718 Plastic Mold Steel

One. Product Description

718 Mold Steel is a grade of pre-hardening hot work mold steel, corresponding to my country's national standard 3Cr2NiMo mold steel. The steel has excellent mechanical properties and machinability, and is widely used in the mold industry, especially the processing and production of plastic molds. In addition, its special production process makes the hardness of 718 mold steel reach 330~370HBW when it leaves the factory, so it can reduce the heat treatment process in the production of ordinary molds and improve economic benefits.

Two. Quality Standard

YB/T129-1997 Standard Specification

Three. Product Specifications

Four. Equivalent Grade of 718 Mold Steel - For Reference Only

Five. Product Features and Uses

Features:

Used for large and long-life plastic injection molds, such as home appliance molds, computer casings, etc. Due to its high hardness, blow molds for plastic products with high surface finish can be used for slider forming tools in plastic molds, and mold parts that can be flame-hardened or nitrided according to production needs.

Steel grade: pre-hardened plastic mould steel

Steel characteristics: good polishing, galvanic corrosion, weldability and machinability

Factory state: tempered to 290-330 HB

1. The steel is vacuum degassed and refined, with high purity, suitable for plastic molds that need to be polished or etched.

2. Supplied in pre-hardened state, without heat treatment, can be directly used for mold processing, shortening the construction period.

3. After forging, the structure is dense, 100% ultrasonic flaw detection, no pores and pinhole defects.

Use:

The use of 718 mold steel is the same as that of P20 mold steel, but due to its better hardenability and superior performance, it can produce large, high-grade plastic mold parts. With the development of plastic molds, there will be more, better and newer improved mold steel grades.

1. Thermoplastic injection mold, extrusion mold.

2. Thermoplastic blow mold.

3. The main parts of the mold are overloaded.

4. Cold structural parts.

5. Commonly used in the manufacture of TV casings, washing machines, refrigerator inner casings, buckets, etc.

Six. Product Detailed Information

718H mold steel, my country's grade 3Cr2NiMo is an improved steel grade of P20H (3Cr2Mo), and the quality has been greatly improved, which can make up for the lack of P20H mold steel and meet the requirements of P20+Ni mold steel.

In addition to the above-mentioned Chinese standard steel grades, the steel grades appearing in my country's mold steel market also include P20+Ni. Sweden 718, 718H (ASSAB), PX5\PX4 (Datong Special Steel, Japan), GS-711, GS-738, GS-312, GS-318 (Germany Thyssen), Austrian M238 ECOPLUS (Bailu Company), CS718 (China) Great Wall Special Steel), SWP20 (Shanghai No. 5 Steel Company), etc. Therefore, it is the most widely used typical steel in general plastic mold steels, but it cannot be used for corroded plastic mold parts. resistance requirements. Often referred to as "premium" plastic mold steel, often exemplified by newly developed new steel grades. Quenched and tempered plastic mold steel, refining treatment, vacuum degassing, pure steel, uniform hardness, excellent polishing performance, good machinability, nitriding, suitable for surface treatment. 718, also known as "P20+Ni", has good hardenability, good performance, and good polishing, electrical corrosion, welding repair and machining properties.

The steel has good machinability and wear resistance with uniform hardness distribution. The polishing performance is good, the processing technology is simple, the price is moderate, and the dosage is large.

It is suitable for large-scale long-life plastic injection molds, such as molds for home appliances, computer casings, etc. High surface finish plastic mold blow molds can be used for slider forming tools in plastic molds due to their high hardness; mold parts that can be flame-hardened or nitrided according to production needs.

The steel has high purity after vacuum degassing and refining, and is suitable for plastic molds that need to be polished or etched.

Supplied in a pre-hardened state without heat treatment, it can be directly used for mold processing and shorten the construction period.

After forging, the structure is dense, 100% ultrasonic flaw detection, no pores and pinhole defects.

Heat treatment

In order to increase the life of the mold to more than 800,000 times, the pre-hardened steel can be quenched and tempered at low temperature. When quenching, preheat at 500-600℃ for 2-4 hours, then keep it at 850-880℃ for a certain time (at least 2 hours), put it in oil and cool it to 50-100℃, let it cool in oil and air. After quenching, the hardness can reach 50-52HRC. In order to prevent cracking, it should be tempered at a low temperature of 200 °C immediately. The hardness can be maintained above 48HRC after tempering.

Nitriding can obtain a high hardness surface structure. After nitriding, the surface hardness can reach 650-700HV (57-60HRC), and the mold life can reach more than 1 million times. The nitrided layer has the characteristics of dense and smooth structure. Improved resistance to humid air and lye corrosion.

Quenching temperature 840~870℃

Tempering temperature 200~500℃

Hardness 50~55HRC

Use

1. Large-scale templates have high requirements on the surface of home appliances.

2. Suitable for large mirror plastic molds such as automobiles, home appliances, audio and video products.

3. Can be used for plastic molds with mirror polishing requirements, suitable for injection molds and blow molds of PA, POM, PS, PE, PP, ABS plastics.

4. The polishing degree is high, and the cavity requirements are high.

718H Material Properties

Physical properties (sample hardness 340HBW, room temperature and high temperature)

1. Temperature 20℃/200℃/400℃, Density 7.8g/cm/7.75g/cm/7.7g/cm.

2. Temperature 20~200℃/20~400℃, Linear expansion coefficient: 12.6×10K/13.5×10K.

3. Temperature 20℃/200℃/400℃, Thermal conductivity 29.0W·(m·K)/29.5W·(m·K)/31.0W·(m·K).

4. Temperature 20℃/200℃/400℃, Elastic modulus：205000MPa/200000MPa/185000MPa.

Mechanical properties (sample hardness 340HBW)

1. Temperature 20℃/200℃/400℃, Tensile strength 1100MPa/1050MP8/850MPa.

2. Temperature 20℃/200℃/400℃, And the conditional yield strength is 980MPa/925MPa/770MPa.

3. Temperature 20℃/200℃/400℃, Area shrinkage rate 49%/51%/52%.

4. Temperature 20°C/200°C/400°C, Elongation 13%/14%/16%.

5. Temperature 20℃/200℃/400℃, Impact toughness (≥) 20J/cm/32J/cm/42J/cm.