Injection Mold Core: Best Usage of 718H, S136 and H13 for Household Appliance Molds

Household appliance injection molds have differentiated requirements for appearance, durability, production volume, and plastic material adaptability. Unlike general industrial molds, home appliance molds focus on stable matte/glossy texture, no surface defects, long service life, and low mass production failure rate. 718H, S136, and H13 are the three most widely used mold core materials for household appliance molds. Each has unique advantages and applicable scenarios. This article elaborates on their best matching usage methods to help mold buyers and engineers select the most cost-effective steel for home appliance projects.

The core difference in steel application lies in hardness, corrosion resistance, texture performance, and high-temperature fatigue resistance. The following basic attributes determine their final applicable household appliance products:

• 718H (1.2738 Pre-hardened Steel): HRC 28-35, no heat treatment required, excellent machinability, uniform hardness, cost-effective, standard steel for medium-end household appliance appearance molds
• S136 (1.2083 Stainless Steel): HRC 48-52 after vacuum heat treatment, ultra-high corrosion resistance, superior polishing and texture uniformity, suitable for high-standard appearance and corrosive plastic materials
• H13 (1.2344 Thermal Work Steel): HRC 48-54 after heat treatment, outstanding high-temperature fatigue resistance and wear resistance, anti-cracking, perfect for high-volume mass production and reinforced modified plastic products

718H is the most cost-effective mainstream steel for conventional household appliance molds, covering 70% of medium-standard home appliance shell projects. It is the preferred choice for non-corrosive plastic materials and medium-lifetime production requirements.

Applicable products: Ordinary PP/ABS household appliance shells, small kitchen appliances, daily-use home appliance housings, non-high-gloss matte appearance parts (VDI12-VDI24 texture)

Applicable plastic materials: ABS, PP, PS, PC+ABS unmodified general plastics

Applicable mold life: 100,000 – 300,000 shots

• Adopt ESR electroslag remelting 718H for all appearance molds to avoid uneven matte texture, yin-yang surface and pinhole defects
• No vacuum heat treatment is needed, which shortens mold making cycle and reduces processing cost
• Key appearance positions adopt slow wire cutting + fine grinding; non-appearance internal structures use fast wire cutting to balance cost and quality
• Suitable for conventional cold runner systems (submarine gate, side gate, direct sprue), compatible with most household appliance mold gating designs

Do not use 718H for flame-retardant plastics, PVC corrosive materials, or long-term mass production above 300,000 shots; it is prone to surface rust, texture blurring and mold cavity collapse.

S136 is the high-end appearance dedicated steel for export household appliance molds, famous for ultra-high surface finish and corrosion resistance. It is the mandatory steel for European and American standard home appliance appearance parts.

Applicable products: High-end matte home appliance shells, transparent household appliance parts, medical-grade small home appliances, VDI6-VDI12 fine texture appearance products

Applicable plastic materials: PC, PMMA transparent materials, flame-retardant modified plastics, slightly corrosive materials

Applicable mold life: 300,000 – 500,000 shots

• Must select ESR grade S136 + professional vacuum quenching and tempering treatment to ensure uniform hardness and no surface impurities
• Full slow wire cutting processing is required to avoid discharge stress and surface micro-cracks, ensuring perfect mirror polishing and uniform fine texture
• Ideal for molds with strict requirements on no weld lines, no pinholes, and consistent matte texture; solves the common defect of uneven surface of high-end home appliances
• Suitable for hot runner and fine water mouth three-plate mold systems, meeting high-standard export mold requirements

It is not recommended to use S136 for ordinary low-cost household appliance molds. Its high material and processing costs will cause cost waste; it is also not suitable for high-fiber reinforced plastics with strong wear resistance.

H13 is a high-fatigue and wear-resistant mold steel, focusing on high-volume mass production and modified plastic household appliance molds. It solves the problems of mold wear, collapse and cracking in long-term continuous production.

Applicable products: High-yield household appliance structural parts, fiber-reinforced home appliance accessories, high-temperature resistant electrical appliance shells, long-life mass production molds

Applicable plastic materials: PA66+GF, PP+GF fiber modified plastics, high-temperature engineering plastics

Applicable mold life: 500,000 – 1,000,000 shots

• Priority to use ESR H13 steel + vacuum heat treatment to achieve HRC 50-52 stable hardness, improving thermal fatigue resistance
• All precision structures and wear-resistant positions adopt slow wire cutting and precision grinding to prevent structural deformation during long-term high-temperature production
• Match optimized cooling water channel design to reduce mold temperature difference and avoid thermal cracking of the cavity
• Can be matched with various gating systems, especially suitable for multi-cavity high-efficiency mass production household appliance molds

H13 steel has ordinary polishing and texture performance, so it is not recommended for ultra-fine matte and mirror high-end appearance household appliance parts, which cannot achieve the optimal surface effect.

According to actual home appliance mold project experience, the most cost-effective matching scheme is summarized for direct selection:

• Ordinary domestic/mid-range household matte shells (PP/ABS): 718H ESR (best cost performance)
• Export high-end appearance/fine matte/transparent home appliances: S136 ESR (best surface quality)
• High-volume mass production/fiber-reinforced home appliance parts: H13 ESR (longest service life)
• Mixed demand (appearance + long life): Front mold S136 + Rear mold H13/718H composite matching

Q1: Which steel is the best for standard VDI24 matte household appliance molds?

718H ESR is the most cost-effective choice for conventional VDI24 matte texture. For export-grade uniform and flawless matte surface, S136 ESR is recommended to avoid yin-yang surface and uneven grain.

Q2: Can H13 steel be used for household appliance appearance molds?

Yes for ordinary matte appearance, but not recommended for high-gloss mirror and ultra-fine texture parts. H13 focuses on wear resistance and fatigue resistance, while its surface finishing performance is inferior to S136 and 718H.

Q3: Why choose ESR steel for household appliance export molds?

ESR electroslag remelting steel has fewer impurities, uniform hardness, stable texture effect, and no surface defects. It fully meets European and American mold inspection standards and ensures consistent mass production appearance of household appliances.

Q4: What is the longest service life among 718H, S136 and H13?

H13 has the longest service life for mass production, followed by S136, and 718H is suitable for medium-life batch production. H13 can support up to 1 million shots of stable production for household appliance molds.

Q5: Which steel is suitable for flame-retardant plastic household appliance molds?

S136 stainless steel is the first choice. It has excellent corrosion resistance and can resist the corrosive gas produced by flame-retardant plastics, preventing mold rust and surface failure.