K85 (SK5) carbon tool steel Standard: JIS G4401 ● Features and Scope: After quenching and tempering has high hardness and wear resistance, but low thermal rigid, poor hardenability, deformation, low ductility and strength. Used needs to have a high hardness and wear resistance of a variety of tools, such as the shape of a simple mold and punch, metal cutting tools, drilling tools, woodworking cutter, countersink drill, axes, chisels, hand saws vertical and fitter assembly tools, dies and other minor rivet tool. ● Chemical Composition: Carbon C: 0.80 ~ 0.90 Si Si :0.10-0 .35 Mn Mn :0.10-0 .50 S S: ≤ 0.030 Phosphorus P: ≤ 0.030 Chromium Cr: to allow the residual content of ≤ 0.25, ≤ 0.10 (bath quenching steel manufacturing lead ) Ni: to allow the residual content of ≤ 0.20, ≤ 0.12 (bath quenching steel manufacturing lead time) Cu: to allow the residual content of ≤ 0.30, ≤ 0.20 (manufacturing lead wire quenching bath) Note: to allow the residual content of Cr + Ni + Cu ≤ 0.40 (bath quenching steel manufacturing lead time) ● Mechanical Properties: Hardness: annealing, ≤ 187HB, indentation diameter ≥ 4.40mm; quenching, ≥ 62HRC ● Heat treatment and microstructure specifications: Heat Treatment Specification: Sample quenching 780 ~ 820 ℃, water-cooled. ● Delivery status: Delivery of steel in the annealed condition. By mutual agreement, can not annealed delivery. For the manufacture of springs or spring-like properties of the steel parts of the class. With a high elastic limit ﹑ fatigue limit (especially notched fatigue limit) and some toughness and ductility, mainly under the impact of dynamic load ﹑ vibration or long cycle alternating stress conditions. So spring working in various states should have a good surface quality and high fatigue resistance. In the process performance, subject ﹑ hardened and tempered spring steel, should have a certain hardenability, easy removal, low thermal sensitivity and high plasticity, easy-forming in the hot state. Manufacturing small wire springs have a uniform hardness and plasticity. Category spring steel according to production methods can be divided into spring steel hot-rolled and cold drawn (rolled) spring steel. Including the manufacture of hot-rolled steel coil spring spring ﹑ torsion bar with a round or trapezoidal steel and manufacturing leaf spring flat steel; cold drawn (rolled), including the manufacture of small size spring steel coil spring and manufacture cold drawn steel wire and a variety of spring The cold rolled spring steel. Manganese alloy spring steel commonly ﹑ ﹑ ﹑ chromium molybdenum vanadium and boron ﹑ ﹑ trace tungsten silicon, alloys of these elements can improve the hardenability of steel, manganese and silicon in the solid dissolved in the ferrite can increase the yield strength. ﹑ ﹑ Tungsten chromium vanadium steel the elastic limit can be increased ﹑ yield ratio and heat resistance. By alloying elements contained in commonly used spring steel can be divided into the following categories: low-carbon spring steel prices, wide range of uses. If the same surface condition and heat tissue, fatigue limit is not less than the alloy spring steel. The disadvantage is that the yield is low hardenability and strength; cross-section larger spring, when oil quenching hardenability can not easily crack when water quenching. Such as increasing the carbon content, although able to improve the strength and elastic limit, but it will reduce the impact toughness and ductility, especially in reducing the low-temperature toughness. China's carbon spring steel 65 75 ﹑ ﹑ ﹑ 70 85 four steel. Pure manganese as spring steel 65Mn, the manganese content is 0.90 to 1.20%. Increase in manganese content can improve hardenability and strength of steel, reducing decarburization tendency; drawback is overheating sensitivity and temper brittleness, and easy to produce quenching cracks, so only suitable for the manufacture of various small flat spring ﹑ round spring . Silico-manganese spring steel is a major hot-rolled alloy spring steel, China has 55Si2Mn 60Si2MnA ﹑ ﹑ ﹑ 60Si2Mn 70Si3MnA four steel. A silicon content of 1.50 to 2.80%, a manganese content of 0.60 to 0.90%. Plus silicon steel can significantly increase the elastic limit and yield ratio, improve the tempering stability; but easy to form silicate inclusions, increased sensitivity of decarburization. When the carbon content of the steel and silicon are high, easy-carbon graphite. Such steel is widely used in the production of the leaf spring and coil spring shock Cars, tractors ﹑ locomotive, as well as requirements to withstand high stress spring. Chromium spring steel is very common in the world, China has 50CrMn and 50CrVA two steel. 50CrMn because it contains about 1% of chromium and manganese, high hardenability, small decarburization tendency; disadvantage is the tendency of chromium and manganese are aggravated temper brittleness, need rapid cooling after tempering, and more for the manufacture of large cross-section and more important spring and coil springs. 50CrVA steel has good hardenability; plus vanadium can refine the organization, not overheating, and improve the strength, toughness, and reduced notch sensitivity. This steel decarburization tendency of small, low-temperature impact toughness, work at higher temperatures, more stable performance, mainly for the manufacture of valve springs and valve spring ﹑ spring to work at higher temperatures. Appropriate increase in other alloying elements on the basis of 50CrVA steel, can get better than the two spring steel mechanical properties and hardenability. Silicon content of 1.40 to 1.80% ﹑ chromium content of 0.90 to 1.20% ﹑ vanadium content of 0.10 to 0.20 percent 60Si2CrVA steel with high hardenability and low thermal sensitivity, when the plasticity index similar tensile strength and yield strength than silicon manganese spring steel, mainly for the production of high stress spring. Tungsten content of tungsten steel, spring steel 65Si2MnWA 0.80 to 1.20 percent, the same as with 60Si2CrVA steel can be used to produce withstand high loads and heat (≦ 350) ﹑ impact resistant springs. 30W4Cr2VA higher alloy content heat-resistant steel is a high strength spring steel, has a high hardenability, primarily for the manufacture of a control valve spring 500 is lower than the conditions of use. The several steel production process more complex, higher prices. Spring working under high temperature conditions, the choice of heat-resistant steel and heat-resistant alloys; corrosive media work in the spring, should be the nature of the medium (oxidation, reduction) choose the appropriate grade of stainless steel. China still 55SiMnVB spring steel, silico-manganese is added on the basis of a small amount of spring steel or micro alloying elements to improve the performance of hardenability, used to make a larger cross-sectional dimensions of the car plate spring. Typical mechanical properties of Chinese spring steel grades, see Schedule China Typical mechanical properties of spring steel grades