Heat Treating the Kitchen Sink
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Heat Treating the Kitchen Sink Situation: A manufacturer of stainless steel kitchen sinks is design constrained by the strain (work) hardening of the stainless material during drawing. Some sinks are relatively shallow, and these can be formed without risk of fracturing. However, deeper bowls will fracture if too much strain is induced. As kids, many of us played with a lot of ordinary things, and one of them might have been a steel coat hanger. If you bent it back and forth numerous times, you would notice the material became harder and harder to bend until it actually broke, or fractured, at the point of the bending. The same basic thing is true for the material sinks are made from. This is where Solar Atmospheres plays a pivotal role in the manufacture of the stainless steel sink. Objectives: • Eliminate work hardening through annealing • Cost-effectively anneal a bulky but lightweight sink • Prevent handling damage of a softened, bulky sink • Optimize thermal cycle to prevent metallurgical problems (scrap) Solution: Most of us have used a stainless steel sink at some point in our lives, but not many have actually thought about how one is made. If you look carefully at one of these sinks, you will quickly see it is monolithic – formed into a shape from one piece of steel. The steel in this case is called austenitic stainless steel – a single- phase, corrosion-resistant steel that cannot be hardened by heat treatment. The sink manufacturer forms the sink bowls from flat sheet product into the basic shape of the sink to a point prior to becoming so hard they fracture. Sinks are then sent to Solar Atmospheres for annealing, which is a process that effectively eliminates the strain-induced work and makes the material ductile, or soft, so it can be further formed. Although simple in concept, this can be logistically challenging. There are several reasons for this. First, when the sink bowls are annealed, they are relatively soft and can be dented fairly easily. Careful handling and attention to detail is required. Secondly, large sinks take up a lot of furnace area without a lot of weight. If you have ever bought a stainless steel sink you know they are reasonably priced, so a large quantity of sinks must go into a furnace batch to afford the customer economy of scale. Of course, Solar Atmospheres has large furnaces that provide for this economy. Annealing time and temperature parameters are critical as well because excessive soak time at elevated temperature can cause metallurgical problems that could render the material scrap. Conversely, under-annealing the product means the bowls could still have residual strain-induced hardness and could fracture when further forming is performed. Developing the parameters is like walking a fence. If you lean too far to either side, you will fall off. We interact with many materials and products every day, and many metal products have had to undergo some sort of heat treatment at some point in the manufacturing process. Solar performs many of these heat-treat processes, and we can truly say we process everything … even the kitchen sink. IH For more information: Contact Mike Moyer, director of sales, Solar Atmospheres, Souderton, Pa. at 215-721-1502 or [email protected]. Find them on the web at www.solaratm.com 20 July 2011 - IndustrialHeating.com Engineering Solutions to Everyday Industrial Problems Problem Solver
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Case study on the heat treatment of a kitchen sink.
Transcript of Heat Treating the Kitchen Sink
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Heat Treating the Kitchen SinkSituation: A manufacturer of stainless steel kitchen sinks is design constrained by the strain (work) hardening of the stainless material during drawing. Some sinks are relatively shallow, and these can be formed without risk of fracturing. However, deeper bowls will fracture if too much strain is induced. As kids, many of us played with a lot of ordinary things, and one of them might have been a steel coat hanger. If you bent it back and forth numerous times, you would notice the material became harder and harder to bend until it actually broke, or fractured, at the point of the bending. The same basic thing is true for the material sinks are made from. This is where Solar Atmospheres plays a pivotal role in the manufacture of the stainless steel sink.
Objectives: Eliminate work hardening through annealing Cost-effectively anneal a bulky but lightweight sink Prevent handling damage of a softened, bulky sink Optimize thermal cycle to prevent metallurgical problems (scrap)
Solution:Most of us have used a stainless steel sink at some point in our lives, but not many have actually thought about how one is made. If you look carefully at one of these sinks, you will quickly see it is monolithic formed into a shape from one piece of steel. The steel in this case is called austenitic stainless steel a single-phase, corrosion-resistant steel that cannot be hardened by heat treatment. The sink manufacturer forms the sink bowls from at sheet
product into the basic shape of the sink to a point prior to becoming so hard they fracture. Sinks are then sent to Solar Atmospheres for annealing, which is a process that effectively eliminates the strain-induced work and makes the material ductile, or soft, so it can be further formed. Although simple in concept, this can be logistically challenging. There are several reasons for this. First, when the sink bowls are annealed, they are relatively soft and can be dented fairly easily. Careful handling and attention to detail is required. Secondly, large sinks take up a lot of furnace area without a lot of weight. If you have ever bought a stainless steel sink you know they are reasonably priced, so a large quantity of sinks must go into a furnace batch to afford the customer economy of scale. Of course, Solar Atmospheres has large furnaces that provide for this economy. Annealing time and temperature parameters are critical as well because excessive soak time at elevated temperature can cause metallurgical problems that could render the material scrap. Conversely, under-annealing the product means the bowls could still have residual strain-induced hardness and could fracture when further forming is performed. Developing the parameters is like walking a fence. If you lean too far to either side, you will fall off. We interact with many materials and products every day, and many metal products have had to undergo some sort of heat treatment at some point in the manufacturing process. Solar performs many of these heat-treat processes, and we can truly say we process everything even the kitchen sink. IH
For more information: Contact Mike Moyer, director of sales, Solar Atmospheres, Souderton, Pa. at 215-721-1502 or [email protected] them on the web at www.solaratm.com
20 July 2011 - IndustrialHeating.com
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