Another Gold Star Quiz in Springmaking Answers

2. A, because of poor ductility.

3. False.

4. D. This equation is also a good method for making an estimate for G if you have a value of E and assume n = 0.3.

5. Definitely not. You expose yourself to hydrogen embrittlement.

6. False. The 1st load tolerance should have a higher percent (%) load tolerance value.

7. True.

8. True.

9. Tell the customer very politely to "go to hell."

10. Thank the customer for all his business, explain just how much you value the relationship and try very hard over lunch to negotiate a decrease somewhat lower than requested.

11. The "fully stress relieved" temperature for Inconel 625 is actually 1000-1400°F for one hour and then air-cooled – as recommended in the Inco Alloys Working Instructions manual. In fact, however, since it is never desirable to fully stress relieve a spring, the accepted temperature for adequate stress relief is, in practice, in the 700-850°F temperature range.

12. False. This simplified equation does not take into account pitch. The difference can be significant especially with springs having a steep pitch angle. The more accurate calculation is:

13. False.

14. A only. It is not recommended to electroplate stainless steel because the oxide that confers its corrosion resistance has to be removed in order to get the plating to adhere. It is not recommended to electroplate silicon chromium springs because the risk of hydrogen embrittlement is much too high, and de-embrittlement is unlikely to be effective.

15. A, B and C. Wear will adversely affect fatigue due to loss of section of the spring material. Impact loading will lead to higher operating stresses than those calculated. External radial legs will have an adverse residual stress from forming that will reduce fatigue life.

16. True.

17. False. Electroplaters are capable of believing their process to be 100% efficient, which is, of course, impossible. Are there any spring manufacturers who would believe such an outrageous claim?

18. D, but A and B would also be correct. Delays between quench and temper give the greatest risk, but A and B are both significant contributing factors. Water in the oil is more likely to lead to soft spots than it is to quench cracks.

19. A only; not B or C.

20. A, B and C.

21. B.

22. True.

23. B. Some of the copper-based alloys with low moduli actually have higher densities than standard stainless steels used for spring applications. Titanium alloys do have lower densities.

24. No. Parts made with 17-7PH must be heated at 900°F for one hour to perform a precipitation hardening process. This answer is open to debate, however. The speed of the in-line oven could be adjusted to give the required soak time. But this may not be practical.

25. False. The minimum tensile strength (MTS) for music wire is less than that for chrome silicon starting at 0.073 in. wire diameter. This may vary slightly from one source of information to another. 0.032 in. music wire MTS = 327,000 psi, and 0.032 in. chrome silicon MTS = 300,000 psi; 0.162 in. music wire MTS = 249,000 psi, while 0.162 in. chrome silicon MTS = 265,000 psi.

26. Cold-wound without question. Closer tolerances can be maintained with cold-wound springs. This would be finally determined by many other factors, such as size, forming equipment and ultimate application.

27. False. The effect is not as dramatic as with spring wire, and wire forms of basic wire are not usually highly stressed, so stress relief is seldom done on basic-wire forms. However, tests have shown that, in many cases, 25% to 50% more load can be applied to basic-wire forms without any permanent set if the wire forms are first stress relieved.

28. Increase.

29. All.

30. 8%. As relaxation is logarithmic with time by plotting a graph on a log scale, it can be estimated.

31. Fracmat testing, almost always. Chemical composition, never. Tensile, cast and ovality, occasionally.

32. True.

33. True.

34. +10% of reading.

35. What it says on the drawing. However, we should inquire about the application to be sure that, based on our experience, the needs of the application will be met.

36. All.

37. Yes. To minimize the effect of unwinding, design the lower platen on the test fixture to rotate.

38. C.

39. No. Use a 0.1 (10%) to 0.25 (25%) shot size to wire size ratio. To peen a part with a large shot can actually be detrimental.

40. False. Although true for many alloys, this statement is not true of all alloys. Final aging heat treatments can result in tensile strengths that are actually lower than the starting material. For example, alloy X750 in the spring-tempered condition has a higher tensile strength than it does after the multi-step aging heat treatment (190 ksi min., compared with 150 ksi min.).

41. No. The maximum operating temperature of 17-7PH is 650°F. Above that, the spring relaxation behavior will be unpredictable. Other materials (nickel alloys) are better suited to this task.

42. Decrease the hook diameter.

43. C.

44. Radial. Garter springs are either extension springs or compression springs that are formed into a circle.

45. Yes, depending on the environment to which the spring is exposed and the process used to manufacture the spring. To prevent this from happening, specify stainless steel shot.

46. True. This means that over a set temperature range, there will be no effects on the load-bearing characteristics of the springs due to temperature changes.

47. No. Most e-coat lines are cathodic these days, which means that during the operation, hydrogen is liberated into the paint. This hydrogen or acidity is controlled in a device called an “anolyte tank.' Some anodic lime remains. In an anodic e-coat, hydrogen will be absorbed by the part, which can lead to hydrogen embrittlement. It is then a good idea to specify what type of e-coat is required.

48. False. The statement given is for springs in series (i.e. alternating in orientation). For springs in parallel (i.e. all in the same direction), the load will be six times that for one washer while the deflection will be same as that for one washer.

49. In the ratio 4:2:1

50. False. If the part is not pickled and/or passivated, the metallic dust left on the part by the peening process will corrode rapidly. Specify stainless steel shot or passivate.