Low temperature carbon steel pipe

Low temperature carbon steel pipeis a carbon structural steel,low temperature carbon steel pipeis operated in low temperature condition, which can withstand a certain low temperature impact, the mechanical performance is better, and the price is low, wide source, so widely used. Its biggest weakness is the low hardenability, section size Japanese high requirements of the workpiece should not be used.

Low temperature carbon steel pipequenching temperature in A3 + (30 ~ 50) ℃, in practice, is usually set to the upper limit. High quenching temperature heat pipe can make low speed, surface oxidation reduction, and can improve work efficiency. The workpiece is uniform austenite, will require sufficient holding time. If the actual installed furnace capacity, would need to be appropriate to extend the holding time. Otherwise, there may be insufficient hardness due to uneven heating caused by the phenomenon. However, the holding time is too long, will also appear coarse grains, oxidation and decarbonization serious ills affecting quenching quality. We believe that if installed furnace is greater than the process documents, heating holding time to be extended 1/5.

Low temperature carbon steel pipe因为低淬透性,它应该采取一种rge cooling rate of 10% salt solution. Workpiece into the water, should hardenability, but not chilled, if 45 # precision steel chilled in brine, it is possible cracking of the workpiece, this is because when the workpiece is cooled to about 180 ℃, the austenite rapidly converted to horse s body tissue caused by excessive stress due. Therefore, when the quenching and tempering steel quickly cooled to this temperature range, the approach should be taken to slow cooling.

As the water temperature is difficult to grasp, accountable experience in operation, when the water stops dithering artifacts, you can water cooled (eg oil cooler can be better). In addition, the workpiece into the water, appropriate action should still be in accordance with the geometry of the workpiece, as regular exercise. Stationary cooling medium plus stationary workpiece, resulting in uneven hardness, stress uneven leaving large deformation of the workpiece, and even cracking.

Low temperature carbon steel pipemember quenched hardness after quenching should reach HRC56 ~ 59, the possibility of large cross-section lower, but not less than HRC48, otherwise, it shows the workpiece has not been completely hardened, the organization may be ferrite or sorbite tissue, such organizations by tempering, still retained in the matrix, which was not quenched purposes.

Low carbon steel pipe tempering after quenching, the heating temperature is usually 560 ~ 600 ℃, hardness is HRC22 ~ 34. Because the purpose is to get quenched mechanical properties, so a relatively wide range of hardness. But drawing a hardness requirements, it is necessary to adjust the tempering temperature according to drawings to ensure hardness. As some cold steel shafts require high strength, hardness is high; while some gear keyway shaft parts, because even after the milling quenched, insert processing, hardness requirements for lower.

About Tempering time, depending on the hardness and size of the workpiece, we believe, depends on the hardness after tempering tempering temperature and tempering little time, but must be returned through the general always work Tempering Time one hour or more.

Steel No.	Standard No.	Type	Chemical composition													Other
			C	Si	S	P	Mn	Cr	Ni	Mo	Other	ób	ós	δ5	HB
09MnNiDR	GB3531	Plate	0.12	0.15-0.5	0.02	0.25	1.2-1.6	0.25	0.3-0.8	0.08	Nb:0.04；AIS：0.015	440 - 570	290	22		Akv J: 27
16Mn	GB6479	Pipe	0.12-0.2	0.2-0.6	0.04	0.04	1.2-1.6				Cu:0.25	490-670	320	21		ak J/cm2:59
16Mng	GB713	Plate	0.2	0.2-0.55	0.03	0.035	1.2-1.6	0.3	0.3	0.1	Cu:0.3	510-655	345	21		Aku J:27
16MnDR	GB3531	Plate	0.2	0.15-0.5	0.025	0.03	1.2-1.6	0.25	0.4	0.08	Cu:0.25	490-620	315	21		Akv J:24
16MnR	GB6654	Plate	0.2	0.2-0.55	0.03	0.035	1.2-1.6	0.3	0.3		Cu:0.3	510-640	345	21		Akv J:31

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Seamless Pipe Low-Temperature( ASTM A333 / ASME SA333 )

Standard Specification for Seamless Steel Pipe for Low-Temperature Service and Other Applications with Required Notch Toughness

ASTM Scope:

This specification covers nominal (average) wall carbon and alloy steel pipe intended for use at low temperatures and in other applications requiring notch toughness. Several grades of ferritic steel are included as listed in Table 1. Some product sizes may not be available under this specification because heavier wall thicknesses have an adverse effect on impact properties.

刺激uct Knowledge:

This ASTM specification is written so that the end user and the manufacturer can agree upon, and clearly understand, the properties and capabilities of the piping product being supplied. In contrast with national codes (like API, ASME or CSA), ASTM A333 is rarely stipulated by national or state-level legal requirements.

There are several grades in A333, each with different steelmaking approach to improve the steel’s impact properties at lower temperatures. Several grades have nickel (Ni) additions, and are capable of high toughness at cryogenic temperatures as low as -320F (-195C). Many of these grades would be considered rare, and in the experience of Bri-Steel, they are expensive to procure and may be difficult to find a capable fabricator with an proven weld procedure. The exception to this is Gr6, which is quite common and is regularly stocked in colder regions of North America. A333 Gr6 has proven impact toughness at -50F (-45C), and is commonly used in applications where the piping is exposed directly to cold environments during construction and/or in operation.

A333 Gr6 is also commonly used for pressure piping of compressed gas, where a crack would be expected to have catastrophic consequences.

Beginning with the 2013 edition, the title of this spec included “other applications with required notch toughness”. This could include applications where cyclic loading and fatigue cracking are concerns, or where corrosion may be expected to contribute to notching of the metal. In these applications, the proven notch toughness of the material would be expected to deter crack initiation and growth.

Note that A333 Gr 6 allows seamless and long-seam pipe manufacturing techniques. That being said, for pipes with long seams, impact toughness of the base metal, weld metal and weld heat-affected zone must be proven and documented.

Rather than “re-invent the wheel”, ASME has recognized the widespread use of this product, and has adopted the A333 standard for use in pressure vessel (BPVC) and pressure piping (B31.X) applications. The details of this can be found in ASME Boiler and Pressure Vessel Code (BPVC) Section IIA, and is identified as SA333. Note that there may be minor exceptions in the SA version of ASTM standards, and the engineers, end users, purchasers and Manufacturer must comply. Note also that there is often a 5 to 10 year lag between the approved ASTM edition and the approved ASME edition. This means that there can be minor differences between the two specifications. Most engineers who spec SA333 product will also prefer to follow the requirements of the more recent ASTM version (which is usually also more strict), resulting in the common notation ASTM/ASME A/SA106 on the product documentation.

请注意,上有一个下限锰(Mn)in ASTM A333 Gr6 of around 0.30% Mn, though you will typically see around three times this much (around 0.90% Mn). For products that are hot rolled, it will be more common to see values of above 1.20% Mn, as the increased alloying is necessary to attain the impact toughness requirements of the standard. Because of these considerations, this product will commonly have a Mn/C ratio of 4 to 8 depending on the production method. Therefore, ASME B31.3 limits the low temp application of SA333 Grade 6 products to above -50F (-45C).

There is also a limitation on Niobium Nb (in the USA, this element is referred to as Columbium Cb). It seems that this limitation was an attempt to reduce the demand for worldwide Niobium, since the ore is generally mined in Africa and has become a conflict mineral. From the engineering perspective, Niobium is still preferred to other microalloying elements for its ability to increase the ductility of the steel during an impact (i.e, the % shear increases with Niobium content).

A106 does not have its own table of pipe dimensions. Rather, like A333 and API 5L, it reverts to ASME B36.10 for the nominal pipe dimensions. Therefore, A106 pipe products are often multi-certified to similar ASTM A53, A333 and API 5L grades, where the requirements of all these specifications are met.

Note that for welding SA333 products, ASME BPVC Section IX considers SA333 Gr6 to be in the P1G1 alloy grouping (along with SA53 GrB, SA106 GrB).

It is interesting that hydrotesting is not required for this standard, provided that non-destructive testing has been performed, such as ultrasonics or eddy current inspection, and was det