Difference Between Stainless Steel 321 and 347

ASTM A213 321 321H 347 347H Chemical Composition:

Grade	321	321H	347	347H
UNS Designation	S32100	S32109	S34700	S34709
Carbon (C) Max.	0.08	0.04–0.10	0.08	0.04-0.10
Manganese (Mn) Max.	2.00	2.00	2.00	2.00
Phosphorous (P) Max.	0.045	0.045	0.04	0.04
Sulphur (S) Max.	0.03	0.03	0.03	0.03
Silicon (Si) Max.	1.00	1.00	0.75	0.74
Chromium (Cr)	17.0–20.0	17.0–20.0	17.0–20.0	17.0–20.0
Nickel (Ni)	9.0–12.0	9.0–12.0	9.0–13.0	9.0–13.0
Molybdenum (Mo)	–	–	–	–
Nitrogen (N)	–	–	–	–
Iron (Fe)	Bal.	Bal.	Bal.	Bal.
Other Elements	Ti=5(C+N) to 0.70%	Ti=4(C+N) to 0.70%	Cb+Ta=10xC-1.0	Cb+Ta=10xC-1.0

A limitation with 321 is that titanium does not transfer well across a high temperature arc, so is not recommended as a welding consumable. In this case grade 347 is preferred – the niobium performs the same carbide stabilisation task but can be transferred across a welding arc. Grade 347 is therefore the standard consumable for welding 321. Grade 347 is only occasionally used as parent plate material.

Like other austenitic grades, 321 and 347 have excellent forming and welding characteristics, are readily brake or roll formed and have outstanding welding characteristics. Post-weld annealing is not required. They also have excellent toughness, even down to cryogenic temperatures. Grade 321 does not polish well, so is not recommended for decorative applications.

TP321 Stainless Steel Tubes

Features:

TP321 is a stabilized stainless steel that offers as its main advantage an excellent resistance to intergranular corrosion following exposure to temperature in the chromium carbide precipitation range from 800 °F to 1500°F (427°C to 816°C). Alloy 321 stainless steel tubing is stabilized against chromium carbide formation by the addition of titanium.

TP347H Stainless Steel Tube:

Features:
It is a stable austenitic heat-strength steel. It has good heat strength and resistance to intergranular corrosion, good welding performance, and good corrosion resistance in alkali, seawater and various acids.347H and 347HFG in higher elevated temperature allowable stresses for these stabilized alloys for ASME Boiler and Pressure Vessel Code applications.

Application:
Heat exchangers for large boiler superheater tubes, reheater tubes, steam lines and petrochemicals. The allowable oxidation temperature in boiler tubes is 750 °C.

Comparision Grade 304 304L 316 316L Corrosion Resistance

As American AISI basic grades, the only practical difference between 304 or 316 and 304L or 316L is carbon content. The carbon ranges are 0.08% maximum for 304 and 316 and 0.030% maximum for the 304L and 316L types. All other element ranges are essentially the same (nickel range for 304 is 8.00-10.50% and for 304L 8.00-12.00%).

There are two European steel of the '304L' type, 1.4306 and 1.4307. The 1.4306 is the variant most commonly offered, outside Germany. The 1.4301 (304) and 1.4306 (304L) have carbon ranges of 0.07% maximum and 0.030% maximum, respectively. The chromium and nickel ranges are similar, nickel for both grades having an 8% minimum. The European grades for the 316 and 316L types, 1.4401 and 1.4404, match on all elements with carbon ranges of 0.07% maximum for 1.4401 and 0.030% maximum for 1.4404.

Effect of carbon on corrosion resistance

The lower carbon 'variants' (316L) were established as alternatives to the 'standards' (316) carbon range grade to overcome the risk of intercystalline corrosion (weld decay), which was identified as a problem in the early days of the application of these stainless steel tube. This can result if the steel is held in a temperature range 450 to 850 for periods of several minutes, depending on the temperature and subsequently exposed to aggressive corrosive environments. Corrosion then takes place next to grain boundaries.

If the carbon level is below 0.030% then this intercrystalline corrosion does not take place following exposure to these temperatures, especially for the sort of time normally experienced in the heat affected zone of welds in 'thick' sections of steel.

Effect of carbon level on weldability

There is a view that the low carbon types are easier to weld than the standard carbon types.

There does not seem to be a clear reason for this and the differences are probably associated with the lower strength of the low carbon type. The low carbon type may be easier to shape and form, which in turn may also affect the levels of residual stress left the steel after is forming and fitting up for welding. This may result in the 'standard' carbon types needing more force to hold them in position once fitted-up for welding, with more of a tendency to spring-back if not properly held in place.

The welding consumables for both types are based on a low carbon composition, to avoid intercrystalline corrosion risk in the solidified weld nugget or from the diffusion of carbon into the parent (surrounding) metal.

Dual-certification of low carbon composition steel

Commercially produced steels, using current steelmaking methods, are often produced as the low carbon type as a matter of course due to the improved control in modern steelmaking. Consequently finished steel products are often offered to the market 'dual certified' to both grade designations as they can then be used for fabrications specifying either grade, within a particular standard.

For example for coil, sheet or plate

304 Types:

BS EN 10088-2 1.4301 / 1.4307 to the European standard.

ASTM A240 304 / 304L OR ASTM A240 / ASME SA240 304 / 304L to the American pressure vessel standards.

316 Types:

BS EN 10088-2 1.4401 / 1.4404 to the European standard.

ASTM A240 316 / 316L OR ASTM A240 / ASME SA240 316 / 316L, to the American pressure vessel standards.

 

When chrome bar/piston rod need Quenched and tempered?

When chrome bar / piston rod need Quenched and tempered ?

Due to the difference in the scope of use and working conditions of the piston rod, sometimes the piston rod must undergo processes such as induction, quenching and tempering, and nitriding. Through these processes, the performance requirements of certain aspects of the piston rod may be more suitable for product applications. However, not all piston rods need to be tempered. The quenching and tempering treatment mainly depends on the material used for the piston rod. Because quenching and tempering is only a dual heat treatment process of quenching and high temperature tempering, the piston rod products after quenching and tempering can obtain the following benefits:

 

1. It can effectively improve the working strength of the material.

 

2. After the piston rod is quenched and tempered, it can have good comprehensive mechanical properties.

 

3. It helps to close the micro cracks on the surface, hinders the expansion of corrosion, and improves the surface corrosion resistance.

 

4. The piston rod is quenched and tempered, which can effectively eliminate the internal stress caused by quenching to obtain the expected mechanical properties.

 

42CrMo4, 40Cr Hard Chrome Plated Bar With Quenched / Tempered For Cylinder

Detailed Product Description

 

1. Material: CK45, ST52, 20MnV6, 42CrMo4, 40Cr

2. Diameter: 6mm - 1000mm

3. Length: 1000mm - 8000mm

4. Tensile strength: Not less than 610 N/MM2

5. ISO9001:2008

 

Detailed Description

1.CHEMICAL COMPOSITION

Material	C%	Mn%	Si%	S%	P%	V%	Cr%
CK45	0.42-0.50	0.50-0.80	0.04	0.035	0.035
ST52	0.22	1.6	0.55	0.035	0.04
20MnV6	0.16-0.22	1.30-1.70	0.10-0.50	0.035	0.035	0.10-0.20
42CrMo4	0.38-0.45	0.60-0.90	0.15-0.40	0.03	0.03		0.90-1.20
40Cr	0.37-0.45	0.50-0.80	0.17-0.37				0.80-1.10

 

2.MECHANCIAL PROPERTIES

Material	T.S  N/MM2	Y.S  N/MM2	E%(MIN)	CHARPY	CONDITION
CK45	610	355	15	>41J	NORMALIZE
CK45	800	630	20	>41J	Q + T
ST52	500	355	22		NORMALIZE
20MnV6	750	590	12	>40J	NORMALIZE
42CrMo4	980	850	14	>47J	Q + T
40Cr	1000	800	10		Q + T

 3. SUPPLY CONDITION

    Ground  and  chrome plated 

4. CHROME THICKNESS

     20 to 30 micron

5. SURFACE ROUGHNESS

     Ra≤0.2 micron and  Rt≤2 micro

6. TOLERANCES ON DIA

    ISO f7 on the diameter

7.OVALITY

Half of the tolerance ISO f7

8. STRAIGHTNESS

   ≤0.2MM/M

9. SURFACE HARDNESS

   850-1150HV (vickers 100g)

10.COHESION

   No cracks,breaking or detaching after thermic shock(warming up at 300 celsius degrees and cooling

   in water)

11 .POROSITY

     Test according to ISO 1456/1458 and result yaluation according to ISO 4540 rating 8-10

12 CORROSION RESISTANCE

     Test in natural salt spray according to ASTM B 117-72hours

     Results evaluation according to ISO 4540 RATING 7-10

13. WELDABILITY 

      Good

14. PACKING

     Anti rust oil to be applied on material and each rod to be packed in paper sleeve

15. CERTIFICATE

     All certificate related with material heat treatment and plating is required