If you are working with 1.2083 stainless mold steel (X42Cr13 / AISI 420 modified), you may have experienced a frustrating issue:

After CNC machining, grinding, or mirror polishing, small defects like pit holes, black dots, or surface pores suddenly appear.

This problem is extremely common in high-polish plastic mold applications, especially in:

• Transparent plastic molds
• Optical lens molds
• Medical device molds
• Cosmetic packaging molds
• High-gloss injection molds

But here is the real truth most suppliers do not explain:

Pit holes are not machining defects — they are hidden metallurgical defects revealed after machining.

What Are Pit Holes in 1.2083 Steel?

Pit holes (surface pitting defects) refer to:

Small cavities, micro-holes, or black dots appearing after machining or polishing.

They are usually visible as:

• Tiny dark spots
• Micro pores
• Surface “sand holes”
• Local surface collapse

These defects are not created during machining.

Instead, machining simply exposes what already exists inside the steel.

Why Do Pit Holes Only Appear After Machining or Polishing?

This is one of the most misunderstood issues in mold steel.

Before machining:

• Defects are hidden under raw surface layer
• Oxide scale or allowance covers internal structure

After machining:

• Surface layer is removed
• Internal inclusions become exposed
• Microvoids open up → pit holes appear

👉 In short:

Machining does not create the problem — it reveals the problem.

How to Prevent Pit Holes in 1.2083 Steel

1. Choose ESR-Grade Steel (Most Important)

ESR refining removes:

• Non-metallic inclusions
• Gas bubbles
• Segregation defects

👉 This is the #1 solution for mirror molds.

2. Require Low Sulfur Specification

Recommended:

• S ≤ 0.003% for high-end molds

Lower sulfur = fewer MnS inclusions.

3. Ensure VD Vacuum Degassing

This reduces:

• Hydrogen porosity
• Oxygen content
• Nitrogen defects

4. Control Heat Treatment Quality

Improper heat treatment can increase:

• Internal stress
• Micro-cracks
• Surface instability

5. Use Proper Polishing Sequence

Incorrect polishing causes defect amplification:

• Too aggressive grinding
• Skipping grit steps
• Uneven pressure

Conclusion

Pit holes in 1.2083 stainless mold steel are not caused by machining mistakes. They are the direct result of:

• Steel cleanliness level
• Steelmaking process quality
• Inclusion control
• ESR refinement level
• Sulfur and oxygen content

If you want mirror-quality mold surfaces, the key is not just choosing 1.2083 steel—but choosing the right production grade of 1.2083.

👉 For high-end mold applications, always prioritize:

• ESR 1.2083
• Low sulfur steel
• Vacuum-degassed material
• Stable steelmaking process

Because in precision molds:

Steel cleanliness determines final surface perfection.

For technical support or premium 1.2083 ESR mold steel supply, you can contact Dongguan Otai Special Steel for professional selection advice and quotations.

📧 Email: rika@otaisteel.com
📱 WhatsApp: +86 136 4282 5398

What is S355 Structural Steel?

S355 is a non-alloy structural steel grade widely used in Europe and global engineering markets.

The naming is simple:

• S = Structural steel
• 355 = Minimum yield strength (355 MPa)

What makes S355 so popular is its excellent balance between strength, weldability, and cost efficiency.

But S355 is not a single material—it has different sub-grades, and that’s where JR and J2 come in.

What Do JR and J2 Mean?

Many machine shops have experienced the same frustrating problem.

A 34CrNiMo6 (1.6582) round bar looks perfectly straight when it arrives. The straightness is within specification. However, after rough turning or removing a significant amount of material, the bar suddenly bends.

The machinist immediately asks:

• Is the steel defective?
• Is the forging quality poor?
• Is the heat treatment incorrect?
• Or is something else happening inside the material?

The answer is usually residual stress.

In this article, we’ll explain why 34CrNiMo6 round bars distort during machining, how residual stress develops, how straightness standards work, and most importantly, how buyers can minimize machining deformation.

Why Does a Straight Round Bar Bend After Machining?

This is probably the most misunderstood issue in steel processing.

The answer is simple:

The bar was straight before machining, but the internal stress was not balanced.

Think of the steel like a compressed spring.

Although the outside looks perfectly straight, internal stresses are “locked” inside the material.

When machining removes material from one side, the stress balance changes.

The remaining material begins to redistribute stress.

The result?

The bar bends.

What Is Residual Stress?

Residual stress is internal stress that remains inside steel after manufacturing.

No external force is applied.

The stress already exists.

Residual stress mainly comes from:

Forging

Large deformation during forging creates uneven plastic deformation.

Heat Treatment

Quenching creates different cooling rates.

The outer surface cools first.

The center cools later.

Different expansion and contraction generate stress.

Straightening

After heat treatment, round bars are often mechanically straightened.

Although straightness improves,

additional stress may be introduced.

Flame Cutting

Thermal cutting locally heats steel.

Rapid cooling creates another stress source.

Why Is 34CrNiMo6 More Sensitive Than Carbon Steel?

Compared with mild steel,

34CrNiMo6 contains:

• Chromium
• Nickel
• Molybdenum

These alloying elements increase hardenability.

However,

they also increase thermal stress during quenching.

Large diameter bars especially develop significant stress differences between the surface and core.

This makes distortion after machining more likely.

Straightness Does NOT Mean Stress-Free

Many buyers confuse these two concepts.

A bar can have excellent straightness but still contain high residual stress.

For example:

Straightness before machining:

✓ 0.8 mm/m

After rough turning:

→ 2.5 mm bending

Nothing was wrong with the straightness inspection.

The stress simply became unbalanced after machining.

How Straightness Is Measured

Straightness only measures the external geometry.

Typical methods include:

• Rolling inspection
• Laser straightness measurement
• Dial indicator
• V-block inspection

These methods cannot detect internal stress.

They only confirm that the bar appears straight.

How Residual Stress Affects Machining

Residual stress can cause several machining problems.

Loss of Straightness

The most common problem.

Especially after rough turning.

Diameter Variation

The workpiece moves during machining.

Tolerance becomes difficult to maintain.

Concentricity Problems

Center holes no longer align.

This affects rotating components.

Surface Finish Issues

Tool pressure changes as the workpiece moves.

Surface roughness increases.

Increased Scrap Rate

High-value components may fail final inspection.

Material cost rises significantly.

Which Sizes Are Most Likely to Distort?

Generally speaking:

The larger the diameter,

the larger the temperature difference during cooling,

and the greater the residual stress.

How Can Manufacturers Reduce Distortion?

Several methods help reduce machining deformation.

Stress Relieving

One of the most effective methods.

Heating to approximately 550–650°C allows internal stresses to relax before machining.

Rough Machining + Stress Relief + Finish Machining

A common process is:

1. Rough turning
2. Stress relieving
3. Semi-finish machining
4. Finish machining

This greatly improves dimensional stability.

Proper Forging Ratio

Adequate forging deformation helps create a more uniform grain structure and reduces localized stress concentrations.

Controlled Heat Treatment

Uniform heating and controlled cooling reduce temperature gradients and minimize residual stress.

Symmetrical Machining

Avoid removing excessive material from only one side of the workpiece.

Balanced material removal helps maintain stress equilibrium.

How Dongguan Otai Controls Straightness and Residual Stress

At Dongguan Otai Special Steel, we understand that supplying steel is not just about meeting chemical composition requirements. It is about ensuring stable machining performance.

For 34CrNiMo6 (1.6582) round bars, we focus on:

• Strict raw material selection
• Controlled forging processes
• Optimized heat treatment parameters
• Straightness inspection before shipment
• Optional stress-relieving treatment for critical applications
• UT testing according to customer requirements
• Mill Test Certificate (EN 10204 3.1)

These measures help customers reduce machining distortion, improve dimensional stability, and lower production costs.

Conclusion

If your 34CrNiMo6 (1.6582) round bar bends after machining, it does not necessarily mean the steel is defective.

In most cases, the real cause is residual stress, not poor straightness.

Understanding the difference between geometric straightness and internal stress is essential for selecting the right material and machining process.

By choosing a supplier with well-controlled forging, heat treatment, and optional stress-relieving processes, manufacturers can significantly reduce distortion, improve machining efficiency, and minimize scrap.

At Dongguan Otai Special Steel, we supply premium-quality 34CrNiMo6 (1.6582) round bars with reliable quality control for demanding engineering applications.

📧 Email: rika@otaisteel.com

📱 WhatsApp: +86 136 4282 5398

Whether you need standard stock sizes or customized forged round bars, our technical team is ready to help you select the most suitable material for your project.

Cr12MoV is generally cheaper than D2 tool steel.

I

n most global markets, Cr12MoV typically costs about 20%–30% less than D2, depending on size, manufacturer, and processing requirements. The main reason is that D2 contains higher amounts of expensive alloy elements like Molybdenum (Mo) and Vanadium (V), which increase both performance and cost.

Why Cr12MoV Is Cheaper Than D2

1. Lower Alloy Content

D2 contains higher levels of Mo and V, which improve wear resistance and tool life — but also increase production cost.

2. Simpler Production Process

Cr12MoV is widely produced in China and is considered a cost-effective alternative to D2.

3. Performance vs Cost Strategy

Many manufacturers choose Cr12MoV when:

• Budget is limited
• Production volume is medium
• Wear resistance requirements are moderate

Price Comparison (Typical Market Situation)

Some industry sources even report that D2 may cost nearly double Cr12MoV, while offering 3–6 times longer service life, depending on application.

When to Choose Cr12MoV (Cost Saving)

Choose Cr12MoV when:

• Medium production volume
• Cost-sensitive projects
• General stamping dies
• Punches and blades

When to Choose D2 (Higher Performance)

Choose D2 when:

• High wear resistance required
• Long production runs
• High precision tooling
• High-speed stamping

Final Answer

• Cr12MoV = Cheaper
• D2 = More expensive but longer life

If your customer is price-sensitive → Cr12MoV is a good alternative
If your customer needs long mold life → D2 is the better choice

Need Cr12MoV or D2 tool steel?

Contact us:

Dongguan Otai Special Steel
Email: rika@otaisteel.com
WhatsApp: +8613642825398

Yes — Cr12MoV can often replace D2 tool steel, but not in all applications. While they are very similar in composition and performance, there are important differences you should understand before making a substitution.

Let’s break it down clearly.

Chemical Composition Comparison: Cr12MoV vs D2

Key Differences

• D2 contains higher Vanadium
• D2 contains higher Molybdenum
• D2 has better wear resistance
• Cr12MoV has slightly lower toughness

Performance Comparison

When Cr12MoV Can Replace D2

Cr12MoV can replace D2 when:

• Medium wear resistance required
• Cost reduction needed
• Small to medium dies
• General cold work tooling

Typical replacement applications:

• Stamping dies
• Shear blades
• Punches
• Cold forming dies

In these applications, Cr12MoV performs very close to D2.

When Cr12MoV Should NOT Replace D2

You should not replace D2 with Cr12MoV when:

• Very high wear resistance required
• Long production runs
• Precision tools
• Heavy load applications

Examples:

• High-speed stamping
• Long-life cutting tools
• Precision molds

In these cases, D2 performs better and lasts longer.

Heat Treatment Comparison

Both steels can achieve similar hardness levels.

Price Comparison

Generally:

• Cr12MoV price is lower
• D2 price is higher

This is why many manufacturers use Cr12MoV as a cost-effective alternative.

Equivalent Grades

Note: D2 = 1.2379 = SKD11
Cr12MoV is similar but not identical.

Final Conclusion

Yes, Cr12MoV can replace D2 in many applications, especially when:

• Cost is important
• Wear resistance requirement is moderate
• Production volume is medium

However, for high-performance tooling, D2 remains the better choice due to:

• Higher wear resistance
• Better carbide distribution
• Longer tool life

Need Cr12MoV or D2 tool steel?

Contact us:

Dongguan Otai Special Steel
Email: rika@otaisteel.com
WhatsApp: +8613642825398

Short answer: Yes — 1.2738 Mold Steel is designed to reduce cracking risk, especially in large molds.

But why?

💡 The Key Reason: Nickel (Ni) Addition

1.2738 contains Nickel, which significantly improves:

✔ Toughness
✔ Hardness uniformity
✔ Resistance to cracking
✔ Structural stability

This makes 1.2738 more reliable than standard 1.2311 or 1.2312, especially for large mold applications.

⚠️ Common Cracking Problems with Standard P20 Steels

When using standard grades like 1.2311 or 1.2312, you may face:

❌ Cracking during machining
❌ Cracking during EDM
❌ Deformation in large blocks
❌ Uneven hardness in thick sections

These problems become more serious when:
• Mold size increases
• Section thickness becomes larger
• Production cycles are long

🚀 Why 1.2738 Performs Better

Because of Nickel addition, 1.2738 offers:

✔ Better toughness in thick sections
✔ More uniform hardness distribution
✔ Lower internal stress
✔ Reduced cracking risk during machining

This is why 1.2738 Mold Steel is widely used for:

• Automotive molds
• Large injection molds
• Home appliance molds
• High-value plastic molds

🔧 When Should You Choose 1.2738?

Choose 1.2738 if you have:

✔ Large mold size
✔ Thick mold blocks
✔ High production volume
✔ High-quality requirements

At Otai Special Steel, we supply high-quality 1.2738 mold steel with:

✔ Strict UT inspection
✔ Stable hardness
✔ ESR grade available
✔ Large block sizes

Looking to reduce cracking risk in your molds?

Let’s connect 👇

📩 Email: rika@otaisteel.com
📱 WhatsApp: +8613642825398

Choosing the wrong mold steel for large plastic molds can lead to serious production problems, increased costs, and shortened mold life. Many mold manufacturers initially choose lower-cost materials like 1.2311 or 1.2312, only to face unexpected issues later.

That’s why 1.2738 mold steel is widely recommended for large mold applications — especially when toughness, uniform hardness, and stability are critical.

Let’s look at the most common problems when NOT using 1.2738 for large molds.

1. Uneven Hardness in Large Mold Blocks

One of the biggest issues with large molds is hardness inconsistency.

When using steels without Nickel alloying (like 1.2311 or 1.2312), hardness often drops significantly from the surface to the core.

What Happens?

• Surface hardness is acceptable
• Core hardness becomes softer
• Mold wear increases
• Mold life becomes shorter

Why 1.2738 Solves This

1.2738 mold steel contains Nickel, which improves hardness uniformity, even in large thickness molds.

2. Cracking Risk During Machining

Large molds require heavy machining, and this introduces internal stress.

Without sufficient toughness, mold steel may develop:

• Micro cracks
• Stress cracks
• Edge cracks

These cracks may not appear immediately, but show up during production.

Why This Happens

Steels without Nickel typically have lower toughness, especially in large sizes.

Why 1.2738 Is Better

1.2738 mold steel offers higher toughness, reducing cracking risks during machining.

3. Poor Polishing Performance

Large molds often require:

• High-gloss surfaces
• Optical finish
• Mirror polishing

But some steels perform poorly in polishing.

Problems You May Face

• Orange peel surface
• Uneven polishing
• Surface defects
• Time-consuming finishing

Why 1.2738 Works Better

1.2738 steel has cleaner microstructure, making it ideal for:

• Mirror polishing
• High surface finish
• Optical plastic products

4. Shorter Mold Life

Using lower-quality mold steel often leads to:

• Faster wear
• Frequent repairs
• Downtime
• Higher production cost

Large molds are expensive. If mold steel fails early, replacement cost is very high.

Why 1.2738 Extends Mold Life

1.2738 mold steel provides:

• Better toughness
• Stable hardness
• Better wear resistance

This results in longer mold life.

5. Deformation During Machining

Large mold plates are prone to deformation during machining.

Without good internal structure:

• Plates bend
• Dimensions change
• Machining becomes difficult

Why This Happens

Lower-grade steels often have:

• Poor stress distribution
• Internal segregation
• Non-uniform structure

Why 1.2738 Reduces Deformation

1.2738 steel has better internal quality, reducing deformation risks.

6. Poor Performance in Large Thickness Molds

Large molds often require thickness over 400mm or even 800mm.

Some steels cannot maintain performance at this size.

Problems Include

• Soft core
• Weak strength
• Cracking risk

Why 1.2738 Is Ideal

1.2738 mold steel is designed for large sections, thanks to Nickel alloying.

7. Higher Maintenance Costs

Using lower-grade mold steel often means:

• Frequent polishing
• Repair welding
• Maintenance downtime

This increases production costs.

1.2738 Reduces Maintenance

Better toughness and uniform hardness reduce maintenance frequency.

8. Poor Surface Texture Results

For textured plastic molds, poor steel quality leads to:

• Uneven texture
• Surface defects
• Inconsistent product appearance

1.2738 Advantage

1.2738 mold steel provides excellent texture performance.

9. Risk of Mold Failure During Production

In large-scale production, mold failure can cause:

• Production delays
• Customer complaints
• Financial losses

Using 1.2738 mold steel reduces this risk significantly.

10. Long-Term Cost Becomes Higher

Some buyers choose cheaper steel to save money upfront.

However, the real cost includes:

• Maintenance
• Repair
• Downtime
• Mold replacement

In many cases, using cheaper steel costs more in the long run.

Comparison: Using 1.2738 vs Not Using 1.2738

Need 1.2738 Mold Steel?
Contact us today:

📧 Email: rika@otaisteel.com
📱 WhatsApp: +8613642825398

1.2738 mold steel is a pre-hardened plastic mold steel with Nickel (Ni) added for improved toughness and uniform hardness. It is widely used for large plastic injection molds.

1.2738 Steel Equivalent Grades

Here are the most commonly accepted equivalents for 1.2738 mold steel:

Why 1.2738 Is Equivalent to P20 + Ni

Standard P20 mold steel typically does not contain Nickel, while 1.2738 mold steel includes Nickel (Ni), which improves:

✅ Toughness
✅ Hardness uniformity
✅ Large section performance
✅ Crack resistance

This makes 1.2738 better for large molds compared to standard P20.

1.2738 vs P20 Comparison

When Should You Choose 1.2738 Instead of P20?

You should choose 1.2738 mold steel when:

• Large plastic molds
• Automotive molds
• Thick mold blocks
• High toughness required
• Better polishing needed

Typical Applications of 1.2738 Steel

• Automotive bumpers
• Dashboard molds
• Large plastic containers
• Home appliance housings
• Industrial plastic molds

Need 1.2738 Mold Steel?

Dongguan Otai Special Steel supplies high-quality 1.2738 mold steel with:

✔ Pre-hardened 28-34 HRC
✔ UT inspection
✔ Fast delivery
✔ Competitive price

📧 Email: rika@otaisteel.com
📱 WhatsApp: +8613642825398

Feel free to send your size and quantity — we’ll quote you within 12 hours 🚀

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

Choosing between 1.2311, 1.2312, and 1.2738 is one of the most common decisions for mold manufacturers, buyers, and engineers. These three steels all belong to the P20 family, but they are designed for different applications, performance levels, and budgets.

So how do you choose the right one?

This guide will help you understand the real differences, avoid common mistakes, and reduce your mold manufacturing cost.

What Are 1.2311, 1.2312, and 1.2738 Steel?

These three grades are pre-hardened plastic mold steels, typically supplied at 28–34 HRC, and widely used for plastic injection molds and mold bases.

Basic Overview

Chemical Composition Comparison

The biggest differences lie in sulfur and nickel content.

Typical Chemical Composition

Why This Matters

• Sulfur (1.2312) → Better machinability
• Nickel (1.2738) → Better toughness and uniform hardness

Common Buyer Mistakes

Mistake 1: Choosing 1.2312 for Mirror Finish

Result:

• Poor surface quality
• Customer complaints

Mistake 2: Using 1.2311 for Very Large Molds

Result:

• Hardness variation
• Deformation risk

Mistake 3: Using 1.2738 for Low-End Applications

Result:

• Unnecessary cost increase

Why Quality Matters More Than Grade

Even the right steel can fail if quality is poor.

Always check:

✔ Steelmaking process (EAF + LF + VD)
✔ ESR (for high-end molds)
✔ UT testing
✔ Hardness uniformity

📩 Need help selecting the right steel?

Contact us:

Email: rika@otaisteel.com
WhatsApp: +8613642825398