Equipment designing requires a lot of knowledge in terms of dimensioning, use of equipment, rules of thumbs and their bases, and even the calculations and formulas itself. Along with these considerations lie a ‘seem to be simple’ yet complicated question: What would this equipment be made of? That is the part of choosing the material of construction qualified for the job.

 

Stainless steels were renowned for their numerous applications in the field of process industries because of its name itself – stainless. There are different stainless steel grades depending on the composition. Although these stainless steel grades share considerable similarities in physical and chemical properties, each one has their own applicability and outstanding property making them distinguished from the other grades.

 

Stainless Steel 430 (SS430) is a ferritic stainless steel because of its high Fe content peaking at 79% by composition with low carbon and up to 18% chromium (ASKZN, 2015). This composition gives the uniqueness in properties to be exhibited. Table 1 summarizes some of the physical properties of SS430:

 

Table 1. Physical properties of grade 430 stainless steels in the annealed condition

Grade Density (kg/m3) Elastic Modulus (GPa) Mean Coefficient of Thermal Expansion
(μm/m/°C)		 Thermal Conductivity
(W/m.K)		 Specific Heat 0-100°C (J/kg.K) Electrical Resistivity (nΩ.m)
0-100°C 0-315°C 0-538°C at 100°C at 500°C
430 7750 200 10.4 11.0 11.4 26.1 26.3 460 600

Source: AZoM.com, 2015

 

Since mechanical properties plays a significant role for the design purposes, it was also included and given by Table 2:

 

Table 2. Mechanical properties of grade 430 stainless steels

Grade Tensile Strength (MPa) min Yield Strength 0.2% Proof (MPa) min Elongation (% in 50mm) min Hardness
Rockwell B (HR B) max Brinell (HB) max
430 483 310 22 85 183

Source: AZoM.com, 2015

 

On the other hand, chemical composition that plays the major role on how applicable a material of construction to the desired design and purpose, were tabulated below:

 

Grade C Mn Si P S Cr Mo Ni N
430 min.

max.

 –

0.12

 –

1

 –

1

 –

0.04

 –

0.030

 16

18

 – –

0.50

 –

Source: AZoM.com, 2015

 

This chemical composition is responsible to its outstanding physical and chemical properties. Some of these chemical properties are heat resistance and corrosion resistance. In intermittent usage, it can resist oxidation up to 870ºC (1598ºF) and up to 815ºC (1499ºF) in continuous usage. Although capable to resist oxidation at high temperature, when heated for a long time at range 400-600ºC (752-1112ºF), tendency to become brittle is a problem but can be solve with annealing. Excellent stress corrosion resistance is exhibited by ferritic stainless grades. Grade 430 is remarkable for its good corrosion resistance to numerous substances such as organic acids and nitric acid. This notable resistance is maximized in well-polished or buffed condition.

 

When it comes to fabrication, grade 430 is easy to bend and form due to its low working hardening rate. On the other hand, its low ductility rate makes it difficult of perform very rough operations. Extreme cold heading can be handled by grade 430 wires while for extreme cold working, sub-critical intermediate annealing may be necessary (AzoM.com, 2015). Methods used include the following: heat treatment, welding, machining, annealing, and cold working.

Heat treatment is a preparatory process for solution annealing and other fabrication methods. Grade 430 is heated to 815 – 845ºC, then has to be slow furnace cooled to 600ºC and followed by quick air-cooling. It should be noted that cooling between 540 and 400º causes embrittlement. Furthermore, heating should be performed to 760 – 815ºC if sub-critical annealing is desired.

Welding requires pre-heating at 150 – 200ºC; high machinability is exhibited in comparison with other grades. Annealing starts at 1500ºF and slowly cooled to 1100ºF at which 430 is in the softest and most ductile condition where it can be used in cold working. Fabrications using cold working includes the operations such as bending, forming, deep drawing and upsetting.

 

When it comes to economic considerations, stainless steels were relatively expensive due to its numerous applications and long term of service. Yet it is stocked by 84 North American distributors and produced by 54 large mills. In Philippines, it was distributed and supplied by some Filipino-owned companies but largely by foreign companies well-established even in other countries. This material is stocked primarily in Flat Rolled Products by 63 distributors but is also available to a lesser extent in Wire Products, Tubular Products, Bar Products, and Fasteners (Metal Suppliers Online, 2015). Increasing demand for stainless steels can be observed due to its toughness and applications from kitchen wares to industrial equipment. Relative high prices of stainless steels were balanced by its excellent service in field of construction of buildings and equipment. Prices ranges from 1000-6000 US dollars per ton depending on the form of the stainless steel needed.

 

For the applications in Chemical Engineering, it can be used from certain chemical applications due to its resistance in nitric acid and other organic acids to handling equipment used in mining and sugar industry. It is also used in pipes and tubes for transport of corrosive chemicals and in heat exchangers for its scaling resistance at moderate temperatures. Moreover, it has paved its way of application in architecture including industrial roofing and wall cladding. Kitchen utensils and sinks were not exemptions from its numerous applications.

 

 

References:

Alibaba.com. 2015. Stainless steel 430. Retrieved from <http://www.alibaba.com/countrysearch/PH/ss-430.html&gt;

ASKZN. 2015. Stainless steel directory: stainless steel grade 430. Retrieved from <http://www.fanagalo.co.za/stainless-steel/tech-grade-430.htm&gt;

AZO Materials. 2015. Stainless steels – specifications, grades and properties, supplier data by Aalco. Retrieved from <http://www.azom.com/article.aspx?ArticleID=2874&gt;

Metal Suppliers Online. 2015. Stainless steel 430. Retrieved from <http://www.suppliersonline.com/Research/Property/result.asp?FamilyID=14&MetalID=1947&Chemical=1&Physical=1&Mechanical=1&gt;

Penn Stainless Products, Inc. 2015. 430 Stainless steel. Retrieved from <http://www.pennstainless.com/stainless-grades/400-series-stainless/430-stainless-steel/&gt;