Nitriding is a heat treatment method in which a workpiece is placed in a certain nitriding agent for heating and holding, so that the active atomic nitrogen in the nitriding agent penetrates into the surface layer of the workpiece to change the chemical composition, structure and properties of the surface of the workpiece. The development process of nitriding process at home and abroad is mainly divided into the following stages:
    Rapid gas nitriding of rare earth infiltration
Adding a rare earth infiltration agent to the gas nitriding process can activate the surface of the workpiece, accelerate the absorption rate of nitrogen atoms, not only shorten the nitriding cycle, but also form fine diffused nitride on the surface of the workpiece to improve the microstructure after nitriding. quality. Among them, the brittleness level, the nitride level and the looseness level can be controlled to level 1 and the surface hardness is increased (30 to 100 HV higher than conventional processes).
For the general structural steel layer depth requirement of 0.3mm, it takes more than 30 hours to maintain the holding time by the conventional nitriding process. However, if the rare earth infiltration agent is added, the holding time is only 14 hours, the shortening time is 53%, and the power saving is 40%. The nitrogen consumption is more than 35%, and the exhaust gas is reduced by 35%, and the whole nitriding cycle is shortened by 32.7%.
Continuous gas nitrocarburizing and blackening
Conventional gas nitriding heat treatment is carried out in a periodic well furnace or a box furnace. For large workpieces, this equipment and process can meet the production needs, but for small and medium-sized workpieces, gas nitriding in such furnaces is prone to problems such as uneven heating, uneven layers, and uneven hardness. In addition, since the periodic nitriding effect is not good, each furnace has an error, so the operation difficulty is greatly increased, and it is difficult to ensure uniform quality of all batches of workpieces.
The invention breaks through the shortcomings of the traditional thinking, creatively nitrites the small and medium-sized workpieces in a continuous furnace, solves many shortcomings of gas nitriding in the conventional periodic furnace, and not only greatly improves the quality and heat treatment process of the product after nitriding. Consistency and continuous adjustment due to temperature and time make operation simple and multiply.
Salt bath nitriding and QPQ composite treatmentThe earliest salt bath nitriding is called low temperature cyanidation, and the temperature is generally 520-560 °C. Commonly used liquid cyanide salt baths usually use neutral salts of sodium chloride, barium chloride, potassium chloride, sodium carbonate, etc. The commonly used cyanide salts are sodium cyanide and potassium cyanide, and are only suitable for high speed steel tools. . In addition, there is a salt bath nitriding called liquid sulfur nitrocarburizing, which is formulated with cerium chloride 30%, sodium chloride 20%, calcium chloride 50%, plus 5% to 10% (neutral salt total weight) ), into the powdery ferrous sulfide, the salt bath contains not less than 0.2% sulfur, and then a certain amount of ammonia (NH3) is introduced to promote the salt bath to flip. The process parameters are: temperature 540 ° C ~ 560 ° C, time 90 ~ 120 minutes.
1. Salt bath nitrocarburizing method
The method of salt bath nitrocarburizing has been proposed abroad, including soft nitriding, Tenifer method, Tufftriding, new Tenifer method, Melonizing, Sulfinuz method and Sur-Sulf method. Foreign salt bath carbonitriding is carried out in a molten salt containing cyanide and cyanate. The thermal decomposition of cyanate in the molten salt and other chemical reactions produce diffusible nitrogen and iron placed in the molten salt. The surface of the workpiece acts as a catalyst as in the case of gas nitriding.
   2.QPQ salt bath composite treatment technology
China's QPQ salt bath composite treatment technology is a national key promotion project during the Ninth Five-Year Plan period. The word QPQ comes from the prefix of the English Quench-Polish-Quench word. The original meaning is quenching (quick cooling)-polishing-quenching (quick cooling). Later, some experts and scholars will combine and increase the salt bath without polishing process. The QPQ technology of the polishing process is combined and collectively referred to as QPQ salt bath composite processing technology. QPQ salt bath composite treatment technology has the following characteristics:
(1) Good wear resistance and fatigue resistance. Mass production applications and tests have proven that this technology can increase tool life by more than 2 times. Strict rolling and sliding wear tests show that after 45P and 40Cr steels are treated by QPQ salt bath, the wear resistance is 15 times higher than that of high frequency quenching, 10 times higher than that of 20 steel carburizing and quenching. And ion nitriding is more than 2 times higher. The quenched 45 steel was improved by 40% after the QPQ salt bath composite treatment.
(2) Excellent corrosion resistance. After 45 steel steel composite treatment by QPQ salt bath, the corrosion resistance in the atmosphere and salt spray test is 70 times higher than that of blackening, 16 times higher than that of hard chromium plating, and even several times higher than 1Cr18Ni9Ti austenitic stainless steel.
(3) Minimal deformation. The size and shape of the workpiece were almost unchanged after the QPQ salt bath composite treatment. In the optimum process state, the amount of expansion and contraction of the workpiece is only 0.005 mm. The shape change of the workpiece is also extremely small. For example, the flatness of the (508 mm × 457 mm × 1.5 mm) 2Cr13 stainless steel sheet can be successfully ensured to be 0.5 mm or less. Therefore, this technique can be used to solve the hardening deformation problem that cannot be solved by conventional heat treatment methods.
(4) Great energy saving. Compared with the conventional heat treatment technology, the technology has a low processing temperature and a short holding time, and can greatly save energy. Compared with carburizing and quenching, it can save more than 50%.
(5) No pollution. Under the large-scale production conditions, the technology is tested on the production site by local environmental protection departments, and all environmental protection indicators are lower than the national environmental emission standards. Digosha was awarded the German Environmental Award for this technology.
The term "composite" of QPQ salt bath composite processing technology indicates that it is not a single technology. The concept of "composite" is first manifested in the combination of nitriding (nitrocarburizing) and oxidation processes; in performance, it is a composite of high wear resistance and high corrosion resistance; in process, it is heat treatment technology. Combined with anti-corrosion technology.
Salt bath titanium nitride
As early as the 1970s, in order to change the shortcomings of gas nitriding time and uneven hardness, the vast number of engineers and workshop workers invested a lot of energy and time to study the addition of electrolytic titanium during nitriding to accelerate the permeation rate. The process of deepening the layer was called titanium-plated nitriding, and it was tested on some products. The comparison between titanium nitriding and ordinary gas nitriding and salt bath nitriding was also carried out.
The actual production shows that titanium nitriding can greatly accelerate the seepage speed and greatly improve the hardness of the workpiece, thereby greatly improving the service life of the drill bit, the cutter, the tool and the mold. Especially for high-speed steel drills and knives, it not only overcomes the disadvantages of other nitriding, which causes the brittleness of the blade and reduces the service life, but also greatly increases the service life. The test results also indicate that for PVD coated drills, titanium can also increase the life by 14.5 times after nitriding.
In order to further ascertain the essence of titanium nitriding, the pre-polished 38CrMoAl steel metallographic sample is subjected to ordinary nitriding and titanium nitriding, and then polished (about 0.02 mm is thrown) to prepare a secondary carbon replica. The electron microscopy of the nitrided layer was observed under a domestic DX-301 electron microscope.
Comparing the above results, it can be seen that, like ordinary nitriding, in addition to the dispersion of small particles on the α-iron substrate, there is also a white bar-like appearance, and the number of such dews after titanium-titanium-nitriding is higher than that of titanium. Nitriding is greatly increased and it is estimated that this appearance is related to titanium.
The practice of the year proved that titanium nitride has the following characteristics:
First, titanium nitridation can obtain a thicker and harder nitride layer in a shorter period of time. The depth of 8 hours of titanium nitriding is deeper than that of ordinary nitriding at 60 hours, and there is no difference in surface hardness; the 12-hour titanium oxynitride effective hardened layer (HV>900) is thicker than the 60-hour ordinary nitrided layer, and the surface hardness is much higher. . In particular, 40Cr steel, 8 hours of titanium nitriding, has a hardness, a depth and an effective hardened layer of more than 60 hours of ordinary nitriding.
Second, the titanium nitridation process can be applied to any steel part, not just to nitrided steel. In addition to 38CrMoAl, 42CrMo, 40Cr, 20Cr, 20 steel, various types of stainless steel, high speed steel, alloy tool steel, Spring steel and 10 steel, Y12 steel and ductile iron can be titanium nitride, and can be compared Satisfying result.
Third, titanium nitrided parts have good impact resistance and fatigue strength, and heat resistance and corrosion resistance are also good. The hot forging die, punch, etc. of the nitrided 3Cr2W8 steel have a longer service life than those heat treated by other methods. Fourth, the titanium nitriding treatment requires a short time and can be processed at a lower temperature, the workpiece is less deformed, the processing cost can be saved, and it is suitable for mass production. In the past ten years, the staff of Dalian Holy Company has continued to work hard to further test and summarize the process of titanium nitriding, and carried out batch tests on drills, tools, molds and other products, and achieved good results, and declared two inventions. patent.
British BODYCOTE and pre-vacuum gas soft nitriding treatment
Baudick (Ningbo) Heat Treatment Co., Ltd. is a subsidiary of the UK-based Baudick International PLC (). The company is the world's number one brand in heat treatment processing and testing. The horizontal pre-vacuum gas soft nitriding furnace of the Baudick Group Wuxi plant is also the leading equipment in the world. This equipment overcomes the shortcomings of the traditional well gas nitriding furnace, which not only reduces the cost, but also the furnace. Uniformity, stability, controllability and adjustability are particularly good. Therefore, the processed products can meet the high-precision technical standards of the automotive and aerospace industries, and can be used after nitriding. Black processing.
French HEF and SURSULF salt bath surface nitriding treatment technology
1. The superiority of Nowshev
The SURSULF process is an advanced surface treatment technology developed by HEF that offers the following advantages over other nitriding processes:
(1) No pollution. The entire process is almost non-polluting, and the cyanide concentration in the SURSULF furnace is less than 0.8%. In most cases, as in Perkins, the cyanide concentration is 0.4% to 0.5%, which is currently the lowest in the world. In other corresponding processes, the cyanide concentration is between 2% and 5%. Therefore, the SUNSHUL process is considered to be "EnvironmentalFriendly Process" or "Environmental Acceptable Process" in the world ("Environmentally Friendly Process" or "Environably Acceptable Process").
(2) High performance. Compared to other surface methods, the workpiece has higher fatigue strength, wear resistance, surface hardness and corrosion resistance, and a lower surface friction coefficient. It has a better surface quality of the workpiece than other nitriding surfaces. One of the reasons is that the continuous automatic filter residue and slag removal system make the salt bath furnace always maintain a high degree of purity. The thickness and structure of the surface layer of the workpiece can be adjusted according to the amount of K2S to meet the requirements of different occasions, such as solving the problems of wear, pitting and fatigue, or solving the problems of bite, adhesion and strain. Therefore, it has an excellent performance price ratio.
(3) High efficiency. Since the element of lithium (Li) is added to the salt bath furnace, the nitriding potential is greatly improved, and the treatment time is greatly reduced under the conditions of the same compound thickness and the thickness of the diffusion layer, and the general treatment time is 30 minutes. By 120 minutes, the thickness of the compound layer can reach 10 to 30 μm.
(4) High precision. Compared with gas nitriding, the workpiece deformation is extremely small, which can meet the requirements of high precision requirements.
(5) Strong adaptability. It can handle a variety of ferrous metals (steel, iron, cast iron, sintered iron, etc.) and complex shapes.
(6) Easy to use. It is very convenient to operate and maintain, and the cleaning of the stove is on average once a week.
2. Comparison of the Qeshev process technology with other heat treatment processes
It is compared with the gas carbon nitrogen process NITEMPER or other similar gas nitriding treatments, such as INDURE, TOUG-HNITE, BELL, etc. The gas nitrogen carbon process is usually carried out in an endothermic atmosphere with 30% ammonia gas at a temperature of 570 ° C. The treatment time of these gases is 4 to 8 hours, which is suitable for all steel workpieces, but causes the workpiece to be deformed. . Using the SURSULF process technology, it has the following advantages: due to the chemical composition of the salt, it can handle all steel and cast iron parts (unlike NITEMPER, since the free graphite has been dissolved in the salt furnace, it will not be on the chemical layer). create pollution). The SURSULF process forms an ε phase combination layer and is therefore not brittle (it has good surface fatigue strength) and has better wear resistance and corrosion resistance than the γ'+ε mixed phase. In addition, the processing time is short, the productivity is high, and the investment is small, and no skilled operator is required.
Brass knurled thread insert Made of brass material, good thermal conductivity and heat resistance.
Widely Used On the Injection molding for Tightly Fixing.
Brass knurled Can be installed by ultrasonic or heat into thread tapered hole, or molded in during injection.
We are manufacturer of Insert Nut in China, if you want to buy Embedment Insert Nut,Brass Threaded Knurled Insert,Insert Thread Nuts please contact us.
knurled insert nut,threaded insert nut,wood insert nut,brass insert nut,furniture insert nut
Shenzhen Lanejoy Technology Co.,LTD , https://www.bbq-grillgrate.com