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

What are the different types/grades of stainless steel?

Stainless steel is an alloy that is produced by combining a variety of different base metals to create a new material. Like with other alloys, the final product is considerably stronger than each of the source materials would be on their own.

The History Of Stainless Steel

People have been experimenting with metal alloys for thousands of years. While examples of iron smelting can be found as far back as 1800 B.C., the introduction of crucible steel goes as far back as 300 B.C.

Stainless steel is a very versatile material. Through the years, engineers have experimented with the production of alloys.

By adding and removing certain metals, they were able to produce different types of stainless steel with different characteristics and applications. For example, it is used in everything from the production of kitchen utensils to components for construction projects.

Producing Different Types of Stainless Steel

When producing stainless steel, several different materials can be used to achieve different results. These include:

1.     Carbon
Stainless steel with high carbon content is much more durable and longer-lasting than other alloys. This type of stainless steel is popular for the production of food-grade utensils and cooking implements.

2.     Chromium
Stainless steel made with chromium is much more resistant to corrosion, stains, and tarnishing. One well-known example of this type of stainless in use is the Gateway Arch in St. Louis.

3.     Nickel
Making stainless steel with nickel improves the formability, weldability, and ductility of the material. This also improves its corrosion-resistant properties. Nickel is what allows for stainless steel to be such a versatile alloy.

The Three Primary Types of Stainless Steel

While there are thousands of different types of stainless steel alloy that can be produced, most alloys will fall into one of the following three categories.

1.     Austenitic stainless steel

There are two main characteristics of this type of stainless steel. First, there is a lot of chromium included during the production of austenitic stainless steel. Items produced with this material are more corrosion-resistant. Second, these items tend to be non-magnetic, although they can become magnetic with a cold forming process. These are the most common types of stainless steel alloys.

2.     Ferritic Stainless Steel

This type of stainless steel is the second most common type of alloy and is also magnetic. Items produced with this alloy can be hardened through cold forming and also tend to be less expensive than other types due to the lower nickel content.

3.     Martensitic Stainless Steel

This material is the least common type of stainless steel alloy. Martensitic stainless steel is used in applications where high tensile strength is needed or a lot of impact resistance. In many cases, this material is also combined with a protective polymer coating to improve corrosion-resistance

Different Grades of Stainless Steel Alloys

Within the three primary categories mentioned above, there are also different grades of stainless steel.

Within the austenitic steel types, there are two main grades – grade 304 and grade 316. Grade 304 is known for its high tensile strength of roughly 621 MPa (90 ksi). Grade 316 stainless steel also has a tensile strength of 579 MPs (84 ksi), making the two grades reasonably similar in this regard.

They also both have a high maximum operating temperature. Grade 304 has a maximum temperature of 870°C (1598°F) and Grade 316 has a maximum of 800°C (1472°F).

When comparing 304 vs. 316 stainless steel, one major difference is resistance to chlorides such as salt. Grade 316 is more resistant to the elements, making it a more desirable stainless steel for things like maritime applications.

Ferritic stainless steel also has two main grades – grade 430 and grade 434. Grade 430 stainless steel isn’t as strong as either of the austenitic steels but offers better resistance to nitric acid. It is also still strong enough for most heavy-duty applications.

Grade 434 steel has high tensile strength and maximum operating temperature and is tougher than the 430 grade, including better pitting resistance.

Martensitic stainless steel has only one grade, grade 420. This grade offers slightly less resistance to chemicals than the austenitic and ferritic steels, but it still has good resistance to things such as some alkalis, mild acids, water, and food compounds. It also has great tensile strength and impact resistance. This makes it ideal for producing items like cutlery.

Duplex Stainless Steel

Duplex stainless steel is a family of stainless steel that is made of austenitic steel and ferritic steel in nearly equal proportions. This type of stainless steel is both stronger and more resistant to corrosion than your typical types of stainless steel. Duplex stainless steel is also more ductile than ferritic grades, however, it is not quite as ductile as the austenitic grades.

One of the main differences in the composition is that duplex stainless steel is made with a higher chromium content and a lower nickel content. This not only makes the material stronger, but it also provides cost benefits. For these reasons, duplex stainless steel is often used in applications like pipes and risers in offshore oil rigs.

Grades of Duplex Stainless Steel

Just as with the other types of stainless steel, duplex stainless steel is also broken down into different grades or groups.  The three primary groups are based on the pitting and the corrosion resistance of the material.

• Standard Duplex Steel

Standard duplex steel has a PREN range of 28-38. This is the most typical type of duplex steel used today. It is also sometimes called Grade EN 1.4462 or 2205.

• Super Duplex Steel

With a PREN range of 38-45, super duplex steel was created for use in the oil & gas industry and the chemical industry. This grade of steel is stronger and far more corrosive resistant but is more difficult and more costly to process than standard duplex steel. This is typically grade EN 1.4410.

• Duplex 2507 Stainless Steel

Duplex 2507 stainless steel is another form of super duplex steel. This material is made with 25% chromium, 4% molybdenum, and 7% nickel. This type of stainless steel is known for its resistance to chloride stress corrosion cracking, high thermal conductivity, and a low coefficient of thermal expansion.

• Zeron 100 Stainless Steel

Zeron stainless steel is a super duplex stainless steel that was developed by Rolled Alloys. It contains 25% chromium, 7% nickel, 3.6% molybdenum, along with copper and tungsten additions.

• Lean Duplex Grades

Lean duplex steel has a PREN range of 22-27 and was created for use in less demanding applications such as general building and construction. While the corrosion resistance is going to be similar to standard austenitic steel, it has better strength and mechanical properties.

Applications of Duplex Stainless Steel

Duplex stainless steels are very commonly used in more demanding applications due to their corrosion resistance properties, high mechanical properties, and how strong the material is. This makes the material very popular in a wide variety of industries.

You can find duplex stainless steel used in the oil and gas industry, chemical engineering industry, water and energy industries, architecture industry, and in the construction of things like bridges, seawalls, tunnels, and piers.

18/10 Stainless Steel and Other Types of Stainless Steel

When discussing stainless steel alloys, you’ll typically hear numbers such as 18/10, 18/8, and 18/0 used. These numbers identify the percentage of chromium and nickel that are present in a particular alloy.

For example, 18/8 stainless steel is 18% chromium and 8% nickel; 18/0 stainless steel is 18% chromium and contains roughly .75% nickel, and so on. The chromium-nickel mixture is important to know when deciding on the right alloy for your needs.

For example, if you’re a professional cook, you may have specific requirements for the strength, durability, or heat resistance of various tools and appliances in your kitchen. Understanding the composition of the alloys used in the production of equipment will help choose stronger, longer-lasting products for each application.

The Melting Points for Different Grades of Stainless Steel

One of the more important considerations when choosing the right type of stainless steel for your component or application is the melting point of the specific grade.

One of the reasons stainless steel is chosen over other types of materials, for example, plastic polymers, is its ability to stand up to high-temperatures and still retain its strength and durability.

When comparing the melting points of steel alloys, the number is usually given in a range due to the variations used in the metals used in the production. That number also relates to the metals’ resistance to stress, corrosion, cracking, and other attributes.

As a general rule, metals that have been heat-treated have the following melting points:

• Grade 304: 1400-1450°C (2552-2642°F)
• Grade 316: 1375-1400°C (2507-2552°F)
• Grade 430: 1425-1510°C (2597-2750°F)
• Grade 434: 1426-1510°C (2600-2750°F)
• Grade 410: 1480-1530°C (2696-2786°F)
• Grade 420: 1450-1510°C (2642-2750°F)

It is also important to remember that the maximum use temperatures recommended are usually lower than the maximum number listed in the above chart.

 

Stainless Steel Description

 

201	Chromium nickel manganese steel was developed as a satisfactory alternate for Type 301 for many applications.
301	Chromium nickel steel capable of attaining high tensile strength and ductility by moderate or severe cold working.
302	General purpose chromium nicke stainless steel. Its corrosion resistance is superior to that of Type 301. It can be cold worked to high tensile strengths but with slightly lower ductility than Type 301.
304	Low carbon chromium nickel stainless and heat resisting steel somewhat superior to Type 302 in corrosion resistance.
304L	Very low carbon chromium nickel steel with general corrosion resistance similar to Type 304 but with superior resistance to intergranular corrosion following welding or stress relieving. It is recommended for use in parts which are fabricated by welding and which cannot be subsequently annealed.
305	A high corrosion-resistant alloy with low rate of work hardening, designed for extra deep drawing and spinning.
309	High corrosion-resistant, chromium nickel grade with carbon limited to .08 to reduce carbon precipitation during welding.
310	Similar to 309 with higher resistance to corrosion and oxidation at elevated temperatures.
316	Chromium nickel stainless and heat resisting steel with superior corrosion resistance to other chromium nickel steels when exposed to many types of chemical corrodents; superior creep strength at elevated temperatures.
316L	Low carbon chromium nickel stainless steel with general corrosion resistance similar to Type 316 but with superior resistance to intergranular corrosion following welding or relieving. It is recommended for use in parts which are fabricated by welding and cannot be subsequently annealed.
316TI	Ti stabalized version of 316 with resistance to sensitization. (The formation of grain boundary chromium carbides at evaluated temperatures.)
317L	Similar to 316L but with additional molybdenum to improve corrosion resistance.
321	Chromium nickel steel containing titanium.Recommended for parts fabricated by welding which cannot be subsequently annealed. Also recommended for parts to be used at temperatures between 800°F and 1850°F.
347	Chromium nickel steel containing columbium and tantalum which is recommended for parts fabricated by welding which cannot be subsequently annealed. Also recommended for parts to be used at temperatures between 800°F and 1850°F.
410	General purpose corrosion and heat resisting chromium steel. Good corrosion resistance and fair machining properties. Can be treated to RC35/45.
420	Chromium steel capable of hardening to a maximum of approximately RC53/58.
430	General purpose grade, corrosion-resistant, straight chromium grade, non-heat-treatable.
430LI	Similar to straight 430 in corrosion and mechanical properties. The low interstitials provide improved transverse bending over straight 430.
434	Modification of Grade 430 designed for automotive trim and resistance to atmospheric corrosion.
440A	High carbon grade, high chromium, capable of being heat treated to a hardness range of RC51/62.
444	A low carbon, low nitrogen, ferritic that provides pitting and crevice corrosion resistance superior to most ferritic grades.
A2864	An iron, nickel chromium alloy designed for service up to 1300°F where high strength and corrosion resistance are required.
AM 3508	Similar to 17-7PH. alloy and PH15-7Mo. alloy, but with slightly higher elevated temperature capability.
CARPENTER ® 20 CB3, 10	A highly corrosion-resistant alloy used in the chemical industry for applications where corrosion resistance is extremely critical,superior to the general run of 300 type stainless.
PH15-7Mo®4	Similar to 17-7PH. alloy, but with molybdenum added for higher strength with heat treatment.

Source: https://www.tfgusa.com/types-of-stainless-steel/