Plastic mold steel.
Plastic die steel is expressed in P, also called plastic mould steel or plastic injection mold steel, is divided into five categories. Carburizing type plastic die steel: P1, P2, P3, P4, P5, P6. This kind of steel carbon content is very low, mainly in the United States early and with extrusion molding, cold extrusion has good plasticity, high performance, molding surface after carburizing quenching improve surface hardness, long service life. Core conditioning type plastic mould: P20, P21. At present, a large amount of plastic mould in P20, have become the mainstay of most of the pre hardened state of use. Medium carbon alloy tool steel for thermosetting plastic mould. The steel has H13, L2 and S7, O1 and A2 can be used. Stainless steel for plastic mould requiring high corrosion resistance, main steel 420414L, 440416. Aging steel after aging treatment is obtained with high performance. Currently on the market are keen on ANK series, ASSAB series and DESON series.
The relevant requirements
Cold working die steel at work. The deformation resistance of materials to be processed is relatively large, the working part of the mold under great pressure, bending, impact and friction. Therefore, the cold die the normal scrap is generally wear. Also due to fracture, collapse and deformation and failure of the ultra poor in advance. Compared to cold die steel and tool steel. There are many things in common.Requirements of the mold with high hardness and wear resistance, high bending strength and toughness sufficient to ensure the smooth progress of the stamping process, the difference is that the shape of the mold and I complex process. And the large area of friction. Wear. So the possibility of grinding it difficult. So the wear resistance of the die working better withstand the punch pressure. Also, due to the complex shape is easy to produce stress concentration, so the requirements of high toughness; die size and complicated shape. The deformation and cracking tendency therefore require a higher hardenability, smaller. In short, permeability, wear resistance and toughness in quenching should be higher than the cutting of steel cold die steel. But in terms of red hardness, low requirements or basically not required (because it is cold forming, so the corresponding) formed some suitable cold working die steel, for example and the development of high wear-resistant steel, micro deformation and high toughness cold working die steel for cold working die. The combination of steel used on the further explanation.
Usually the cold die using conditions, choice of steel can be divided into the following types:
1) die of small size, simple shape, light load of cold. For example, small punch, cut off the steel scissors and other optional T7A, T8A, T10A, T12A and other carbon tool steel. The advantage of this type of steel; machinability is good, the price is cheap, easy source. But its disadvantages are: low hardenability, poor wear resistance, large deformation hardening. Therefore, only suitable for the manufacture of a number of small size, simple shape, light load of tools and requires no depth of hardened layer and high toughness such as cold as the model.
2) die of large size, complex shape, light load of cold. The steel used has 9SiCr, CrWMn, GCr15 and 9Mn2V low alloy steel. The steel in the quenching oil in large diameter is more than 40mm. The 9Mn2V is a steel die without Cr cold in the development of China's steel. Can replace or partially replace the steel containing Cr.
9Mn2V carbide of steel and hardened steel CrWMn cracking tendency than small, decarburization tendency than 9SiCr steel, and hardenability than carbon tool steel. Its price is only about 30% higher than the latter so it is worth to promote the use of steel.
But there are some shortcomings such as 9Mn2V steel, the impact toughness is not high, found in the production and use of fragmentation phenomenon. In addition the tempering stability is poor, the tempering temperature is not more than 180 DEG C flexural strength at 200 DEG C when the tempering and toughness of low value began to appear.
Quenching quenching medium 9Mn2V steel in nitrate, moderate cooling capacity in hot oil. Die for some strict deformation and hardness requirements is not high, the Austenite Isothermal quenching.
3) die of large size, complex shape of heavy-duty cold. To be used in the alloy or high alloy steel. Such as Cr12Mo, Crl2MoV, Cr6WVCr4W2MoV etc., there is also a selection of high speed steel.
With high speed steel as the tendency of cold working die Pakistan is increasing, but it should be pointed out that this is not unique to high-speed steel redhardness strengths. And with its high hardenability and high wear resistance. In the heat treatment process should also be different from.
Made of high speed steel made cold mold. Should use low-temperature quenching to improve the toughness. For example, W18Cr4V steel cutting tool used when the quenching temperature is 1280-1290 DEG C. Do cold die, you should use low temperature quenching of 1190 DEG C.And as W6Mo5Cr4V2 steel. Low temperature after quenching can greatly improve the life, particularly a significant reduction in the discount rate.
4) die impact load cold and thin knife between the. As mentioned before. Three kinds of performance requirements of steel with high wear resistance are the main to adopt high carbon eutectoid steel's steel cold die. To some cold die jiaqie side buildings, blanking die. The use of thin counterparts. When the impact load should be based on the impact toughness of high. In order to solve this problem. You can take the following measures. To reduce the carbon content. The sub eutectoid steel. In order to avoid the one and two times of carbide and induced the decrease of the toughness of steel; the accession to the Si., Cr and other alloy elements. In order to improve the stability of tempering and tempering temperature (240 270 C steel tempering) this is conducive to fully eliminate the quenching stress to improve sharawadgi. But will not reduce the hardness; II joined W refractory carbide forming elements to refine grains and improve the toughness. The commonly used high toughness cold working die steel with 6SiCr, 4CrW2Si and 5CrW2Si.
Steel material properties
In the Cr12 steel or high speed steel cold die, a very prominent problem is the brittleness of steel. The use of easy to crack. Therefore, the method must be fully forged fine carbides. Besides the development of new steel. The starting point of the development of new steel, carbon content should be reduced and the number of carbide forming elements of steel. Several national research and promotion of new products.
Cr4W2MoV has the advantages of high hard steel giant, high wear resistance and good hardenability. Tempering and has good stability and mechanical properties. For manufacture of silicon die. Can live longer than Cr12MoV steel increased 1 ~ 3 times but this narrow range of temperature of steel forging, forging river county cracking. Forging temperature should be strictly controlled and operating regulations recognize Cr2Mn2SiWMoV steel quenching deformation hardening, low temperature and high hardenability. Free quenched micro deformation of die steel 7W7Cr4MoV steel and Cr12MoV steel. W18Cr4V is characterized by carbide of steel and toughness are greatly improved.
Steel material life
The increase of the content of inclusions
Is the origin of inclusions in the steel mould internal crack. Especially brittle oxide and silicate inclusions, the thermal processing is not plastic deformation, thus causing brittle fragmentation and the formation of micro cracks in the heat treatment and further, the crack further caused the die cracking. For example. Cold punching die made of Cr4W2MoV steel for stamping parts of watches, the punch through rough machining, heat treatment and grinding, found the center of the head has many small holes, resulting in a number of punches are discarded, by the analysis of a steel containing chainlike distribution of silicate inclusions were large, machined after spalling caused by small holes.
The carbide distribution caused by uneven failure
Cr12, Cr12MoV, Cr12Mo1V1 and ledeburite steel, with a large number of eutectic carbide, when small forging ratio or pouring temperature control was not appropriate, easy to strip or reticular carbide segregation in the steel, the die parts crack along the strip or reticular carbide is terrible when quenching, or in use in the process of internal cracks caused by the failure of further expansion. For example, the diameter of 50mm eutectic carbide inhomogeity more than 4 grade steel punch in the use process is easy to fracture.
3 forging due to poor quality failure
Steel forging quality, directly affect the service life of the die. The heating system of forging and the deformation process properly, will cause the steel material burning, surface crack, internal crack, corner crack defect. These will reduce the service life of the die, even directly discarded.For high carbon high chromium ledeburite steel, due to poor thermal conductivity, if the forging heating speed, heat preservation time is insufficient, resulting in a large temperature difference between inside and outside of billet forging, internal crack.
The poor surface quality
If the alloy die steel surface decarbonization serious in machining, Kunshan plastic mould steel There is still residual decarburization layer, in this heat treatment die eventually, because of the different inner and outer layer of tissue without causing obvious stress, leading to quenching crack of the die; on the other hand, the surface layer of low hardness after quenching, and the hardness distribution is not uniform, reduces the service life of the mould.