Full Answer
What is the difference between bhn and BHN?
4. Low hardness. BHN ranges from 125 to 220 BHN. Relatively more hard. Bhn ranges from 140 to 245 BHN. 5. Highly ductile and percentage of elongation is more. 3. Hardening: Hardening is a heat treatment process carried out to increase the hardness of Steel.
What is the heat treatment process?
In very simple words I am going to explain the heat treatment process consists of a succession of heating and cooling cycles applied to a metal or alloy in order to obtain the desired properties, such as hardness, ductility, tensile strength, toughness, grain size, etc.
What is heat treatment of steel?
This heat treatment process carried out for steel parts which have been already hardened, in order to reduce bitterness and unequal stress develop as a result of hardening. This process reduces brittleness and hardness but improves the tensile strength of Steel. It increases the toughness of Steel at the expenses of loss of some hardness.
What makes a good heat treater?
Good heat treatment specifications include the material as expressed in the standards—AISI 1040 for a carbon steel, for example, or SAE 4140 for an engineering alloy. It’s not enough to tell a heat treater you’d like a harder part because there are many ways to do that.
What is hardness in heat treatment?
Hardening heat treatments invariably involve heating to a sufficiently high temperature to dissolve solute-rich precipitates. The metal is then rapidly cooled to avoid reprecipitation; often this is done by quenching in water or oil.
What does the Brinell hardness number mean?
The Brinell hardness number is a number proportional to the load or test force of a hard steel ball to the calculated curved area of the indentation formed. The ball diameter is 1, 2.5, 5, or 10 mm.
What is RC in heat treatment?
Rockwell Hardness (RC) Values of Heat Treated Mild Steel Springs.
What does HRC mean in heat treatment?
Source publication. +2.
What is BHN and HRC?
Rockwell Hardness (HRC, HRB) to Brinell Hardness (HB or BHN) Conversion. Hardness is very important for producing rough metal castings, heat treatment and machining process. Rockwell Hardness (HRC and HRB) and Brinell Hardness (HB or BHN) are most commonly used for steel and iron castings.
How do you measure BHN hardness?
Brinell hardness is determined by forcing a hardened steel or carbide ball of known diameter under a known load into a surface and measuring the diameter of the indentation with a microscope.
What is RC 60 hardness?
The higher the number on the RC scale, the harder the steel is. Conversely, the lower the RC scale number is, the softer the steel. Most alloys in knife blades range from soft steels in the RC45 range to hard metals rated in the RC60 category.
What does HRC stand for hardness?
Hardness Rockwell Scale CThere are different Rockwell scales of hardness. The important scale for knife steel is Hardness Rockwell Scale C, often shown as HRC, which is further abbreviated to just Rc.
Is RC and HRC the same?
The HRC — which also goes by other abbreviations like RC — lets you know the hardness of the steel. A low HRC number means the steel is softer and a higher number means it's harder. It's easy to assume that a higher number is better because it's stronger, but that's not always the case.
How hard is 50 HRC?
For example, the average axe has an HRC of about 50, so the sharpened edge can withstand the impact of being hurled into a solid piece of wood without snapping off. An HRC rating of 52-54 is soft but would make a reasonable, inexpensive kitchen knife.
How hard is 54 HRC?
Hardness of knives steel 52-54 HRC: Quite soft steel, reasonable quality. 54-56 HRC: The hardness of many French chefs' knives. The steel is hard enough for kitchen use, but regular use of a sharpening steel is required to keep the knife sharp. Knives of this hardness are usually easy to sharpen.
What is HRA HRB HRC?
Hra means rockwell hardness measured on a scale hrb This preview shows page 2 - 5 out of 5 pages. HRA means Rockwell hardness measured on A scale. HRB means Rockwell hardness measured on B scale. HRC means Rock well hardness measured on C scale.
What is hardness in heat treating?
Hardness is the nearly universal measurement of heat treating performance. This is because specific materials processed to the required hardness perform well under certain loads. For example, spring steel at a hardness of Rockwell C45 performs well as a spring. Experience has shown that a hardness of Rc45 in spring steel correlates with toughness, resilience, and high fatigue strength. The correlation is consistent and Rc45 is accepted as a quality hardness in heat-treated springs, even though the hardness itself is not an important characteristic of a spring. For many parts where tensile strength, toughness, or fatigue strength may be the desired characteristics, these features correlate with hardness values. Most frequently, hardness is specified as the heat treat requirement only because hardness is easy to measure.
What is Rockwell hardness?
The Rockwell method of measuring hardness is a system of several different kinds of penetrators that may be applied to test pieces under a variety of loads. The various combinations of penetrators and loads determine a number of Rockwell hardness scales – each combination of load and penetrator is denoted by a letter. The system is divided into two divisions: superficial and standard. The superficial division employs very light loads and is intended mainly for use on thin work or work with a very thin case. Some Rockwell testing machines are adapted for both the standard and superficial scales and the testing equipment may be manual, which requires an operator, or automated. Many leading heat treating companies will use both methods of testing hardness.
Clearly Identified Materials
The chemical makeup of a part is one of the most critical determinants of how it is heat treated. It’s not enough to state on the spec that a piece is steel alloy.
Specific Process Required
It’s not enough to tell a heat treater you’d like a harder part because there are many ways to do that. Does it need to be through hardened? Case hardened? Does it require stress relief via annealing? Specs that dictate which process is to be used help heat treaters shape the rest of the heat treatment steps that follow.
Hardness Tolerance
For through hardened parts, a prescribed hardness should be included on the spec and expressed as a range.
Case Depth Tolerance
For case hardened materials (i.e., those that are carburized or carbonitrided), specs should indicate whether the desired hardness is expressed as effective case depth or total case depth. Total case depth refers to the distance carbon has diffused into the part. This is usually specified for parts that have thinner case depths after treatment.
Avoid Too Much Information
Sometimes, though, too much specificity can lead to trouble.
Correct Hardness Scales
The scale on which a part’s hardness is determined depends on the heat treatment applied to the part. In the U.S., we typically use the following four hardness scales: Rockwell Hardness, Brinell Hardness, Microhardness and Leeb Hardness.
Inspection Points
Heat treatments are carefully designed to achieve specific results on specific areas of parts, so owners need to clearly identify those areas on which hardness tests are to be conducted. For example, the critical part of the theoretical gear mentioned above is its teeth; case hardening is designed to strengthen that part of the gear while leaving other areas relatively soft and ductile.
Clearly identified materials
The chemical makeup of a part is one of the most critical determinants of how it is heat treated. It’s not enough to state on the spec that a piece is steel alloy. Consult materials standards and use the correct material designation on the spec.
Specific process required
It’s not enough to tell a heat treater you’d like a harder part because there are many ways to do that. Does it need to be through hardened? Case hardened? Does it require stress relief via annealing?
Hardness tolerance
For through hardened parts, a prescribed hardness should be included on the spec and expressed as a range. Tolerances are always more useful than uniform hardness levels because parts can have different hardness values in different regions due to material thickness or closeness to an edge.
Case depth tolerance
For case hardened materials (i.e., those that are carburized or carbonitrided), specs should indicate whether the desired hardness is expressed as effective case depth or total case depth.
Avoid too much information
Sometimes, though, too much specificity can lead to trouble. Specs that include too much process information can paint metallurgists into a corner, forcing them to abide by strict requirements that can end up thwarting their efforts to deliver improved parts.
Correct hardness scales
The scale on which a part’s hardness is determined depends on the heat treatment applied to the part. In the U.S., we typically use the following four hardness scales: Rockwell Hardness, Brinell Hardness, Microhardness, and Leeb Hardness. Become familiar with each scale and which parts and processes should be tested with each.
Inspection points
Heat treatments are carefully designed to achieve specific results on specific areas of parts, so owners need to clearly identify those areas on which hardness tests are to be conducted.
