Choosing between 1.2311, 1.2312, and 1.2738 may seem simple at first. After all, they all belong to the P20 plastic mold steel family and share similar hardness ranges.

But in reality, many buyers make costly mistakes when selecting these materials. These mistakes can lead to:

• Mold cracking
• Poor polishing performance
• Uneven hardness
• Short mold life
• Increased manufacturing cost

In this guide, we’ll walk through the most common buyer mistakes and explain how to avoid them.

Mistake #1: Choosing 1.2312 for High-Polishing Applications

This is one of the most common mistakes buyers make.

Why It Happens

Buyers often select 1.2312 because it offers:

• Better machinability
• Lower machining cost

However, they forget one critical factor:

👉 1.2312 contains higher sulfur content.

What Happens Next

Sulfur forms MnS inclusions inside the steel, which can cause:

• Surface streaks
• Pitting
• Poor mirror finish

Real Example

Using 1.2312 for:

• Transparent plastic molds
• Optical products
• Cosmetic packaging

Result:
❌ Poor surface finish
❌ Customer complaints
❌ Rework cost

How to Avoid This Mistake

Choose instead:

Mistake #2: Using 1.2311 for Very Large Molds

Another common mistake is selecting 1.2311 for large mold blocks.

Why It Happens

1.2311 is:

• Widely available
• Cost-effective
• General-purpose

So buyers assume it works for everything.

The Problem

For large molds, 1.2311 may show:

• Hardness variation
• Lower toughness
• Risk of deformation

Why This Happens

1.2311 does not contain nickel, which improves:

• Hardenability
• Toughness
• Uniform hardness

Result

❌ Uneven hardness in thick sections
❌ Shorter mold life
❌ Higher maintenance cost

How to Avoid This Mistake

For large molds:

👉 Choose 1.2738 (Ni-added steel)

Mistake #3: Choosing 1.2738 for Low-End Applications

Some buyers assume 1.2738 is always better, so they use it everywhere.

Why This Is a Mistake

1.2738 offers:

• Better toughness
• Better uniformity

But it also comes with:

• Higher cost

When It’s Unnecessary

Using 1.2738 for:

• Small molds
• Low-cost consumer products
• Short production runs

Result:
❌ Increased material cost
❌ Reduced profit margin

How to Avoid

Use this rule:

• General molds → 1.2311
• Cost-sensitive molds → 1.2312
• Large/high-end molds → 1.2738

Mistake #4: Choosing Only Based on Price

This is one of the most dangerous mistakes.

What Buyers Often Do

They compare:

• Price per kg
  instead of
• Total manufacturing cost

Real Impact

Cheap steel may cause:

• Cracking
• Poor machinability
• Tool wear

Result:
❌ Higher total cost

Smart Buying Strategy

Consider:

• Machining time
• Tool wear
• Mold life
• Maintenance cost

Mistake #5: Ignoring Steelmaking Process

Not all 1.2311 / 1.2312 / 1.2738 steels are equal.

Key Differences

Risk of Poor Quality Steel

• Inclusions
• Porosity
• Cracking

Solution

Always ask supplier:

✔ Steelmaking process
✔ UT testing
✔ Heat treatment details

Mistake #6: Not Considering Machining Efficiency

Some buyers choose 1.2311 without considering machining cost.

The Reality

1.2312 offers:

• Faster machining
• Lower tool wear

When This Matters

• Large mold bases
• High-volume production

Better Choice

👉 Choose 1.2312 to reduce machining cost.

Mistake #7: Ignoring Polishing Requirements

Surface finish requirements must be considered.

Comparison

Mistake

Using 1.2312 for high surface quality molds.

Result:
❌ Poor product appearance

Mistake #8: Not Considering Mold Size

Mold size plays a big role in steel selection.

General Rule

Mistake #9: Ignoring Application Environment

Material selection must match plastic type.

Example

Glass fiber plastic:

• High wear
• High stress

Using 1.2311 or 1.2312 may lead to:

❌ Fast wear
❌ Short mold life

Better choice:

• 1.2738
• 1.2344 (if higher wear resistance needed)

Mistake #10: Not Consulting Steel Supplier

Many buyers rely only on past experience.

But each project is different.

Consulting your supplier can help:

✔ Reduce cost
✔ Improve performance
✔ Avoid risks

Need Help Choosing the Right Steel?

At Dongguan Otai Special Steel, we help customers worldwide select the right materials.

📩 Contact us:

Email: rika@otaisteel.com
WhatsApp: +8613642825398