the 2K cylinders with pores on the top surface reach 40% to 50% at most, and 20% to 30% when there are few. %. Although the use of surface repair welding can save such defects, it also brings a lot of inconvenience to production. The production process of the 2K cylinder is a clay wet sand mold made of static pressure molding equipment, and the inner cavity and the two ends are shell core (coated sand) resin sand core. The defect situation is shown in the drawing.
Regarding the problem of the occurrence of pores on the top surface of the 2K cylinder, many attempts were made by the foundry. Only the iron oxide powder type sand film test and the sand oxide plus iron oxide powder test can substantially eliminate the pores on the top surface of the cylinder block. Although it is relieved, the addition of iron oxide powder to the molding sand during the production of the cylinder brings a lot of inconvenience to the production organization, causing a large amount of crusting (peeling) waste in the brake drum casting, and the addition of the iron oxide powder enables the production of the casting. The cost has increased a lot.
(a) (b)
2K cylinder top surface porosity defect
First, the cause analysis of the generation of pores
Determination of the porosity of the top surface of 1.2K cylinder
According to the analysis, the top pore of the 2K cylinder is a nitrogen hole.
The mechanism of generating nitrogen pores according to the casting: When the molten iron is poured into the resin sand type, the nitrogen-containing resin is rapidly decomposed by heat to a plurality of constituent gases including NH 3 , wherein the active NH 3 is decomposed into the primary "N" and " H", both 2NH 3 → N 2 + 3H 2 or 2N + 6H, in the case of sufficient oxygen, the following reaction NH 3 + O 2 → NOx + H 2 O (this reaction mainly depends on the amount of oxygen present), when the degree of "N" enrichment A bubble nucleus is generated when the critical value is reached.
In addition, from the irregular characteristics of the surface of the top surface of the 2K cylinder, it also conforms to the characteristics of the nitrogen hole.
Since the nitrogen gas pores are generated in a reducing atmosphere: NH 3 + Fe 2 O 3 → Fe + NOx + H 2 O, the addition of the iron oxide powder provides an oxidizing atmosphere for the solidification interface, thereby effectively preventing the generation of nitrogen gas pores.
2. Source of nitrogen
The molten iron is in contact with air during smelting at a high temperature, so that nitrogen in the air is dissolved in the molten iron. According to relevant information, nitrogen content in the molten iron exceeding 0.01% will produce nitrogen pores. The sand core of the 2K cylinder is composed of a shell core, the hardener of the shell core resin is urotropine, namely hexamethyltetramine (CH 2 ) 6N 4 , and the urotropine contains 40% N (mass fraction). The amount of urotropine added was 16% of the amount of shell core resin, the nitrogen content of the shell core resin was 6.4%, the resin content of the shell core sand was 4%, and the nitrogen content of the shell core sand was 0.256%. Related studies have shown that nitrogen content in the molding material of more than 0.15% will produce nitrogen pores, and nitrogen content of more than 0.25% will produce severe nitrogen pores. Therefore, the nitrogen content of the core sand for the 2K cylinder provides the necessary conditions for the occurrence of the pores on the top surface of the 2K cylinder.
Second, the test plan and results
1. Determination of the test plan
(1) Production test of cylinder core and iron oxide powder. The process of replacing the sand and iron oxide powder with the core sand and the iron oxide powder is more reasonable. The addition of iron oxide powder to the core sand can directly exert the action of the iron oxide powder, supply oxygen at a high temperature, form an oxidizing atmosphere, promote the release of NH 3 from the resin, and react in the form of NH 3 + O 2 → NOx + H 2 O. The NH 3 released from the resin is reduced, and the reaction is carried out in the form of 2NH 3 →N2+3H 2 or 2N+6H to prevent the occurrence of nitrogen pores.
(2) Production test of adding an overflow tank to the pore portion of the cylinder type. Eliminate the gas and debris in the pores of the cylinder and reduce the nitrogen content here.
2. Test results
(1) Tested in the cylinder production line of the foundry, and produced 10 pieces of 2K cylinder round bar core plus iron oxide powder, of which 3 pieces produced pores; 10 pieces of sand and iron oxide powder were produced, among which 5 pieces of air holes were generated; 10 pieces of the overflow groove were formed in the air hole part (1 piece was lost), and 4 of them produced air holes. It can be seen from the test results that the iron oxide powder core test scheme is better than the current process. It is not possible to see that the test plan for opening the drainage groove in the vent area is worse than the current process.
(2) According to the 2K cylinder round bar core and the front and rear end cores simultaneously added iron oxide powder process trial production of 16 pieces, one of which produces pores; the sand and iron oxide powder process trial production of 15 pieces, of which 10 pieces produce pores, accounting for 2 /3 or so. The test confirmed that the sand core plus iron oxide powder process has a significant effect on solving the pores on the top surface of the 2K cylinder.
(3) The production test of iron oxide powder is added only to the front and rear end cores of the 2K cylinder. The number of tests is one shift (320 cylinder parts), and the addition of iron oxide powder in the molding sand is cancelled. After shot blasting, 143 pieces of test pieces of iron oxide powder core were detected, 59 cases had pores, and the ratio of the number of pore parts was 41%, which was lower than the ratio of the current parts of the hole parts by about 66%. Effect. In the 290 pieces of test piece with iron oxide powder added to the front and rear end cores of the 2K cylinder, the porosity after processing was 9%, which was also lower than the porosity of about 20% after the current process.
The number of test pieces is larger, which further proves that the core sand plus iron oxide powder has better effect than the sand and iron oxide powder, and the effect of adding iron oxide powder to the round core and the front and rear cores is better.
Third, the test results analysis
(1) It can be seen from the above sand core plus iron oxide powder production test that the above understanding of the top hole of the 2K cylinder is a nitrogen hole, and the sand core plus iron oxide powder process is effective for solving the top hole of the 2K cylinder. . Since the pores on the top surface of the 2K cylinder are in contact with the molding sand, the iron oxide powder in the sand core cannot directly act on the pores, and the iron oxide powder only produces an oxidizing atmosphere, which is combined with the nitrogen in the resin to reduce The nitrogen content in the molten iron acts to solve the pores on the top surface of the 2K cylinder.
(2) The closer the sand core of the iron oxide powder is to the location where the pores are generated, the more obvious the effect. From the above sand core plus iron oxide powder production test, it can be seen that the round bar core and the front and rear end cores simultaneously have the best effect of adding iron oxide powder. The iron oxide powder content of the round rod core and the front and rear end cores simultaneously added with iron oxide powder is not much higher than the iron oxide powder content of the iron oxide powder added only in the round rod core (because the front and rear end cores are small), the effect is much more obvious. The main reason is that the oxidized atmosphere is more likely to reach the pores because the front and rear cores are closer to the pores, so the effect on the pores is more obvious.
(3) Regardless of the sand type or the sand core, the nitrogen pores on the top surface of the 2K cylinder can be exerted only when the amount of the iron oxide powder is sufficient. From the above sand core plus iron oxide powder production test, it can be seen that the test effect of adding the iron oxide powder to the round rod core and the front and rear end cores is better than that of the front and rear end cores separately added with iron oxide powder, mainly because of the former iron oxide. The powder is much more than the latter.
This type of sand plus iron oxide powder also has this situation. At the beginning, the amount of iron oxide powder in the molding sand is 1.7%, and the pores on the top surface of the 2K cylinder are few. Then the amount of iron oxide powder in the molding sand is reduced to 0.4%, 2K. The porosity of the top surface of the cylinder is obviously increased, the porosity before processing is 50% to 70%, and the porosity after processing is as high as 20%.
In addition, tests were carried out to add iron oxide powder to sand core coatings and sand coatings. These tests have had little effect on solving the pores on the top surface of 2K cylinders.
Practice has proved that only when the amount of iron oxide powder added reaches a sufficient content can the nitrogen pores on the top surface of the 2K cylinder be acted upon.
(4) Calculation of the amount of iron oxide powder required. The hardener urotropine of the shell core resin, the initial products of thermal decomposition are H 3 N and CN, the two products are unstable, decomposed into N 2 , H 2 , C elements, and N 2 enters the iron liquid to form a nitrogen gas hole. To avoid the generation of nitrogen pores, it is necessary to avoid the formation of N 2 in the form of NOx (i.e., NO or NO 2 ). The calculated nitrogen content of the core sand is about 0.256%. The iron oxide powder is added to convert the nitrogen amount into NOx (NO or NO 2 ) form, and the amount of iron oxide powder to be added in the core sand is required. It is 1.95% to 3.9%. It can be seen that the ability of the iron oxide powder to neutralize nitrogen is very weak, and only when the amount of iron oxide powder is added to a sufficient amount can the nitrogen pores be exerted.
The pores on the top surface of the 2K cylinder are directly in contact with the sand type, and are not in contact with the sand core. Although the iron oxide powder added to the sand core can well solve the problem of the pores on the top surface of the 2K cylinder, the utilization rate of the iron oxide powder is still not high. If you can change the part process of the 2K cylinder, add a sand core to the top hole of the 2K cylinder to cover the pores on the top surface of the 2K cylinder. This will make the top hole of the 2K cylinder directly and sand. The contact becomes directly in contact with the sand core, which makes it easier to solve the problem of the pores on the top surface of the 2K cylinder.
The use of a sand core in the top surface of the 2K cylinder body has a small influence surface, which can be implemented without changing the current sand molding process and the core sand process; the targeted iron oxide powder can be added only to the sand core. Moreover, the amount of the iron oxide powder to be added is not limited, and the iron oxide powder can be added to 3% or even to 4%, so that the effect of eliminating the nitrogen pores of the iron oxide powder is more fully and more targeted.
Fourth, production verification
According to the principle of combining material technology and part process, a sand core is added to the top surface of the 2K cylinder to cover the pores of the top surface of the 2K cylinder, and 3% iron oxide powder is added to the sand core. First, test 5 pieces of 2K cylinders, no pores were observed on the surface observation and anatomy. According to this scheme, 31 pieces of 2K cylinder test pieces were produced for trial processing. As a result, after 31 pieces of test pieces were processed, no pores were found in the parts covered by iron oxide powder sand core, and it was found about about 15 mm from the iron oxide powder core. The piece has a small hole with a pinhole size, the position is fixed, and the degree of the air hole is obviously reduced. As long as the iron oxide powder core is extended by 20 mm, the hole portion can be completely covered to solve the problem.
The production process of adding a sand core to the top surface of the 2K cylinder to cover the pores of the top surface of the 2K cylinder and adding 3% iron oxide powder to the sand core has achieved a very good effect. Great economic benefits. The process of adding iron oxide powder in molding sand has been eliminated, and only one less iron oxide powder can save more than 1 million yuan per year.
wall mounted, hanging or Recessed are available. No matter it's to light the way to fire safety or to help your workforce identify the quickest exit, you will find the right solution for every environment.