Introduction of the hottest age hardening plastic

Introduction to age hardening plastic die steel

the common characteristics of this kind of steel are low carbon content and high alloying. After high temperature quenching (solution treatment), the steel is in a softening state, and the structure is a single supersaturated solid solution. However, after aging treatment of this solid solution, that is, heating to a lower temperature and holding for a period of time, fine and dispersed metal compounds will precipitate in the solid solution, resulting in the strengthening and hardening of steel. Moreover, the size and shape changes caused by this strengthening process are minimal. Therefore, when using this kind of steel to make plastic molds, the mold can be mechanically formed after solution treatment, and then the strength and hardness of the mold in use can be obtained through aging treatment, which effectively ensures the accuracy of the final size and shape of the mold

in addition, this kind of steel often adopts vacuum smelting or electroslag remelting. The experimental machine of steel has high purity as a high-precision detection instrument, so the mirror polishing performance and photo etching performance are good. This kind of steel can also be treated by chromium plating, nitriding, ion beam enhanced deposition and other surface treatment methods to improve the wear resistance and corrosion resistance. The following describes several age hardening plastic mold steels

(I) 25crni3moal steel

25crni3moal is a low nickel cobalt free age hardening steel, which is a new type of age hardening steel developed with reference to the composition of similar foreign steels and based on the characteristics of China's smelting industry and the performance requirements of users, filling the gap for the special steel for age hardening precision plastic molds in China

1. Chemical composition and transformation point

25crni3moal steel chemical composition is shown in the table

table 25chemical composition (mass fraction) of crni3moal steel (%)

C Cr Ni Mo Al Si m in China's plastic machinery market n s, P

0.2 ~ 0.3 1.2 ~ 1.8 3.0 ~ 4.0 0 0.2 ~ 0.4 1.0 ~ 1.6 0.2 ~ 0.5 0.5 ~ 0.8 0.03

phase transition points ac1740 ℃, ac3780 ℃, ms290 ℃

2. Mechanical properties

(1) hardness: the hardness of 25crni3moal steel after solid solution and aging treatment at different temperatures is shown in table and table respectively

table 25crni3moal steel hardness after solution treatment at different temperatures

heating temperature/℃ (holding for 30min) 830 920 960 1000

hardness HRC 5048.5 46.4 45.6

table 25crni3moal steel hardness after aging treatment

aging temperature/℃ 500 520 540

hardness HRC 35.5 ~ 38 39 ~ 41 39 ~ 42

(2) room temperature mechanical properties: 25crni3moal steel after 880 ℃ solid solution, and 680 ℃ tempering, The mechanical properties after aging treatment at 540 ℃ for 8h are shown in the table

table 25room temperature mechanical properties of crni3moal steel

HRC b/mpa s/mpa (%) (%) k ①/(j/cm2)

39 ~ 42 1260 ~ 1350 1170 ~ 1200 13 ~ 16.8 55 ~ 59 45 ~ 52

① K value is the impact toughness value of Charpy U-shaped specimen

3. Heat treatment process

(1) it is used as a general precision plastic mold: quenching and heating temperature is 880 ℃, air cooling or water cooling quenching, quenching hardness is 48 ~ 50HRC, and then after 680 ℃, 4 ~ 6h high temperature tempering, air cooling or water cooling, tempering hardness is 22 ~ 23hrc, and it is formed by machining. After aging treatment, the aging temperature is 520 ~ 540 ℃, the heat preservation is 6 ~ 8h, the air is cooled, and the aging hardness is 39 ~ 42hrc. Then it is assembled and used after grinding, polishing or photolithography. The aging deformation rate is about -0.039%

(2) for high-precision plastic molds: quenching and heating temperature 880 ℃, and then tempering at 680 ℃, the rest of the process is the same as above. However, after tempering at high temperature, rough machining and semi precision machining are carried out on the mold, and then heat preservation at 650 ℃ for 1h to eliminate the residual internal stress after machining, and then finish machining is carried out. Thereafter, the aging, grinding, polishing and other processes are still the same. After this treatment, the aging deformation rate is only -0.01% ～ -0.02%

(3) for plastic molds that do not require high impact toughness: the annealed forging stock is directly roughened and refined, aged at 520 ~ 540 ℃ for 6 ~ 8h, and then ground, polished and assembled. After this treatment, the hardness of the die is 40 ~ 43hrc, and the aging deformation rate is 0.05%

(4) plastic mold used for cold extrusion cavity process: after the die forging blank is softened, the extrusion surface of the mold is processed, ground and polished. Then the cold extrusion die cavity and die shape are trimmed, and finally the die is assembled and used after vacuum aging treatment or surface nitriding treatment

4. Practical application

maraging steel 06ni6crmovtial has been applied in chemical industry, instrumentation, light industry, electrical appliances, aerospace and national defense industries respectively, and has been used to make plastic molds for parts such as tape cartridges, cameras, teletypewriters, etc., with good results

the service life of the plastic mold of the tape recorder cassette made of this steel can reach more than 2million times, and the quality of the pressed product can be comparable to that of the imported mold; The average service life of plastic molds for tape cassette recorders is more than 1.1 million times

(IV) 10ni3cualmos (PMS) mirror plastic mold steel

optical plastic lenses, transparent plastic products and various thermoplastic shell forming molds with smooth, bright and high quality appearance are usually made of mirror plastic mold steel with low surface roughness, high brightness, small deformation and high precision in foreign countries

plastic mold steel with excellent mirror performance requires not only certain strength and hardness, but also good cold and hot processing performance and small heat treatment deformation. In particular, the purity of steel should be high to prevent pinholes, orange peel, stripes, rust and other defects in the mirror

pms mirror plastic die steel is a new precipitation hardening plastic die steel, which has good cold and hot workability and comprehensive mechanical properties, simple heat treatment process, small deformation, high hardenability, suitable for surface strengthening treatment, and extrusion forming of die cavity in softening state

1. Chemical composition and transformation point

the chemical composition of PMS steel is shown in the table. The carbon mass fraction is limited to less than 0.2% to ensure the hot workability and toughness of the steel after heat treatment. Ni and Al are added to ensure the hardness of the steel after age hardening (about 40HRC)

table chemical composition (mass fraction) (%)

C Si Mn Ni Cu al Mo P, s.

0.06 ~ 0.16 0.35 1.4 ~ 1.7 2.8 ~ 3.4 0.8 ~ 1.2 0.7 ~ 1.1 0.01

phase transformation points ac1675 ℃, ac3821 ℃, ar1382 ℃, ar3517 ℃, ms270 ℃

2. Process performance

(1) forging: PMS steel has good forging performance, with forging heating temperature of 1120 ~ 1160 ℃, final forging temperature of 850 ℃, air cooling or sand cooling after forging

(2) solid solution treatment: the purpose of solid solution treatment is to fully dissolve the alloy elements in the matrix, homogenize the solid solution, soften it and facilitate machining. After heating at 840 ~ 850 ℃ for 3h, the hardness after air cooling is 28 ~ 30hrc

(3) aging treatment: the final service performance of the steel is obtained by tempering aging treatment. The temperature at which the steel has the hardening peak is about 510 ℃ 10 ℃, and the hardness after aging is 40 ~ 42hrc

(4) deformation rate: the deformation rate of PMS is very small, the shrinkage is less than 0.05%, the total deformation rate is -0.11% ~ 0.041% in radial direction and -0.021% ~ 0.026% in axial direction, which is close to maraging steel

3. Mechanical properties

the mechanical properties of PMS steel after heating and insulation at 840 ~ 850 ℃ and air cooling solid solution treatment, and then aging at 510 ℃ and 530 ℃ are shown in the table

Table mechanical properties of PMS steel aged at different temperatures

steel aging temperature/℃ hardness/hrc b/mpa s/mpa 5 (%) (%) k/(j/cm2)

PMS steel (including s) 510 42.5 1303.5 1169.1 1649.2 14.7 ~ 17.1

530 41.4 1292.7 1194.6 15 52.7 20.6

PMS steel (low S) 510 42.7 1331.9 1264.5 14.7 47.8 21.6

530 41.8 1252.5 1191.7 14.6 55.7 21.6

4 Practical application

pms mirror plastic mold steel is suitable for manufacturing all kinds of optical plastic lenses, injection molds with high mirror and high transparency, and plastic molds of various household appliances with high appearance quality requirements

for example, the appearance quality of machine plastic shell products produced by machine shell molds has reached the advanced level of similar foreign products, and the service life of molds has also been significantly improved. Another example is the injection mold for large-scale double card radio recorder. The shell produced is of high appearance quality. The injection mold was originally made of 45 steel, and the mold life is 150000 mold; The life of the injection mold made of PMS steel is 400000

pms steel is aluminum containing steel, which has good nitriding performance, and the aging temperature is close to the nitriding temperature. Therefore, aging treatment can be carried out at the same time as nitriding treatment. After nitriding, the surface hardness, wear resistance and bite resistance of the mold are improved, which can be used for precision forming molds for injection of glass fiber reinforced plastics

pms steel also has good welding performance, and the damaged mold can be repaired by repair welding. PMS steel is also suitable for cold extrusion forming of high-precision cavities

(V) y20crni3almnmo (SM2) steel

1 Chemical composition and transformation point

y20crni3almnmo (SM2) is an age hardening plastic mold steel, and its chemical composition is shown in the table

table SM2 steel chemical composition (mass fraction) (%)

Jinan experimental machine factory in order to reduce oil absorption resistance and avoid oil absorption difficulties

C Mn s p Cr Ni Mo Al Si

0.17 ~ 0.23 0.80 ~ 1.20 0.080 ~ 0.150 <0.030 0.80 ~ 1.20 3.00 ~ 3.50 0.20 ~ 0.50 1.00 ~ 1.50 <0.40

phase transition points ac1710 ℃, ac3795 ℃, ms405 ℃

2. Process performance

(1) forging: good forging performance, no special requirements for forging

(2) softening treatment: heating at 870 ~ 930 ℃, oil cooling, tempering at 680 ~ 700 ℃ for 2h, oil cooling, hardness 30hrc

(3) heat treatment process: heating at 870 ~ 930 ℃, oil quenching, oil cooling at 680 ~ 700 ℃, aging at 500 ~ 560 ℃

3. Mechanical properties

after the above treatment, the mechanical properties of SM2 are shown in the table

Table mechanical properties of SM2 steel

b/MPa 0.2/mpa 5 (%) (%) k/(j/cm2) hardness HRC

1176 980 15455435

4 Practical application

y20crni3almnmo steel to produce our great motherland is very powerful, the process is simple and easy, the performance is superior and stable, and the service life is long. After being popularized and applied in electronics, instruments, household appliances, toys, daily hardware and other industries, the effect is remarkable