The analysis study of the new standard 《 seamless steel tube used in oil cracking》

Thepetrochemical industry is one of important basic industry in national economicconstruction. With the development of our economy, petrochemical industrytechnology is approaching the direction of oil chemical integration, depth processing and clean efficientproduction process. Seamless steel tubes are the main raw materials in petrochemicalindustry factory building, equipment manufacturing, and in the operation andmaintenance. Main working feature condition of seamless steel tube used for petrochemicalis high temperature (or low temperature), high pressure and high corrosionresistance, contact medium is often poisonous and harmful, inflammable andexplosive dangerous goods, etc. Regarding to the seamless steel tubes inpetrochemical plant, especially furnace tube, heat exchanger tube and runningtube are used widely.

With the change of structures of crude oil in China'spetrochemical industry (in crude oil, the average sulfur content change fromthe current 1.0% to about 2.0%), and with the development of constantly towardslarge-scale for petrochemical plant, adopting new techniques and new equipment,the variety and quality of seamless steel tube are put forward higherrequirements. Since new edition national standard GB9948-2013 《Seamless steel tubes forpetroleum cracking》issued on September 18, 2013, was formally implementedon July 1, 2014, Anhui Tianda has a deep understanding of the standard, study petrochemicalindustry design in-depth, do research of technical requirements and demand ofpetroleum cracking tubes in current situation, optimizes the production process,heat treatment and quality inspection, etc., step out of a characteristicdevelopment way of petroleum cracking tube accord with its own development, andmeet the different demands of petrochemical industry.

For example, 12Cr5Mo (elder version standard grade 1cr5mo), there are two kinds of delivery conditions for the new standardsrequirements, annealing and normalizing + tempering condition respectively, distinctionwith 12Cr5MoI and 12Cr5MoNT. technology department of Anhui Tianda, optimize thedifferent production process according to different requirements of two kindsof delivery status. Using the universal rolling technology, namely billet test → billet cutting →billet centering→ billet annular furnace heating → piercing → hot rolling →step furnace re-heating →sizing →cooling.Using technology of controlled rolling and controlled cooling, the surfacequality of tubes is good, and has high dimensional accuracy, uniformorganization. And heat treatment takes special process requirements, 12Cr5MoIadopts full annealing process, reduce the hardness of steel tubes, improvestoughness and subsequent processing performance. 12Cr5MoNT adopts normalizing +tempering process, and improve the strength of steel tube, refine the grain,improve performance of heat resistant and corrosion resistantance. mechanicalproperties requirements for steel pipe of different heat treatment system atroom temperature as follows:

GRADE

REQUIREMENTS

TENSILE STRENGTH

Rm/MPa

YIELS STRENGTH

ReL/MPa

ELONGATION RATE A/%

IMPACT ENERGY KV2/J

BRINESS HARDNESS

longitudinal

transverse

longitudinal

transverse

≥

≤

12Cr5MoI

STANDARD VALUE

415~590

205

22

20

40

27

163HBW

MILL CONTROL VALUE

430~580

225

23

21

45

30

160HBW

12Cr5MoNT

STANDARD VALUE

480~640

280

20

18

40

27

--

MILL CONTROL VALUE

500~630

300

21

19

45

30

--

Annealing condition 12Cr5MoI steel tube ismore suitable for petrochemical pipe processing, connection pipes of oilrefinery, etc., mainly used in the coal liquefaction project. While normalizing+ tempering condition 12Cr5MoNT steel tube is more suitable for furnace tube ofoil refinery and tubes for heat exchanger, mainly used for high pressurehydrocracking and ethylene projects in high sulfur and high acid corrosiveenvironment. Accord with SH/T 3129-3129 《 Material selection for design of equipment and piping inunits processing sour crude oils》, SH/T 3096-2012《Material selectionguideline for design of equipment and piping in units processing sulfur crudeoils》, NACEMR0103《Materials Resistant to Sulfide Stress Cracking in Corrosive PetroleumRefining Environments》, etc..

The new edition GB9948-2013 standard combineswith production and current application status of China's petroleum crackingtube, adopt parts of terms and clause of international advanced standard suchas ASTM A335 / A335M - 10 《Standard Specification for SeamlessFerritic Alloy-Steel Pipe for High-Temperature Service》, ASTM A213 / A213M - 10, 《Standard Specification forSeamless Ferritic and Austenitic Alloy-Steel Boiler, Superheater, andHeat-Exchanger Tubes》, and EN 10216-2：2002《Seamless steel tubes forpressure purposes - Technical delivery conditions - Part 2 : non-alloy andalloy steel tubes with specified elevated temperature properties》, the index is not lower than the relativestandards. Advanced and reasonable technology, not only conforms to China'snational conditions, but also can satisfy the requirement of specialenvironment application.

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