模具熱處理質(zhì)量的影響因素分析及預(yù)防

1、-Analysis and prevention of influencing factors for heat treatment quality of die partsAbstract: in machinery manufacturing, die due to poor quality of heat treatment, deformation defects and lead scrap control mold heat treatment deformation is a key issue in the production. Conventional heat treat

2、ment of the mold, the mold surface treatment technology and mold heat treatment, hardness testing method to analyze the mold heat treatment defects, e*plore the the deformation defects factors mold heat treatment, at the same time, it is pointed out that the prevention measures to improve mold quali

3、ty and service life.Keywords: mold heat treatment; quality; factors; analysis0 Introductionmon mold in the heat treatment, particularly in the mold in the quenching process, the temperature difference caused due to the inconsistencies in the heating and cooling rate of the various parts of the mold

4、sectional, so that the mold cross-sectional volume of the various parts of swelling and shrinkage unevenness, organization transition unevenness, thereby causing "organizational stress. When inner stress e*ceeds the yield limit of the mold, will cause deformation of the mold. Therefore, the red

5、uction and control of sophisticated mold deformation is a key issue in the production.1 A conventional heat treatment method of a moldAnnealing is a heat treatment process after the steel is heated to a certain temperature, and incubated for a period of time, with the furnace cooled slowly (or burie

6、d in the following the cooling sand or lime) to 500 ° C, cooling in air. The fully annealed also known as recrystallization annealing, generally referred to as annealing, this annealing is mainly used for a variety of carbon and alloy steel forgings and hot-rolled profiles, the hypoeutectoid in

7、gredients sometimes used for welding structure. monly as the final heat of the light quality of the workpiece atProcessing, or as a pre-heat treatment of certain workpieces. Ball annealing mainly used eutectoid carbon steel and alloy workersWith steel (such as: manufacture of cutting tools, measurin

8、g tools, mold steels). Its main purpose is to reduce the hardness, to improve the machinability, and to prepare for the subsequent quenching. Stress relief annealing, also known as low-temperature annealing (annealing or tempering this is mainly used to eliminate the residual stress of castings, for

9、gings, weldments, hot-rolled and cold-drawn pieces, etc. If these stresses are not eliminated, will cause the steel deformed or cracks after a certain time, or in a subsequent machining process.Quenching is a process of heat treatment the steel is heated to a certain temperature, the incubation peri

10、od of time, was cooled in a certain medium (water, oil, etc.). The most monly used cooling medium is a brine, water, and oil quenching. Brine quenching of the workpiece, and easy to get high hardness and smooth surface, not prone to quench hard soft spot, but easy to make the deformation of the work

11、piece serious, even cracking. Oil for quenching medium only apply to the stability of supercooled austenite alloy steel or carbon steel workpiece size large quenching.Normalizing is steel or steel is heated to a certain temperature or higher, the heat treatment process, to keep a certain time after

12、the cooling in air.The tempering is heated through the hardening of the workpiece to the appropriate temperature below the critical point AC1 maintain a certain time followed by the method to meet the requirements of the cooling in order to obtain the desired microstructure and properties of the hea

13、t treatment process. The purpose of low-temperature tempering in the premise of maintaining the hardened steel of high hardness and high wear resistance, and reduces the quenching stress and brittleness, in order to avoid using chipping or prematurely damaged. It is mainly used for a variety of high

14、-carbon cutting and cutting tools, measuring tools, Die, Rolling carburized parts, tempering hardness is generally 58 to 64 of H RC. The Tempers purpose is to obtain a high yield strength, the elastic limit and a high toughness. Therefore, it is mainly used for a variety of spring and hot mold proce

15、ssing, tempering hardness is generally 35 5O HRC. High-temperature tempering (500 650 ) habits will be quenched bination of high-temperature tempering heat treatment called quenching, its purpose is to obtain better mechanical properties of strength, hardness, ductility and toughness. Therefore, imp

16、ortant structural parts are widely used in automobiles, tractors, machine tools, such as: connecting rods, bolts, gears and shafts. After tempering hardness of 200 330 HB. The purpose of tempering steel is to reduce brittleness, eliminate or reduce the internal stress, the presence of a large intern

17、al stress and brittleness in the steel after quenching, if not timely tempering, often make the steel deformed even cracking; workpiece by the required mechanical properties . The limitation is the alloy after heat treatment, left at room temperature or slightly above room temperature to maintain th

18、eir performance over time, and changing phenomenon. Steel carbonitriding to the surface layer of the steel at the same time into the process of carbon and nitrogen. Habits on the carbon and nitrogen permeation, also known as cyanide, permeation-temperature gas carbonitriding and low-temperature gas

19、carbonitriding (ie gas soft nitriding) is widely used. Temperature gas carbonitriding the main purpose is to improve the hardness, wear resistance and fatigue strength of steel. The cryogenic gas carbonitriding Nitriding mainly, its main purpose is to improve the wear resistance and seizure resistan

20、ce of the steel. Quenching and tempering treatment is a bination of quenching and high temperature tempering heat treatment. Quenching and tempering treatment is widely used in a variety of important structural parts, especially in the alternating load working rod, bolts, gears and shafts, etc. Quen

21、ched and tempered sorbite body tissue, its mechanical properties than the same hardness normalizing sorbite organization was e*cellent. Its hardness depending on the high-temperature tempering temperature and is related to the stability of a tempering steel and the workpiece cross-sectional dimensio

22、n, usually between 200 350 HB 1.2 die surface treatment technologyMold in addition claim substrate has a sufficiently high strength and toughness with a reasonable work, its surface properties the essential mold performance and service life. These surface features include: wear resistance, resistanc

23、e to corrosion, friction factor and fatigue performance. Improve and enhance the improvement of the performance of the matri* material alone is very limited, it is not economical surface treatment technology, can achieve a multiplier effect, which is the reason for the rapid development of surface t

24、reatment technology. Mold surface treatment technology, surface coating, surface modification or posite processing technology to change the the mold surface morphology, chemical position, organizational structure and the stress state in order to obtain the desired surface properties of systems engin

25、eering. From the surface treatment can be divided into: chemical methods, physical methods, physical and chemical methods and mechanical methods. While increasing the mold surface properties of new processing technologies continue to emerge, but more mold manufacturing nitriding, carburizing and har

26、dening film deposition.The nitriding process gas nitriding, ion nitriding and liquid nitriding, etc. way, each nitriding way has several kinds of the nitriding technology, can be adapted to the requirements of different workpieces of different kinds of steel. Due to the e*cellent performance of surf

27、ace nitriding technology can form, and good coordination nitriding process and mold steel quenching process, nitriding temperature, without intense cooling after nitriding, very small deformation of the mold, so the mold surface hardening is an early adopter of nitriding technology, is the most wide

28、ly used. Mold carburizing purposes, mainly in order to improve the overall strength and toughness of the mold, i.e. the working surface of the mold having a high strength and wear resistance, thereby introducing the technical idea is, the lower levelThe material, i.e., by carburizing and quenching i

29、nstead of high-level material, thereby reducing manufacturing costs. Hardened film deposition technology is more mature, CVD, PVD. In order to increase the bonding strength of the coating layer of the workpiece surface, and now the development of a variety of enhanced CVD, PVD technology. Hardening

30、of the earliest film deposition technology tools (cutting tools, cutting tools, measuring tools on the e*cellent results, a variety of knives have been hardened coating film as a standard process. Molds since the last century 8O, Began hardened coating film technology. Current technical conditions,

31、the cost of the hardened film deposition technology (equipment), still only in the application on precision, long life die, hardened coating film costs will be greatly reduced if the establishment of heat, more mold using this technology, we can improve our overall level of mold manufacturing. Pre-h

32、ardened mold material, mold manufacturing process can be simplified to shorten the manufacturing cycle of the mold, mold manufacturing precision. It can be predicted that, with the advances in processing technology, pre-hardened mold material will be used for the mold type.3 die heat treatment hardn

33、ess testingDie steel is the main material of the mold industry, according to the different mold conditions of service, the environment and the state of die steel should have different characteristics. Production in the life of mold and made part of the accuracy, quality, appearance and performance,

34、in addition to mold design technology, manufacturing precision, and precision machine tools and manufacturing operations, isThe correct selection of mold material and heat treatment process is also crucial. Hardness is an important performance indicators of the mold material and finished mold. The s

35、tress state of the mold in the work is plicated, such as: hot die is usually in the alternating temperature field e*posed to alternating stress, and therefore, it should have good blocking mold into a relatively soft or plastic state capacity , and in the long-term work environment, and still mainta

36、in the mold shape and dimensions of the same accuracy. General hardness of the finished mold, cold mold often choose of 59 60 HRC, the hot die often choose around 48 HR. Important performance indicators of wear resistance of the finished mold. Parts forming metal and the surface of the mold cavity w

37、hen relative motion occurs, wear of the cavity surface, leading to change the size and shape of the mold, accuracy and surface roughness VALID. The wear resistance of the mold is by a heat treatment of the mold, especially surface heat treatment decisions, the evaluation of mold wearability is mainl

38、y based hardness. Mold steel hardness test for the three cases (1) mold steel hardness testing; (2) After the heat treatment of semi-finished mold hardness detection; (3) require high wear resistance of the surface of the mold after heat treatment, surface hardness testing . The surface heat treatme

39、nt surface hardening heat treatment and chemical heat management, its hardness testing method is as follows. Surface hardening, heat treatment usually by induction heating, or flame heating. The main technical parameters of surface hardness, the local hardness and effective case depth. Hardness test

40、 Vickers hardness tester can be used, and may be used the Rockwell or surface Rockwell hardness. The choice of test force (ruler) of the effective case depth and surface hardness. Vickers hardness is an important means of testing heat treatment surface hardness, it can choose the test force of 0.5 t

41、o 100 kg, the test thin surface-hardened layer to a thickness of 0.05 mm, and its accuracy is the highest, can distinguish the heat-treated workpiece minor differences of the surface hardness. Effective hardened layer depth but also by the Vickers hardness meter to detect the surface heat treatment

42、or a large number of units of the workpiece surface heat treatment with a Vickers hardness tester is necessary. Mold heat treatment quality and the use of performance usually hardness as the basis of the judgment. In order to take care of other properties such as toughness, the mold hardness range i

43、s a relatively narrow range, therefore, how in the field using portable instruments quickly and accurately test the hardness of the mold, mold manufacture and use of the unit has a very important significance. It can enhance the the mold product quality and mold manufacturing technology level, to e*

44、tend the life of the die.4 Mold heat treatment defects cause analysis and prevention(1) mold burst. Mold burst There are many reasons for the stamping process, different working conditions. Die life of different materials are often different. For this end, for the material of the die working parts,

45、the two basic requirements: the use of properties of the material should have a high hardness and high strength, and having a high wear resistance and sufficient toughness, heat deformation small, certain thermosetting; Process Performance is good. The die working parts manufacturingThe process is g

46、enerally more ple*, and therefore must have the adaptability to a variety of processes, such as: malleability, machinability, hardenability hardenability, quench cracking susceptibility and grinding, etc. Generally, according to the stampings of the material properties, the production volume, and pr

47、ecision requirements, select the mold material with e*cellent performance, while taking into accountAnd economy of the process.(2) The mold surface with a soft point. Soft point will affect the wear resistance of the mold, reducing the life of the mold surface mold heat treatment. Mold prior to heat

48、 treatment surface o*ide scale, rust, and local decarburization; mold quenching, cooling improper selection of quenching medium, quenching media of impurities too much or aging. Should be adopted in the descaling, rust, mold heat treatment before quenching appropriate to protect the surface of the m

49、old, vacuum furnace, salt bath furnace and PaulCare atmosphere furnace heating; cooling after the heating of the mold quenching, should choose a suitable cooling medium, and long-term use of the cooling medium should always be filtered or periodic replacement.(3) poor mold before heat treatment orga

50、nizations. Mold the final ball of the organization coarse uneven spheroidization imperfect, mesh, ribbon and chain carbide organization, which will allow the mold easily cracks after quenching, resulting in mold scrapped. Poor forging process, such as: forging heating temperature is too high, a smal

51、l amount of deformation, stop forging temperature, slow cooling after forging the forging organizations coarse mesh, ribbon and chain carbide e*ists so spheroidization annealing is difficult to eliminate. The spheroidizing poor, such as: the annealing temperature is too high or too low, etc. isother

52、mal annealing time, can cause uneven ball annealing organization or nodulizing. According to the working conditions of the mold, the Toughening performance of the production volume and the material itself, choose a good quality mold steel material.(4) molds produce quenching cracks. The mold cracks

53、quenched mold heat treatment process defects lead to mold scrap production and great economic losses. Serious mold material mesh carbide segregation; machining or cold plastic deformation stress there is in the mold; mold improper heat treatment operations (heated or cooled too fast, improper select

54、ion of quenching medium, low cooling temperature and cooling time is too long. ); ple* shape of the mold, and uneven thickness, with sharp corners and threaded holes, so that the thermal stress and stress is too large; mold quenching temperature is too high to produce hot or burning; mold after quen

55、ching and tempering is not timely or Tempering insufficient time; mold rework quenching, without intermediate annealing again heated quenching; improper mold heat treatment, grinding process; EDM mold after the heat treatment, the hardened layer has a high drawing stress and microcracks. Strict cont

56、rol mold of the originalIntrinsic quality of materials, improved forging and spheroidizing to eliminate mesh, ribbon, chain carbides, improve the uniformity of the ball of the organization; mold machining or cold plastic deformation should retreat to the stress ( > 600 ) and then heated quenching

57、; asbestos plug screw holes should be used to the ple* shape of the mold, bandaged dangerous section and thin-walled office, and grading quenching or austempering.(5) mold quenching coarse microstructure. The mold after quenching organizations coarse, will seriously affect the mechanical properties

58、of the mold, the mold will crack, and seriously affect the life of the mold. Steel mold, confusion, the actual steel quenching temperature far below the requirements of the mold material the quenching temperature (the GCrl5 steel as the steel 3Cr2W8V); die steel quenched without correct the spheroid

59、ization treatment process, poor ball of the organization; mold quenching temperature improper placement of mold in the oven near the electrode or heating element region prone to overheating; inappropriate choice of the cross-section changes the mold, the quenching process parameters, in thin sections and sharp corners overheating or long holding time; Steel storage should be strictly tested to strictly prevent steel confuse misplacing; mold quenching before the correct forging and ball annealing, to ensure a good ball of the organi