Grades of Stainless Steel - Cromanite

Cromanite Technical Data

Please note that Columbus has discontinued manufacturing this material and that the following information is published for academic purposes alone.

Summary
 
CROMANITE is a high nitrogen austentic stainless steel which has a unique combination of strength, toughness, ductility, work hardenability and corrosion resistance. The steel performs exceptionally well in materials handling applications, where there is wet sliding abrasion and high impact abrasion. Cromanite is also an excellent candidate material for a variety of high strength applications even at elevated temperatures. In addition, cromanite is a weldable stainless steel that can be readily cut, machined and formed.

Plate can be supplied in the hot rolled and annealed condition (HRA) or in the hot rolled, annealed and descaled condition (No 1).

Properties

CHEMICAL COMPOSITION
Cromanite contains a nominal 19% chromium,  10% manganese and 0.5% nitrogen.  The steel has received a European standard EN 10 088 listing designated as type 1.3820.

MECHANICAL PROPERTIES
In the annealed condition, cromanite has a typical yield strength of 550 MPa, a tensile strength of 850 MPa and an elongation of 50%.  The hardness level is typically 250 HB which increases to a level of approximately 500 HB under impact conditions.  It has an impact toughness of about 250 J.

CORROSION RESISTANCE
The resistance of cromanite to reducing acids is similar to that of the ferritic stainless grade AISI 430, while its pitting resistance (in chloride solutions) is similar to that of the austenitic stainless steel grade AISI 304.

Like AISI 304, cromanite is susceptible to chloride cracking, but it is largely resistant to hydrogen embrittlement.  In addition, sensitization after welding does not occur.

CORROSION WEAR RESISTANCE
Cromanite has been specifically designed to have a combination of high strength, toughness and ductility with a high work hardening rate. Cromanite will work harden under impact conditions to a level of 500 HB.  This work hardening behaviour is similar to Hadfields manganese steel.

However, unlike Hadfields manganese steel, cromanite is a stainless steel with excellent weldability and thus it can also be easily fabricated.

Cromanite performs exceptionally well in high impact wear environments, especially where the environments are corrosive.

A high impact environment will ensure that cromanite will work harden, resulting in the steel being able to absorb large amounts of energy before wear occurs.

CUTTING
Cromanite, like other stainless steels, cannot be cut with a conventional oxy-acetylene torch due to the high chromium content.

Plasma cutting and profiling of cromanite is the fastest and most economical thermal cutting method available and thicknesses of up to 50 mm can be cut successfully.

Laser cutting and profiling of cromanite can be done up to a thickness of 10mm.

Cromanite can be sheared successfully.  It has a shear strength 50% higher than the 300 series stainless steels.  This should be taken into account when determining the maximum shearing capacity on any particular shear.

WELDING
Good results have been obtained using filler metals such as stainless steel types 309 and 307 and duplex types such as 2507/P100, 22/09 and CN 23/12Mo - A, welded by the MMA (SMAW or stick welding) method.

The welding of cromanite to itself is quite straightforward using the manufacturers recommended parameters.

Due to the higher thermal conductivity of cromanite versus the resistively of the electrodes,  these electrodes must be run at the higher end of the recommended amperage range and if necessary even higher.

Care should be taken to avoid damage to electrode coatings due to overheating.  Distortion effects are similar to the 300 series stainless steels and care must be taken to reduce or eliminate this.

When welding cromanite to 3CR12 with the MMA process, electrodes such as types 307 and 309 should be used.  When welding cromanite to mild steel, type 309 electrodes with their higher chromium content are preferred, thus reducing dilution effects.

The higher end of the amperage range should be used to avoid lack of fusion type defects.  Distortion effects are similar to the 300 series stainless steels and care must also be taken to reduce or eliminate this.

When selecting a filler material for welding cromanite, it is important that application be considered.  This is due to the fact that the strength of the weld metal may not match that of the parent metal.

MACHINING
When machining cromanite, heavier feeds and slower speeds should be used to reduce tool build up and minimise work hardening.  Fabricators with experience in machining stainless steels have not encountered problems with the machining of cromanite plate.

Cromanite showed no significant differences in machinability compared to 316L stainless steel in various trials.  If difficulty is experienced with machining, then Ti nitrided tools should be used.  

Applications

Cromanite is an excellent candidate for materials handling applications involving wet sliding abrasion and wet high impact abrasive wear.  This is because it has an excellent combination of strength and toughness, has the work hardening ability of Hadfields manganese steel, and the added advantage of good corrosion resistance.

In addition, cromanite has great potential for variety of high strength applications due to its excellent strength both at room temperature and at elevated temperatures.

Uncoated materials exposed to corrosive environments can form a protective corrosion film on the surface.  Abrasion removes this surface film and damages the newly exposed bare metal, which is left vulnerable to further corrosive attack.  In such cases, materials with poor corrosion resistance, such as carbon steels, have an unacceptable wear rate.  

Technical Data
 
CHEMICAL COMPOSITION  

Carbon	0.08 % maximum
Silicon	1.00 % maximum
Manganese	9.50 - 11.00 %
Phosphorus	0.045 % maximum
Sulphur	0.015 % maximum
Chromium	18 - 20 %
Nickel	1.00 % maximum
Nitrogen	0.4 - 0.6 %

All values given are for 20^oC unless otherwise specified.  

TYPICAL PHYSICAL PROPERTIES  

Density	7 810 kg/m3
Young's Modulus	200 GPa
Poisson's Ratio	0.29
Specific heat capacity	410 J/kgK
THERMAL CONDUCTIVITY
20oC	36.9 W/mK
100oC	32.2 W/mK
500oC	39.0 W/mK
COEFFICIENT OF THERMAL EXPANSION
0 - 100oC	15.7 x 10-6K-1
0 - 300oC	17.3 x 10-6K-1
0 - 500oC	18.7 x 10-6K-1
ELECTRICAL RESISTIVITY
20oC	75 mWcm
100oC	85 mWcm
500oC	117 mWcm

MECHANICAL PROPERTIES 

	MINIMUM	TYPICAL
0.2% Proof Strength (MPa)	450	550
Ultimate Tensile Strength (MPa)	800	850
% Elongation (proportional)	40	50
Impact Toughness (J)	N/A	250
Hardness (HB)	N/A	250

Mechanical properties at room temperature (20^oC)

TYPICAL MECHANICAL PROPERTIES AT ELEVATED TEMPERATURES  

	500oC	800oC
0.2 % Proof Strength (MPa)	270	200
Ultimate Tensile Strength (MPa)	570	330

Short time elevated temperature tensile strength.


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Grades of Stainless Steel - Grade 430

SX 430 Technical Data

Summary

SX430 is a low-carbon plain chromium ferritic stainless steel. The steel has good corrosion resistance in mildly corrosive environments and good resistance to oxidation at elevated temperatures. In the annealed condition the steel is ductile, does not harden excessively during cold work and can be formed using a large variety of roll forming or mild stretch-bending operations, as well as the more common drawing and bending processes. The steel has limited weldability and should not be used in the as welded condition for dynamic or impact loaded structures. Being a ferritic material, 430 is liable to brittle fracture at sub-zero temperatures, and cannot be used in cryogenic applications. As the steel does not contain nickel or molybdenum, it is cheaper than any of the 300 series steels.

Typical Applications

430 is a simple corrosion and heat-resisting grade and finds application in areas where mildly corrosive conditions occur or where scaling resistance at moderate temperatures is required. Typical applications include: Automotive trim, architectural applications such as industrial roofing and wall cladding, kitchen utensils, sinks, washing machine parts and industrial pipe and tube. Materials handling equipment in the mining and sugar industry. Heat resisting applications up to 759^oC.

Chemical Composition
 

Analysis %	oC	Mn	P	S	Si	Cr
ASTM A 240	0.12 max	1.0 max	0.045 max	0.03 max	1.0 max	16.0-18.0
Typical	0.05	0.7	0.021	0.024	0.6	17

Typical properties in the annealed condition

The properties quoted in this publication are typical of mill product and unless indicated should not be regarded as guaranteed minimum values for design purposes. For these purposes refer to the relevant specification.

1. Mechanical properties at room temperature
 

	Typical	Minimum
Tensile Strength, MPa	530	450
Proof Strength, 0.2 % , MPa	360	205
Elongation (Percent in Lo=5.65 So) MPa	25	22
Hardness	160	-

2. Properties at elevated temperatures

Short time elevated temperature tensile strength

Temperature, oC	300	400	550	650	750
Strength, MPa	450	430	220	120	50

Creep data
Stress for a creep rate of 1% in 10 000 h

Temperature, oC	550	600	650	700	750
Stress, MPa	50	30	15	5	3

Recommended maximum service temperature

(Oxidising Conditions)

Continuous Service            750 ^oC
Intermittent Service             850 ^oC

Note: Service in the temperature range 425 -525 ^oC for over 100 hours will cause the steel to be brittle on cooling to room temperature.

3. Corrosion resistance

3.1 Aqueous
 

Temperature oC	20	80
Concentration, % mass	1     5     10     20     80     100	1     5     10     20     80     100
Sulphuric Acid	2     2      2       2       2        1	2     2      2       2       2        2
Nitric Acid	0     0      0       0       1        2	0     0      0       1       1        2
Phosphoric Acid	0     0      2       2       1        0	0     0      2       2       1        1
Acetic Acid	0     0      1       1       1        0	0     2      2       2       2        0

 Key:         0 = resistant    -    corrosion rate less than 100 m/year
                 1 = partly resistant    -    corrosion rate less than 1000 m/year
                2 = non resistant    - corrosion rate more than 1000 m/year

3.2 Atmospheric

The performance of 430 compared with other metals in various environments is shown in the following table. The corrosion rate is based on a 10 year exposure.
 

Environment	Corrosion Rate (um/year)
	SX 430	Aluminium-3S	Mild Steel
Rural	0.0025	0.028	4.3
Marine	0.0381	0.424	25.7
Marine-Industrial	0.0406	0.546	37.1

Welding

430 has adequate weldability for many applications. However it is prone to embrittlement in the weld/haz. The fatigue properties of 430 in the welded condition are poor and it is not recommended for applications where applied tensile or impact loading will be experienced.

Thermal Processing

1. Annealing

Annealed 430 is in the softest and most ductile condition, and may be used for cold-working operations. The annealing temperature range is 760^oC followed by cooling in air.

2. Stress relieving

Stress relief after welding is not usually required, although 200-300^oC is the recommended stress relieving temperature range.

3. Hot working

Initial forging and pressing temperature range:    1100  - 1150^oC
Finishing temperature:                                        below 750^oC

Avoid extended holding times above 1000^oC as excessive grain growth takes place, which severally reduces ductility

 

Note: Soaking times to ensure uniformity of temperature are longer for stainless steels than for carbon steels. Use up to 1/2 times the time employed for the same thickness of mild steel.

 Cold Working

430 can readily be fabricated by cold working. Typical operations include bending, forming, deep drawing and upsetting.

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Corrosion Resisting Steel - Grade 3CR12

3CR12 Technical Data

Summary

3CR12 is a chromium containing corrosion resisting steel developed as an alternative material of construction where the mechanical properties, corrosion resistance and fabrication requirements of other materials such as mild steel, galvanised or aluminised steel, aluminium or pre-painted steels are unsuited.

Originally 3CR12 was not included in any international specifications. However, a 12 per cent chromium steel developed from 3CR12 has been designated DIN type 1,4003 and ASTM/ASME 41003. The former has been incorporated into two Euronorm Standards viz. EN 10088 and EN 10028, 3CR12 conforms to the requirements of the above specifications and is multi certifiable to 3CR12, 1.4003 and 41003, due to its inclusion in the above specifications. 3CR12 vessels and tanks can be designed in accordance to BS5500, ASME, AD Merkblatter codes and the Euronorm design specification currently in preparation.

Although 3CR12 is recognised as the World's most specified 12% Chromium utility steel, it is by no means universal and should not be substituted for higher grades of stainless steel unless detailed corrosion testing has been carried out. Columbus Stainless can be consulted for advice in this regard.

 

3CR12 was designed as a corrosion resisting steel and, as such, will exhibit staining when exposed to aggressive atmospheric conditions. In applications where aesthetic appearance is important, it is recommended that 3CR12 is painted, or a higher grade should be used.

A long term atmospheric corrosion programme conducted over 20 years bv the CSIR has shown 3CR12 to have very good atmospheric corrosion resistance, Stainless steels, with their higher chromium contents, exhibited very low corrosion rates. Because of 3CR12's inherent corrosion resistance, it has been used successfully under wet sliding abrasion conditions such as found in the mining and bulk handling industries. In the case of mild or low alloy steels the presence of moisture in the solids being transported aggravates deterioration of the working surfaces. Not only does the surface rust wear away rapidly exposing bare metal to further corrosion, but corrosion of the working surface leads to 'hang-up' and interrupted flow. 3CR12 resists the corrosive attack and thereby improves flow and reliability, while extending the life of the solids handling equipment.

Although 3CR12 performs very well in corrosion-abrasion applications, no real benefit can be gained by using it under dry abrasion conditions. 3CR12 is not especially suitable under conditions of impact abrasion. (See: A Guide to the Use of 3CR12 in Corrosion Abrasion Applications).

3CR12 has been extensively used in aqueous environments, and has been successful in many applications involving exposure and/or immersion. It is important when using 3CR12 in aqueous environments that the decision be based on a thorough water quality analysis and microbial count. (See: A Guide to the use of 3CR12 in Water).

3CR12 is designed with ease of fabrication in mind and its composition and properties result in good forming, drawing, blanking and punching characteristics. The steel is easily welded by any of the recognised welding processes and should be post weld pickled/cleaned and passivated.

3CR12 has been included in SABS 0162 Part 4 - Code of Practice for the Structural Use of Steel. When replacing carbon steel with 3CR12, it is necessary to redesign mild and constructional steel components using the mechanical and corrosion resisting properties of 3CR12 in order to gain full advantage of potential material and fabrication savings.

This document covers black (hot rolled and annealed) 3CR12 as well as pickled (No1 and 2B) material, 3CR12 is available in the following finishes HRA, No 1, 2D and 2B, Whereas the latter three finishes can be used for all suitable 3CR12 applications, the HRA finish should only be used in applications where wet sliding abrasion occurs. It should never be used in immersion conditions The mechanical properties of the HRA material are similar to those of the No 1 finish material. A long term atmospheric programme conducted over 20 years by the CSIR has shown 3CR12 to have very good atmospheric corrosion resistance.

Properties of 3CR12
  Chemical Composition
 

%C	%Ni	%Mn	%Si	%P	%S	%Cr	Other
0.03   Max	1.5   Max	1.5   Max	1.0   Max	0.03   Max	0.03  Max	11.0 - 12,0	Ti  0.6 Max

  1. Mechanical Properties
 

Ultimate Tensile Strength (Transverse)	450 MPa Min
0.2% Offset Proof Strength   (Transverse)	< 6,0 mm thick  -  320 MPa Min  > 6,0 mm thick  -  280 MPa Min
Elongation (in 50mm)	< 6,0 mm thick  =  20% Min
	> 6,0 mm thick  =  18% Min
Hardness	< 12.0 mm thick  -  220 Brinell Max
	> 12.0 mm thick  -  250 Brinell Max
Charpy Impact (Ambient temperature)	35 J/cm2 Min

2. Fatigue

Extensive testing has shown that 3CR12 behaves in a similar manner to constructional steels such as BS4360 Grade 43A in terms of fatigue. Accepted procedures when desgning for fatigue loaded structures should be followed. BSBS7068 can be used.
 
3. Physical Properties

At Room Temperature.
Density		7 740 kg/m3
Elastic Modulus (Tension)		200 GPa
Specific Heat Capacity		478 J/kg K
Thermal Conductivity	@ 100oC	30.5 W/m K
	@  500oC	40.0 W/m K
Electrical Resistivity		66 x 10-9Wm
Co-efficient of	0-100oC	11,1 mm/mK
thermal expansion	0-300oC	11.7 mm/mK
	0-700oC	12.3 mm/mK
Melting Range		1'430 - 1'510oC
Relative Permeability		Ferromagnetic

4. Corrosion Resistance

3CR12, with chromium as its major alloying element, is not intended as a material for use in contact with process solutions such as acids, salts, etc.  It is more suited to applications involving ancilliary equipment on process plants such as cable racking, stairways, flooring, handrailing, etc.  3CR12 is a "corrosion resistant" rather than "stainless" steel and as such, will tend to form a light, surface rust or discolouration when exposed to aggressive environments.  This patina is superficial and does not affect the mechanical properties of the steel.
Should aesthetic or hygienic qualities be of prime importance, stainless steels rather than 3CR12 should be considered, although 3CR12 can be successfully painted with a number of paint systems.

Aqueous Corrosion

It is recommended that consultations be held with Columbus Stainless technical staff on the use of 3CR12 in water.
At the design stage, efforts must be made to avoid crevices, sedimentation, stagnancy, high operating temperatures etc., as these facts will have a negative impact on the performance of the steel.
3CR12 is not recommended for use in hot water systems unless detailed testing has previously been carried out.

Atmospheric Corrosion

A long term atmospheric corrosion programme conducted over 10 years by the CSIR has shown 3CR12 to have very good atmospheric corrosion resistance.  Data on the performance of various materials at different test sites is available from VRN Technical staff.

5.  Fabrication of 3CR12

Note:  A detailed 3CR12 fabrication guideline is available from Columbus Stainless.

Cutting

For general fabrication requirements, the most effective cutting methods are:                       
                                                         

Abrasive disc	- use dedicated discs
	- avoid overheating
	- vitrified or resinoid aluminium oxide discs  recommended
Plasma	- oxygen-free nitrogen is the most economical primary cutting gas.    (Other gasses can be used)
	- heat discolouration must be removed prior to use in a corrosive   environment
Guillotine	- use well sharpened and correctly alligned and set blades to avoid sheared breaks and rollover.
	- capacity of guillotine (rated in terms of mild steel thickness) must be   downrated by 40% of 3CR12.

Forming

It is important to note that due to the higher proof strength of 3CR12, more power is required for most forming operations, than would be needed for mild steel.
When bending 3CR12 it is important to maintain a minimum inner bend radius equal to twice the material thickness.  Reverse bending at ambient temperatures is not recommended - the bend area should be preheated to +- 150^oC .  Edge cracks can be avoided by placing the cut face on the outside radius of the bend and the sheared face on the inside.  This type of cracking can also be prevented by grinding the outside radius point of bending into a rounded profile, thus eliminating the natural stress concentration point.

Welding

Manual metal arc, metal inert gas and tungsten inert gas are the common procedures used.  All welding procedures must ensure that heat inputs are kept to a minimum.  Down-hand welding is the preferred welding position and bead runs rather than weaving should be used.  Austenitic stainless steel filler metals such as AWS ER 309L, 308L, or 316L should be used.
In order to ensure adequate corrosion resistance in weld zones, it is necessary to remove all heat tint by pickling or by some mechanical means and passivating with a cold 10% nitric acid solution after cleaning.  Thorough washing with clean, cold water pickling and passivating is essential.

Machining

In the annealed condition, 3CR12 has machining characteristics similar to AISI 430 i.e. a machinability rating of 60.  The reduced extent of work-hardening compared to austenitic stainless steel eliminates the need for special cutting tools and lubricants.  Slow speeds and heavy feeds with sufficient emulsion lubricant will prevent machining problems.

Fastening

Where 3CR12 sections are to be bolted, stainless feel fasteners such as type 304 or 431 are preferred.  If bolted structures are to be used in humid or wet environments, it is strongly recommended that compressible, non-absorbant gaskets such as rubber be used.

Thermal Processing

Annealing
3CR12 is supplied in the annealed condition, its softest and most ductile state.  After severe cold forming operations or after hot forming operations above 750^oC, annealing may be required.  Annealing is carried out at 700-750^oC  followed by air cooling.
Soaking times are 12 hours per 25mm section.

Stress Relieving
Stress relieving is not recommended for 3CR12.  If it is essential, temperatures of not more than 450^oC  should be employed.

Hot Forming
Any hot forming should preferably be conducted at temperatures below 750^oC. The recommended temperature range is between 600^oC and 700^oC and annealing should be performed after forming. 

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