Various Materials for Piston Rods and Applications.ppt

Medium Carbon Steels (range between 1035 to 1045 CS grades) M / R to CuS04
- Typical tensile strength range 500 - 700 MPa
- Fairly good strength and impact properties, plus good machinability
- It can be successfully flame or induction hardened resulting in surface hardness of up to 54 - 60 Rc

Cr / Mo Alloy Steels ( e.g. AISI 4130 and 4140) M / R to CuS04
- Typical tensile strength range 850 - 1000 MPa
- Good strength and impact properties, plus good machinability
- These alloys can be further surface hardened by flame or induction hardening and by nitriding.

Ni / Cr Alloy Steels ( e.g. AISI 4340, EN25, EN26) M / R to CuS04
- Typical tensile strength range 930 - 1300 MPa
- High strength and toughness (applications requiring higher tensile and yield strength than 4140)
- These alloys can be further surface hardened by flame or induction hardening and by nitriding.
STANDARD SERVICE (lube or non-lube & non-corrosive service):

AISI 4140 (Also known as EN19 or 709M40)

A high tensile chrome molybdenum alloy steel 0.4% carbon, 1.0% chrome, 0.2% molybdenum

Ultimate tensile strength (UTS) = 60 ton/sq. inch = 900 Mpa Hardened and Tempered (H & T)

Hardness 28-32 Rc as received in bar form

Stress relieved to 18-22 Rc before induction hardening

Induction hardened to 50-55 Rc in packing area
STANDARD SERVICE (lube or non-lube & non-corrosive service):

AISI 4140 (Also known as EN19 or 709M40)

A high tensile chrome molybdenum alloy steel 0.4% carbon, 1.0% chrome, 0.2% molybdenum

Ultimate tensile strength (UTS) = 60 ton/sq. inch = 900 Mpa Hardened and Tempered (H & T)

Hardness 28-32 Rc as received in bar form

Stress relieved to 18-22 Rc before induction hardening

Induction hardened to 50-55 Rc in packing area
VERY CORROSIVE SERVICE:

AISI 630 (Also known as 17/4PH Stainless Steel�17/4PH (precipitation hardened) stainless steel

carbon, 16% chrome, 4.0% nickel, 0.25% niobium, 3.7% copper
UTS = 70 ton/sq. inch (1080 Mpa) Condition A
Hardness 30-42 Rc.
17/4PH has excellent corrosion resistance equivalent to AISI 304 stainless steel.
17/4PH is a martensitic age hard-enable steel which can only be hardened by solution treatment (similar to annealing) and subsequent precipitation hardening heat treatment (ageing at particular temperatures) to achieve various levels of hardness. Primary ageing will give approximately 42 Rc hardness and secondary ageing will give approximately 35 Rc hardness.
Further age hard-enable alloys with even higher corrosion resistance are available on request.
Piston Rods have soft cores to allow for flexing during compression, core hardness 18 – 22 Rc.


The only section of rods to be hardened is the surface where the packings and oil scrapers run - to increase life and improve sealing.�
Induction Hardening:�·  NC process where the rod is passes through an induction coil of approximately 150 kW of electrical energy then immediately quenched. This allows the rod to be ha

1. 1
Piston Rods -General
Air Compressors
•are generally unhardened in packing region, typically 30 Rc hardness, with
screw cut threads.
Process gas compressors
•minimum standard is induction hardened in packing region to 45 –55 Rc.
Nitriding is occasionally used to harden the rod to 50 Rc. Must have rolled
threads for safety –fatigue consideration.
Coated piston rods
•thermal and plasma sprayed coatings, as well as electroplating are
generally used to increase surface hardness. Most coatings produce a
surface hardness of 60 to 70 Rc.
•according API 618 only High-velocity and high impact thermal coating
processes are acceptable. Fusion techniques that require temperatures
high enough to effect the mechanical characteristics of the base material
are unacceptable. Metal spray techniques requiring roughening of the
surface of the base metal are not recommended. Use of sub coating under
the main coating is not recommended.

2. 2
Piston Rods -Materials
Piston Rods come in variety of steels and high tensile alloys depending on
manufacturer, gas duty, hardness and customer/supplier preference.
Medium Carbon Steels (range between 1035 to 1045 CS grades) M / R to CuS04
-Typical tensile strength range 500 -700 MPa
-Fairly good strength and impact properties, plus good machinability
-It can be successfully flame or induction hardened resulting in surface hardness of up to 54 -60 Rc
Cr / Mo Alloy Steels ( e.g. AISI 4130 and 4140) M / R to CuS04
-Typical tensile strength range 850 -1000 MPa
-Good strength and impact properties, plus good machinability
-These alloys can be further surface hardened by flame or induction hardening and by nitriding.
Ni / Cr Alloy Steels ( e.g. AISI 4340, EN25, EN26) M / R to CuS04
-Typical tensile strength range 930 -1300 MPa
-High strength and toughness(applications requiring higher tensile and yield strength than 4140)
-These alloys can be further surface hardened by flame or induction hardening and by nitriding.

3. 3
Martensitic Stainless Steels -(e.g. AISI 410, 420 grades) M / N to CuS04
-Typical tensile strength range 700 -930 MPa
-Good strength, reasonable impact properties and fairly good corrosion resistance. It is resistant to
ammonia, blood, carbonic acid, crude oil, detergent solutions, dilute nitric acid, fresh water, food acids,
many petroleum products, steam and vinegar.
-It has an excellent hardenability. Capable of being through hardened up to 50Rc or higher depending
upon carbon content
Chromium-nickel austenitic stainless steel-(e.g. AISI 304, 316 grades) N / N to CuS04
-Typical tensile strength range 580 -680 MPa
-Good strength and excellent corrosion resistance as supplied in the annealed condition with a typical
brinell hardness of 175.In general atmospheric corrosive environments it exhibits excellent resistance to
most oxidizing agents, general foodstuffs, sterilizing solutions, dyestuffs, most organic chemicals, plus a
wide variety of inorganic chemicals also hot petroleum gases, steam combustion gases, nitric acid and to
a lesser extent sulphuric acid. It displays good oxidation resistance at elevated temperatures and has
excellent weldability.
-These alloys cannot be hardened by thermal treatment, but strength and hardness can be increased
substantially by cold working, with subsequent reduction in ductility.

4. 4
Martensitic precipitation hardening Stainless Steels -(AISI 630, 17-4 PH S/S)
-Typical tensile strength range 800 -1300 MPa. m / N to CuS04
-It is characterised by high tensile strength and high yield strength obtained by solution annealing,
followed by a single or double low temperature (precipitation) age hardening treatment. Coupled with a
corrosion resistance comparable to 304 austenitic stainless steel in many corrosive environments
-This alloys can be hardened by solution annealing, followed by a single or double low temperature
(precipitation) age hardening treatment
Monel (Ni & Cu alloy) n / N to CuS04
-Typical tensile strength of 550 MPa,
-Good resistance to sulfuric and hydrofluoric acids. Excellent resistance to chloride ion stress corrosion
cracking.May be used to handle hydrochloric acid, but the presence of oxidizing salts will greatly
accelerate corrosive attack. Resistance to neutral, alkaline and acid salts is shown, but poor
resistance is found with oxidizing acid salts such as ferric chloride. Good mechanical properties from
subzero temperatures up to about 480C.
-Can be age hardened. Hardness range 110 -264 BHn.
Hastalloy (Ni alloy) Typical tensile strength of 700 -900 MPa,
-nickel-based alloy with excellent corrosion resistance to hydrochloric, sulfuric, acetic and phosphoric
acids. It also withstands attack by hydrogen chloride and has excellent resistance to pitting, stress
corrosion cracking, knife-line and heat affecting zone attacks.