5251 aluminum is a 2% magnesium, 0.3% manganese sheet and plate alloy, registered by the Aluminum Association and specified in EN 485 and AS/NZS 1734 — but it holds no row in ASTM B209. State the applicable EN or AS/NZS standard in the order so the supplier knows which strength limits to meet.
5251 is sometimes offered instead of 5052, but it is not automatically interchangeable. Composition limits differ, and proof-strength requirements depend on the standard, temper and thickness.
5251是什么以及标准在哪里规定它
5251 is a non-heat-treatable aluminum-magnesium alloy, designated EN AW-5251 and AlMg2 in the older German and ISO notation. It sits above 5005 and below 5052 in magnesium, and gains strength from magnesium in solid solution and from cold working. Composition is fixed by EN 573-3, 规定，板材、带材和厚板的力学性能由 EN 485-2, ，2024年新增 AS/NZS 1734 used in Australia and New Zealand. BS 1470 历史上曾涵盖该合金，现已废止；; ASTM B209 未列出该合金。.
A North American drawing citing ASTM B209 5052 cannot be satisfied with 5251, and a certificate headed “5251 to ASTM B209” describes a specification that does not exist.
Chemical Composition: How 5251 Differs From 5052
限值为EN 573-3数值，同时列出5052是因为这是买家最常问的对比。.
| 要素 | 5251（EN 573-3） | 5052（ASTM B209） | 该元素的作用 |
|---|---|---|---|
| 镁 | 1.70–2.40 | 2.2–2.8 | 决定强度和耐海水性能 |
| 锰 | 0.10–0.50 | 最大 0.10 | 细化晶粒，减缓焊缝区软化 |
| Cr | 0.15 最大值 | 0.15–0.35 | 控制晶粒长大和应力腐蚀敏感性 |
| 铁 | 最大 0.50 | 0.40（上限） | 杂质；越低越有利于延展性 |
| Si | 0.40（上限） | 最大 0.25 | 杂质 |
| 铜 | 0.15 最大值 | 最大 0.10 | 杂质；为耐腐蚀而保持低含量 |
| 锌 | 0.15 最大值 | 最大 0.10 | 杂质 |
| Ti | 0.15 最大值 | Check other-element limits | Can act as a grain refiner |
| 其他 | 各0.05 / 合计0.15 | 各0.05 / 合计0.15 | — |
The limits differ, but are not completely separate: chromium can meet both at 0.15%, and manganese at 0.10%. This narrow overlap does not make the grades interchangeable. Any dual certification must meet all composition, mechanical and product-standard requirements.
力学性能：屈服强度上25%的差距
限值为EN 485-2中1.5–3.0 mm厚度带材的数值，该牌号大部分在此厚度区间采购。单值为最小值；范围为抗拉强度窗口。.
| 脾气 | 抗拉强度Rm（MPa） | 0.2%屈服强度Rp0.2（MPa） |
|---|---|---|
| O | 160–200 | ≥60 |
| H22 | 190–230 | ≥120 |
| H24 | 210–250 | ≥140 |
| H26 | 230–270 | ≥170 |
| H32 | 190–230 | ≥120 |
| H34 | 210–250 | ≥140 |
| H36 | 230–270 | ≥170 |
| H38 | ≥255 | ≥200 |
For the H32 conditions compared here, the listed proof minima are 120 MPa for 5251 under EN 485-2 and 160 MPa for 5052 under ASTM B209. That is a 25% difference between these specified limits, not every product. A design requiring 160 MPa cannot rely on material guaranteed only to 120 MPa. Check the exact standard edition and thickness before substitution.
Do not substitute H2x for H3x without approval. H22 is strain hardened then partially annealed; H32 is strain hardened then stabilised. Matching values in this table do not make their processing identical. Both must meet the requirements of the ordered standard. Supply the temper named on the drawing.
The standard changes the acceptance limits. EN and AS/NZS requirements can differ for the same alloy and temper. A result may pass one specification and fail another. State the standard edition and thickness in the enquiry, and explicitly request the proof-strength requirement used in your design.
成形性与状态选择
Check elongation as well as strength when selecting a forming temper. In the same 1.5–3.0 mm band EN 485-2 guarantees ≥16% at O, ≥8% at H22 and H32, ≥6% at H24 and H34, ≥5% at H26 and H36, and ≥3% at H28 and H38.
O suits deep drawing and roll forming; H22 and H24 hold shape without hard forming; H32 is the workhorse, quarter-hard, stabilised, widest range of gauges; H34 adds 20 MPa of proof at a real cost in elongation; H36 and H38 leave little but shearing and generous-radius bending.
The bend radii below are recommendations, not guarantees; t means sheet thickness. Confirm the bend-line orientation relative to the rolling direction before using them.
| 脾气 | 0.4 mm | 0.8 mm | 1.6 mm | 3.2 mm |
|---|---|---|---|---|
| O | 0t | 0t | 0t | ½t |
| H32 | 0t | 0t | 1t | 1½t |
| H34 | 0t | 1t | 1½t | 2t |
| H36 | 1t | 1t | 1½t | 2½t |
| H38 | 1t | 1½t | 2½t | 3t |
Actual bend limits depend on bend-line orientation, tooling condition, die width and the supplied temper. H22 and H32 may behave differently despite similar strength values. For tight bends, test a strip of the material with the intended tooling first.
Corrosion and Service Temperature
5251 has good resistance to seawater, salt spray and atmospheric exposure. Check the actual environment before deciding whether a protective finish is needed.
High-magnesium 5xxx alloys can form magnesium-rich phases along grain boundaries during prolonged elevated-temperature exposure, reducing resistance to intergranular corrosion and stress corrosion cracking. This explains the caution around sustained service above 65 °C. With no more than 2.4% Mg, 5251 is less susceptible to this mechanism, but its allowable temperature still depends on strength, weld filler and service conditions. H116 or H321 does not remove the high-temperature risk in 5083.
For continuous immersion, compare corrosion requirements and test data before replacing specified 5083 with 5251. Magnesium content alone does not establish equivalence.
For a uniform decorative anodized finish, approve a sample first. Composition, surface condition and processing affect appearance. Consider 5005 or 1050 if the result is unsuitable.
焊接：被误引用的填充材料选择
5251易于通过GMAW和GTAW焊接，填充材料的选择范围比大多数数据表所暗示的更窄。.
5356 is commonly recommended for 5251-to-5251 joints and some dissimilar-alloy joints. Confirm suitability for both base metals and the service conditions; its composition differs from 5251.
4043 may suit certain joints between 5251 and lower-magnesium or non-magnesium alloys. Do not decide by alloy family alone: check filler guidance for the exact pair of base metals and qualify the procedure. It is not automatically unsuitable merely because both parts are 5251.
Welding softens cold-worked material in the heat-affected zone, and heat treatment cannot restore that strengthening. Use the applicable welded-joint design values, not unwelded H-temper strength.
5251 vs 5052、5754和5083
| 合金等级 | 5251 | 5052 | 5754 | 5083 |
|---|---|---|---|---|
| 标准 | EN 485-2、AS/NZS 1734 | ASTM B209、EN 485-2 | ASTM B209、EN 485-2 | ASTM B209、B928 |
| 镁含量（%） | 1.70–2.40 | 2.2–2.8 | 2.6–3.6 | 4.0–4.9 |
| Cr（%） | 0.15 最大值 | 0.15–0.35 | 0.30（上限） | 0.05–0.25 |
| H32屈服强度最小值（MPa） | 120 (EN, conditions above) | 160 (B209, conditions above) | Check standard and thickness | Check standard and thickness |
| 船用状态 | 不适用 | 不适用 | 不适用 | H116、H321 |
| ASTM B209 row | 否 | 是 | 是 | 是 |
与5052对比, check the specified alloy and standard first. A drawing requiring B209 5052 cannot be met with 5251 without an approved change. Likewise, replacing specified 5251 with 5052-H32 needs approval and checks of strength, forming and corrosion requirements.
与5754对比, the magnesium ranges differ: 5251 is 1.70–2.40%, while 5754 is 2.6–3.6%. Both can suit welded sheet work, but are not automatic substitutes. Compare standard requirements at the ordered temper and thickness, then verify the supplied material against them. Any alloy change needs design and welding review.
与5083对比 在浸没服役环境中无可比性。当图纸要求腐蚀控制的船用状态时，, 5083 才是拥有该状态的牌号。.
可行/不可行，以及5251的使用场景
可行 when 5251 meets the drawing, material standard and approved fabrication procedure. For formed or welded assemblies, check the actual load, corrosion exposure and temperature. Low magnesium reduces one sensitization risk; it does not set the assembly’s temperature rating. For prolonged hot service, review the weld filler as well as the sheet: 5356 can introduce a high-magnesium weld deposit.
不可行 when 5251 is outside the specified product standard, the selected temper cannot guarantee the required proof strength, or a required marine corrosion temper is unavailable. For decorative anodizing, approve a sample before committing.
Typical applications include small-craft hulls and superstructures, vehicle panels, silos, containers and architectural pressings. At 2.69 g/cm³, it weighs about one-third as much as steel at equal volume. This weight advantage does not establish load capacity; structural parts still need design checks.
指定与采购5251
Include these four requirements in your order:
- 明确标准，而不仅仅是合金。. “5251-H32 to EN 485-2”不留任何解释空间；仅写“5251-H32”则允许证书对应具有不同限值的标准。.
- 注明你需要的屈服强度。. If the design requires 160 MPa, state it and check which temper guarantees it. The H32 minimum listed here does not.
- 精确注明状态。. H22和H32即使表格数值相同也不可互换。.
- 要求EN 10204 3.1证书。. 该证书载有该炉次的实际分析和力学结果，由生产工厂签署，可让你对照所指定的限值核查材料。.
We roll 5251 sheet and coil in O, H22, H24, H32, H34 and H38, and cut plate to your drawing; our 5251铝板和卷材 page carries the gauges and widths we run. For non-stock sizes and tempers, ask us to confirm production options and lead time, typically 10–60 days on low-MOQ runs. For bar, tube or wire, confirm the applicable product standard and required properties rather than applying sheet values.
结论
5251 and 5052 have different composition limits and cannot be treated as automatic substitutes. Their guaranteed strength also depends on standard, temper and thickness. Specify 5251 under an applicable product standard, check forming and service requirements, and obtain approval for substitutions. Its low magnesium content reduces high-magnesium sensitization risk, but does not remove temperature or welding checks.
We supply 5251 to the applicable standard agreed for your order, with the temper and proof minimum written onto the order and a 3.1 certificate carrying that heat’s actual results.
发送你的图纸，注明标准编号、状态和所需屈服强度，我们将确认5251是否是正确答案，或者5754是否能以更少的文书工作达到目的。.
常见问题
5251和5052相同吗？
No. The composition limits differ, although they overlap at the chromium and manganese boundaries. Matching chemistry alone does not establish equivalence. Check the specified standard, temper, thickness and mechanical requirements before substitution.
为什么5251不在ASTM B209中？
Product standards list selected alloys and tempers; registration alone does not ensure inclusion. 5251 is specified in EN 485 and AS/NZS 1734 rather than B209. If B209 is required, assess a covered alloy such as 5052 or 5754 and obtain substitution approval.
5251应使用什么焊丝？
5356 is a common option. Depending on both base metals and service requirements, 4043 may also be suitable. Check filler guidance for the exact joint and confirm the choice through procedure qualification, especially for dissimilar alloys or elevated-temperature service.
5251板材的交货周期和最低起订量是多少？
可提供低MOQ定制批次；常备规格交货更快。典型交货周期为10–60天，取决于厚度、宽度和状态，每笔订单均随附MTC。.
