1.4021 สแตนเลส | X20Cr13 | UNS S42000

1. การแนะนำ

1.4021 is a martensitic stainless steel widely known by the designation X20Cr13 and commonly cross-referenced to เอไอเอส 420 in supplier literature.

It belongs to the family of chromium stainless steels that can be hardened by heat treatment, which makes it fundamentally different from the more familiar austenitic grades used for general corrosion resistance.

ในทางปฏิบัติ, 1.4021 is chosen when a designer needs a combination of moderate corrosion resistance, high hardness potential, and useful wear resistance rather than maximum corrosion performance.

The material is especially important in cutlery, ใบมีด, เพลาปั๊ม, ส่วนประกอบไฮดรอลิก, เครื่องจักร, และชิ้นส่วนตกแต่ง, because its property balance is well suited to parts that must be strong, ขัดได้, and serviceable in moderately corrosive environments.

That is the central idea behind 1.4021: it is not a universal stainless steel, but a technically targeted one.

2. คืออะไร 1.4021 สแตนเลส?

1.4021 คือ martensitic chromium สแตนเลส with a chromium content in the 12–14% range and carbon in the 0.16–0.25% พิสัย.

Supplier datasheets describe it as a hardenable steel used in the quenched-and-tempered condition for constructional and fastener applications where ความต้านทานการกัดกร่อนปานกลาง เป็นสิ่งจำเป็น.

It is also described as a cutlery and blade steel, which reflects its ability to achieve relatively high hardness after heat treatment.

This grade is ferromagnetic, has good machinability and forgeability, and is suitable for use up to about 550–600 ° C depending on the property being considered.

One datasheet states that it is “scale resistant up to 1100 °F,” which is about 593องศาเซลเซียส, while another notes good resistance to oxidizing atmospheres up to about 600องศาเซลเซียส.

Those values are consistent with the idea that 1.4021 is a serviceable hot-working stainless, but not a high-temperature corrosion alloy.

Core characteristics

At a practical level, 1.4021 is valued for four things:

• มันสามารถเป็นได้ แข็ง to high strength and hardness,
• 1.4021 stainless steel has ความต้านทานการกัดกร่อนปานกลาง in chloride-free media,
• มันสามารถเป็นได้ polished to a high-gloss finish,
• มันคือ แม่เหล็ก, which may be useful or undesirable depending on the application.

3. Chemical Composition and Material Identity

4. คุณสมบัติทางกายภาพและเชิงกลของ 1.4021 สแตนเลส

The properties of 1.4021 depend strongly on heat treatment condition. In the annealed state it is relatively workable; after quenching and tempering it becomes much harder and stronger.

The tables below summarize representative room-temperature values from published datasheets.

คุณสมบัติทางกายภาพ

คุณสมบัติทางกล

5. การรักษาความร้อน, การแข็งตัว, และโครงสร้างจุลภาค

การรักษาความร้อน

1.4021 คือ สแตนเลสมาร์เทนซิติก, so its performance is governed by a heat-treatment cycle rather than by the as-received condition alone.

ในสถานะอบอ่อน, it is softer and more workable; หลังจากดับและทำให้อารมณ์เสีย, it transforms into a much harder and stronger material.

That hardenability is the core reason the grade is used for blades, เพลา, รัด, and other wear-prone components.

Published datasheets describe the soft-annealed condition as obtained by holding at 745–825°C followed by slow air cooling, while hardening is performed by heating to about 950–1050°C and cooling in air or oil.

การแข็งตัว

The resulting microstructure is fundamentally martensitic after quenching, and the tempering step is used to tune the balance between hardness and toughness.

For practical production, the tempering range is selected according to the target property set: one source gives QT700 ที่ 650–750 ° C และ QT800 ที่ 600–700 ° C, while another notes that the desired strength determines the tempering temperature.

This is not a “one-size-fits-all” alloy; it is a material whose final behavior is deliberately engineered through thermal processing.

โครงสร้างจุลภาค

A critical metallurgical detail is the embrittlement window. The datasheet warns that the range between 400° C และ 600 ° C should be avoided because undesirable phases may precipitate and embrittlement can occur.

That means the alloy can be made very hard, but it must also be handled with thermal discipline.

กล่าวอีกนัยหนึ่ง, the same heat-treatment sensitivity that makes 1.4021 useful also makes it unforgiving if the process is poorly controlled.

The welding-related microstructural behavior follows the same logic. หลังการเชื่อม, the workpiece should be cooled to below the martensite start region, ประมาณ 120องศาเซลเซียส, before tempering.

This reduces the risk of cracking and helps restore a more stable property balance in the heat-affected zone.

A second source notes that the grade is not commonly welded because of its air-hardening behavior, which is another way of saying that heat input and cooling history strongly affect final performance.

Heat-treatment summary

6. Corrosion Performance in Different Environments

1.4021 stainless steel offers ปานกลาง ความต้านทานการกัดกร่อน, not the broad corrosion immunity associated with austenitic grades such as 304 หรือ 316.

One datasheet says it performs well in moderately corrosive, chloride-free environments such as soaps, detergents, and organic acids, while another notes resistance to the atmosphere, น้ำจืด, กรดเจือจาง, and alkalis.

That makes it useful, but not universal. The alloy also has clear limitations.

Swiss Steel states that it is not resistant to intergranular corrosion in the as-delivered or as-welded condition, และ 1.4021 should therefore not be treated like a corrosion-specialist stainless steel in welded chemical service.

Its corrosion performance is best when the surface is finely ground or polished, and one source explicitly notes that optimal corrosion resistance is attained when the surface is finely ground or polished.

Corrosion perspective

• Good for atmosphere, น้ำจืด, กรดเจือจาง, ด่าง, soaps, detergents, and organic acids.
• Not a good choice for chloride-heavy or strongly corrosive service.
• Surface finish matters: polished surfaces perform better.
• Welding and delivery condition can reduce corrosion resistance unless properly managed.

7. การผลิต, การเชื่อม, and Machining Considerations

Fabrication behavior

1.4021 is a martensitic stainless steel, so its fabrication behavior is tied closely to its hardness level and thermal history.

ในสภาพที่อบอ่อน, it is relatively workable, and supplier data describe its forgeability as good, its cold forming as feasible, and its machinability as good.

The same datasheets also note that it can be used in hot- and cold-rolled sheet, strip, บาร์, ลวด, ส่วนต่างๆ, and bright products, which reflects a fairly broad industrial processing window.

A practical way to think about 1.4021 is this: it is not a “difficult” stainless steel in the fabrication sense, but it is also not a soft austenitic grade.

Its workability changes meaningfully with hardness, and the final property target should be decided before forming or machining begins.

ด้วยเหตุผลนั้น, fabrication planning and heat-treatment planning should be treated as one combined problem rather than two separate steps.

การตีขึ้นรูปและการทำงานที่ร้อน

Hot working is well established for this grade. One datasheet recommends gradual heating to about 850องศาเซลเซียส, then faster heating to 1150–1180°C, with forging carried out between 1100° C และ 900 ° C, followed by slow cooling to promote controlled structure development.

Another source notes that the grade is used successfully in constructional and fastener applications and has good forgeability.

These details show that 1.4021 responds well to forging, but only when temperature control is disciplined.

การเชื่อม

This is not a grade that rewards casual welding practice.

The reason is structural: as a martensitic steel, it can harden during cooling, which raises the risk of brittle weld zones and property imbalance unless preheat and tempering are used correctly.

A separate datasheet is even more blunt, stating that 1.4021 is “not commonly welded” because of its air-hardening behavior.

The practical takeaway is clear: welding is feasible, but it should be planned as a controlled metallurgical operation, not just a joining step.

เครื่องจักรกล

Machinability is one of the more favorable features of 1.4021. Swiss Steel describes the grade as having good machinability, and thyssenkrupp notes that it machines similarly to carbon steels of the same hardness.

That means the machining burden is largely governed by hardness level rather than by unusual stainless-steel behavior.

ในทางปฏิบัติ, that makes the alloy especially attractive for parts that are expected to be machined before final hardening or used in a tempered condition where dimensional control still matters.

Surface finishing and polishability

การตกแต่งพื้นผิว is more than cosmetic for 1.4021; it also affects corrosion performance.

Supplier documentation says the knife-blade variant can be polished to high-gloss finishes and that optimal corrosion resistance is attained when the surface is finely ground or polished.

That makes surface finishing a functional part of the design rather than a final decorative step.

This is particularly relevant for cutlery, decorative parts, and visible mechanical components.

A smoother surface does not turn 1.4021 into a corrosion-specialist stainless steel, but it does help the alloy perform closer to its best possible level within its intended service envelope.

8. Advantages and Disadvantages of 1.4021 สแตนเลส

ข้อดี

1.4021 stainless steel is attractive because it combines ความแข็ง, การแปรรูปที่ดี, and a finishable surface.

As a martensitic stainless steel, it can be heat treated to much higher hardness and strength than austenitic grades, making it suitable for blades, เพลา, รัด, and wear-prone parts.

Published data show hardened conditions in the QT700–QT800 range with tensile strength up to roughly 700–950 MPa, depending on temper.

Stainless steel is also relatively easy to machine and can be polished to a high-gloss finish, which is why it is used in cutlery, decorative parts, and precision mechanical components.

Its magnetic response can also be useful in some applications. In moderately aggressive, chloride-free environments, it offers acceptable corrosion resistance.

ข้อเสีย

Its main limitation is only moderate corrosion resistance. It is not a substitute for austenitic grades such as 304 หรือ 316 in chloride-rich or strongly corrosive service.

It is also not resistant to intergranular corrosion in the as-delivered or as-welded condition, so welding and heat history must be managed carefully.

The alloy is therefore better viewed as a hardenable stainless steel for mechanical performance, not a general corrosion-resistant stainless.

9. การใช้งานอุตสาหกรรมของ 1.4021 สแตนเลส

1.4021 stainless steel is not selected primarily because it is the most corrosion-resistant stainless steel.

It is selected because it can be hardened, ขัดเงา, and machined into components that need strength, ความต้านทานการสึกหรอ, and a decent stainless surface in moderately aggressive environments.

กรณีการใช้งานทั่วไป

• knives and cutlery
• surgical and dental instruments
• ปั๊ม shafts and hydraulic parts
• fasteners and mechanical components
• แม่พิมพ์, ตาย, and tooling elements
• decorative stainless parts
• automotive and petrochemical hardware

10. Equivalent Grades in International Standards

11. เปรียบเทียบกับเหล็กกล้าไร้สนิมอื่น ๆ

12. บทสรุป

1.4021 สแตนเลส, or X20Cr13, is a martensitic chromium stainless steel with a very clear technical purpose: to combine hardenability, ความต้านทานการกัดกร่อนปานกลาง, ความต้านทานการสึกหรอ, and good polishability in a single grade.

Its density, โมดูลัส, and magnetic response make it a robust engineering metal, while its heat-treatment response lets it be tuned from relatively workable annealed stock to a much harder quenched-and-tempered condition.

The alloy’s limits are equally important. It is not a universal corrosion stainless; it is better understood as a stainless steel for moderately corrosive environments where hardness, เรขาคณิต, and service performance matter.

Once that framing is understood, the material becomes easy to place: 1.4021 is the kind of stainless steel you choose when you need more edge, more wear resistance, and more hardenability than an austenitic grade can provide.

คำถามที่พบบ่อย

คืออะไร 1.4021 สแตนเลส?

1.4021 is a martensitic stainless steel also known as X20Cr13, and it is commonly cross-referenced to เอไอเอส 420 in supplier literature.

เป็น 1.4021 สแตนเลสแม่เหล็ก?

ใช่. Supplier datasheets describe it as a ferromagnetic grade with magnetizability ใช่.

เป็น 1.4021 stainless steel good for welding?

It can be welded, but it is not the easiest welding stainless.

Datasheets recommend preheating and post-weld tempering, and one source notes that it is not commonly welded because of its air-hardening behavior.

ทำ 1.4021 stainless steel resist corrosion well?

It has ปานกลาง ความต้านทานการกัดกร่อน, especially in chloride-free media such as soaps, detergents, organic acids, น้ำจืด, and dilute acids/alkalis. It is not a high-chloride stainless grade.

สามารถ 1.4021 stainless steel be hardened?

ใช่. It is a hardenable martensitic stainless steel, typically quenched from about 950–1050°C and then tempered.