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China ASTM A350 LF1, LF2, LF3 Carbon/Alloy Steel Suppliers and Factory for Pipeline and Forged Flanges
GENERAL CHARACTERISTICS
These grades of steel are used as pipeline steels and also in the production of forged flanges. They are suitable for use down to –20ºF (LF1), –50ºF (LF2) and –150ºF (LF3).
Designation by Standards
| Mat. No. | DIN | EN | AISI |
|---|---|---|---|
| 1.5622 | 14Ni6 | - | A350 |
CHEMICAL ANALYSIS
LF1:
| C% | Mn% | Si% | S% | P% | Cr% | Ni% |
|---|---|---|---|---|---|---|
| 0.30 max | 0.6/1.35 | .15/.30 | .040 max | .035 max | 0.30 max | 0.40 max |
LF2:
| C% | Mn% | Si% | S% | P% | Cr% | Ni% |
|---|---|---|---|---|---|---|
| 0.30 max | 0.6/1.35 | .15/.30 | .040 max | .035 max | 0.30 max | 0.40 max |
LF3:
| C% | Mn% | Si% | S% | P% | Cr% | Ni% |
|---|---|---|---|---|---|---|
| 0.20 max | 0.90 | .20/.35 | .040 max | .035 max | 0.30 max | 3.3/3.7 |
APPLICATIONS
These steels are primarily used for pipelines and forged flanges.
FORGING
LF1 and LF2 grades would ideally be forged at around 2250-2300ºF (1230-1260ºC) and can’t be forged below 1650-1700ºF (900-925ºC). The LF3 grade would be forged at around 2150-2200ºF (1175-1205ºC) and can’t be forged below 1700ºF (925ºC).
WELDING / HEAT TREATMENT
Heat treatment of pipeline steels will no doubt be done on a continuous basis after welding. The structure of these steels will be initially determined by the rolling/forging process. The pipeline itself will be supplied from hot-rolled steels, the flanges etc. from forgings. The actual welding process will be primordial in ensuring the suitability and security of the pipeline and its subsequent performance. Preheat and post heat treatments are essential.
The three grades listed here are easily weldable by all tried and tested methods.
MACHINABILITY
In the case of forged fittings and flanges, these grades can be machined as required, and ongoing experience will determine if machining is best done on an as-forged structure, a normalized structure or an annealed structure. In either case, in view of the critical nature of the end use, advice should be taken from a recognized heat treatment company.
Frequently Asked Questions (FAQ)
Q1: What are the minimum service temperatures for LF1, LF2, and LF3 steel grades?
LF1 is suitable for use down to –20ºF, LF2 is suitable down to –50ºF, and LF3 is suitable for lower temperature environments down to –150ºF.
Q2: What standard designations correspond to these steel grades?
According to standard designations, these grades correspond to Material Number 1.5622, DIN standard 14Ni6, and AISI standard A350.
Q3: How does the chemical composition of LF3 differ from LF1 and LF2?
LF3 has a lower maximum carbon content (0.20% max compared to 0.30% max in LF1/LF2) and a significantly higher nickel content of 3.3% to 3.7% (compared to 0.40% max in LF1 and LF2).
Q4: What are the forging temperature limits for LF1, LF2, and LF3?
LF1 and LF2 are ideally forged at 2250-2300ºF (1230-1260ºC) and cannot be forged below 1650-1700ºF (900-925ºC). LF3 is forged at 2150-2200ºF (1175-1205ºC) and cannot be forged below 1700ºF (925ºC).
Q5: Are these steel grades easily weldable?
Yes, all three grades (LF1, LF2, and LF3) are easily weldable by all tried and tested methods. However, preheat and post heat treatments are essential to ensure the suitability and security of the pipeline.
Q6: How should the machinability structure of forged fittings and flanges be selected?
Machining can be done on an as-forged, normalized, or annealed structure based on ongoing experience. Due to the critical nature of their end use, it is recommended to take advice from a recognized heat treatment company.