|Subject on This Issue:
|* Steels & Properties
|* Heat Treatment
REVIEW QUESTIONS ON
BASIC HEAT TREATMENT MATERIALS AND PROCESSES
Heat Treatment Processes
- What is heat treatment?
- What heat treatment does?
- How many types of heat treatment processes?
- Describe the purposes for conducting quenching, tempering, annealing.
- What are the differences in processing parameters among the heat treating processes?
- What is the difference between martempering and austempering?
- Describe the difference between annealing and normalizing?
- What is the difference between stress relieving and annealing?
Iron-Cementite Phase Diagram
- Sketch and label the steel section of the iron-carbon system, using the terms austenite, ferrite and cementite.
- Explain the terms critical points A1, A3, and Acm
- What means eutectoid, hypo-eutectoid and hyper-eutectoid?
- How do the structures of hypo-eutectoid and hyper-eutectoid steels differ at room temperature as a result of them being slowly or fast cooled from the austenitic state?
- What is the effect of the percentage of carbon in steel on properties?
- Explain the effects of cooling rate and carbon content on the microstructure and properties of steels.
- Describe the forms of the microstructure of eutectoid alloy steel.
- How to relate the phase diagram to heat treatment?
- How to select soaking temperatures for normalizing, annealing and quenching by reference to the phase diagram?
- What would be the expected structure of 2363 if it were cooled slowly from the austenitic state?
- How would the answer to Problem 10 have differed if the steel had been quenched?
- A carbon steel with 1.1% carbon is to be given a full annealing treatment. What temperature and cooling rate are necessary for such a treatment?
- Explain, by reference to the iron-carbon thermal equilibrium diagram, the procedures used for case hardening of a low carbon steel.
- Is the hardness of martensite identical?
- How many types of TTT curves?
- What is the difference between IT and CCT diagram?
- State what is meant by the critical cooing rate.
- What is the hardness value if the microstructure contains 50% pearlite and 50% martensite?
- How to apply TTT diagrams into heat treating operation?
Materials and alloys
- What means ferrous and non-ferrous alloys? How many types of ferrous alloys?
- How to classify low, medium and high carbon steels?
- How to classify tool steels and stainless steels?
- How many types of tool steels are heat treated in Hitech? Please write down.
- What means alloying elements? Which elements are the austenite stabilizer?
- In what way does the alloying element affect the structure of the steels?
- Explain AISI 1008, AISI 4140, 760, DF2, 2510: Which group? Difference?
- Grain size 2 and 6, which one is finer?
- How does the grain size affect the properties of the tool steels?
- How to control grain size during heat treatment?
- Why do the materials have different hardnesses?
Heat Treatment of Steels
- Describe the following heat treatments applied to tool steels:
- Full annealing
- Stress relieving
- How many types of heat treating processes in Hitech?
- What means bright annealing?
- When does the expansion or shrinkage occur during hardening?
- State the form of heat treatments needed to effect the following changes:
- 0.4 carbon steel to be made as soft as possible;
- 0.4 carbon steel to be made as hard as possible;
- D2 tool steel to be made as hard as possible;
- D2 tool steel to be made as soft as possible.
- Alloy steels are typically hardened by oil quenching while plain carbon steels are generally water quenched. T or F
- Oil quenching steel DF2 cannot be quenched by gas. T or F
- The proper austenitizing temperature for hardening is typically 50º - 90ºC over the upper critical transformation temperature. T or F
- Annealing, normalizing and hardening of a given steel are typically done at the same temperature. T or F
- It is important to know the stock allowance on parts prior to hardening because:
- It will help determine how much distortion is acceptable.
- It will determine the type of atmosphere that can be used.
- It will determine the quality requirements for surface contamination.
- All of the above.
- Soak times are a function of:
- The section thickness of the part
- The time required for the furnace to reach temperature.
- The time required to ensure that the center of the most massive part has reached temperature and the necessary transformation has taken place.
- a and c
- a and b
- The longer the soak time, the better properties the parts. T or F
- What is the function of preheating during heating up?
- Why do some alloys need two preheating stages?
- Give example. How would the hardness of 0.6% carbon steels differ if the following heat treatments were applied?
- Heat and soak at 800ºC and then quench in cold water.
- Heat and soak at 800ºC and then quench in oil.
- Heat and soak at 800ºC and then slowly cool in furnace.
- How does increasing the temperature at which a tool steel is tempered change the final properties of the steel?
- How does the hardness of the steel differ for HSP41 as a result of the differing tempering temperatures?
- Why do some alloys adopt 2 or 3 times tempering?
- Which types of stainless steel can be hardened?
- Describe the forms of the microstructure of a tool steel.
- How does the presence of retained austenite affect the properties of the tool steels?
- What type of heat treating procedures would you suggest for hardening XW41, D2, SKD11 and 2510?
- Explain how AISI H13 and ASSAB 760 steels would be hardened. Give details of the temperatures involved.
- Why are cylindrical objects quenched vertically?
- Decarburization and scaling are the same thing. T or F
- What is the most reactive constituent in air?
- To fully anneal austenitic stainless steels they usually must be heated to 1060-1090ºC and water quenched. Rapid cooling is required to prevent:
- Excessive oxidation
- Grain boundary carbide precipitation
- Excessive distortion
- Spotty hardness
- What is hardenability?
Inspection and Testing
- The hardness of a material is it’s resistance to plastic deformation by penetration. T or F
- A Rockwell hardness tester must be calibrated to comply with ASTM standard E-18. T or F
- Rockwell hardness test blocks when completely filled with test impressions should be:
- Turned over and used on the other side
- None of above
- Rockwell hardness testers are out of calibration when the reading on a test block is:
- Below, but not above, the certified range
- Above, but not below, the certified range
- Above and below the certified range
- Any of the above
- When Rockwell testing using a 1/16” ball, a piece of steel with high hardness is tested by mistake, the ball should be:
- Visually examined for deformation and reused if none is noted.
- Replaced with a new ball
- Rotated to a new spot before being reused.
- None of the above
- Some factors that determine the suitability of a certain Rockwell scale, include:
- Type and hardness of the material
- Thickness of the material being tested
- Depth of case
- All of the above
- When Rockwell testing, the surface condition of the test area is not important because the minor load will compensate for any irregularities. T or F
- The standard Rockwell C diamond and the superficial N diamond are interchangeable if used only a short time. T or F
- If Rockwell hardness readings are erratic the cause(s) may be:
- The back surface of part is uneven
- The diamond indentor is chipped.
- The sample was burned during preparation
- There is dirt under the indentor or anvil
- All of the above
- A correction factor must be used when Rockwell testing cylindrical parts. These numbers are ____ the observed number.
- Three readings should be taken on a single part inspection so that if one is out of spec it can be ignored. T or F
- The Brinell hardness can be used to determine approximate tensile strength of quenched and tempered steel. T or F
- A Brinell test is typically used for checking the components with low hardness. T or F
- Brinell, Rockwell and microhardness readings are all obtained by measuring the size of the impression. T or F
- Grinding an area deep enough to remove surface decarburization is not recommended because it may cause the part to be scraped. T or F
- The minor load applied during a hardness test is the same for HRC, HRA and HR15N. T or F
- The effective case depth can be measured by etching a sectioned test pin. T or F
- A Rockwell C test could be considered a destructive test on finished parts. T or F
- The back surface of a part being Rockwell inspected must be smooth, clean and parallel to the surface being tested. T or F
- When hardness testing thin parts, some deformation of the back surface is acceptable. T or F
- Brinell testing is normally performed using either 3000 or ______kg loads.
- Rockwell testing is normally performed using either 100 or ______kg loads.
- Vickers testing is normally performed using either 1000 or ______g loads.
- Specify the hardness test methods most appropriate for the following:
- Quench and tempered steel parts over ½ in. section, _____________________
- Annealed steel plate under ¼ in. thick, _______________________________
- Carburised and hardened parts with 0.020/0.025 in. case, _________________
- Carburised and hardened parts with 0.03 in. plus case, ___________________
- Aluminum casting in T6 condition, ___________________________________
- Hardened tool steel part, ___________________________________________
- Nitriding part, ___________________________________________________
- Define “effective case depth” and how is it measured.
- Unlike standard Rockwell hardness testing, microhardness test impressions are not affected by how close they are to each other because of their small size. T or F
- What is the purpose of mounting a specimen prior to preparing it for metallographic examination?
- Microscopic examination is normally performed at magnification from 100x to 750x. T or F
- Hardness can be tested by the microscopic examination. T or F