Project Description

15-7PH (UNS S15700), also designated as 1.4532, X8CrNiMoAl15-7-2, SUS632, and 07Cr15Ni7Mo2Al, is a molybdenum-bearing semi-austenitic precipitation hardening (PH) stainless steel that extends the 17-7PH chemistry with a deliberate 2.0–3.0% molybdenum addition for significantly improved resistance to pitting and crevice corrosion in chloride-containing environments. This makes 15-7PH particularly well-suited for offshore and subsea oil and gas equipment where seawater exposure, produced water, and sour well fluids demand both high mechanical strength and reliable corrosion performance. SHUNFU METAL, certified to ISO 9001:2015 and API Q1, produces 15-7PH stainless steel bars through controlled electric arc furnace (EAF) melting with AOD refining, precisely calibrating the molybdenum and aluminum additions to ensure consistent precipitation hardening response and corrosion resistance across every production lot.

15-7PH Stainless Steel Bar — Overview

Also known as PH 15-7 Mo, this grade achieves its high strength through a low-temperature aging treatment that precipitates NiAl intermetallic phases within a martensitic matrix, delivering tensile strengths up to 1586 MPa in Condition RH 950 with minimal distortion. Compared to 17-7PH, the molybdenum content raises the pitting resistance equivalent number (PREN), providing superior resistance to localized corrosion in chloride-rich oilfield environments. SHUNFU METAL supplies 15-7PH bars for subsea valve stems, offshore pump shafts, wellhead fasteners, downhole springs, riser tensioner components, and subsea manifold instrumentation, with every heat verified by in-house optical emission spectrometry (OES) and mechanical testing, supported by MTC documentation per EN 10204 Type 3.1.

15-7PH Equivalent Grades — International Standards

Standard Designation
ASTM A564 / A693 Grade 632 / UNS S15700
AMS AMS 5657 (bar), AMS 5520 (sheet)
EN 10088-3 / DIN 1.4532 / X8CrNiMoAl15-7-2
JIS G4303 SUS632 / SUS632J1
GOST 5632 03Х17Н7АЛ
GB/T 1220 07Cr15Ni7Mo2Al

SHUNFU METAL supplies 15-7PH bars certified to ASTM A564, AMS 5657, EN 10088-3, and GB/T 1220 with full heat traceability and API Q1 documentation provided as standard with every shipment.

15-7PH precipitation hardening stainless steel round bar by SHUNFU METAL
15-7PH (UNS S15700) Stainless Steel Bar
SHUNFU METAL

15-7PH Applications — Oil & Gas Industry

The molybdenum-enhanced corrosion resistance of 15-7PH makes it the preferred choice over 17-7PH for offshore platforms, subsea installations, and sour-service wellhead equipment where chloride attack and hydrogen sulfide exposure are operational realities. SHUNFU METAL supplies 15-7PH bars to manufacturers of the following petroleum components, with every production lot verified against ASTM A564 and AMS 5657 requirements:

Subsea Valve StemsGate and ball valve stems for subsea Christmas trees and manifold blocks exposed to seawater.
Offshore Pump ShaftsMultistage injection and produced-water pump shafts for floating production platforms.
Sour-Service FastenersHigh-strength stud bolts and nuts for API 6A wellhead flanges in H₂S-containing streams.
Downhole SpringsSubsurface safety valve springs and packer energizing elements in corrosive well fluids.
Riser Tensioner PartsTensioner ring components and load-bearing shafts for marine riser systems.
Subsea InstrumentationPressure transducer bodies, sensor housings, and subsea electronic enclosure fasteners.
Compressor Valve PlatesReciprocating compressor reed valves and springs for offshore gas lift and injection systems.
Seal RetainersMetallic gasket rings and seal support rings for high-pressure flange connections.
ROV Tooling InterfacesRemotely operated vehicle torque tool shafts and subsea intervention hardware.

Supply Range — 15-7PH Bar Dimensions

SHUNFU METAL maintains comprehensive production capability for 15-7PH bars across hot-rolled, cold-finished, and forged product forms, processed through ISO 9001:2015 controlled workflows. Ultrasonic testing per ASTM A388 / EN 10228-3 is available on request for critical subsea applications where internal soundness is mandatory. The following dimensional ranges are offered as standard, with custom sizes accommodated through our in-house forging and precision machining facilities:

Product Form Diameter / Thickness Range Width Range Length (Standard) Condition
Hot Rolled Round 10 mm – 300 mm — 3000 – 6000 mm Solution Annealed (Condition A)
Cold Finished / Peeled Round 3 mm – 100 mm — 2000 – 6000 mm Condition A, TH 1050, RH 950
Hot Rolled Flat 10 mm – 150 mm 50 mm – 500 mm 2000 – 6000 mm Solution Annealed (Condition A)
Forged Round 100 mm – 800 mm — 1000 – 6000 mm Solution Annealed (Condition A)
Forged Flat / Block 50 mm – 400 mm 100 mm – 1000 mm 1000 – 5000 mm Solution Annealed (Condition A)

All bars are supplied with EN 10204 Type 3.1 Mill Test Certificates documenting heat number, chemical analysis (including molybdenum verification), mechanical test results, and dimensional compliance. Batch-specific corrosion testing data is available upon request for offshore project qualification requirements.

15-7PH Chemical Composition per ASTM A564

The defining characteristic of 15-7PH chemistry is the 2.0–3.0% molybdenum addition, which distinguishes it from 17-7PH and significantly enhances pitting and crevice corrosion resistance in chloride-containing oilfield environments. At SHUNFU METAL, every heat is verified by in-house optical emission spectrometry (OES) against ASTM A564 Grade 632 / AMS 5657 limits, with the molybdenum and aluminum contents tightly controlled to ensure consistent precipitation hardening response:

Element C Mn Si P S Cr Ni Mo Al
Wt % 0.09 max 1.00 max 1.00 max 0.040 max 0.030 max 14.00–16.00 6.50–7.75 2.00–3.00 0.75–1.50

Composition conforms to ASTM A564 Grade 632 (UNS S15700) and AMS 5657. The molybdenum addition elevates the PREN (Pitting Resistance Equivalent Number) to approximately 18–20, compared to 16–18 for 17-7PH, providing measurable improvement in resistance to localized chloride attack. At SHUNFU METAL, API Q1 certified traceability links every finished bar to its original heat analysis.

15-7PH Mechanical Properties by Heat Treatment

The mechanical performance of 15-7PH stainless steel bars follows the same precipitation hardening mechanism as 17-7PH, with the molybdenum content having negligible impact on strength while substantially improving corrosion resistance. SHUNFU METAL conducts in-house tensile testing (ASTM E8) and Rockwell hardness testing (ASTM E18) on every production lot, with full results documented on the MTC. The following values represent minimum guaranteed properties per AMS 5657 for bar products:

Condition Tensile Strength
(MPa / ksi)		 Yield Strength
(0.2% offset, MPa / ksi)		 Elongation
(% in 4D)		 Reduction
of Area (%)		 Hardness
(HRC / HRB)
A (Solution Annealed)
1065°C ±15°C, air/oil quench		 895 max / 130 max 380 max / 55 max 35 min — HRB 85 max
TH 1050
760°C + 565°C aging		 1241 min / 180 min 1034 min / 150 min 6 min 15 min HRC 38 min
RH 950
-73°C + 510°C aging		 1586 min / 230 min 1475 min / 214 min 6 min 10 min HRC 46 min

Values per AMS 5657 and ASTM A564 for bar products. Condition A offers maximum ductility for machining and cold forming. TH 1050 provides an optimal balance of high strength and reasonable toughness, while RH 950 delivers the maximum attainable strength through sub-zero transformation followed by low-temperature aging. SHUNFU METAL’s ISO 9001:2015 accredited laboratory validates all mechanical properties on representative specimens from each heat treatment batch, with API Q1 ensuring full material traceability from mill to end user.