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SECTION 12 HARDNESS TESTING

SECTION 12 HARDNESS TESTING. EXPERIMENT : 1. FIND : 1. THE MATERIAL OF SPECIMENS 2. HARDNESS OF SPECIMENS 3. THE EFFECTS OF HEAT TREATMENT TO HARDNESS. EXPERIMENT : 1. Hardness scale. + Brinell + Vickers + Shore + Rockwell.

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SECTION 12 HARDNESS TESTING

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  1. SECTION 12HARDNESS TESTING EXPERIMENT : 1

  2. FIND : 1. THE MATERIAL OF SPECIMENS2. HARDNESS OF SPECIMENS3. THE EFFECTS OF HEAT TREATMENT TO HARDNESS EXPERIMENT : 1

  3. Hardness scale + Brinell + Vickers + Shore + Rockwell • Hardness is a property of a material in the solid phase that give it high resistance to various kinds of shape change when force is applied. • Scratch hardness: Resistance to fracture or plastic (permanent) deformation due to friction from a sharp object • Indentation hardness: Resistance to plastic (permanent) deformation due to a constant load from a sharp object

  4. How to measure Hardness ? 1 • Principle • Choosing the appropriate scale • having a known object pressed against the specimen • The mark left on the object imply to the hardness of the specimen • the deeper the mark is the lower the hardness of the specimen

  5. ROCKWELL <<< choose this one 2 STEPS OF LOAD The Rockwell test determines by measuring the depth of penetration of an indenter under a large load compared to the penetration made by a preload. You can read the hardness from the machine Don’t need to measure again then this one have Less uncertainty

  6. SCALE B SCALE C ABBRE.HRB ABBRE.HRC LOAD 150 kgf LOAD 100 kgf Indenter 120° diamond cone Indenter 1/16-in Diameter Steel Ball ROCKWELL <<< choose this one

  7. How to measure Hardness ? Scale B Scale C Choosing Scales Calibration Before Using

  8. Hardening Heat treatment by Oil Quenching

  9. What is Quenching ? Heat treatment is one of the way of hardening, making the material reorganize the grain. Quenching is one way of heat treatment to make the high temperature drop very quickly.

  10. to do oil quenching… 4 • We need to know the temperature that the material will reorganize the grain FOR EACH SPECIMENS, ……WHAT IS THE APPROPRIATE TREATMENT TEMPERATURE?........

  11. What to know… + material + temperature • To determine which type of material the specimen is • HOW? By Finding its density, strength, …., …. , etc.Then compare with the property table of materials. • The easiest way is DENSITY.

  12. What to know… + material + temperature Dimension and Volume1 Weight 2 Density 3 Calculation

  13. + material • Mass volume • Density table

  14. Finding Recrystallize Temp 5 Heat Treatment Finding Recrystallize temperature from “Phase diagram”

  15. + Phase diagram STEEL IRON PHASE DIAGRAM 5 3

  16. BRASS PHASE DIAGRAM 5

  17. STEEL BRASS ALUMINUM T = 900 C T= 600 C T= 400 C time 50 min time 50 min time 50 min No 1 No 2 No3 Heat Treatment No 1No 2No3 3

  18. Heat Treatment Go to the OVEN Set the Desired Temperature Eg. For steel at 900 C 3

  19. Heat Treatment Put in the Oven that has the Desired Interior Temperature Oil Quenching 3

  20. The process

  21. The Process Collect Hardness Data of Each Specimen Clarify the Material of Each Specimen 1 2 4 3 Heat Treatment Collect the Hardness Data of Treated Specimen

  22. Data lab. Rockwell C&B Scale : AVERY Type 6402 PAT No. 512520 Resolution : 1 HRC/HRB Scale Range : 0 – 100 HRC/HRB Scale  **t( a/2, v) = 2.2622 @ 95%C

  23. Data lab.

  24. conclusion • HARDNESS : • steel > brass > aluminium • Hardening by heat treatment • is not suitable for all material

  25. Thank you! MEMBER Krisanapong PatanTeeratorn KadeetumTeerawat WatcharasiritumNatwilai UtoomprukpornNarit Tangsirivanich

  26. ADDITION 1. The Hardness Testing Machine2. Rockwell Scale Hardness Testing3.Calibration4.Oil Quenching5. Heat Treatment Temp ( Phase Diagram)

  27. The Brinell scale characterizes the indentation hardness of materials through the scale of penetration of an indenter, loaded on a material test-piece. Other scale : Brinell

  28. The Vickers hardness test was developed in 1924 by Smith and Sandland at Vickers Ltd as an alternative to the Brinell method to measure the hardness of materials. Other scale : VICKERS SCALE

  29. 1 The Hardness Testing Machine หน้าปัทม์ load แท่นวาง ล้อเลื่อนแท่น คันโยก

  30. 1 The Hardness Testing Machine หน้าปัทม์วงใน (B Scale) หน้าปัดเล็ก (Preload) หน้าปัดวงนอก (C Scale)

  31. ROCKWELL 2

  32. ROCKWELL 2

  33. ROCKWELL 2 การทดสอบความแข็งแบบร็อคเวลล์ (Rockwell Hard Test) วิธีทดสอบความแข็งแบบร็อคเวลล์ประกอบด้วยการกดวัสดุทดสอบด้วยหัวกดเพชรรูปกรวยหรือหัวกดลูกบอลเหล็กชุบแข็ง ให้ภาระหัวกดกดวัสดุทดสอบภายใต้ภาระเริ่มต้น 10 กิโลกรัมแรง เมื่อถึงภาวะคงที่ โดยเข็มชี้จะเคลื่อนที่ตามการเคลื่อนที่ของหัวกดและยังตอบสนองต่อการเปลี่ยนแปลงความลึกของรอยกดจากหัวกด ถูกกำหนดให้เป็นตำแหน่งศูนย์ ในขณะที่ให้ภาระเริ่มต้นก็เพิ่มภาระหลักด้วย ส่งผลต่อการเพิ่มขนาดของรอยกด เมื่อถึงภาวะคงที่อีกครั้ง ภาระหลักได้ถูกเอาออก แต่ภาระเริ่มต้นยังคงไว้ การเอาภาระหลักออกส่งผลให้มีการคืนตัวบางส่วน เป็นผลให้ความลึกของรอยกดลดลง การเพิ่มขึ้นความลึกของรอยกดอย่างถาวรเป็นผลจากการเพิ่มและเอาภาระหลักออก ใช้คำนวนค่าความแข็งร็อคเวลล์

  34. ROCKWELL 2

  35. Calibration 3 Rockwell C&B Scale : AVERY Type 6402 PAT No. 512520 Resolution : 1 HRC/HRB Scale Range : 0 – 100 HRC/HRB Scale แผ่นมาตรฐาน สเกล B 71.5 – 73.5 แผ่นมาตรฐาน สเกล c 59.5 – 73.5 3

  36. Before Start To MINIMIZE error, all specimens will be grinded.By Using Hand Grinding.

  37. Clarifying Material 1 Clarify the Materials Collect Hardness Data of Each Specimen Heat Treatment Collect the Hardness Data of Treated Specimen

  38. STEEL BRASS ALUMINUM T = 900 C T= 600 C T= 400 C time 50 min time 50 min time 50 min No 1 No 2 No3 5 3

  39. Finding the Materials Collect Hardness Data of Each Specimen Clarify the Material of Each Specimen 2 Collect the Hardness Data of Treated Specimen Heat Treatment

  40. STEP3 Heat Treatment Collect Hardness Data of Each Specimen Clarify the Materials Collect the Hardness Data of Treated Specimen Heat Treatment 3

  41. STEP4 Collect Hardness Data Collect Hardness Data of Each Specimen Clarify the Materials 4 Heat Treatment Collect the Hardness Data of Hardened Specimen

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