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Stainless steel grade comparison

304 vs 321 Stainless Steel

Compare 304 and 321 stainless steel by chemistry, titanium stabilization, intergranular corrosion resistance, elevated-temperature performance, mechanical properties, welding, surface finishing and product form.

Quick answer: choose 304 for general-purpose corrosion resistance, forming, welding and surface-finish flexibility. Choose 321 when titanium stabilization is required to reduce sensitization-related intergranular corrosion during welding or repeated elevated-temperature exposure.

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General-purpose 18/8 vs titanium-stabilized CrNi steel

304

EN 1.4301 · UNS S30400

Structure Austenitic
Typical C 0.04%
Typical Cr 18.1%
Typical Ni 8.1%
PRE ≈18
Main role General purpose

321

EN 1.4541 · UNS S32100

Structure Austenitic
Typical C 0.04%
Typical Cr 17.3%
Typical Ni 9.1%
Stabilizer Titanium
Main role Heat / IGC stability

Typical manufacturer chemistry. 321 is a titanium-stabilized grade; the titanium addition is intended to improve resistance to sensitization and intergranular corrosion rather than to make 321 a higher-PRE chloride grade.

M03 · Decision summary

304 or 321 stainless steel: which one should you specify?

Both grades are conventional austenitic Cr-Ni stainless steels with similar room-temperature physical properties. The important difference is titanium stabilization: 321 is designed to retain better resistance to intergranular corrosion after sensitizing thermal exposure.

Decision first: use 304 for ordinary ambient-temperature fabrication where corrosion resistance, formability, surface finish and broad availability control the purchase. Use 321 where repeated heat exposure, welded sections or service in a sensitization-prone temperature range makes titanium stabilization valuable.

Choose 304

General corrosion and fabrication are the priority

Best for Kitchen equipment, consumer products, architectural components, food equipment, storage tanks and general-purpose fabrication.

Not recommended for Applications relying on repeated sensitizing heat exposure while resistance to intergranular corrosion is critical.

Key trade-off Broad fabrication and surface-finish flexibility, but without titanium stabilization.

Alternative 304L when the issue is primarily conventional welding and low-carbon resistance to sensitization.

Choose 321

Thermal exposure and intergranular-corrosion resistance matter

Best for Automotive exhaust components, annealing covers, stack liners, welded pressure vessels, flanges and valves exposed to elevated temperature.

Not recommended for Projects choosing 321 only because they expect a major improvement in chloride pitting resistance.

Key trade-off Titanium stabilization improves thermal sensitization resistance, but surface polishing is less flexible than 304.

Alternative 347 where niobium stabilization is preferred, or 321H where a high-temperature grade specifically designed for creep service is required.

Reconsider both

Chlorides or high-temperature design exceed the comparison

Review when Warm seawater, high chloride concentration, severe SCC, critical creep loading or extremely high oxidation temperature controls life.

Why Titanium stabilization mainly addresses carbide precipitation and intergranular corrosion; it does not create a Mo-bearing chloride grade.

Alternative 316L, duplex, 321H, 347H, 310S or another high-alloy grade depending on the controlling failure mode.

Engineering reversal conditions: if the component only needs protection from sensitization caused by conventional welding, 304L may be a simpler alternative to 321. If the component will operate at elevated temperature, temperature alone is not enough: stress, exposure time, atmosphere, thermal cycling and creep must also be defined.

M04 · Technical data

304 vs 321 stainless steel properties

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At room temperature the two grades are relatively close. The important engineering difference appears after welding or elevated-temperature exposure, where titanium stabilization changes 321's resistance to sensitization.

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Typical chemical composition

Typical manufacturer values by mass. The governing standard and material test certificate control acceptance.

Element / feature	304 / S30400	321 / S32100	Selection significance	Basis
Carbon, C	0.04%	0.04%	Typical carbon content is similar; 321 addresses sensitization through stabilization.	Typical manufacturer chemistry
Chromium, Cr	18.1%	17.3%	304 has the slightly higher cited chromium level.	Typical manufacturer chemistry
Nickel, Ni	8.1%	9.1%	321 has the slightly higher cited nickel level.	Typical manufacturer chemistry
Molybdenum, Mo	No intentional addition	No intentional addition	Neither is a molybdenum-alloyed chloride grade.	Grade design
Titanium, Ti	—	Approx. 0.40% typical	Titanium forms stable carbides and helps prevent chromium-carbide sensitization.	Typical manufacturer chemistry
PRE	≈18	≈17	321 should not be selected as a chloride-resistance upgrade over 304.	Manufacturer PRE reference
Microstructure	Austenitic	Austenitic, Ti stabilized	The stabilizer is the key metallurgical distinction.	Grade classification

EN 10088-2 mechanical properties at 20°C

Same-source reference values for cold rolled, hot rolled and quarto plate conditions.

Product condition	304 / 1.4301	321 / 1.4541	Units	Selection meaning
Cold rolled	Rp0.2 230 · Rp1.0 260 · Rm 540–750 · A 45	Rp0.2 220 · Rp1.0 250 · Rm 520–720 · A 40	MPa / %	304 has slightly higher cited room-temperature minimums in this condition.
Hot rolled	Rp0.2 210 · Rp1.0 250 · Rm 520–720 · A 45	Rp0.2 200 · Rp1.0 240 · Rm 520–720 · A 40	MPa / %	Tensile range is similar; 304 has the higher cited elongation.
Quarto plate	Rp0.2 210 · Rp1.0 250 · Rm 520–720 · A 45	Rp0.2 200 · Rp1.0 240 · Rm 500–700 · A 40	MPa / %	Use product-specific values rather than generic grade assumptions.

Thermal exposure and sensitization

This is the area where 321 has the clearest metallurgical advantage.

Factor	304	321	Engineering significance	Buyer action
Sensitization control	Unstabilized	Titanium stabilized	321 reduces the tendency for chromium-carbide precipitation at grain boundaries.	Define thermal history and corrosion requirement.
Critical heat exposure	Intergranular-corrosion risk increases with significant exposure around 550–850°C	Improved resistance to sensitization in an extended temperature range	Repeated heating can make stabilization important.	State continuous, intermittent and peak temperatures.
Thick-section welding	Low-carbon grade may be preferred	Ti stabilization provides additional intergranular-corrosion resistance	Weld thermal history affects grade selection.	Compare 304L and 321 if welding is the main issue.
Elevated-temperature use	Application-dependent	Designed for improved performance after elevated-temperature exposure	321 is a common stabilized choice.	Check creep, oxidation, atmosphere and design code.
High-temperature creep service	Requires design data	Requires design data	Stabilization alone does not establish allowable creep stress.	Consider 321H or other heat-resistant grades where appropriate.
Solution annealing	Use applicable product-standard procedure	Ti-stabilized heat treatment requires appropriate temperature control	Incorrect heat treatment can affect corrosion performance.	Follow approved manufacturer / project procedure.

Corrosion and fabrication comparison

Separate general corrosion from sensitization-related intergranular corrosion.

Factor	304	321	Selection meaning	Buyer action
General corrosion	Good	Broadly similar in many environments	321 is not automatically a general-corrosion upgrade.	Define actual medium, pH and temperature.
Intergranular corrosion after heat input	Thermal-history dependent	Improved by Ti stabilization	This is one of 321's main reasons for use.	State welding and operating temperature.
Chloride pitting / crevice corrosion	PRE ≈18	PRE ≈17	Neither grade contains intentional molybdenum.	Consider 316L or duplex for more severe chlorides.
Chloride SCC	Susceptible	Susceptible	Both remain austenitic Cr-Ni grades.	Review stress, temperature and chloride level.
Weldability	Excellent	Good / excellent with suitable WPS	Both are weldable, but 321 filler and thermal requirements should be specified properly.	Use project-approved WPS.
Polishing / decorative finish	Broad finish flexibility	More limited by titanium alloying	304 is generally the easier choice for highly polished decorative work.	Specify finish before ordering.

Typical physical properties

EN 10088-1 manufacturer reference values. The basic room-temperature physical properties are effectively the same.

Property	304	321	Condition	Selection significance
Density	7.9 kg/dm³	7.9 kg/dm³	Reference	No meaningful difference.
Elastic modulus	200 GPa	200 GPa	20°C	Same cited stiffness.
Thermal expansion	16.0 ×10⁻⁶/K	16.0 ×10⁻⁶/K	20–100°C	Same cited thermal movement.
Thermal conductivity	15 W/m·K	15 W/m·K	20°C	No useful selection difference.
Specific heat	500 J/kg·K	500 J/kg·K	20°C	Same cited value.
Electrical resistivity	0.73 Ω·mm²/m	0.73 Ω·mm²/m	20°C	Same cited value.
Magnetizable	No*	No*	Annealed reference	Cold deformation can increase magnetic response in austenitic stainless steel.

Key point: 321 should not be described as “304 with better corrosion resistance.” Their general aqueous corrosion performance is relatively close. The main value of 321 is titanium stabilization and improved resistance to intergranular corrosion after thermal exposure.

M05 · Product form matrix

Product forms and supply routes for 304 and 321

Both grades are available across stainless flat-product programs, but 304 is the broader general-purpose grade while 321 is often selected where the finished component will experience welding or elevated-temperature service.

Availability note: this matrix describes typical product and application routes only. It is not live inventory. Confirm thickness, width, product standard, finish, heat-treatment condition and actual availability on the quotation.

Product / route	304	321	Status	Procurement note
Cold-rolled coil / sheet	Typical product form	Published product form	Typical product form	Confirm gauge, width and surface finish.
Hot-rolled coil / sheet	Typical product form	Published product form	Typical product form	Confirm annealed / pickled condition.
Quarto plate	Typical product form	Published product form	Confirm availability	For welded pressure fabrication, define grade and thermal-service requirement.
Precision strip	Published product form	Published product form	Supplier-dependent	Confirm thickness, width, temper and finish.
Automotive exhaust components	Possible depending on temperature	Established 321 application family	Application-specific	State normal temperature, peak temperature, cycle frequency and atmosphere.
Stack liners / annealing covers	Service review required	Published 321 application family	Thermal-service specific	Check oxidation, thermal cycling and structural loading.
Welded pressure vessels	Use specification-appropriate 304 family grade	Established stabilized route	Code-dependent	Use the governing pressure-vessel code and approved allowable stresses.
Flanges / valves	Common alloy family	Published application family	Product-standard dependent	Verify forged, wrought or cast product standard.
High-temperature tube / pipe	Application-dependent	321 / 321H product family available	Engineering review	Do not apply flat-product properties to tube or pressure service automatically.

M08 · Applications & limitations

Where 304 works, where 321 is preferred, and where another grade is required

Discuss Your Application

304 is primarily the broad general-purpose option. 321 is selected when a similar austenitic Cr-Ni material must retain better resistance to sensitization through welding or thermal exposure.

304

Typical reasons to choose 304

Kitchen equipment
Household appliances
Consumer goods
Architectural cladding
Handrails and fittings
Food and beverage equipment
General storage tanks

321

Typical reasons to choose 321

Automotive exhaust systems
Annealing covers
Stack liners
Welded pressure vessels
Flanges and valves
Hot process piping
Thermal-cycle components

Review

Conditions that may require another grade

Warm seawater
High chloride concentration
Severe crevice conditions
Critical chloride SCC risk
Very high creep-controlled temperature
Strong reducing acids
Very high oxidation-temperature service

Failure modes that can reverse the recommendation

304 sensitization after thermal exposure

Welding of thick sections, heat treatment within approximately 550–850°C and slow cooling can increase the risk of chromium-carbide precipitation and intergranular corrosion in conventional austenitic grades.

Incorrect assumption that 321 cannot sensitize

Titanium stabilization greatly improves resistance to sensitization, but the heat-treatment route still matters. Improper high-temperature processing can alter the intended stabilized condition.

Creep at elevated temperature

321 is commonly used for elevated-temperature applications, but titanium stabilization alone does not establish allowable stress. Long-duration loaded service requires approved creep and design-code data.

Chloride pitting and crevice corrosion

Neither grade contains intentional molybdenum. The cited PRE is approximately 18 for 304 and 17 for 321. 321 should therefore not be selected as a chloride corrosion upgrade over 304.

Chloride stress-corrosion cracking

Both grades are austenitic and can become susceptible to chloride SCC when tensile stress, temperature and chloride concentration reach a critical combination. Titanium stabilization does not remove this failure mechanism.

Surface-polishing limitations on 321

Titanium-containing inclusions can make demanding decorative polishing less straightforward. If a premium cosmetic finish is the main requirement, 304 may be the better starting point.

Weld heat tint and oxide scale

Stabilization does not eliminate the effect of weld oxides. Where localized corrosion matters, appropriate cleaning, pickling or passivation may still be required.

Selecting 321 when 304L would solve the problem

If the only concern is ordinary welded-service sensitization and the part does not need repeated elevated-temperature exposure, a low-carbon 304L specification may provide a simpler solution.

Inspection guidance: for thermal-service components, record actual operating temperature, thermal cycles, distortion, oxide scale and weld condition. For corrosive service, inspect heat tint, crevices, deposits and localized attack rather than relying on grade name alone.

Material image comparison

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304 stainless steel

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321 stainless steel

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M10 · Standards & equivalence

304 and 321 stainless steel grade designations

Both grades belong to the austenitic Cr-Ni stainless family, but 321 is a distinct titanium-stabilized grade. A cross-reference should not be treated as automatic permission to substitute one grade for the other.

Designation / standard	304	321	Procurement caveat
ASTM / AISI type	304	321	321 is a stabilized grade, not a direct 304 equivalent.
UNS	S30400	S32100	Use the exact UNS when grade identity matters.
EN material number	1.4301	1.4541	Distinct European material designations.
EN name	X5CrNi18-10	X6CrNiTi18-10	“Ti” identifies the titanium-stabilized chemistry.
JIS	SUS304	SUS321	Verify the exact product specification.
GB reference	Verify against project standard	Verify against project standard	Do not use informal equivalence charts as a contractual specification.
ASTM A240/A240M	Plate / sheet / strip grade family	Plate / sheet / strip grade family	Check current revision and specified product condition.
EN 10088-2	Flat-product reference	Flat-product reference	Compare properties in the same product condition.
ASTM A182	Verify specified forged grade	F321 family	Flanges and forgings must use the appropriate forged-product specification.
321H relationship	Not applicable	Separate S32109 high-temperature grade	Do not treat 321 and 321H as identical without specification review.

304 · S30400 Classic general-purpose Cr-Ni austenitic stainless steel.

304 · 1.4301 EN X5CrNi18-10 general-purpose designation.

321 · S32100 Titanium-stabilized austenitic stainless steel.

321 · 1.4541 EN X6CrNiTi18-10 stabilized designation.

Equivalence remains specification-dependent. Verify chemistry, mechanical properties, product form, heat treatment, temperature requirements and current standard revision before substitution.

M11 · Direct answers

304 vs 321 stainless steel FAQ

Direct answers to common engineering and procurement questions about 304 versus 321 stainless steel.

What is the main difference between 304 and 321 stainless steel?

Both are austenitic chromium-nickel stainless steels, but 321 contains titanium for stabilization. The titanium helps control chromium-carbide precipitation and improves resistance to intergranular corrosion after thermal exposure.

Is 321 more corrosion resistant than 304?

Not universally. Their general corrosion performance is relatively similar, and the cited PRE is actually approximately 18 for 304 and 17 for 321. 321's main corrosion advantage is resistance to sensitization-related intergranular attack after heat exposure.

Why is titanium added to 321 stainless steel?

Titanium has a strong affinity for carbon and forms stable carbides. This reduces the amount of carbon available to form chromium carbides at grain boundaries, helping preserve intergranular corrosion resistance.

Which is stronger, 304 or 321?

At room temperature they are close. In the cited EN 10088-2 cold-rolled condition, 304 has Rp0.2 of 230 MPa and Rm of 540–750 MPa, while 321 has 220 MPa and 520–720 MPa. High-temperature design, however, must use temperature-specific allowable or creep data.

Is 321 better for high-temperature service?

321 is commonly selected where elevated-temperature exposure and resistance to sensitization are important. This does not mean it has an unlimited service temperature. Atmosphere, stress, duration, oxidation and creep must still be evaluated.

Should I use 304L or 321 after welding?

If the main requirement is resistance to sensitization from conventional welding at moderate service temperature, 304L may be sufficient. 321 becomes more attractive when the finished component will also experience repeated elevated-temperature exposure.

Is 321 better than 304 in seawater?

No general seawater advantage should be assumed. Neither grade contains intentional molybdenum. For more demanding chloride environments, 316L, duplex or a higher-alloy stainless steel may be more appropriate.

Can 321 be polished like 304?

321 can be finished, but demanding polishing is more limited because of its titanium alloying. If a high-quality decorative polished finish controls the project, 304 may provide the easier route.

M13 · Sources & technical review

Technical basis for this 304 vs 321 comparison

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This comparison separates general corrosion from sensitization-related intergranular corrosion, and distinguishes room-temperature properties from elevated-temperature material selection.

Primary technical references

Outokumpu Core Range Datasheet 304/4301 and 321/4541 typical chemistry, PRE, EN mechanical properties, physical properties, product forms and fabrication guidance.
Outokumpu Core 304/4301 General-purpose 18Cr-8Ni austenitic grade with good corrosion resistance, formability and weldability.
Outokumpu Core 321/4541 Titanium-stabilized austenitic stainless steel with improved resistance to intergranular corrosion for an extended temperature range.
Alleima 321 / 1.4541 technical data Stabilized 321 metallurgy, corrosion guidance, high-temperature properties, welding and tube / pipe data.
EN 10088-1 Grade designation and physical-property framework.
EN 10088-2 Flat-product mechanical and technical-delivery reference.
ASTM A240/A240M Plate, sheet and strip specification framework for applicable 304 and 321 products.
ISO 15510 / worldstainless designation reference 321 / S32100 / 1.4541 / X6CrNiTi18-10 / SUS321 designation mapping.

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M14 · Ask an engineer

Still deciding between 304 and 321?

Send the actual operating temperature, thermal cycle, welding, corrosion and product-standard requirements so the grade can be reviewed against the finished component.

304, 321, 304L, 321H or alternative grade under consideration
UNS S30400 or S32100 requirement
EN 1.4301 or 1.4541 requirement
Sheet, coil, strip, plate, tube, pipe or fabricated component
Thickness, width, diameter and dimensional tolerance
Required yield and tensile properties
Normal operating temperature
Peak operating temperature
Continuous or intermittent thermal exposure
Number and severity of thermal cycles
Welding process and joint configuration
Section thickness and heat input
Intergranular-corrosion requirement
Process medium and chloride concentration
Oxidizing, reducing or sulfur-bearing atmosphere
Creep or pressure-code design requirement
Surface finish or polishing requirement
Quantity, destination and due date
MTC, inspection and documentation requirement

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