Welding
High-Mg Al-Mg-Zn alloys weld by MIG and TIG with Al-Mg fillers chosen under the approved welding procedure. Low copper and zirconium additions help limit hot cracking.
Russian alloy guide
1985ч (1985ch) Aluminium Alloy: Marine Sheet and Plate
1985ч (often written 1985ch in Latin script) is a Russian heat-treatable aluminium alloy with high magnesium and a zinc addition, made for hull plating and other welded marine structures. It is supplied mainly as sheet and thick plate under GOST R 56371-2015 and GOST R 56370-2015, in the 1985чАТ (clad) and 1985чТ (unclad) quenched and naturally aged conditions. This guide decodes the designation, the tempers and the data you need to order it.
- System
- Al-Mg-Zn, heat-treatable
- Tempers
- 1985чАТ · 1985чТ
- Thick plate
- 12 – 35 mm
- Standards
- GOST R 56371 / 56370
What is 1985ч aluminium alloy?
1985ч is a wrought alloy in the Russian 19xx family, the group reserved for zinc-and-magnesium-bearing aluminium alloys. Unlike 1980, where zinc is the larger addition, 1985ч carries about 5 – 6 % magnesium with roughly 2.2 – 2.8 % zinc. The result behaves like a strong AMg-type marine alloy that can also be hardened by heat treatment.
The suffix "ч" (Cyrillic "ch") stands for chistyi, meaning "pure". In Russian practice it marks a higher-purity version of a grade with tighter limits on iron, silicon and other impurities. That is why the same alloy appears as 1985ч, 1985ch, 1985Ch or "1985 ч" in different documents; they all refer to the same material.
The alloy was developed for shipbuilding, where hull plating must be weldable, tough and resistant to seawater while saving as much weight as possible. A small beryllium addition protects the high-magnesium melt from oxidation during casting, and manganese, chromium and zirconium keep the grain structure fine. Copper is held very low, because even small amounts reduce corrosion resistance in seawater.
Standards for 1985ч products
| Document | Product | Notes |
|---|---|---|
| GOST R 56371-2015 | Sheet for shipbuilding | Covers 1561, 1561Н, 1980, 1985ч, 1941 and 1943 sheet |
| GOST R 56370-2015 | Thick plate for shipbuilding | 1985чТ and 1985чАТ plate |
| OST 1 92063-78 | Strip and flat strip | Older industry standard, still referenced on legacy drawings |
| OST 1 92073-82 | Strip and flat strip | Check which edition is called up |
| OST 1 92041-90 | Panels with longitudinal ribs | Integrally stiffened extruded panels |
| OST 5.9466-88 | Chemical composition reference | Commonly cited for composition limits |
Shipbuilding standards also call for classification-society approval of the material maker in many projects. Tell us if your order is under Russian Maritime Register (RS) or another class rules.
1985ч chemical composition
Composition limits as commonly quoted from the governing industry standard are shown below. The certificate supplied with each lot gives the actual analysis.
| Element | Content (wt %) | Role |
|---|---|---|
| Magnesium (Mg) | 5.0 – 5.9 | Main strengthening element; solid-solution strength and weldability |
| Zinc (Zn) | 2.2 – 2.8 | Combines with Mg to form precipitates on ageing |
| Manganese (Mn) | 0.25 – 0.50 | Grain control, stress-corrosion resistance |
| Chromium (Cr) | 0.10 – 0.20 | Inhibits recrystallisation |
| Zirconium (Zr) | 0.08 – 0.20 | Refines grain, stabilises structure |
| Beryllium (Be) | 0.0002 – 0.005 | Protects high-Mg melt from oxidation during casting |
| Iron (Fe) | ≤ 0.30 | Impurity |
| Silicon (Si) | ≤ 0.20 | Impurity |
| Copper (Cu) | ≤ 0.10 | Kept low for seawater corrosion resistance |
| Titanium (Ti) | ≤ 0.07 | Grain refiner |
| Others each / total | ≤ 0.05 / ≤ 0.10 | |
| Aluminium (Al) | Balance | About 89.7 – 92.2 % |
How to read 1985чА, 1985чАТ and 1985чТ
Russian temper codes are letters added after the grade. They are not the same as ANSI tempers, so translate them carefully on purchase documents.
| Code | Meaning | Typical product |
|---|---|---|
| 1985чА | Normal cladding (А). Describes the surface layer only, not a heat treatment | Clad sheet in the as-produced condition |
| 1985чАТ | Normal cladding + quenched and naturally aged (Т) | Marine sheet and plate |
| 1985чТ | No cladding, quenched and naturally aged | Thick marine plate |
Natural ageing continues for some time after quenching, so the measured strength depends on how long after quenching the test is made. Some acceptance values in the 1985ч standards are tied to a stated natural-ageing period. State the temper and, if required, the test timing on your order so the mill certificate matches your acceptance procedure.
Mechanical and physical properties
Values below are typical ranges for quenched and naturally aged sheet and plate. Guaranteed minimums depend on thickness, cladding and test direction and are set by GOST R 56371 or GOST R 56370; use those for design.
| Property | Typical range |
|---|---|
| Tensile strength Rm | 350 – 420 MPa |
| Yield strength Rp0.2 | 250 – 320 MPa |
| Elongation δ5 | 8 – 12 % |
| Brinell hardness | 90 – 110 HB |
Physical properties (reference)
- Density
- about 2.65 – 2.70 g/cm³; high magnesium lowers density slightly
- Modulus of elasticity
- about 70 GPa
- Thermal expansion
- about 23.5 × 10⁻⁶ /°C (20 – 100 °C)
- Thermal conductivity
- roughly 120 – 150 W/m·K
Estimating values only; not acceptance data.
For comparison, 5083-H116 marine plate typically yields at about 215 – 230 MPa, so 1985ч offers a meaningful strength gain for hull plating while staying in a weldable, low-copper chemistry.
1985ч sheet and plate sizes
| Product | Temper | Thickness | Width | Length |
|---|---|---|---|---|
| Sheet / plate | 1985чАТ | 4.0 – 10.0 mm | 1200 / 1500 mm | 3000 – 7000 mm |
| Thick plate | 1985чТ, 1985чАТ | 12 – 35 mm | 1200 / 1500 mm | 2000 – 7000 mm |
| Strip / flat strip | Per OST | To order | To order | To order |
| Ribbed panels | Per OST 1 92041 | To drawing | To drawing | To drawing |
A frequently requested thick-plate size is 20 × 1500 × 4000 mm. Plate can be sawn into blanks with machining allowance, and plate weight is easy to estimate: at about 2.67 g/cm³, every millimetre of thickness weighs roughly 2.67 kg per square metre, so a 20 × 1500 × 4000 mm plate weighs about 320 kg.
Welding, forming and protection
Forming
Bend and roll plate in the condition and radius set by the yard procedure. Heavy cold work after ageing reduces ductility.
Cladding
Clad (А) material carries a thin, more anodic surface layer that sacrificially protects the core; avoid grinding it away on finished surfaces.
Corrosion
High-magnesium alloys can become sensitised by long exposure to warm temperatures, which raises the risk of intergranular corrosion. Keep service temperatures moderate and follow coating schemes.
Machining
Machines like other medium-strength marine alloys; sharp tools and good chip clearance prevent smearing.
Galvanic contact
Insulate from steel, stainless fasteners and copper alloys in seawater with washers, sleeves and sealants.
Where 1985ч is used
- Shipbuilding: hull structural plates, superstructure plating, reinforcement plates, ribbed panels and repair replacement plates
- Aviation-related structures: structural and reinforcement plates and integral stiffened panels where low weight and stability matter
- Industrial structures: equipment panels, support plates, machining blanks and cut-to-size plates in marine atmospheres
Where a project does not specifically require 1985ч, Western marine grades such as 5083, 5383 or 5059 are usually easier to source and approve. Metline supplies those grades as well and can help compare them.
Information for a 1985ч enquiry
- Grade and temper1985чАТ or 1985чТ, plus cladding requirements.
- StandardGOST R 56371-2015, GOST R 56370-2015, OST or project TU, including the year.
- DimensionsThickness, width, length, tolerances and flatness; drawings for panels or cut parts.
- DocumentsMill test certificate, chemical analysis, mechanical tests, dimensional report, classification approval if needed.
- LogisticsQuantity, EXW, FOB, CIF or DAP terms, destination and packing (film, interleaving, wooden cases).
References and standards
- GOST R 56371-2015 – Aluminium alloy sheets for shipbuilding. Specifications
- GOST R 56370-2015 – Aluminium alloy thick plates for shipbuilding. Specifications
- OST 1 92041-90 – Panels with longitudinal ribs of aluminium alloys
- GOST 4784 – Aluminium and wrought aluminium alloys. Grades (Russian grade system)
- ASTM B928 – High-magnesium aluminium-alloy sheet and plate for marine service (comparison grades)
1985ч (1985ch) aluminium alloy: frequently asked questions
Are 1985ч and 1985ch the same material?
Yes. "ч" is the Cyrillic letter transliterated as "ch". It marks a higher-purity version of the grade. 1985ч, 1985ch and 1985 ч all refer to the same alloy.
What is the difference between 1985чАТ and 1985чТ?
Both are quenched and naturally aged (Т). 1985чАТ also has normal cladding (А) on the surface for added corrosion protection; 1985чТ is unclad and is used mainly for thick plate.
What are common 1985ч thick plate sizes?
Thick plate to GOST R 56370-2015 is typically 12 – 35 mm thick, 1200 or 1500 mm wide and 2000 – 7000 mm long; 20 × 1500 × 4000 mm is a common size.
Can 1985ч be used for marine applications?
Yes, that is its main purpose. It is used for hull, superstructure and reinforcement plating in welded ship structures, with suitable coatings and galvanic isolation.
Does 1985ч have an ASTM or EN equivalent?
No direct equivalent exists. High-magnesium marine grades such as 5083, 5383 and 5059 fill similar roles but are non-heat-treatable, so substitution needs approval from the designer or classification society.
Can I enquire without complete drawings?
Yes. Grade, temper, thickness, approximate size, quantity and the application are enough for a first review; drawings can follow for cut parts.
Need 1985ч sheet or thick plate?
Tell us the temper, standard, sizes and destination. We will reply with availability, certification and a delivered price.
