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Katherine Johnson’s mathematical calculations helped guide some of America’s most important early space missions while she confronted the racial and gender barriers faced by Black women in twentieth-century America.
MORE →Reflects the personal views, recollections, and perspective of the author, Mike Davis.
This is a personal recollection on the Move fire on May 13, 1985
| Steels |
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| Phases |
| Microstructures |
| Classes |
| Other iron-based materials |
| Steel production intermediates |
Spring steel is a name given to a wide range of steels[1] used in the manufacture of different products, including swords, saw blades, springs and many more. These steels are generally low-alloy manganese, medium-carbon steel or high-carbon steel with a very high yield strength. This allows objects made of spring steel to return to their original shape despite significant deflection or twisting.
Many grades of steel can be hardened and tempered to increase elasticity and resist deformation; however, some steels are inherently more elastic than others:
| SAE grade (ASTM grade) |
Composition | Yield strength | Hardness (HRC) | Comments | |
|---|---|---|---|---|---|
| Typical | Maximum | ||||
| 1070 | 0.65-0.75% C, 0.60-0.90% Mn, max .050% S, max .040% P | Normally supplied annealed | 165vpn | 180vpn | CS70, CK67, C70E |
| 1074/1075[2] | 0.70–0.80% C, 0.50–0.80% Mn, max. 0.030% P, max. 0.035% S[3] | 62–78 ksi (430–540 MPa)[4] | 44–50[5] | 50 | Scaleless blue, or Polished Bright |
| 1080 (A228) | 0.7–1.0% C, 0.2–0.6% Mn, 0.1–0.3% Si[6] | Piano wire, music wire, springs, clutch discs | |||
| 1095 (A684)[2] | 0.90–1.03% C, 0.30–0.50% Mn, max. 0.030% P, max. 0.035% S[7] | 60–75 ksi (410–520 MPa), annealed | 48–51[5] | 59 | Blue, or polished bright spring steel |
| 5160 (A689)[8] | 0.55–0.65% C, 0.75–1.00% Mn, 0.70–0.90% Cr[9] | 97 ksi (670 MPa) | 63 | Chrome-silicon spring steel; fatigue-resistant | |
| 50CrV4 (EN 10277) | 0.47–0.55% C, max. 1.10% Mn, 0.90–1.20% Cr, 0.10–0.20% V, max. 0.40% Si | 170 ksi (1,200 MPa) | Old British 735 H1steel, SAE 6150, 735A51 | ||
| 9255 | 0.50–0.60% C, 0.70–0.95% Mn, 1.80–2.20% Si[9] | ||||
| 301 spring-tempered stainless steel[10] |
0.08–0.15% C, max. 2.00% Mn, 16.00–18.00% Cr, 6.00–8.00% Ni[9] | 147 ksi (1,010 MPa) | 42 | Equivalents EN 10088-2 1.4310, X10CrNi18-8 | |
 | This section needs more citations. (March 2009) |
Bibliography
Source: Wikipedia. Article content is retrieved live through the MediaWiki API.
Spring steel is a name given to a wide range of steels used in the manufacture of different products, including swords, saw blades, springs and many more. These steels are generally low-alloy manganese, medium-carbon steel or high-carbon steel with a very high yield strength. This allows objects made of spring steel to return to their original shape despite significant deflection or twisting.
A spring is a device consisting of an elastic but largely rigid material (typically metal) bent or molded into a form (especially a coil) that can return into shape after being compressed, extended or twisted. Springs can store energy when compressed, when extended, and/or when twisted. In everyday use, the term most often refers to coil springs, but there are many different spring designs. Modern springs are typically manufactured from spring steel. An example of a non-metallic spring is the bow, made traditionally of flexible yew wood, which when drawn stores energy to propel an arrow. When a conventional spring, without stiffness variability features, is compressed or stretched from its resting position, it exerts an opposing force approximately proportional to its change in length (this approximation breaks down for larger deflections). The rate or spring constant of a spring is the change in the force it exerts, divided by the change in deflection of the spring. That is, it is the gradient of the force versus deflection curve. An extension or compression spring's rate is expressed in units of force divided by distance, for example or N/m or lbf/in. A torsion spring is a spring that works by twisting; when it is twisted about its axis by an angle, it produces a torque proportional to the angle. A torsion spring's rate is in units of torque divided by angle, such as N·m/rad or ft·lbf/degree. The inverse of spring rate is compliance, that is: if a spring has a rate of 10 N/mm, it has a compliance of 0.1 mm/N. The stiffness (or rate) of springs in parallel is additive, as is the compliance of springs in series. Springs are made from a variety of elastic materials, the most common being spring steel. Small springs can be wound from pre-hardened stock, while larger ones are made from annealed steel and hardened after manufacture. Some non-ferrous metals are also used, including phosphor bronze and titanium for parts requiring corrosion resistance, and low-resistance beryllium copper for springs carrying electric current.
An ideal constant-force spring is a spring for which the force it exerts over its range of motion is a constant, that is, it does not obey Hooke's law. In reality, "constant-force springs" do not provide a truly constant force and are constructed from materials that do obey Hooke's law. Generally, constant-force springs are constructed as a rolled ribbon of spring steel such that the spring is in a rolled-up form when relaxed.
A volute spring, also known as a conical spring, is a compression spring in the form of a cone (somewhat like the classical volute decorative architectural ornament). Under compression, the coils slide past each other, thus enabling the spring to be compressed to a very short length in comparison with what would be possible with a more conventional helical spring. There are two typical types of volute spring: The first has a shape for the initial spring steel (or other material for the wound spring) as a "V", with one end wider than the other The second is the double volute, having two "V" shapes facing away from each other, which forms a distorted cylinder having a wider diameter at the centre than at the ends, forming symmetric attachment points Double volute springs can frequently be found as a component of garden pruning shears. Short posts anchored in each side of the handles, and inserted into each narrow end of the spring, keep the spring in position. However, the applications of volute springs are not limited to such light-duty purposes as gardening shears. For example, volute springs are used to cushion the impact between railway cars and as a core element of the suspension system of Sherman tanks. A volute spring buffer device for railway cars was invented by John Brown in 1848.
Before the 1921 destruction of Tulsa’s Greenwood District, Black residents had created a remarkable center of business and community life. The district included stores, professional offices, entertainment venues and homes owned by Black citizens. Understanding Greenwood means learning what was built—not only what was burned.
MORE →Madam C.J. Walker