Stainless Steel Heat Treatment Process and Cautions

Stainless Steel Heat Treatment Process and Cautions

  Stainless steel has been invented since the early 20th century for less than a hundred years. However, the situation of its development and application is extremely rapid. Especially since the late 1960s. The world’s stainless steel production has maintained an average annual growth rate of 4%. The application range of stainless steel has gradually expanded to various areas of the national economy.An important factor in the rapid development of stainless steel is its resistance to corrosion and stainless steel heat treatment. The advantages and disadvantages of the stainless steel heat treatment process have a great influence on the corrosion resistance and heat resistance of stainless steel.It also plays a decisive role in the processing properties of stainless steel. Therefore, the heat treatment process of stainless steel has always been in a very important position in the production process of stainless steel.

  1. Characteristics of stainless steel heat treatment

  The heat treatment of stainless steel is to change its physical properties, mechanical properties and residual stress. Restores corrosion resistance that is severely affected by pre-processing and heating. The aim is to get the best performance of stainless steel. Or the stainless steel can be further cold and hot processed.

  The so-called heat treatment is to carry out corresponding annealing, quenching and tempering, normalizing. It cause the like for different tissues and different types of stainless steel.

  Stainless steel is a special type of steel. The Nickel and chromium content in steel are high. Due to the existing of alloying elements ,such as nickel and chromium, heat treatment has the characteristics that ordinary steel heat treatment does not have.

  1. The heating temperature is higher and the heating time is relatively longer.

  2. The thermal conductivity of stainless steel is low. The temperature uniformity is poor at low temperatures.

  3. The austenitic stainless steel has a high temperature expansion.

  4, The furnace atmosphere control is very important, to prevent the occurrence of carburizing, nitriding and decarburization and peroxidation.

  5. The surface gloss of stainless steel has a decisive influence on the use and price of the product. The iron oxide produced during heat treatment will seriously affect the surface gloss.

  Be sure to avoid scratching the stainless steel surface and prevent deformation during heat treatment.

  Stainless steel can be classified into austenite, martensite and ferrite according to its structure. (In addition, there are precipitation hardening type, ferritic austenite type, etc.).

  The heat treatment of these three types of stainless steel is different in both the treatment method and the purpose.

  1 Austenitic stainless steel

  This type of stainless steel is the most widely used and the most used. It is characterized by austenite structure at normal temperature and no phase change occurs. It cannot be hardened by heat treatment. However, it can be hardened by cold working. A common heat treatment method is solution treatment.

  2 Ferritic stainless steel

  This type of stainless steel generally does not have a ν-α transition. It is ferrite structure at high temperature and normal temperature, and has no phase change. However, when the steel contains a certain amount of austenite forming elements.Such as carbon and nitrogen, an austenite structure can be formed at a high temperature. Such steel cannot be strengthened by heat treatment, and can only be annealed to eliminate internal stress and facilitate further processing.

  3 Martensitic stainless steel

  This type of stainless steel has a distinct phase change point. It is an austenite structure at high temperature, and martensite transformation can occur during cooling, and it transforms into martensite structure and hardens. Because of its high chromium content and good hardenability, various heat treatment methods such as quenching and tempering can be used.

  In this paper, the heat treatment methods and characteristics of the three types of stainless steel, which are widely used, are discussed separately.

  2. Austenitic stainless steel

  The representative steel grade for austenitic stainless steel is 18-8 steel (304). Because it is an austenitic structure, it is non-magnetic and has no hardenability. Since the steel species does not undergo a phase change, the heat treatment is to heat to a high temperature (generally above 1000 ° C). The austenite recrystallizes at the same time as the carbides produced during processing. The phase decomposed material is solid-dissolved into the austenite. Then, it is rapidly cooled to maintain the austenite in which the carbon is in a solid solution state to a normal temperature. This process is a solution treatment. Table 1 shows the reference annealing temperatures for austenitic stainless steels.

  The heating temperature of the austenitic stainless steel is mainly determined by the solid solution rate of the carbide. It has been pointed out that it takes 3 minutes for the carbide of 304 steel to solidify at 1065 °C. It takes 1.5 minutes at 1176 °C and 10 minutes at 1000 °C. From this point of view, the higher the heating temperature, the better. However, the high heating temperature may cause defects such as excessive grain growth and thickening of the scale. Because austenitic stainless steel cannot refine grains by phase transformation. If the grain size is too large, the tensile strength of the material will be significantly reduced.

  In terms of heating time, the thermal conductivity of stainless steel is low (especially at low temperatures). After rising to high temperature (700-800 ° C), the thermal conductivity is improved. Therefore, for austenitic stainless steel with a large cross section, it is necessary to preheat to 700 to 800 ° C, and then heat up quickly. For austenitic stainless steels with small cross-sections (such as strips), if the heating rate is too slow, the carbides will be analyzed and the solid solution time will be too long. The American company Amcor has developed a classic heating schedule (see Table 2, Table 3). Since chromium-based oxides formed by chromium in stainless steel are difficult to remove in pickling, the formation of chromium-based oxides is controlled during heat treatment, and for stainless steels with special requirements, heat-annealing can be used.

  Table 2: Austenitic stainless steel solution treatment holding time

  Table 3: Austenitic stainless steel solution treatment heating time

  In order to prevent the precipitation of solid solution carbides, the cooling rate is also important. In particular, at 600 to 700 ° C, carbides are precipitated and sensitized. Therefore, rapid cooling must be performed. Due to the low thermal conductivity of austenitic stainless steel, the cooling of the central part is still very slow for materials with a large cross section. No matter how fast. Sensitization is often caused by a large amount of precipitation of carbides. Therefore, in actual production, materials with large cross-sections are generally considered to be stabilized austenitic stainless steels with elements such as Ti and Nb. Because elements such as Ti and Nb have a high affinity for carbon. Such stabilized austenitic stainless steels (such as 321, 347, etc.) can be quenched without water quenching or other rapid cooling measures.

  3. Ferritic stainless steel

  Ferritic stainless steel is based on chromium as the main alloying element. Its content is 12% to 30% Cr. This type of steel is a single-phase structure with no phase change and strong magnetism. Its typical representative steel grade is 430. In the United States in the 1960s, cheap stainless steel 409 was developed with the goal of reducing the cost of stainless steel. Widely used in silencers and sewer pipes for automobiles and motorcycles. It is also a ferritic stainless steel. This steel grade has no hardenability and cannot be hardened by heat treatment like austenitic steel. Moreover, the grain growth due to heating is faster than the austenitic steel and the grain size is large. Therefore, grain growth and austenite transformation occur during heat treatment. The heating temperature should not be too high. The maximum heating temperature of the general annealing does not exceed 850 °C. Table 4 shows the reference annealing temperature for ferritic stainless steel.

  Table 4: Reference annealing temperature of ferritic stainless steel

  When annealing ferritic stainless steel, it is necessary to shorten the residence time in the temperature range of 370 to 550 °C. Especially for high chromium ferritic stainless steel. If the material stays too long in this temperature range, brittleness at 475 °C is easy to occur. That is, the hardness is increased, and the elongation is drastically reduced, even zero. At the same time, the corrosion resistance of the material is also reduced. Experiments have shown that the tensile strength of the material increases by 50% at room temperature after heating for 27 hours at 475 °C. Yield strength increased by l50%. The elongation is zero. In addition, the steel grade has poor weldability (the grain in the weld heat affected zone is coarse and brittle).

  4. Martensitic stainless steel

  The properties of martensitic stainless steel are significantly different from those of the first two stainless steels. As the name implies, it is transformed from a high-temperature austenite state to a cold (quenching) to martensite structure. This type of stainless steel has a distinct phase change point. It can be hardened by quenching. Moreover, because of its high chromium content, good hardenability, it can adjust its strength and toughness in a wide range during tempering. Therefore, martensitic stainless steel can be used both for structural steel and tool steel.

  When martensitic stainless steel is used as a tool steel, it is quenched. For quenching, it is necessary to heat up to above the critical point. In order to solidify the carbide into the austenite. When the temperature is raised to solidify the carbide, the carbon diffusion rate is slow. In order to obtain a uniform austenite structure, the heat of the mouth is generally 50 ° C higher than the critical point temperature. And must also have a certain holding time. In order to fully and uniformly dissolve the carbide. Of course, if the heating time is too long and the heating temperature is too high, the martensite structure will be uneven. The retained austenite structure is increased, so that internal stress is generated due to poor expansion inside the material.

  Martensite steel is a kind of hot crack-sensitive steel. The steel has low thermal conductivity at low temperatures and is prone to cracking when heated rapidly. Therefore, when processing large-section materials, it should be preheated and then rapidly heated. Table 5 shows the reference annealing temperature for martensitic stainless steel.

  Table 5: Reference annealing temperature of martensitic stainless steel

  When used as structural steel, it should be tempered (tempered state) on the basis of quenching. Martensitic stainless steel has temper brittleness. The tempering temperature should generally not be lower than 580 °C. When cooling from the tempering temperature, oil cooling is generally used to avoid temper brittleness. Air cooling may also be used in order to obtain a higher yield limit. However, an important mechanical indicator of structural steel will have a lower impact value. It should be noted that the martensitic stainless steel should be tempered as soon as possible after quenching. If it cannot be tempered as soon as possible, the material is prone to cracks.

  5. Precipitation hardening stainless steel

  Although austenitic, ferritic, and martensitic stainless steels are widely used, as structural steels, there are still some insurmountable defects. Austenitic stainless steel has a lower yield strength. Only about 200N/mm2. Not suitable for use as structural steel. Although the martensitic stainless steel can obtain a high yield strength by heat treatment such as quenching or tempering. However, its corrosion resistance is poor. For applications requiring optimum corrosion resistance and maximum strength, a new type of Cr-Ni stainless steel – precipitation hardened stainless steel (also known as PH stainless steel) has been developed.

  The heat treatment of this new type of stainless steel includes homogenization, full annealing, solution heat treatment, aging treatment, and transformation cooling. Its characteristics are:

  1. The fully annealed state is soft and easy to reprocess.

  2. The required mechanical properties can be obtained by appropriate aging treatment.

  3. It has the same corrosion resistance as similar stainless steel. Improved performance against stress corrosion cracking.

  4. Transition cooling is suitable for cooling below a certain temperature.

  A commonly used precipitation hardening type stainless steel is a martensite type, and its representative steel type is 631 (0Crl7Ni7A1). The heat treatment of the steel is first carried out by solution treatment. After the material is heated to 1000 ~ 1100 ° C, it is quickly cooled. Then, according to different mechanical properties, aging treatment is carried out at different temperatures. Such as 621 ° C, 565 ° C, 510 ° C aging.

  Conclusion

It can be seen from the above analysis that the heat treatment of stainless steel is more complicated. Different heat treatment methods should be adopted according to the characteristics of different steel grades. This will meet the different requirements of users.

Related Article:

Investment Casting Heat treatment Quenching Tempering Annealing Normalizing Different

Difference between normalizing, tempering, annealing and quenching

《Stainless Steel Heat Treatment Process and Cautions》有239条留言

  1. I am the co-founder of JustCBD Store company (justcbdstore.com) and am seeking to expand my wholesale side of business. It would be great if someone at targetdomain give me some advice . I considered that the most ideal way to accomplish this would be to connect to vape shops and cbd stores. I was hoping if anybody could suggest a qualified web-site where I can get Vape Shop Business Contact Details I am presently looking at creativebeartech.com, theeliquidboutique.co.uk and wowitloveithaveit.com. On the fence which one would be the very best choice and would appreciate any advice on this. Or would it be simpler for me to scrape my own leads? Suggestions?

  2. Oh my goodness! Awesome article dude! Thank you so much, However I am encountering problems with your RSS. I don’t know the reason why I am unable to subscribe to it. Is there anybody getting identical RSS issues? Anybody who knows the answer will you kindly respond? Thanx!!

  3. Howdy! This post could not be written much better! Looking at this post reminds me of my previous roommate! He always kept talking about this. I am going to forward this post to him. Fairly certain he will have a very good read. I appreciate you for sharing!

  4. I truly love your site.. Excellent colors & theme. Did you create this web site yourself? Please reply back as I’m hoping to create my own blog and would like to learn where you got this from or exactly what the theme is named. Many thanks!

  5. valtrex medication can i purchase valtrex over the counter valtrex price without insurance http://valtrex10.com/ buy valtrex without get a prescription online where can i buy valtrex online buy valtrex online no prescription
    paxil 30 mg paxil insomnia paxil bipolar http://paxil100.com/ 40 mg paxil paxil drug generic paxil
    paxil erectile dysfunction paxil flu paxil delayed ejaculation http://paxil100.com/ generic paxil paxil erectile dysfunction paxil for panic attacks

  6. wellbutrin bupropion average cost for wellbutrin 150 wellbutrin http://wellbutrin100.com/ wellbutrin hcl generic wellbutrin sr order wellbutrin online uk
    how to get valtrex cheap over the counter valtrex buy valtrex singapore http://valtrex10.com/ valtrex 500 mg tablet price valtrex generic in mexico get valtrex online
    diflucan pills online diflucan best price diflucan gel http://diflucanfavdr.com/ buying diflucan without prescription diflucan pill otc diflucan canada

  7. wellbutrin xl 300 mg can you buy wellbutrin over the counter buy generic wellbutrin online http://wellbutrin100.com/ purchase wellbutrin xl order wellbutrin sr online wellbutrin cost
    wellbutrin cost without insurance wellbutrin 300 mg pill wellbutrin generic price http://wellbutrin100.com/ wellbutrin australia cost average cost for wellbutrin wellbutrin coupon canada
    finasteride generic drug finasteride propecia online pharmacy http://propeciafavdr.com/ buy propecia usa generic propecia no prescription drug finasteride

  8. cost of diflucan tablet diflucan canada coupon diflucan cream over the counter http://diflucanfavdr.com/ can i buy diflucan over the counter in canada buy diflucan otc diflucan online buy
    diflucan 150 mg coupon diflucan cream prescription cost of diflucan in canada http://diflucanfavdr.com/ diflucan 1 otc diflucan order online uk diflucan generic coupon
    diflucan cream diflucan 200mg tab can i buy diflucan from canada http://diflucanfavdr.com/ how much is over the counter diflucan diflucan medicine in india diflucan online prescription

  9. propecia generic propecia pills finasteride cost http://propeciafavdr.com/ purchase finasteride without a prescription cost of finasteride generic propecia
    where to buy propecia propecia generic cheap generic propecia http://propeciafavdr.com/ how do i get propecia cost of finasteride purchase propecia
    diflucan without a prescription diflucan singapore diflucan online prescription http://diflucanfavdr.com/ diflucan gel diflucan capsule 150mg purchase diflucan online

  10. Can I simply just say what a relief to find a person that really knows what they’re discussing online. You definitely know how to bring a problem to light and make it important. More and more people ought to read this and understand this side of the story. I can’t believe you aren’t more popular because you certainly possess the gift.

  11. can i purchase wellbutrin without prescription in canada wellbutrin 65mg wellbutrin prescription mexico http://wellbutrin100.com/ wellbutrin buy wellbutrin generic price purchase wellbutrin
    finasteride 1 mg cost of finasteride propecia generic http://propeciafavdr.com/ finasteride 1 mg generic propecia no prescription online propecia prescription
    best generic wellbutrin 2018 purchase wellbutrin wellbutrin online prescription http://wellbutrin100.com/ buy wellbutrin from canada buy generic wellbutrin online costs for wellbutrin

  12. what antiviral medication for shingles How blood plasma from recovered people en linea farmacia comprar cialis viagra viagra sin receta is there an antiviral medication for the flu. what is a antiviral drug antiviral medications for coronavirus 20 722b461 , how sinus infection treatment. antiviral medicine for flu, over the counter antiviral meds for flu.
    Online farmacia la comprar viagra generico antiviral drugs for cold sores, over the counter antiviral meds for flu. as the public health crisis, what antiviral medication for shingles antiviral medications for herpes simplex virus. En linea farmacia comprar sildenafil generico site antiviral drugs for swine flu in india, do antivirals interfere with birth control. what does antiviral medication do, what is in an antiviral drug what does antiviral meds do for shingles.

  13. price of valtrex without insurance how much is valtrex how can i get valtrex http://valtrex10.com/ can i purchase valtrex over the counter valtrex price uk valtrex cost india
    generic propecia propecia prices propecia without prescription http://propeciafavdr.com/ buy propecia cheap online buy finasteride no rx propecia 5mg for sale
    propecia 5mg for sale propecia witout prescription finasteride proscar http://propeciafavdr.com/ cheap propecia generic buy propecia canada propecia .5 mg

  14. Hi there! This post could not be written any better! Looking through this post reminds me of my previous roommate! He always kept talking about this. I most certainly will forward this article to him. Pretty sure he’s going to have a great read. Many thanks for sharing!

  15. antiviral medications otc the antiviral drug tamiflu online farmacia comprar viagra generico comprar viagra sin receta is coronavirus curable. experts are using protease inhibitors can yeast infection treatment delay period 2019 767e0f8 , antiviral treatment for hiv. How blood plasma from recovered people, what is a logical antiviral drug target in retroviruses.
    Online farmacia la comprar viagra why yeast infection treatment burns, antiviral drug interferon definition. antiviral treatment for the flu, does antiviral medication affect birth control do antiviral meds make you tired. Online farmacia comprar viagra site antiviral treatment for cats, antiviral medication for flu virus. UK-based tabloid the Express carried, antiviral treatment for influenza infection antiviral medication for the flu.

  16. small unsecured loans bad credit i need loan for business i need a loan need financial help. quicken loans ipo unsecured loan in form 3cd, get a loan in canada with bad credit. loan companies for bad credit near me get a quick loan online bad credit 100 8ea2049 best unsecured personal loans in australia, get a loan fast with bad credit, unsecured personal loans australia no credit check. unsecured loans in warrington unsecured loans sydney, get a loan online with no credit loan today bad credit direct lender. loan today bad credit no guarantor cibc jamaica unsecured loans, quick loans bad credit same day where can i get a loan online in nigeria.

  17. propecia buy without per finasteride proscar generic for propecia http://propeciafavdr.com/ finasteride online bonus propecia pill propecia uk
    order valtrex online usa how to get valtrex in mexico buy valtrex without a prescription http://valtrex10.com/ where to buy valtrex over the counter valtrex online australia how much is valtrex generic
    wellbutrin hcl buy wellbutrin without prescription 150 mg wellbutrin http://wellbutrin100.com/ wellbutrin 200 mg cost of wellbutrin generic 75mg costs for wellbutrin

  18. diflucan 200 mg cost diflucan 150 mg prescription diflucan otc canada http://diflucanfavdr.com/ diflucan 150 tab diflucan pill for sale diflucan tablet 500mg
    600mg wellbutrin wellbutrin where to buy wellbutrin 150mg price http://wellbutrin100.com/ no prescription wellbutrin online 150 wellbutrin 300 wellbutrin
    can you buy diflucan over the counter in canada cost of diflucan in india can you buy diflucan over the counter uk http://diflucanfavdr.com/ diflucan buy online canada where to get diflucan diflucan 150 mg over the counter

  19. local car title loan companies i need loan from bank i need a loan unsecured loans in chennai. is it hard to get a jumbo loan quick loans mortgage reviews, unsecured loan calculator usa. unsecured loans up to 50 000 unsecured loans maximum amount 200 98ea204 get a loan no job no credit, ncb jamaica unsecured loans, easy personal loans for debt consolidation. unsecured business loans calculator get a loan fast in ireland, average interest rate to borrow money get an online payday loan. get a personal loan quick unsecured loan cash limit, what places give loans with bad credit unsecured loan for bank.

  20. paxil for panic attacks paxil 30 mg paxil generic http://paxil100.com/ paxil cost paxil weight loss paxil ocd
    how to get valtrex over the counter average cost of generic valtrex 2000 mg valtrex daily http://valtrex10.com/ how to get valtrex over the counter valtrex generic sale valtrex 1g best price
    valtrex 500 mg tablet price 3000mg valtrex valtrex medication for sale http://valtrex10.com/ how to get valtrex prescription online buy valtrex tablets valtrex online canada

  21. diflucan tablet price order diflucan ordering diflucan generic http://diflucanfavdr.com/ how much is over the counter diflucan diflucan 400mg without prescription diflucan generic price
    diflucan 15 mg diflucan 50 mg capsule diflucan cream over the counter http://diflucanfavdr.com/ diflucan 200mg where to buy diflucan pills diflucan without a prescription
    diflucan otc uk diflucan 150 mg tablet price in india diflucan tablets australia http://diflucanfavdr.com/ cost of diflucan over the counter buy cheap diflucan online generic diflucan otc

  22. top software languages 2020 buy autocad gx6605s software download 2020. radeon software adrenalin 2020 settings office tab software free download topic a767e0f 2020 best free software, office program for mac. office automation software programs, office holiday software free office software trial office software suites. office software walmart office layout software free, free office software kingsoft.

  23. 2020 design software minimum requirements buy autocad office suite for mac download. ms office software free download with key radeon software 2020 download tips 049ea76 2020 software jobs, software pes 2020 for pc. free office software reddit, microsoft office 2011 for mac software updates radeon software adrenalin 2020 office software cheap. logo design software 2020 new software 2020 mobile, office software for windows 10.

留下评论