板金 材料 Selection: 鋼, アルミニウム & Stainless

重要ポイント

• Three families cover 95% of 板金 work: 炭素鋼 (cheapest, strongest per dollar), ステンレス鋼 (corrosion resistance without coatings), and aluminum (one-third the weight, naturally corrosion-resistant).
• 冷間圧延鋼 (DC01/SPCC) is the indoor default — 140–280 MPa yield, excellent forming and 溶接, but it must be painted, powder coated, or plated to survive humidity.
• 亜鉛メッキ鋼 buys outdoor life at carbon-steel prices; the zinc layer sacrifices itself so the base metal doesn’t rust — but cut edges and welds break the protection.
• 304ステンレス handles most corrosive environments; 316 adds molybdenum for chlorides, salt air, and 化学的s — both run 205 MPa yield / 515 MPa tensile in annealed sheet.
• 5052 aluminum is the sheet-forming champion (228 MPa tensile, marine-grade corrosion resistance); 6061-T6 is stronger but crack-prone in tight bends.
• Choose by environment first, then load, then forming — material price is only part of the story once coating, weight, and lifetime enter the math.

Every 板金 RFQ starts with the same line item — and the same hesitation: which of the 板金 materials should this part actually be? 鋼, stainless, and aluminum overlap enough that all three “work” on paper, yet the wrong pick shows up later as rust streaks on an outdoor bracket, a doubled invoice for stainless nobody needed, or cracked bends in an alloy that was never meant to fold.

This metal selection guide compares the common sheet grades we run through 繰り返し注文の一貫性が保たれます。 every week — cold rolled and 亜鉛メッキ鋼, 304/316 stainless, and 5052/6061 aluminum — with real numbers, honest trade-offs, and a six-question framework that settles the choice.

3つの板金ファミリーの概要

Before grade-level detail, three physical facts frame every selection. Density: steel and stainless weigh ~7.85–8.0 g/cm³; aluminum ~2.7 g/cm³ — a third of the weight for the same volume, which is why aluminum dominates anything carried, shipped in volume, or mounted overhead. Corrosion strategy: 炭素鋼 needs a coating, stainless and aluminum protect themselves. Relative cost: 炭素鋼 is the baseline, aluminum typically lands in the middle, and stainless costs a clear multiple of CRS — which is exactly why “stainless everywhere” is the most expensive habit in 板金 purchasing.

炭素鋼 Sheet: Cold Rolled, Hot Rolled & Galvanized

冷間圧延鋼 (DC01 / SPCC / St12) is the workhorse of industrial 板金: yield strength 140–280 MPa, tensile 270–410 MPa per EN 10130, with smooth surfaces, tight thickness control, and predictable 曲げ加工. It laser-cuts and welds without drama and takes powder coat or paint beautifully — the default for enclosures, panels, chassis, and indoor brackets. Its one non-negotiable weakness: bare CRS rusts quickly, so every part needs a finish.

Hot rolled steel takes over in thicker gauges (roughly 3 mm and up) where surface finish matters less than section strength — machine bases, weldments, heavy support brackets. Expect mill scale, looser thickness tolerance, and a lower price per kilogram.

亜鉛メッキ鋼 (e.g. DX51D) is CRS with a zinc jacket, applied either hot-dip (thicker, tougher, slightly rough) or electro-galvanized (thin, smooth, paint-ready). The zinc corrodes sacrificially so the steel underneath doesn’t — an economical answer for outdoor brackets and mounts, HVAC parts, and agricultural equipment. Two caveats: laser-cut edges and weld zones lose their coating (spec zinc-rich touch-up or post-galvanizing for harsh sites), and zinc fumes make 溶接 a ventilation job.

最適な用途: indoor structure (CRS + coating), thick weldments (HRS), budget outdoor parts (galvanized).
Avoid when: washdown 化学的s, salt exposure without maintenance, or weight matters — step up to stainless or aluminum.

ステンレス鋼板：304 vs 316

Austenitic stainless brings corrosion resistance in the metal itself — no coating to chip, scratch, or age. Annealed 304 and 316 sheet both spec at 205 MPa yield / 515 MPa tensile (ASTM A240), form well despite noticeable springback, and work-harden as you bend them. 304 (18% Cr / 8% Ni) covers food equipment, medical housings, architectural trim, and general washdown duty. 316 adds 2–3% molybdenum, which is what resists chlorides — coastal installations, road-salt exposure, process 化学的s, and marine hardware. The premium over 304 is real, so reserve 316 for genuine chloride environments rather than specifying it “to be safe.”

Practical notes: stainless cuts and bends harder than CRS (expect slightly higher fabrication cost), shows fingerprints on bright finishes — brushed or bead-blasted surfaces hide handling — and must be kept free of carbon-steel contamination during fabrication to avoid rust spotting. A dedicated stainless workflow matters more than the mill certificate.

最適な用途: hygiene and washdown (304), chlorides and coastal air (316), any part where a coating failure is unacceptable.
Avoid when: a coated CRS part meets the life requirement — you’re paying a multiple for resistance you don’t need.

アルミニウム板：5052と6061

5052-H32 is the sheet-metal aluminum: 228 MPa tensile / 193 MPa yield, the best formability of any common structural alloy, and corrosion resistance good enough for marine panels and fuel tanks. It takes tight bend radii without cracking, welds well, and anodizes cleanly — the natural choice for lightweight enclosures, covers, and formed brackets. 6061-T6 is stronger (310 MPa tensile / 276 MPa yield) and doubles as a machining alloy, but that strength costs ductility: tight bends crack unless you design generous radii or bend across the grain. The practical split: form in 5052, machine in 6061, and when a part needs both, keep bend radii generous. For the full alloy-by-alloy breakdown — including 7075, 2024, and 陽極酸化 behavior — see our CNC aluminum grades guide.

最適な用途: weight-critical parts, marine and outdoor service without coatings, formed enclosures and covers (5052); formed-plus-machined hybrids (6061).
Avoid when: maximum stiffness per euro is the only metric — steel wins on pure structure-per-cost.

板金材料の比較

選び方：決定を下す6つの質問

1. What does the environment do to metal? Dry indoor → coated CRS. Weather → galvanized or aluminum. Chlorides, 化学的s, washdown → stainless (316 if salt is involved).
2. Does weight matter? Anything carried, shipped in quantity, or mounted on moving equipment leans aluminum — the stiffness gap is designable with flanges and ribs.
3. How hard is the forming? Deep bends and tight radii favor CRS or 5052. Springback and work-hardening make stainless the fussiest; 6061 cracks if you treat it like 5052.
4. Will it be welded, and how visible is the joint? CRS is effortless; stainless TIG-welds cleanly; galvanized needs coating repair at the weld; aluminum wants experienced hands.
5. What finish does the 用途 demand? Powder coat covers CRS economically; stainless and anodized aluminum carry their own finish — factor the coating chain into cost, not just the sheet price.
6. What tolerance class do the critical features need? Formed sheet parts live comfortably at ISO 2768 general 公差 — reserve tight callouts for hole patterns and mating faces, per our guide to standard vs tight 公差.

Real-world example: a European equipment builder specified 316 stainless for a full indoor control cabinet line — habit from a previous coastal project. DFM review split the BOM: 316 stayed only on two washdown-exposed covers, the rest moved to powder-coated DC01. The cabinets passed the same service requirements, and the material line on the quote dropped by more than half. Environment-first selection, applied per part rather than per project, is where 板金 budgets are won.

安全な板金だけでなく、適切な板金を選ぶ

鋼, stainless, and aluminum each earn their place when the environment, load, and forming route are named honestly — and waste money when chosen by reflex. If your drawing still says “material: TBD,” 送信 it over: BravoFabs fabricates all three families daily — レーザー切断, CNC 曲げ加工, 溶接, and finishing under one roof in Dongguan, China — for industrial clients across Europe and North America, and every RFQ includes a free DFM review with a material recommendation and the reasoning behind it.